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The Diversity and Abundance, with Aspects
of Ecology, of Lizard Species in Lago Preto,
Yavari Valley, Peru.
By
Jennifer Carr
Brindled forest gecko Gonatodes humeralis
Practical Research Project DI512
BSc. Biodiversity Conservation and Management
Durrell Institute for Conservation and Ecology,
University of Kent at Canterbury
~2008~
1
Acknowledgements
I am greatly indebted to Dr Richard Bodmer for providing me with the opportunity to study in the
Peruvian Amazon, and for his assistance as my supervisor. I am also very grateful to Richard Griffiths
for his contribution towards the development of this study in its latter stages.
I would also like to thank Santiago Cariajano Sandi for his priceless help in the field.
Finally, I thank my friends and family, especially my mother Janet Carr and partner Robert Boulter, for
their support and encouragement throughout my undergraduate education.
2
Abstract
Over a period of 18 days in May/June 2007, surveys for lizards were conducted in three habitats (varzea,
palm swamp and terra firme) in Lago Preto, Peru. A total of 9km of transect was extensively surveyed
during this time. A total of eighteen confirmed species from six families were recorded. Four individuals
were also observed that were unidentified. Lizards were found in all habitats sampled. Varzea had the
greatest diversity of species, whilst palm swamp had the lowest, and terra firme was intermediate
between these two habitats. This was postulated to be due to the greater heterogeneity of microhabitats
providing a wider variety of available niches within varzea compared to terra firme. Palm swamp
represented the most disturbed habitat and so was the most homogenous. Seasonality and lizard migration
are also suggested as possible explanation for this finding. Lizard densities were also calculated for each
habitat using DISTANCE 5.0 software and the fixed-width formula. These showed palm swamp to
contain a significantly greater density of lizards, than terra firme and varzea. These results are likely to be
due to the greater availability of resources for specialised lizards in palm swamps, in contrast to terra
firme, which has greater resource competition. Aspects of the ecology of the species observed are
reported, including microhabitat use and species level interactions. A wider aim of the study was to
contribute to the growing knowledge concerning Neotropical lizards and their ecology for conservation
and to provide a basis for future studies in comparable areas.
Keywords: Lizards, assemblage, terra firme, varzea, palm swamp, Yavari valley, Peru, abundance,
diversity, density, ecology.
CONTENTS
1.0 INTRODUCTION
1.1 Taxonomy
1
1
3
1.2 Global Conservation Status of Lizards
2
1.3 Conservation Status of Neotropical Lizards
3
1.4. Lizard Biology
4
1.4.1 Thermoregulation
5
1.4.2 Reproduction
6
1.4.3 Foraging and Feeding
6
1.4.4 Social Behaviour
7
1.4.5 Microhabitat Use
8
1.5 AIMS
2.0 METHODS
10
11
2.1 Study Site
11
2.2 Habitat Types Surveyed
12
Terra firme forest (Upland forest)
12
Varzea
12
Palm swamp
13
2.3 Data Collection
3.0 ANALYSIS
13
15
3.1 Species Accumulation Curve
15
3.2 Relative Abundance
15
3.3 Species Richness
15
3.4 Diversity
16
3.5 Evenness
16
3.6 Dominance
17
3.7 Density
17
3.8 Significance
18
4.0 RESULTS
19
4.1 Lizard Assemblage
19
4.2 Species Accumulation
20
4
4.3 Abundance
22
4.4 Relative Abundance
22
4.5 Diversity
23
4.5.1 Species Richness
23
4.5.2 Shannon Index of Diversity
23
4.5.3 Shannon Index of Evenness
24
4.5.4 Berger-Parker Index of Dominance
25
4.6 Density
26
4.7 Aspects of ecology
29
4.8 Microhabitat Occupancy
30
4.8.1 Species Specific Microhabitat Occupancy
31
4.8.2 Niche Overlap
32
4.9 Lizard Activity
33
4.9.1 Time
33
4.9.2 Temperature
34
4.9.3 Species Level Interactions `
35
4.9.4 Intraspecific Interactions
35
4.9.5 Interspecific Interactions
36
5.0 DISCUSSION
37
5.1 Lizard Assemblage and Community Structure
37
5.2 Comparisons with other studies
38
5.2.1 Richness
38
5.2.2 Composition
39
5.3 Species Diversity
41
5.3.1 Terra firme
41
5.3.2 Varzea
42
5.3.3 Palm Swamp
43
5.4 Density
43
5.5 Species Specific Microhabitat Occupancy
44
5.6 Lizard Activity
47
5
5.7 Niche Overlap
47
5.8 Conservation Implications of Study
48
5.9 Limitations
48
5.9.1 Further Research
49
REFERENCES
50 - 51
APPENDIX 1. Summary Data Table
APPENDIX II. Lizard Specimens Caught
TABLE OF FIGURES
Table 1. Conservation status of reptiles and lizards according to the
2
6
US Fish and Wildlife Service (FWS), Convention on International Trade
in Endangered Species (CITES) and The World Conservation Union (IUCN).
Figure 1. Map displaying the location of Lago Preto on the Yavari River
11a
and habitat types
Table 2. Macrohabitat Occurrence of Species
20
Fig. 2. Species accumulation curve for the duration of the study period
21
Fig. 3. Bar graph displaying the total relative abundance of lizards species from CPUE
22
for each macrohabitat surveyed (including unidentified individuals).
Fig. 4. Bar graph displaying the species richness for the three macrohabitats surveyed
23
Fig. 5. Bar graph displaying Shannon index of diversity values for each macrohabitat
24
and standard deviation.
Fig. 6. Bar graph displaying the Shannon Evenness values for each habitat
25
Fig. 7. Bar graph displaying the dominance value for each habitat, calculated using
26
the Berger-Parker dominance index.
Fig. 8. Graph displaying the density of each species per km² for each macrohabitat.
27
Table 3. DISTANCE density estimates for all lizards in each macrohabitat
27
Fig 9. Fixed-width density estimates of the number of lizards per km² for
28
each macrohabitat
Fig 10. Fixed-width density estimates of G. humeralis per km ² in each macrohabitat
29
7
Table 4. Classification system of microhabitats used by lizards at Lago Preto
30
Fig. 11. Bar graph displaying the proportional percentage abundance of lizards
30
occupying the predetermined microhabitat types.
Fig. 12. Bar Graph displaying the microhabitat preferences of the most observed species 31
Table 5. Microhabitat niche overlap for most abundant species (n>2).
33
Fig. 13. Line graph displaying lizard observations in relation to time of day (hours).
34
Fig. 14. Line graph displaying lizard observations in relation to temperature
35
Table 6. Comparisons of lizard species richness studies within Amazonia
38
Table 7. Comparison of lizard compositions identified in past studies in lowland
40
forest habitats in north-eastern Peru
8
1.0 INTRODUCTION
Reptiles arose from the first backboned animals on earth three hundred million years ago, long before
birds and mammals, even before any flowering plants. They were the first to develop mating strategies
that didn’t require water to transport sex cells and the first to colonise deserts (Attenborough, 2008).
Today, lizards are one of the most abundant groups of vertebrates and have successfully adapted to
occupy habitats ranging from swamp to desert on every continent except Antarctica. Most species are
diurnal and in many parts of the tropics they are very abundant, being more numerous than birds and
mammals in some parts of Central America (Avery, 1979). Worldwide there are 16 families of lizards
and some 5,066 species (Bartlett, 2003). These range in size from diminutive geckos only 3cm long to
the komodo monitor lizard, which is 3 meters long. About 80% of extant lizard species weigh less than
20 grams and are insectivores (Pough, 1999).
1.1 Taxonomy
Reptiles are classified into four main groups: Testudines (turtles), Sphenondontia (tuataras), Crocodilia
(alligators and crocodiles) and Squamata (snakes and lizards). Lizards are the most recently evolved out
of the four extant orders that form the class Reptilia and are the most numerous and diverse reptiles alive
today (Campbell,2002). Lizards themselves belong to the suborder Sauria, which is comprised of five
super-families. The taxonomic classification of lizards is under constant revision as studies advance in
both discovery and phylogenetics (Bartlett, 2003; Gibbons, 2000).
In the Amazon Basin there are currently 8 well known lizard families; Amphisbaenia, Gekkonidae,
Gymnophthalmidae, Iguanidae, Hoplocercidae, Polychrotidae, Tropiduridae, Teiidae and Scincidae.
These are known to exhibit the widest morphological, ecological and ethnological diversity. In the
department of Loreto there are known to be both diurnal and nocturnal species. These are insectivores,
omnivores and herbivores. There are arboreal species, terrestrial species, fossorial species and semiaquatic species. Amazonian lizards vary in size from 6 cm long geckos to iguanas, which often exceed
1.8 m in length for an adult male (Bartlett, 2003).
9
1.2 Global Conservation Status of Lizards
Whilst new species of lizard continue to be described to science, it appears that worldwide this taxon is in
decline. It has been recognised that this is likely to be due to human induced threats such as habitat loss
and degradation, introduced invasive species, environmental pollution, disease, unsustainable use and
global climate change (Gibbons, 2000). Thus, it is now recognised that reptiles are one of the most
threatened group of terrestrial vertebrates (Gardner, 2007). Unfortunately, it is difficult to monitor the
rate of this decline as most reptiles have not been comprehensively assessed, especially in comparison to
birds and mammals (Gibbons, 2000). Indeed, by 2000 only 178 species of lizards had been investigated
by The World Conservation Union (Crossley, 2004). Of these species, 30 were deemed to be
endangered whilst 66 were classified as vulnerable (see Table 1). It is clear that such figures should
cause concern. A pattern is emerging that shows a significant proportion of lizard species are at risk of
extinction, with the current primary threat being habitat destruction (Garner, 2007). This is further
supported by similar research conducted by the Convention on International Trade in Endangered Species
and the US Fish and Wildlife Service.
FWS²
Taxon
Endangered
Reptiles
Number
of
species¹
7150
70
Lizards
5066
14
CITES³
Threatened
IUCN⁴
Appendix
I
Appendix II
Appendix III
Extinct
18
70
383
19
8
16
238
0
Endangered
Vulnerable
20
100
153
11
30
66
Table 1. Conservation status of reptiles and lizards according to the US Fish and Wildlife Service
(FWS), Convention on International Trade in Endangered Species (CITES) and The World
Conservation Union (IUCN).
¹The approximate number of species for each taxon is from Plough et al (1998) and excludes subspecies and populations.
²Data from FWS (2000)
³Appendix I species are threatened with extinction and are affected by trade, Appendix II are not currently threatened but are
likely to become so unless trade is restricted, Appendix III species are listed to prevent or restrict exploitation. Data from CITES
(2000).
⁴Extinct refers to complete taxonomic extinction, rather than the IUCN category "extinct in the wild", “endangered includes
those species listed by IUCN as "critically endangered", "vulnerable" indicates that species are likely to become extinct if
current trends continue. Data from IUCN (2000).
* Table adapted from Gibbons, 2000.
In the future, the most significant threat to the continued survival of many lizard species is climate
change, with the obvious effects being mediated through changes in habitat. Although many habitats are
expected to undergo dramatic changes, predictions of species habitat shifts in response to global warming
10
cannot be based solely on analyses of climate-space changes, because species distributions are also a
function of dispersal ability and biotic interactions. Because of their limited dispersal abilities and
ectothermic thermoregulatory mechanisms, lizards are especially vulnerable to rapid habitat changes and
so are likely to suffer many more extinctions (Gibbons, 2000).
1.3 Conservation Status of Neotropical Lizards
Species diversity is greatest in tropical and desert habitats (Vitt, 1997). With around 75-plus species
known to inhabit the Amazon region (Bartlett, 2003), lizards form an important component of neotropical
ecosystems and can greatly increase the biomass of where they are found (Elzinga, 2001). This has
important ecological consequences as lizards (along with birds) are the principle agent for the biological
control of arthropod abundance, many of which are noxious for crops, humans and other animals. Lizards
also provide one of the main sources of food for carnivorous birds and mammals (Hutchinson, 2002).
The biogeographical regions known to support the greatest lizard species richness are deserts, with those
found in tropical regions being of a comparable level (Vitt, 1997). Tropical forests are amongst the most
productive habitats due to the relatively stable climate that provides an enormous diversity of ecological
niches. Lizards may live on the forest floor, on the trunks of trees, at many different levels on branches
or high in the canopy (Avery, 1976). Levels of tropical diversity are remarkable high when considered
against temperate regions. For example, only three native species occur in the British Isles
(Beebee, 2000).
Species of lizard which are harvested for meat and skins in South America include the green iguana
(Iguana iguana) and golden tegu (Tupinambis teguixin), which are both currently listed on Appendix II
of CITES (Gibbons, 2000). Therefore, these species may be at risk of becoming extinct if trade is not
strictly monitored and controlled.
Research is needed to gain a better understanding of the ecology and importance of lizard communities,
especially within the Amazon as the area is under considerable threat from habitat destruction as a result
11
of logging and agricultural expansion. Yet, lizards remain one of the least studied taxon. While, many
studies on a single Amazonian species have been conducted (Sartorius, 1999; Vitt, 1997) there are few
examples that focus on ecology and community structure of lizard assemblages in undisturbed
Neotropical forests. For example, up to 1997 only 25% of studies of South American lizards had
concentrated on ecology (Vitt, 1997). Documentation of natural abundances and assemblages of
Neotropical lizards must become a conservation imperative in order to provide a ‘baseline’ for
comparison to more disturbed areas (Gibbons, 2000). This will enable the affects of anthropogenic
pressures upon lizards in these regions to be further understood, in order to identify and mitigate future
declines.
This study was conducted in order to provide further information on lizard assemblages in undisturbed
natural environments. While an inventory of lizard species for the region had previously been compiled,
only one project had been conducted at the site into the ecology or species assemblages of lizard
communities. Therefore, this study aims to add to the knowledge of lizard diversity at Lago Preto and
contribute to the wider understanding of Amazonian lizard ecology for conservation.
1.4. Lizard Biology
Lizards possess several adaptations for terrestrial living. Scales containing the protein keratin waterproof
the skin, preventing dehydration in dry air. These are shed at intervals throughout the life of an
individual. They also have lungs for gaseous exchange, ventilated by ribs through costal ventilation
(Roberts, 2000).
An unusual feature of lizards is their ability to move their upper as well as lower jaw. This is due to a
cartilaginous hinge located at the rear of the skull which allows flexion in the upper jaw when the lizard
is handling a large food item. However, the most remarkable feature of lizard physiology is the fracture
planes in some of the tail vertebrae and tissues. If a lizard is subject to attack, it contracts muscles in the
tail so that it breaks off at one of these planes. This process is known as autotomy and gives the lizard a
chance to escape by sacrificing its thrashing tail to a distracted predator. Eventually, a new tail grows
12
around a rod of cartilage develops to replace the lost vertebrae, although the length remains stunted.
Also, this cartilage is not capable of autotomy a second time round. Therefore, if a second attack should
occur, the lizards’ only option is to fracture a higher vertebra if one exists. There are costs associated
with autotomy and these included reduced ability to run, climb and balance, as well as the associated cost
in energy to grow a new tail (Beebee, 2000).
Lizards that exploit space in different ways have evolved a variety of morphological features to enable
them to utilise that space. Subterranean (fossorial) species typically have either much reduced
appendages or none at all. Diurnal arboreal lizards are usually long-tailed and slender. Terrestrial
species that forage in the open generally have long hind legs relative to their size, while those that forage
closer to cover usually have proportionally shorter hind legs (Pianka, 1973).
1.4.1 Thermoregulation
Lizards are ectothermic tetrapods as they absorb external heat rather than generating their own. This can
be from direct solar radiation, from hot rocks or barks, or (rarely) from hot springs (Avery, 1979).
Internal temperatures are regulated by behavioural adaptations whereby individuals move into sunshine
or onto hot rocks when they are too cool and then into shade when too hot. The extensive repertoire of
thermoregulatory mechanisms employed by ectotherms allows many species to keep body temperatures
within the range of a few degrees during the part of the day when they are active. Many species of
lizards have body temperatures between 33 and 38°C (Pough, 1999). By generating heat in this manner
rather than through the metabolic breakdown of food, a lizard can survive on less that 10% of the calories
required by a mammal of equivalent size (Campbell, 2002).
This method of thermoregulation places ecological and behavioural constraints upon lizards. It has been
proposed that lizards in temperate regions show less extensive social behaviour than do tropical lizards as
thermoregulatory behaviour in cooler climates requires so much time (Avery, 1979). Ectothermy also
sets restrictions on the time of year individuals may be active, with hibernation the only option during
13
colder months. Furthermore, temperature ranges may define ecological niches for some species, being
only able to occupy habitats where this range is maintained (Mattison, 1989).
1.4.2 Reproduction
The reproductive organs, ovaries in females and testes in males, are paired structures with the right
member lying anterior to the left. Male lizards possess a pair of hemipenes. At rest these form a bulge at
the base of the tail which often allows the sex of an individual to be ascertained. During mating only one
hemipene is used for copulation. Fertilization is internal in all reptiles (Beebee, 2000).
Within lizards there is a complete spectrum of reproductive methods with oviparity and viviparity at the
extremes. There are also intermediate species that use ovoviviparity, whose eggs hatch immediately prior
to laying (Mattison, 1989). However, most lizards utilize oviparity as the mode of reproduction and lay
shelled amniotic eggs on land. However, some species are viviparous, with their extraembryonic
membranes forming a placenta that enables the embryo to obtain nutrients from its mother
(Campbell, 2002). Viviparity has costs as well as benefits. For example, the agility of a female lizard is
substantially reduced when her embryos are large. Thus, the females of some lizard species become
secretive during pregnancy, in response to increased vulnerability to predation (Pough, 1999).
The phenomenon of parthenogenesis is displayed by six families of lizard and is particularly widespread
in teiids and lacertids and occurs in several species of geckos (Pough, 1999). In situations where females
are in a region containing no male counterparts, they are capable of producing fertile eggs from which
viable offspring that are genetically identical to the mother are produced (Roberts, 2000).
1.4.3 Foraging and Feeding
Most lizards are insectivorous and fairly opportunistic feeders, taking in a wide variety of arthropods
from a broad range of sizes (Pianka, 1973). The most notable exceptions to this are large lizards, such as
Iguana iguana, which are mostly herbivores (Pough 1999).
14
The activity patterns of lizards span a range from extremely sedentary species that spend hours in one
place, such as iguanians (sit and wait predators) to species that are in constant motion (Pough, 1999). An
example of the later is provided by the family Teiidae (which includes the Amazonian genera Ameiva and
Kentropyx). This morphologically and ecologically conservative lizard taxon is comprised of members
that are all fast moving, active foragers with streamlined bodies ( Sartorius, 1999). Studies into Ameiva
have shown it to be active for around 5 hours during the middle of the day, being in motion for 70% of
this time. This is comparable to small mammal species (Pough, 1999). Those species that exhibit
intermediate activity patterns are labelled as cruising foragers.
Lizards with different foraging modes use different methods to detect prey. Sit and wait lizards remain in
one spot from where they can survey a broad area. These motionless lizards detect the movement of prey
visually and capture it with a quick dash from their observation site. Active foragers spend most of their
time on the ground surface. These lizards seem to rely on chemical cues to detect local concentrations of
patchily distributed prey such as termites. Widely foraging species appear to consume smaller insects
than sit and wait predators. Thus, differences in foraging methods have lead to differences in diet, even
amongst species occurring in the same habitat (Pough, 1999.)
1.4.4 Social Behaviour
Squamates employ a variety of visual, auditory, chemical and tactile signals in the behaviours they use to
maintain territories and to choose mates. For example, iguanians use mainly visual signals, whilst some
gekkotans use vocalization. An example of the use of visual displays can be observed in male Anolis
species. These possess gular fans beneath the chin that can be distended during displays. The brightly
coloured scales and skin are used as conspicuous signalling devices along with head movements
(Pough, 1999).
Pheromone communication occurs primarily in scincomorphs and is mediated by the vomeronasal organ.
Behaviours observed in males include the rubbing of secretions from femoral glands onto objects within
their territories (Pough, 1999).
15
Many lizard species show dominance hierarchies or territoriality. The signals used in agonistic
encounters between individuals are often similar to those used for species and sex recognition during
courtship. Parental attendance at a nest during incubation period of eggs does occur, but extended
parental care of the young is unknown (Pough, 1999).
1.4.5 Microhabitat Use
The number of species coexisting within communities can differ in four distinct ways (Pianka, 1973);

More diverse communities can contain a greater variety of available resources and so have more
niches.

Their component species may, on average, use a smaller range of these available resources and so
have smaller niches.

Two communities with identical ranges of resources and average utilization patterns per species
can also differ in species density with changes in the average degree of overlap in the use of
available resources, with greater overlap implying that more species exploit each resource
(greater niche overlap).

Some communities may not contain the full range of species they could possibly support and so
species density might then vary with the extent to which available resources are actually
exploited by as many different species as possible.
Animals partition environmental resources in three basic ways: temporally, spatially and trophically.
Among lizards these three fundamental niche dimensions are often fairly distinct and more or less
independent of each other. However, they can sometimes interact; for example, the mode of foraging can
influence all three dimensions (Pianka, 1973).
16
The use of space varies widely among lizard species. A few are entirely subterranean (fossorial), many
others are completely terrestrial, while still others are almost exclusively arboreal. Various degrees of
semifossorial and semiarboreal activity also occur (Pianka, 1973).
17
1.5 AIMS

To investigate diversity and abundance of lizard species found in the Lago Preto Reserve, Peru.

To determine the effects of habitat variation on lizard species richness, composition and diversity
in three macrohabitats.

To identify species’ microhabitat use in order to further analyse lizard community structure and
ecology.

To place results within the context of previous studies on Amazonian lizards in order to compare
lizard population status in Neotropical lowland rainforests.

To contribute to the current knowledge of Amazonian lizards and provide a basis for comparison
in future studies.
18
2.0 METHODS
2.1 Study Site
Lizard surveys were conducted over eighteen days from the 25th May until the 13th June 2007 at the end
of the wet season in the Lago Preto, situated in Northeastern Peru within the department of Loreto. The
study site is located on the Rio Yavari (4°30'S, 71°43'W), a white water tributary of the Amazon River.
The Yavari valley is approximately 175km from Iquitos and forms part a 1.1 million-ha area that has
been proposed as a Zona Reservada. This is a first step towards formal protection, and Lago Preto is
currently being considered as a biological station due to the rich diversity of wildlife (Pitman, 2003).
The mean annual temperatures in the Amazon basin vary from 23 to 27°C, and the variations through the
year are small, although polar air sometimes sweeps the continent from the south and temperatures drop
to 10–15°C. In the Peruvian lowland Amazon, the northern parts are the most humid and precipitation is
around 1500 mm per year. The departments of Loreto, Ucayali, and Madre do Dios cover 556,446km²,
corresponding to 82% of the total Peruvian lowland area (Kvist & Nebel, 2001). Therefore, the climate
of the site is typical of humid lowland tropical forests and the mean temperature during the surveys was
26.3°C.
Historically, the Amazon basin was viewed as a continuous ocean of forest, however today the lowlands
are recognised as a complex patchwork of forest types (Vitt, 1997). Lago Preto is unusual as it is
comprised of three distinct macrohabitat types in close proximity to one another. These are clearly
defined and are composed of discrete vegetation structures. The habitat known as ‘aguajal’ or palm
swamp forest is dominated by Mauritia flexuosa, high ‘terra firme’ forests contain high floral diversity
and the varzea forest is a more open habitat that is regularly flooded by white water
(Bodmer, pers comm).
19
2.2 Habitat Types Surveyed
Terra firme forest (Upland forest)
In very old secondary forests, typical rainforest epiphytes such as bromeliads, orchids, aroids and ferns
recolonise both arboreal and terrestrial situations. Primary forests are characterised by an enormous array
of plant species, including a vast number of epiphytes and lianas colonizing a multitier canopy. It is
common for these trees to utilise stilting and buttressing as means of support. Very little light reaches the
forest floor except for in tree fall sites, where a break in the canopy occurs. Due to this the herbaceous
understory is largely non-existent except in less shaded areas. A few plants that are more shade tolerant
dominant the understory and include ferns, prayer plants and palms. A thick layer of leaf litter is usually
present on the forest floor (Bartlett, 2003).
Varzea
In Peru more than 60, 000km² of alluvial lands are exposed to annual flooding by sediment rich rivers
originating in the Andes, which corresponds to 12% of the region. In addition, extensive areas are
flooded by water from local streams and rivers. Taking these regions in account, flood plains may
constitute 20% of the Peruvian lowland Amazon region (Kvist, 2001).
In wetland ecosystems, the flooding pattern has profound impacts upon flora and fauna, and is the main
factor distinguishing these areas from other ecosystems. The inundation of flood plains from large rivers
often follows a predictable monomodal pattern with considerable amplitudes. The monthly average
water levels observed through daily measurements from September 1987 to February 1997 in Iquitos at
the Amazon River showed the average peak period was March – May and the lowest water levels
occurred in August – October (Kvist 2001).
20
The varzea habitat at Lago Preto is flooded with white water from the Yavari River. These rivers contain
large amounts of suspended sediments as well as a considerable concentration of nutrients. New
sediment deposits can reach 0.3-1m every year, so that there is a high nutrient input into the ecosystem
that becomes more productive as a result (Junk, 1980). Another consequence is that there are high levels
of erosion and new land formations, making the habitat dynamic. Thus, varzea forests are characterised
by a high diversity of species and adaptation against extended flooding. Water-logging and submergence
can last up to 210 days per year, with a water column of up to 7m (Parolin, 2004).
Palm swamp
In Lago Preto, the palm swamps exist in the lowland regions of the forest. It is a diverse assemblage of
forest, with thicker undergrowth than terra firme or varzea due to a more broken canopy. The dominant
palm species Mauritia flexuosa, created a canopy at a height of approximately 20m (Hutchinson, 2003).
During the course of the survey, this habitat was completely inundated with water, due to the high water
table and clay soil with poor drainage (Kahn, 1988).
2.3 Data Collection
The sampling of lizard species in Lago Preto was conducted along pre-cut transect lines marked out every
100m using pre-measured lengths of rope. These ran through the three habitats for varying distances.
During each day visual encounter surveys were conducted along one 500m of transect for an average of
2.2 hours between 07:30 and 15:00, which varied due to the distance to the start point. This occurred for a
total of 39.75 hours over 18 days. Terra firme was surveyed for seven days covering 3.5km of transect,
varzea for six days covering 3km and palm swamp for five days covering 2.5km, so that a total of 9km
were surveyed. The time at the start and finish of the sample period were noted, along with the
temperature (°C) and general weather conditions to enable comparisons on lizard catchability to be made.
21
Visual searches were conducted at a slow pace to minimise noise and, thus, avoid disturbance. Surveys
also involved active searches of possible refugia. These included tree trunks, tree roots, tree fall sights,
logs, sunspots and leaf litter, in adjacent areas up to 3m from the transect line for an average of 2.2 hours
per survey. If a lizard was encountered, the macrohabitat and microhabitat of its location were recorded,
along with its distance in relation to the transect length (in metres along the transect line), time of sighting
and perpendicular distance from transect (in metres). For sexually dimorphic species, the gender was also
recorded. Where possible, any lizards observed were photographed prior to attempted catches, to enable
identification to be confirmed if it was not possible in the field. When opportunities arose, lizards were
caught to enable the measurement of snout-vent length (SVL) and total body length for further
identification purposes.
Identification was carried out using photographs presented in a publication by R. Bartlett and those
provided by Pedro Perez Pena on the research vessel. All data gathered was compiled into a summary
table that was updated daily.
One pilot night transect was conducted with the aid of torches, to asses the potential of this method as a
means for gathering data on nocturnal lizard species or those sleeping on exposed vegetation. As only
one sighting of a sleeping Gonadatodes humeralis was recorded, this method was deemed unsuitable for
inclusion.
22
3.0 ANALYSIS
Methods used in the analysis were based upon those included in previous studies into lizard assemblages
in this area of the Amazon by Hutchinson (2003) and Crossley (2004), in order to enable relative
comparisons between results.
3.1 Species Accumulation Curve
A species (or higher taxon) accumulation curve records the total number of species revealed during the
process of data collection. Additional individuals or sample units are added to the pool of all those
previously observed until all data is incorporated (Gotelli, 2001).
3.2 Relative Abundance
The relative abundances of lizard species’ for each habitat (varzea, palm swamp and terra firme) were
calculated in accordance with catch per unit of effort. This was required to standardize results as
differences in numbers of individuals counted may reflect differences in sampling effort or conditions for
observation. The results provide the number of lizards observed per kilometer of transect surveyed,
which was calculated using the equation (Bodmer, 2006):
C = n/e
Where catch per unit effort (C) is equal to the number of individuals observed for all species (n) divided
by the length of transect surveyed or effort (e). This was applied to the data for each macrohabitat.
3.3 Species Richness
The simplest method used to describe regional communities or diversity is species richness. This
variable is measured as the total number of species in a sample and is the basis of many ecological
23
models of community structure (Magurran, 1992). Quantifying species richness is important for basic
comparisons between sites. Maximizing richness is often a goal of conservation, and current rates of
species extinctions are calibrated against patterns of species richness (Gotelli, 2001).
3.4 Diversity
The Shannon Index of diversity is a measure of the likelihood that the next randomly selected individual
from the population will be the same as the previously selected one. This method assumes that the species
sampled are from an effectively infinite population and that all species in the population are represented
in the sample (Magurran, 1992). It is expressed by the formula:
H’ = - ∑pi ln pi
Where species diversity (H’) is equal to the negative of the sum of proportional abundance of individuals
in the sample (pi) multiplied by the natural log (ln) of the proportional abundance.
The Shannon measure H’ increases with the number of species in the community and in theory can reach
very large values. However, for biological communities H’ does not seem to exceed 5.0 (Krebs, 1999).
3.5 Evenness
Shannon’s evenness index indicates relative abundances of species in terms of evenness and is based on
the Shannon index of diversity. It was applied to the data for each macrohabitat and is calculated as
(Samson, 1996):
E = H’/lnS
Where evenness (E) is equal to diversity (H’) divided by the natural log (ln) of species richness (S). Both
the Berger-Parker dominance measure and Shannon evenness index are important measures of
heterogeneity.
24
3.6 Dominance
The Berger-Parker dominance measure expresses the proportional importance of the abundant species
(Magurran, 1992). Low values indicate lowered dominance by any one species in a sample and are
generally accompanied by increased evenness of a species. It was calculated for each macrohabitat using
the equation (Magurran, 2003):
D = Nmax/N
Where dominance (D) equals the number of individuals in the most abundant species (Nmax) divided by
the total number of individuals (N).
3.7 Density
The software program DISTANCE version 5.0 (RUWPA, 2007) was used to estimate the density of the
total number of lizards in each macrohabitat and the most common lizard species. This was possible as
the sample size for each category was large enough to allow computation (n>20).
Distance sampling methods are widely-used for estimating the density and/or abundance of biological
population from line transects and point transect. Thus, the DISTANCE software was an appropriate
application to use in the treatment of the data gathered. The main assumption underlying this statistical
test is that not all individuals the observer passes will be detected during sampling, but that all those on
the transect line are detected. This method therefore recognises that objects become harder to detect with
increasing distance from the line, resulting in fewer detections with increasing distance. Furthermore, the
software fits the most appropriate detection function (including half normal cosine, uniform cosine and
hazard rate models) to the observed distances, and uses this fitted function to estimate the proportion of
objects missed during sampling (Thomas, 2002). Thus, this analysis is used to produce a more
representative density estimate for the lizards in the area surveyed. One drawback of this method is that
detections of objects beyond the strip are ignored and so could prove wasteful for recording scare species.
Due to this, transects surveyed were of a predetermined fixed width.
25
Due to the survey being conducted along fixed width transects and the data on individual species being
too small to allow the use of DISTANCE, the fixed-width density estimator was also applied to the data
using the formula (Bodmer, pers comm.):
D = n/2wL
Where density (D) is obtained by dividing the total number of individuals in the sample (n) by 2
multiplied by the width (w) multiplied by the length of the transect (L). This enabled the densities of rarer
species to be calculated.
3.8 Significance
One-way analysis of variance (ANOVA) was performed to test perceived biological trends for statistical
significance between different habitat types using the statistical package SPSS.
26
4.0 RESULTS
The results examine the community structure of the saurofauna sample data gathered at the Lago Preto
site. The overall species diversity and the relative abundance of each species was calculated to enable
comparisons between the three macrohabitats surveyed (varzea forest, palm swamp and terra firme
forest), to be made. Investigations into the microhabitat use and niche overlap of lizard species are also
presented.
4.1 Lizard Assemblage
Eighteen lizard species from six families were found over the eighteen survey days. A total of 70
individuals were observed and recorded, with a further four being unidentified. A third of the species in
the sample (n = 6) are represented by one individual (Anolis bombiceps, Anolis trachyderma, Anolis
punctatus, Anolis nitens tandai, Cerosaura ocellata and Alopglossus buckleyi). The greatest numbers of
species were found from the family Polychrotidae and this was composed of six anole species. A total of
three species per family were found for Gekkonidae, Teiidae and Gymnophtalmidae.
Individuals from the species Gonatodes humeralis were the most frequently encountered in all
macrohabitats (n=26) at a sex ratio of 1:1 and comprised 35% of the sample. The only two other species
recorded in all three macrohabitats was Anolis fuscoauratus and Ameiva ameiva. A. fuscoauratus was
also the third most abundant species (n = 6, which equates to 8% of the sample) after Kentropyx pelviceps
(n = 7, which equates to 9.5% of the sample).
K. pelviceps was only observed in the palm swamp, which was also the case for Pseudogonatodes
guianensis, A. punctatus, and A. buckleyi. Other species recorded in one macrohabitat were A.
bombiceps, Anolis nitens scypheus, A. trachyderma and Leposoma parietale in varzea and A. n. tandai,
C. ocellata and Enyalioides laticeps in terra firme.
27
Two species were found in both varzea and palm swamp (Gonatodes concinnatus and Mabuya
nigropunctata), one species was found in terra firme and varzea (Iphisa elegans), and only Kentropyx
altamazonica was observed in palm swamp and terra firme forest.
Family
GEKKONIDAE
Species
Varzea
Palm Swamp Terra-firme TOTAL
G. humeralis
12
10
4
26
G. concinnatus
2
1
0
3
P. guianensis
0
3
0
3
A. fuscoauratus
3
2
1
POLYCHROTIDAE
6
A. bombiceps
1
0
0
1
A. n. scypheus
2
0
0
2
A. trachyderma
1
0
0
1
A. punctatus
0
1
0
1
A. n. tandai
0
0
1
1
A. ameiva
1
1
1
TEIIDAE
3
K. altamazonica
0
2
1
3
K. pelviceps
0
7
0
7
2
0
1
GYMNOPHTALMIDAE I. elegans
3
L. parietale
2
0
0
2
C. ocellata
0
0
1
1
A. buckleyi
0
1
0
1
M. nigropunctata
4
1
0
SCINCIDAE
5
E. laticeps
0
0
1
HOPLOCERCIDAE
1
Unidentifed
2
0
2
4
TOTAL
18
32
29
13
74
Table 2. Macrohabitat Occurrence of Species
4.2 Species Accumulation
In order to investigate whether the sample was a true representation of the entire lizard assemblage for the
study site, the occurrence of new species was plotted over time. In principle, for a survey of well-defined
spatial scope, an asymptote would eventually be reached with no new species being added (Gotelli,
2001).
28
Fig. 2. Species accumulation curve for the duration of the study period*
* Study period excludes non-surveying days.
This sampling curve rises relatively rapidly at first, and then much more slowly in later sample days as
increasingly rare species are added. The greatest accumulation of new species was made on the fifth and
sixth day. Although the increase of the curve diminishes with time, it still has positive slopes, even on
the last day. Therefore, it is likely that additional species remained to be found (especially more elusive
ones) and that the sample did not contain individuals representing all species in the community. It is
known that there are 29 species in Largo Preto (Pedro Perez Pena, pers comm) and so the sample
collected during the course of this study represents 62% of the known assemblage. This highlights the
importance of long-term studies into community structure in order to discover fauna that exist at low
densities or exhibit a secretive lifestyle. This graph supports current species knowledge for the area that
shows new species would have been found if the survey had been extended (Doan, 2002).
29
4.3 Abundance
Throughout the survey of varzea, palm swamp and terra firme habitats, thirteen lizrads were caught and a
further four remained unidentified. The greatest number of individuals were recorded in varzea (n =32)
followed by palm swamp (n = 29) and terra firme (n = 13). Similarly, varzea also contained the greatest
number of different species (n = 11), followed by palm swamp (n = 10) and then terra firme (n = 9). One
species, G. humeralis, dominated the sample.
4.4 Relative Abundance
To correct for differences in sampling effort that arose due to variations in observer ability to search
between the three macrohabitats, it was necessary to obtain an estimate of abundance corrected for effort
for each habitat. The relative abundances of species in each habitat were calculated using the Catch per
Unit Effort model (CPUE). This gave an estimate of the number of lizards per kilometre of habitat
surveyed and corrected abundance measures that were a result of more time being spent in the more
expansive high forest terra firme and varzea habitat.
F2, 15 = 4.119, P = 0.36
Fig. 3. Bar graph displaying the total relative abundance of lizards species from CPUE (n = 74) for
each macrohabitat surveyed (including unidentified individuals).
30
Palm swamp showed the greatest relative abundance of individuals per kilometre of survey, followed by
varzea which had a slightly lower abundance (1.07 less). Terra firme had the least lizards per kilometre
The greatest difference in relative abundance was between terra firme and palm swamp. This could be a
reflection of the greater dissimilarity between these habitats. However, the differences observed between
habitats were not significant.
4.5 Diversity
4.5.1 Species Richness
The species richness for each macrohabitat was analysed from total counts of the number of different
species. Varzea was shown to contain the greatest richness, followed by palm swamp and then terra
firme. However, the difference between each habitat was only one species.
Fig. 4. Bar graph displaying the species richness for the three macrohabitats surveyed
4.5.2 Shannon Index of Diversity
Values were calculated for the Shannon Index of diversity to allow the relationship between diversity and
habitat type to be explored. (Magurran, 1992). The results show that all three habitats had very similar
31
indices. The most diverse macrohabitat was varzea, which had a slightly higher index than terra firme
and palm swamp had the lowest value. The differences between habitats were not significant. Terra
firme had the greatest standard deviation. This was followed by palm swamp, with varzea having the
lowest standard deviation value. Although the values of the Shannon indices appear low, it is unlikely in
biological systems for the value to be greater than 4; therefore, they may show considerable diversity
(Krebs, 1999).
F2, 15 = 1.125, P = 0.351
Fig. 5. Bar graph displaying Shannon index of diversity values for each macrohabitat and standard
deviation.
4.5.3 Shannon Index of Evenness
This evenness approach has been scaled upon one of the heterogeneity measures relative to its maximum
value when each species in the sample is represented by the same number of individuals (Krebs, 1999).
As this measure of evenness is not independent of species richness, the results will be biased from the
Shannon diversity indices it is based upon. The evenness values range from 0 to 1.0, the latter represents
all species within the sample being of equal abundance.
32
F2, 15 = 1.174, P = 0.336
Fig. 6. Bar graph displaying the Shannon Evenness values for each habitat
The bar graph shows that the terra firme habitat has the greatest evenness measure, followed by varzea
and palm swamp. This would account for the greater diversity values for varzea and terra firme forests.
The evenness values for all three habitats are high, showing the composite of species to be in relatively
equal abundance. This is further supported by the results of ANOVA, which show there to be no
significant difference between habitats.
4.5.4 Berger-Parker Index of Dominance
Another measure of heterogeneity is dominance. The Berger-Parker dominance measure was used in
order to identify possible sources of evenness. As the results show, the habitat with the lowest
dominance is terra firme, which would explain the higher level of evenness shown by the Shannon
equitability equation. However, the next lowest dominance is shown for the palm swamp habitat, but this
did not have the next highest level of evenness. This was calculated using the Shannon evenness measure
to be varzea, but this has the highest level of dominance. This could be due to the greater abundance of
individual lizards found in the varzea habitat. There was no significant difference between habitats.
33
F2, 15 = 3.264, P = 0.067
Fig. 7. Bar graph displaying the dominance value for each habitat, calculated using the BergerParker dominance index.
4.6 Density
As this community ecology study was standardised on the basis of sampling effort, comparisons of
diversity are actually comparisons of species density. Due to this the abundance of each species will
identically reflect trends shown by density (Bodmer, pers comm). In order to avoid such repetition, only
species densities for each macrohabitat calculated using fixed-width is shown here.
34
Fig. 8. Graph displaying the density of each species per km² for each macrohabitat.
G. humeralis was the species found to have greatest density in all three habitats, even at exactly the same
density in the varzea and palm swamp habitat. The next largest density was for K. pelviceps, which was
the most abundant in palm swamps. Other species found in considerable densities in palm swamp were
P. guianensis, K. altamazonica and A. fuscoauratus (the latter two being equal). The third densest value
was in varzea for the M. nigropunctata population. Other species of notable density in varzea were
A. fuscoauratus followed in equal densities by G. conninnatus, A. n. scypheus, L. parietale and I. elegans.
Habitat
Detection
Function
Density
Estimate
% CV
df
95%
Confidence
Interval
Uniform/Hermite 2294.4
24.27
7.34
1310.0 Varzea
4018.6
Uniform/Cosine 2900.0
29.56
4
1298.3 Palm
6477.8
Swamp
18.31
6
396.95 Terra firme Uniform/Cosine 619.05
965.41
Table 3. DISTANCE density estimates for all lizards in each macrohabitat
35
The greatest density was estimated to be for the palm swamp habitat, followed by varzea. Terra firme
was shown to have a considerably lower density. However, as the % CV exceeded 20% for palm swamp
and varzea, the estimate made is not to a high degree of accuracy, which is shown by the large range of
variance of estimate values at the 95% confidence interval (5179.5 and 2708.6 for palm swamp and
varzea respectively). Due to this margin for error, the fixed-width density estimator was also applied to
the data for comparison.
F2, 15 = 4.2, P = .036
Fig 9. Fixed-width density estimates of the number of lizards per km² for each macrohabitat
The results of the fixed-width calculations supported the trend shown by DISTANCE. However, the
difference between palm swamp and varzea was reduced. Interestingly, the estimated density for terra
firme was very close to that given by the DISTANCE programme. This density had a %CV fewer than
20% and so was a more robust and accurate estimate. As this was further supported by the fixed-width
result, it is reasonable to assume that the fixed-width estimates are more accurate. However, the fixed
width estimates of density have large standard deviations, increasing the likelihood of error. The results
of ANOVA showed there to be a significant difference between habitats, the majority of which is likely
to originate from that observed between terra firme and palm swamp.
36
As there were enough observations of the most common species, it was also possible to perform fixedwidth analysis on the G. humeralis data to obtain estimated densities for this species in each habitat.
F2, 15 = 2.8, P = .095
Fig 10. Fixed-width density estimates of G. humeralis per km ² in each macrohabitat
One-way ANOVA was also performed to investigate trends. This showed that there was not a significant
difference between G. humeralis densities between habitats. Interestingly, the difference in G. humeralis
densities between habitats reflects the trends shown by the lizard population as a whole.
4.7 Aspects of ecology
Further data was also collected concerning the microhabitat occupancy of the individuals observed in
order to draw generalised conclusions relating to the aspects of ecology relating to each species. As only
details of microhabitat type were recorded and numbers of individuals representing each species were
low, it became apparent that extensive analysis of niche segregation and community structure would be
beyond the scope of this study, which was short-term in nature. However, there was sufficient data on
resource use to permit a preliminary analysis of niche partitioning within the lizard community sampled.
It is worth noting here that spatial separation of sympatric or synoptic lizard species can’t be adequately
37
described by microhabitat use alone, as additional dimensions at the local level, such as sun availability,
should also be taken into account (Vitt, 1998).
Qualitative observations concerning observations on the general ecology of the species sampled,
including microhabitat occupancy and activity times, that may have applications for more detailed
studies, are reported.
4.8 Microhabitat Occupancy
Microhabitat use is an important ecological factor to consider when investigation community structure.
For this reason, microhabitat types were predetermined based on previous studies, so that the lizard
occupancy within them could be recorded.
Microhabitat
Tree Crevice (TC)
Leaf Litter (LL)
Description
A hollow or split in a dead tree trunk
Fallen and decomposing foliage on the forest
floor
Fallen Log (L)
A dead tree trunk laying horizontally in a tree
fall site
Tree Buttress (TB)
The root of a tree, at the base of the trunk
Tree Trunk (TT)
At the centre of the tree, observations made
to a height of 1.5 metres
Table 4. Classification system of microhabitats used by lizards at Lago Preto
Fig. 11. Bar graph displaying the proportional percentage abundance of lizards occupying the
predetermined microhabitat types.
38
This graph shows that overall; the most proportionally utilized microhabitat was the tree trunk, with this
being shown to be the most preferred by the species sampled. The next most preferred microhabitat type
was leaf litter, which was only slightly lower that the tree trunk (1.35% less). The next proportionally
abundant microhabitat used was the tree buttress at 9.46% less that leaf litter. There is then a large drop
(14.85%) between this and the next microhabitat, which is a log in a tree fall site, which may reflect the
rarity of this micohabitat compared to others. The least proportionally occupied microhabitat was a tree
crevice, with only two individuals being found in one at the same time. The distinctions between
microhabitat uses can provide more detailed information on the community structure of the surveyed
lizard assemblage. For example, details of the method of thermoregulatory mechanisms used by the
species sampled can be estimated. Such assumptions require that the microhabitat use for each species be
investigated.
4.8.1 Species Specific Microhabitat Occupancy
In order to increase the accuracy in the identification of trends in microhabitat utilization, only the most
observed species (n>2) were included in analysis.
Fig. 12. Bar Graph displaying the microhabitat preferences of the most observed species (n = 68)
39
A clear pattern is shown for the preferred habitat use for the most abundant species, G. humeralis. This
species was most commonly observed on tree trunks and so would account for this being shown to be the
most preferred microhabitat. A. fuscoauratus was also recorded the most whilst occupying this habitat.
The next most favoured microhabitat was again shown to be occupied by G. humeralis on tree buttresses,
with no other species displaying such a preference for this ecological situation. K. pelviceps was shown
to prefer leaf litter and was found in the third most abundant number for a microhabitat. This location
was also preferred by A. ameiva, I. elegans and M. nigropunctata, which would explain why this
microhabitat is the second most utilized in total. K. altamazonica was shown to prefer log fall sites and
so this species is likely to be a heliotherm. Indeed, A. ameiva and M. nigropunctata were also found to
occupy log fall sites and so it could reasonably be assumed that these species are also likely to use this
method of thermoregulation. G. concinnatus, P. guianensis and A. fuscoauratus displayed a similar
preference towards leaf litter and tree buttresses, with G. concinnatus and P. guianensis also showing a
similar preference for tree trunks. This would suggest that these three species prefer shaded habitats and
so, along with G. humeralis, are unlikely not to be heliotherms. As K. pelviceps and I. elegans were
shown to prefer leaf litter, it is difficult to estimate the method of thermoregulation as this microhabitat
on its own could be in the shade or the sun
4.8.2 Niche Overlap
Only those species with more than two observations were included in the analysis of niche overlap as
those recorded fewer times than this would not provide enough data for reliable comparisons. It is further
noted that even with this stipulation, only G. humeralis was found to have a high enough abundance for
comparison. It is therefore emphasised that the niche overlap performed was very preliminary in nature
and is only used for generalisation to be made on resource utilisation (Pianka, 1986).
40
A. ameiva
K. altamazonica
K. pelviceps
I. elegans
M. nigropunctataa
A. fuscoauratus
A. fuscoauratus
P. guianensis
P. guianensis
G. concinnatus
X
G. concinnatus
G. humeralis
G. humeralis
0.81
0.81
0.80
0.00
0.00
0.17
0.00
0.00
X
1.00
0.87
0.19
0.05
0.68
0.50
0.32
X
0.87
0.19
0.05
0.68
0.50
0.32
X
0.02
0.01
0.31
0.06
0.04
X
0.96
0.37
0.39
0.95
X
0.10
0.11
0.83
X
0.97
0.62
X
0.64
A. ameiva
K. altamazonica
K. pelviceps
I. elegans
M. nigropunctata
X
Table 5. Microhabitat niche overlap for most abundant species (n>2).
The analysis showed there to be a great deal of niche overlap between G. humeralis, G. concinnatus and
P. guianensis. These species are all within the same family and so this was to be expected. However,
there is also a great deal of overlap with A. fuscoauratus, which must also inhabit a similar ecological
niche. Similarly, there was a great amount of overlap between A. ameiva and K. altamazonica in the
Teiidae family. Surprisingly, K. pelviceps was shown to have a greater degree of niche overlap with
Gekkonidae. Scincidae and Hoplocercidae species than those within the same family. Complete niche
overlap was found between G. concinnatus and P. guianensis.
4.9 Lizard Activity
4.9.1 Time
In order to investigate the activity of the lizard species sampled, the time each individual was caught was
recorded. Once these times for all specimens had being pooled, it became apparent that the peak time of
41
activity was between 10:00 and 13:00 hours, with the greatest number of lizards being caught between
11:00 and 12:00 hours. The majority of surveys were conducted between 10:00 and 14:00. A preference
for sunny conditions was also recorded as the majority of observations (56.8%) were made on days with
sun or sunny spells. A large proportion of lizards were also surveyed on in cloudy conditions (39.2%),
but very few were found during rain (4%).
Fig. 13. Line graph displaying lizard observations in relation to time of day (hours).
4.9.2 Temperature
The results showed that the main peak temperature for activity was between 25 - 26°C, with another
considerable peak at between 28 -29°C. There was also a third, but lesser peak in activity at between 3233°C. It is worth noting, however, that these temperatures were recorded at different times of day, with
the peaks roughly coinciding with peak activity times of day. Thus, these results are unlikely to reflect a
direct relationship between temperature preference and activity.
42
Fig. 14. Line graph displaying lizard observations in relation to temperature
4.9.3 Species Level Interactions
A small number of intra and interspecific species level interactions were observed during the course of
this study and are reported as follows:
4.9.4 Intraspecific Interactions
From the data collected it is aparent the on the vast majority of occasions G. humeralis was observed in
isolation. However, during the study two observations showed a male and a female to be in close
proximately to one another (<1m). Such observations have been made previously, with reports stating the
occurance of up to four individuals on one tree (Crossley, 2004).
Species level interactions were found to be more common in other species.

K. pelviceps – individuals of this species were observed as a pair on two occasions, with three
individuals recorded alone. In all instances, the members of this species were observed travelling
through the forest.
43

I. elegans – only two individuals were encountered during sampling and these were found
foraging together.

L. parietale – again, the two individuals recorded were found as a pair.

K. altamazonica – of the three individuals observed, two were recorded basking as a pair.

M. nigropunctata – this species displayed the greatest intraspecific interaction as four indiviuals
were recorded foraging at one site.
Such observations are likely to be consequence the same resource requirements and thus, utilization
amongst members of the same species.
4.9.5 Interspecific Interactions
On two occasions individuals from different species were observed together. On the first occasion four
M. nigropunctata and two L. parietale lizards were found foraging in the leaf-litter in the varzea forest.
This is likely to be a consequence of both species using active foraging methods to locate prey in an area
with locally abundant prey items. On the second occasion one N. nigropunctata lizard was observed
basking alongside two K. altamazonica lizards on a log in a tree fall site in the palm swamp. A likely
explanation for this is that both species are heliotherms and so are attracted to the same sunspots.
44
5.0 DISCUSSION
Although this study was preliminary in nature, 18 species were identified within the study site.
Furthermore, observations permitted general relationships between lizard species and their interactions
with the environment to be made.
5.1 Lizard Assemblage and Community Structure
In this study lizards were observed in all three macrohabitats. However, differences were recorded in the
abundance and organisation of species within each. The greatest total abundance of lizards was found in
varzea forest (n = 32), followed by palm swamp (n = 29), with terra firme forest having considerably
fewer individuals (n = 13). However, once abundance was corrected for sampling effort, palm swamp had
the greatest relative abundance, followed by varzea and terra firme. Three of the least encountered
species were found in terra firme (E. laticeps, C. ocellata and A. n. tandai), which were represented by
one individual. Two more species that were comprised of just one observation were found in varzea (A.
bombiceps and A. trachyderma), whilst a further two were found in palm swamp (A. buckleyi and A.
puncatatus). The low recording of these species could be a consequence of low population densities
within the study site or low detectability, which would result in underrepresentation within the data. This
is likely to be the case for more cryptic species, such as A. punctatus (Vitt, 2002).
The species accumulation curve highlighted the likelihood of further species being discovered in a more
long-term project. As the incline of the curve had periodic plateaus it can be assumed that common
species had been found. However, with the discovery of two new species over the last three days, it is
reasonable to predict that not all species were recorded and that with continued sampling, rare species
would be discovered. Upon the basis of this trend, it is unlikely that the lizard assemblage recorded
during surveying is a true reflection of the total assemblage found at Lago Preto. This has further
implications for the subsequent measures of species diversity and density, which may also be
underrepresented as a result.
45
The greatest species richness was observed in varzea, followed by palm swamp and terra firme
respectively. This demonstrates a preference amongst the lizard species sampled towards more humid
conditions. It has been estimated that 0.0073 reptile species are found per km² in Peru as a whole (World
Resource Institute, 2001). The total number of lizard species per km of transect during this study was 2,
which emphasises the importance of rainforest habitats to reptile communities.
5.2 Comparisons with other studies
5.2.1 Richness
In order to place the findings of this study in context and identify the differences between other areas of
the Amazon in terms of species richness and composition, the results were compared against a number of
relevant studies.
Region
Lago Preto
PacayaSamiria
Yavari
Valley
Roriama,
Brazil
Cocha
Cashu,
Peru
Manauas
Region,
Brazil
Authors
Carr
Crossley
Hutchinson
Vitt and
Zani
Rodriguez
and Cadle
Rodrigues
and
Zimmerman
Year of
study
2007
2004
2003
1998
1990
1990
Species
richness
reported
18
18
19
16
16
23
Table 6. Comparisons of lizard species richness studies within Amazonia (table adapted from
Crossley 2004).
In comparison with past studies previously conducted, the findings of the present study found the same
species richness as in Pacaya-Samiria, with one fewer species being recorded for the Yavari Valley. This
is likely to be due to the studies being conducted within a similar habitat and time frame. However, in
comparison to those studies conducted more extensively in lowland tropical forest within Amazonia (i.e.
Dixon and Soini documented 42 species within the Iquitos region of Peru in 1995), the species richness
46
found in this study and those to which it has been compared, would appear to be unrepresentative of the
true species richness for this habitat type. Indeed, Rodriguez and Cadle reported that only 50% of the
lizard species within the Cocha Cashu area were likely to have been recorded in their survey (Crossley,
2004).
5.2.2 Composition
In terms of habitat type surveyed, the species composition of the assemblages found by Hutchinson
(2002) and Crossley (2004) are the most comparable. Huchinson’s study was conducted in the same area
of lowland forest in the Yavari valley in the same habitats. Those studied by Crossley included levee,
backswamp and riverbank. Whilst these are are recognised as being different, levee is structurally similar
to terra firme (although with a differing floristic composition) and backswamp is comparable to varzea in
terms of seasonal inundation (Crossley, 2004). Thus, comparisons of the species compositions found in
these past studies are made.
47
Family
Species identified by
Hutchinson (2002)
Species identified by
Crossley (2004)
Species identified in this
study (2007)
GEKKONIDAE
G. humeralis
G. humeralis
G. humeralis
T. rapicauda
-
-
C. amazonicas
-
-
G. underwoodi
-
-
-
-
G. concinnatus
-
-
P. guianensis
IGUANIDAE
I. iguana
-
-
POLYCHROTIDAE
A. fuscoauratus
A. fuscoauratus
A. fuscoauratus
A. n. tandai
A. n. tandai
A. n. tandai
A. chyrysolepis
-
-
A. trachyderma
-
A. trachyderma
A. bombiceps
-
A. bombiceps
A. transversalis
-
-
-
A. n. scypheus
A. n. scypheus
-
-
A. punctatus
T. ochrocolias
-
-
-
T. plica
-
-
T. umbra
-
T. teguixin
T. teguixin
-
K. altamazonica
-
K. altamazonica
-
K. pelviceps
K. pelviceps
-
-
A. ameiva
A. atriventris
-
-
-
P. O’Shaugnessy
-
-
-
-
-
-
-
-
-
M. nigropunctata
M. nigropunctata
A. buckleyi
M. nigropunctata
-
M. bistrata
-
E. laticeps
-
E. laticeps
TROPIDURIDAE
TEIIDAE
GYMNOPHTALMIDAE
I. elegans
L. parietale
C. ocellata
SCINCIDAE
HOPLOCERCIDAE
Table 7. Comparison of lizard compositions identified in past studies in lowland forest habitats in
north-eastern Peru (Table adapted from Crossley, 2004)
48
This table shows that sampling during this study added eight species that had not been recorded on the
past two research projects in the area, but did not add any new species to the known overall inventory for
the Yavari valley. It also shows that there are considerable differences between the lizard species
compositions shown in past studies. Such differences are likely to be attributed to variations in the
habitats surveyed and the evolutionary histories of the lizards occurring within them, as the primary
determinants of lizard assemblage structure are species interactions, resource use patterns and historical
relationships among taxa comprising the assemblage (Mesquita, 2007).
The greatest similarity exists between this study and that previously carried out in the Yavari valley. This
is to be expected as the habitats surveyed were the same. Overall, the differences in composition found at
the different sites highlight the importance of heterogeneity with the lowland forests of Peru to lizard
species diversity.
5.3 Species Diversity
The macrohabitat classification used for the purpose of this study was broad and generalised, and it is
recognised that within each there is likely to be a mosaic of complex habitat types. Indeed, it has been
suggested that up to sixteen habitat types can be classified within the Peruvian flood planes (Kvist, 2001).
5.3.1 Terra firme
Terra firme forests are most distinguishable from the other habitats surveyed based upon elevation and
relative climatic stability compared to varzea and palm swamp which are seasonally inundated. With
undisturbed conditions, terra firme forests have increased productivity enabling a more diverse florist
community to persist as fewer plant species posses the necessary adaptations to tolerate inundation
(Kvist, 2001). A consequence of this will be the increased availability of resources. This would be of
considerable benefit to lizards as they exploit the environment in three dimensions and are most sensitive
to plant community structure (Hutchinson, 2003). Therefore, terra firme forests provide the most
49
heterogenous habitat, with more ecological niches. This in turn would allow for the provision of more
specialist species to coexist with more generalised ones, thus increasing overall diversity. However,
although the range of resources may be high, which would account for the high species diversity, there
may be increased competition for these resources. Therefore, inter and intaspecific competition could act
as a regulatory mechanism in this habitat, which could account for the lower abundance of lizards
recorded. This is further supported by the evenness data which showed the species composition to be at
almost equal abundance with species dominance also being the lowest of the habitats surveyed.
5.3.2 Varzea
Varzea forests were also shown to be very diverse. However, the assemblage of species in this habitat
was markedly different to that of terra firme. Most notable was the increased diversity of Anole species
such as G. humeralis, A. fuscoauratus and A. trachyderma. This is a result of the preference of these
species towards habitats containing water. Varzea forests have increased levels of incoming solar
radiation due to a broken canopy cover from seasonal inundation. This is of particular consequence to A.
fuscoauratus as this species is known to bask occasionally (Vitt, 2003). This would also explain the
increased observations of M. nigropunctata and A. ameiva, which are heliotherms (Sartorius, 1999). The
high diversity of lizard species observed in the varzea is also likely to be a consequence of the time of
year. As this study was conducted at the end of the wet season, water levels in the varzea had fallen
dramatically and so increasing habitat accessibility and niche availability (Bodmer, pers comm.). This
would have encouraged the migration of lizards from adjacent forest into these areas in order to exploit
these resources. Therefore, it is worth noting that the diversity observed in the varzea may be
considerably different at another time of year.
50
5.3.3 Palm Swamp
The lowest diversity recorded was found for this habitat. This is to be expected as palm swamps
represent the most disturbed habitat sampled, with a less diverse plant community, dominated by one
species. However, palm swamp was shown to have the greatest relative abundance of lizards. This may
be attributable to the fact that the majority of those species encountered were heliothermic, with
K. pelviceps being the most notable example. As palm swamps are almost continuously inundated with
water, the tree communities are less densely organised. There were also a greater number of tree fall sites
as the soil was waterlogged and unstable. This served to open up the canopy so that considerably more
solar radiation reached the understory of the forest compared to terra firme and varzea. Thus, the
availability of basking spots would be considerable in this habitat type, which would account for the
greater abundance of lizard species that require high temperatures and solar availability for
thermoregulation and activity.
A combination of various ecological differences within the lowland forests of Lago Preto was found to
have a considerable impact upon species diversity. Furthermore, lizard assemblages were found to be
fundamentally different in the three habitat types. The unusual proximately of these different habitats to
one another is, therefore, likely to have increased the lizard diversity of this region as it is able to support
a more complex community structure owing to its increased levels of heterogeneity. Due to this, the site
should be considered of great importance for the maintenance of a diverse range of lizard species
populations.
5.4 Density
The overall lizard density for Lago Preto was estimated using DISTANCE to be 5813.45/km². However,
the confidence levels for varzea and palm swamp were high and so this estimate is not likely to be
accurate. The density for the study site given by fixed-width was a much lower value of 1370.37/km².
51
As trends of density mirror those of abundance, further fixed-width and DISTANCE analysis was found
to support the trend shown by relative abundance calculations, with palm swamp containing the greatest
density of lizards/km², followed by varzea and terra firme. In order to investigate this relationship
further, ANOVA was performed on the density estimates for each habitat to test for significance. It was
found that there was a significant difference in lizard density between the three habitats. This indicates
palm swamps to provide a significantly greater availability of resources for the species that utilize that
habitat, so that a dense community of these species are able to exist. This would support the lower
diversity found here, as specialised species would prevail in greater density due to less interspecific
competition.
The density of the most common species, G. humeralis, was also calculated using fixed-width. This gave
a density estimate of 481.48/km² for Lago Preto. The distribution of this density was investigated and
ANOVA was performed on the different habitat densities. This found there to be no significant
difference between the three habitats, indicating G. humeralis to be an adaptable species that can occupy
any of the habitats. This would explain why it is one of the most widespread and abundant Amazonian
lizard species (Vitt, 2000).
5.5 Species Specific Microhabitat Occupancy
General observations of the microhabitat occupancy of each species enabled some determination of
ecological requirements. Those found in tree fall sites are likely to be heliotherms that bask in order to
raise body temperatures for activity. These species are also more likely to be larger and utilize active
foraging strategies. This is emphasised by the family Teiidae (which includes the Amazonian genera
Ameiva and Kentropyx) whose members are all fast moving, active foragers with streamlined bodies. At
most rainforest sites several species occur together where they generally use different habitat types
(Sartorius, 1999). Those species found on tree trunks and buttresses are likely to gain heat from contact
with their surroundings and utilize sit-and-wait foraging methods (Pough, 1999). Furthermore,
differences in either predation regimes or resource availability suggest that tress buttress microhabitats
52
posses distinct biotic properties from the surrounding leaf-litter, offering more ecological niches
(Whitfield, 2005).
Many of the findings on species microhabitat occupancy permit assumptions into their ecology to be
made (these are also supported by previous research):
The teiid lizard Ameiva ameiva is a medium sized, fast moving and active lizard that feeds on a variety of
arthropod and vertebrate prey. As an active foraging heliothermic lizard, it was mostly found on leaf litter
or basking in tree fall sites in open habitats. Due to high temperature requirements, this lizard is largely
restricted to habitats that provide basking opportunities for long periods of the day. If the sun is
temporarily unavailable, they take basking positions until the sun becomes available again: if sun remains
unavailable for long periods of time they seek shelter in burrows. Ameiva cope with suboptimal thermal
conditions by avoiding low temperature habitats and not being active at all when temperatures are low
(Sartorius, 1999).
G. humeralis lives primarily on tree trunks and is more common in forest adjacent to rivers. It is arboreal
and most frequently found in shade. Of the 19 species of Gonatodes, only G. humeralis occurs
throughout the entire Amazon Basin. The species is active on cloudy and sunny days and prefers shaded
microhabitats (Vitt, 2000). The known predators of this species include five snake species (B. arox,
R. lentiginosum, T. compressus, X. argenteus, and T. brevirostris [Vitt, 2000]). Sexual dimorphism is
apparent with males possessing bright head markings and a longer snout-vent length than females. This
would suggest territorial behaviour, which is likely to be a major factor dictating the spacing of males
(Vitt, 2000).
A. trachyderma occupy low vegetation and leaf litter microhabitats in well-shaded, damp rain forest.
They are likely to be active on cloudy as well as sunny days. This species is a member of the
fuscoauratus species group of anoles (Vitt, 2002). The specimen observed for this species was found on
leaf litter, which is where foraging occurs. Previous studies have also shown this species to occur on tree
trunks and on leaves (Vitt, 2002). It is also known that this species has a preference for damp habitats in
lowland areas (Vitt, 2002), which is supported by the findings of this study as it was found in varzea.
53
A. trachyderma is strictly diurnal with activity being restricted to late morning until early afternoon
(Vitt, 2002).
G.concinnatus exhibits similar ecological preferences to G. humeralis, occurring on tree trunks, tree
buttresses and in the leaf litter at the base of trees. This species has a more limited distribution and only
occurs throughout western Amazonia (Vitt, 2000).
M. nigropunctata is known to be heliothermic, which explains the findings of this study as individuals
were found on leaf litter in the sun and on logs in tree fall sites. This species is an active forager that
seeks out prey whilst moving through the habitat. Their association with open patches results from high
activity temperature requirements in an environment where sun availability is low (Vitt & Zani, 1997).
A. n. tandai were found to be largely restricted to leaf litter microhabitats in undisturbed terra firme
rainforest where light levels are low. This habitat preference is widely reported and this species occurs
throughout the Amazon basin (Vitt, 2003). Past studies have shown that elevated perches are also
utilized occasionally, but individuals of this subspecies climb much less frequently than A. n. scypheus
(Vitt, 2001). It has been postulated that the main factor restricting this species to shaded habitat is an
increased ability to escape from visually orientated predators such as teiids, as lizards are much more
visible against sunlit habitats.
A. fuscoauratus is a small forest anole that was mainly found living off the ground on tree trunks. They
were found in shade, although it is known that basking does occur (Vitt, 2003). Activity off the ground
as well as in shade offers some protection from heliothermic lizards.
Microhabitat occupancy was shown to result from a variety of ecological requirements, particularly
thermoregulation and species level interactions. For example, it has been shown for many smaller shade
lizards that average body temperatures are kept slight elevated above the temperatures of their
surrounding microhabitat. This provides them with a behavioural advantage over larger heliothermic
predators as when all else is equal, larger bodied predators would gain heat at a slower rate and thus lag
behind smaller lizards. Because the performance of diurnal lizards is linked to temperature, a slightly
warmer individual would be more able to escape than a cooler one (Vitt, 2003).
54
Small-scale geographic features such as local hydrology, soil types and resulting forest types appear to be
important in shaping lizard communities, as expressed by differences in species microhabitat occupancy
(Doan, 2002). This supports past studies that have shown that the composition of tropical lizard
assemblages is related to multiple environmental gradients (Gardner, 2007). Thus, the lizard assemblage
sampled was shown to be structured in terms of microhabitat distribution, being dominated by species
with strict and predictable habitat requirements.
5.6 Lizard Activity
The largest proportions of lizards were observed in the hours of late morning and late afternoon. This
coincides with the portion of the day that is the sunniest as the sun is directly overhead. This displays a
clear preference amongst the lizard species sampled towards warmer conditions. This was further
supported by the increase in lizard sightings on sunny versus overcast days. The most likely explanation
for this trend is due to ectotherms having specific thermal requirements for activity and survival.
5.7 Niche Overlap
Comparisons of microhabitat occupancy by the most abundant species were used in order to identify
levels of resource sharing and niche overlap between pairs of species. Not surprisingly, the greatest
amount of overlap was observed between species of the same family, reflecting similar adaptations for
resource exploitation as a result of close evolutionary history and relatedness. However, the overlap
matrix produced was incomplete due to the absence of some species, making it is difficult to surmise any
more of the results as it may not be a true representation of the microhabitat use of the lizard assemblage
of Lago Preto. Studies of this nature are also difficult as community niche structure can frequently
change both temporally and spatially (Pianka, 1986).
55
5.8 Conservation Implications of Study
Past studies into lizard conservation has stressed the need for further research into the relationships
between lizards and their environment in order to assess the ecological consequences of microhabitat use
so that the potential impacts of anthropogenic habitat changes can be identified an appropriate
conservation measures applied (Smith, 2001).
Due to the results obtained in this investigation, it is reasonable to assume that rainforest anoles and other
lizard species that live in leaf litter and prefer shaded microhabitats would be very severely impacted by
deforestation. The combination of sun avoidance and extended periods of activity would place these
species at risk when the forest is removed. Exposure of the forest floor to direct sunlight not only creates
a thermically extreme environment, but would also attract heliothermic teiid lizards, which compete with
and prey on smaller lizards (Vitt, 2002).
The lizard assemblage for each macrohabitat was found to differ in the composition of species in
significantly different densities. Therefore, the protection of forested areas, such as those found at Lago
Preto, should be a priority in order to maximise the diversity and survival prospects of a wide range of
lizard populations. The area also serves as an excellent location for the study of lizards due to habitat
variation and low levels of disturbance. This will aid conservation through the advancement of scientific
understanding into lizards and their interactions with the environment.
5.9 Limitations
Errors may have been introduced into the study due to lack of experience and knowledge on the part of
the author. Also, the method used to sample lizard species would not have detected those beneath the
leaf litter. One of the main assumptions for using density estimates from line transect data is that all
those individuals on the transect will be observed. However, secretive and elusive species may have
retreated under leaf-litter prior to detection, which is why quadrat sampling is also often used to sample
lizards (Elzinga, 2001). Further to this, it is known that not all species found in Lago Preto were included
56
in the sample, which undermines one of the assumptions for the Shannon Index, and is likely to lead to
error.
5.9.1 Further Research
As the findings of this study are designed as a guide to future research, it is recommended that any repeat
surveys into lizard assemblages at Lago Preto be conducted at between 10am and 1pm so as to sample at
the most active time of day. It is also recommended that a record of temperature ranges at these times be
kept, to enable further ecological knowledge into the temperature preferences of each species to be
identified.
Although this study documented patterns in microhabitat use, identifying the mechanisms responsible for
increased abundance within them was beyond the scope of this study. Tree buttresses, tree trunks and
leaf-litter were found to contain the greatest abundance of species, which supports past studies into these
microhabitats that suggests microhabitat heterogeneity can contribute to the maintenance of high
biodiversity in tropical regions (Whitfield, 2005).
Based upon the results of this study it is recommended that future sampling of tropical lizards continues
to include multiple localities for each region studied in order to examine microgeographic patterns of
relative abundance, species composition and regional diversity. Species accumulation curves should be
used in order to asses the proportion of the community sampled and estimate those species yet to be
recorded. As this was a rapid study, the diversity sampling was incomplete and so in future longer
periods of sampling during the peak activity times are advocated. This would then allow determination
of the dynamics of the patterns that arose in this investigation in order to conduct a more valid population
and community analysis. Furthermore, long-term monitoring of reptile populations is essential so that
any population declines are less equivocal (in terms of protracted declines versus natural fluctuations)
and thus, the causes less mysterious (Gibbons, 2000). This will enable more effective conservation and
management strategies to be implemented in order to preserve lizard communities.
57
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