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CHAPTER 5
Factors That Limit Distribution & Abundance:
BIOTIC COMPONENTS
1
Learning Outcome
• Define biotic factors
• Acquire
knowledge
on
the
interrelationship between organism
• Describe the criteria proposed for predator
to restrict its prey
• Explain resource partitioning
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What is biotic factors?
• Biotic factors are factors produced by
living organisms that affect the ability of
other living organisms to survive in an
environment.
• Example: disease, parasitism, predation,
allelopathy and competition.
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PREDATION
1)PREDATOR RESTRICT PREY
• Works by Kitching & Ebling (1967) – studies in Ireland
on the mussel (Mytilus edulis).
• Exposed rocky shores = small mussels
• Sheltered area = larger mussels
• Kitching transferred rock with attached mussels from
one area to another
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Results
• Small mussels transplanted to/within the are –
survived only on open coasts while in other
areas they disappeared-because of the influence
of predators.
• Large mussels only survived in their natural
habitat but disappeared in transplanted areas
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How predator restrict its prey?
Area
Mussel Predator type
type
Lough
Ine,
exposed
area
(Site A)
Small Small musselmussel Carcinus
maenas (crab)
Portunus
puber (crab)
Nucella
lapillus (snail)
Large Large musselmussel Marthasterias
glacialis
(Starfish)
Shelter,
shallow
(Site B)
Predator
Predator
distribution/habitat Abiotic
Tolerance
Exposed areaStrong
Marthasterias
wave,
glacialis (Starfish) High
salinity-
Shallow waterCarcinus maenas
(crab)
Portunus puber
(crab)
Nucella lapillus
(snail)
Weak
wave,
Low
salinity-
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Example 2
• Kitching & Ebling (1961) – relationship
between sea urchin, Paracentrotus lividus
and algae.
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• The predator (sea urchin) lives in the shallow
part of the sublittoral zone (under beach) – just
below the tide level.
• In areas where there is abundant sea urchins the
area is relatively free of algae
• In areas where there is little sea urchin the algae
are abundant
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• They did experiments of clearing 1957 sea
urchins (290 m2)
- Algae immediately began to colonize and grow
in the sea urchin cleared area.
• In adjacent areas where there were sea urchin,
algae cover was not visible.
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• The authors then transferred the sea
urchin into areas that had high growth of
algae – the areas began to be clear of
algae.
• There was thus a reverse relationship
between sea urchin and algae cover
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Example 3
• Small kangaroos a.k.a rock
wallabies (prey) have been
driven to extinction by:
1. Predation of introduced sp.
i.e, the red fox (predator).
2. Competition for food with
rabbits.
• Habitat: Rocky hills
• Declining and numerous
colonies have become extinct
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• Kinnear et al. (1998) tested the hypothesis that
red fox predation was sufficient to limit the
population and size distribution of rock
wallabies
Test: They poisoned red foxes around experimental
colonies at rocky hills
Result:
– 1. it showed that the populations of wallabies
recovered (in absence of red fox)
– 2. Without foxes, wallabies ranged further from rocky
sites to feed – better species distribution.
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Example 4 – Rat Kangaroo
• Previously found extensively over Australia.
• Presently only found at 3 islands off the coast of
Western Australia where there are no red foxes.
• 1992 - Reintroduced to mainland, isolated by electric
fence to prevent fox immigration and poisons to
eliminate foxes.
• Reintroduction was a success.
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• 4 criteria for predator to restrict its prey:
1) Suspected predator is able to kill prey in lab
(experiment) and field (nature)
2) Suspected predator is responsible for
destruction of prey in transplantation
experiments
3) prey survives after transplanted if they are
protected from predators
4) prey distribution and suspected predator are
inversely related
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PREDATION
2) PREY RESTRICT PREDATOR
- plant (food) vs herbivore (insect)
- herbivore vs carnivore
- Such predators are called specialists or monophagous
predators
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Example 1
• Chrysolina quadrigemina introduced in US to control the Kalmath weed,
Hypericum perforatum.
• Adults and larvae of beetle will only feed on the Hypericum or they will
die if feed on other plants
• Adult beetles display an obligatory feeding response to the chemical
hypericin (Schoeps et al., 1996)
• The beetles refuse to stand on other leaves that have different surface
feature to that of Hypericum
• The life history, feeding habits, behavior and distribution of the beetle
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(predator) is restricted by its single plant (prey)
• Insects that feed on only one host plant (monophagous
insects) could be limited in their distribution by the
host plant.
• To date there is no indication that the ranges of food
plants and their monophagous insect herbivore
coincide (Quinn et al., 1998)
• Example of the butterfly in Britain – no association
between food plant distribution and butterfly
distribution
• Even for widespread species of butterflies the host
plant occurs in many areas in which the butterfly does
not – something else must limit butterfly distribution
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Disease & Parasitism
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Disease & Parasitism
• Parasites and pathogens can limit and restrict
distributions
• Example - native bird fauna of Hawaii
• Native birds of Hawaii have become extinct due to
introduced disease – (Warner, 1968):
1. avian pox (initially) and 2. avian malaria (later) were
instrumental in causing extinction in the Hawaiian
Islands
Bill tumors results of avian pox
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• The idea that disease might be involved
arose from observations that:
• native birds occupy upperland in Hawaii
and are relatively common only at
elevation above 1500 m
• while introduced birds occupy lowland
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Female Culex quinquefasciatus
• The malarial vector, Culex quinquefasciatus is
conversely most common in lowland areas
Male Culex quinquefasciatus
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• The initial extinction of native birds was initially
influenced by habitat clearing for agriculture
and introduction of rats, cats, and pigs and avian
pox (before 1900) and subsequent extinction by
introduction of avian malaria.
• Birds that went extinct at this time (early 1900)
lived in the mid-elevation forests where malaria
parasites are most common.
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Allelopathy
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Allelopathy
• Definition: The inhibition of growth and development
in one species of plants by chemicals produced from
another species. Plant vs plant.
• Impact :
- Decrease in yields - did not increase even after adding of
fertilizers.
- E.g Grass and apple trees
- Experiment: Apple trees supplied with 3 different sources of water:
a.
a primary source: tap water
b. a secondary source: water passing through grass and soil
c.
water that passed through soil only
•
The growth of apple seedling was inhibited by something
produced by the grass and carried by water.
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25
alfalfa plants
Example 2
• Effect of black walnut trees (Juglans nigra)
on grass and alfalfa plants.
– Roots secrete a toxin to which tomatoes
and alfalfa could not grow but others
like corn and beet showed no ill effect
– The chemical is juglone, 5 –hydroxy-αnapthaquinone) from roots and hulls of
black wallnut.
– Some close relatives of black walnut
(Juglans regia, J. bindsii, J. califronica) do
not produce toxins
– Inhibitor of seed germination
– Tomatoes and alfalfa wilt when grown
near black walnuts, and their seedlings
die if their roots contact walnut roots.
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Juglans nigra
• Presence of other organisms may limit
distribution
of
some
species
through
competition.
• Allelopathy is one specific type of competition
for living space.
• Allelopathy vs competition.
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Competition
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• Competition happen when 2 or more species uses the
same resources and live in the same places.
• Birds, rodents and ants may compete for seeds in desert
environments.
• Herbs and shrubs compete for water in dry areas.
• Competition among animals is usually for food, mate,
habitat.
• Plants compete for sunlight, nutrients, water, even
pollinators
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• How do we know if competition is restricting
geographic distribution?
– when sp A is absent, sp. B lives in a wider
range of habitats.
• In some extreme cases a habitat will contain only
sp A or B and never both.
• The difficulty is that competition is only one of
the several hypotheses that can account for the
observed distributions.
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Example 1, Checkerbord
distribution
• Checkerboard distribution of closely related sp –
ecologically related sp. in an island archipelago –
interdigitating distributions (become interlocked)– each
island supporting only 1 sp.
• The fruit pigeon in the Bismarck Archipelago – Ptilinopus
rivoli and P. solomonensis.
• The successful colonist is either first-come-first basis or
on the basis of slight competitive advantage.
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Resource partitioning
•
i.
When 2 sp compete for resources:
one will always be a better competitor and the other
will lose out and disappear.
ii.
evolves together, adapt to
escape/ minimize competition
•
2 evolutionary strategies a weaker competitor species
can develop:
i.
ii.
Resource
partitioning
avoid the superior competitor by selecting different part of
the habitat (E. umbrinus –arboreal)
avoid the superior competitor by selecting a different diet
(diet shift)
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Example 2
• Competition among cliff chipmunks – Eutamias dorsalis,
E. umbrinus
• E. dorsalis (lower elevation) excludes E. umbrinus (higher
elevation)
• The 2 sp interact at about 2100 m where the levels of
competition are highest.
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Eutamias dorsalis
Eutamias umbrinus
Habitat structure
• E. dorsalis
- lower elevation prefers lives on the ground, less trees
- aggressive to its own and other chipmunk sp.
• E. umbrinus
- higher elevation
- lots of trees
- spends its time on trees
- moves from tree to tree along interlocking branches
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• At lower elevation where trees are sparse,
E. dorsalis exludes E. umbrinus by its superior
aggression.
• Aggression become ineffective when tress are
close (dense) spaced because the arboreal
umbrinus escapes through the trees.
• Competitive success of E.
determined by habitat structure.
umbrinus
is
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Example 3
• Crossbill finches – extract seeds from cones – 3 sp live in
Eurasia and are adapted for eating different foods
i) Small crossbill – (Loxia leucoptera) – small bill feeds on larch seeds –
cones are soft
ii) Medium sized crossbill (L. curvitrostra) – eats spruce seeds
iii) Large crossbill (L. pytyopsittacus) eats the hard cones of Scotch
pines.
• This minimizes dietary overlap in regions where all three
possible competitors live.
Loxia leucoptera
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Loxia pytyopsittacus