Download Latitudinal gradients of biodiversity: pattern, process, scale and

Tropical ecology
Tropical biodiversity:
species richness,
diversity of life strategies
(January Weiner)
READINGS
J. Weiner,
"śycie i ewolucja
biosfery",
2nd ed/
PWN (2003)
Rozdz. 11
Part Two
Chapters 4 - 7
2009
1992
2010
1999
Simon & Schuster 1984, 1985
(appr. $10 at Amazon.com)
Princeton University Press
1997
2005
Journal papers
• Willig MR, Kaufman DM, Stevens RD (2003):
Latitudinal gradients of biodiversity:
pattern, process, scale and synthesis.
Annu. Rev. Ecol. Evol. Syst. 34: 273-309
• Turner JRG (2004): Explaining the global
biodiversity gradient: energy, area,
history and natural selection. Basic and
Applied Ecology 5: 435-445
• Mittelbach GG et al. (2007): Evolution and
the latitudinal diversity gradient:
speciation, extinction and biogeography.
Ecology Letters, 10: 315–331
Classic text to read:
Joseph H. Connel, 1978:
Diversity in Tropical Rain Forests
and Coral Reefs
Science, V. 199, 4335: 1302-1310
Problems:
• Clinal variation of biotic diversity on Earth
• Hypotheses explaining species richness in
the tropics
• Adaptive strategies of tropical biota
Problems:
• Clinal variation of biotic diversity on Earth
• Hypotheses explaining species richness in
the tropics
• Adaptive strategies of tropical biota
Alfred Russel Wallace (1823 – 1913)
Darwin, Wallace and others:
• Adaptations in temperate zone depend on
abiotic factors (climate);
• In the tropics – on the interactions
between organisms;
• Fischer (1960): [therefore in the tropics]
faster differentiation, more quiet time...
Global diversity of vascular plants
Kier et al. 2005
AVAILABILITY ADN QUALITY OF DATA
CONCERNING PLANT DIVERSITY
Kier et al. 2005
Number of species per 10000 km2
<100
100-200
200-400
400-1000
1000-1500
1600-2000
2000-3000
3000-4000
4000-6000
>5000
Latitudinal diversity gradient of fossil
Foraminifera (after Stehli et al. 1969)
LATITUDINAL GRADIENT OF FAMILY RICHNESS
Vascular plants
Reptiles
Amphibians
Mammals
Gaston et al.. 1995
LATITUDINAL GRADIENT OF SPECIES (a)
AND GENERIC (b) RICHNESS OF BIVALVES
(Flessa & Jablonski 1995)
Latitudinal gradient of extant species of corals
(Fraser & Currie 1996)
Taxonomic diversity of the tropics: Phyla
ONLY OCEANIC
TERRESTRIAL AND AQUATIC
•
•
•
•
•
•
•
Annelida
Arthropoda
Chordata
Mollusca
Nematoda
Platyhelminthes
Rotifera
ONLY TERRESTRIAL
• Onychophora
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Acanthocephala
Brachiopoda
Bryozoa
Cnidaria
Ctenophora
Echinodermata
Echiura
Ectoprocta
Gastrotricha
Kinoryncha
Loricifera
Nemertea
Phoronida
Pogonophora
Porifera
Priapulida
Sippuncula
BIRDS OF POLAND:
227 breeding specoes
(Tomiałojć & Stawarczyk 2003)
Birds of Venezuela:
1382 species
(Hilty, 2003)
CLOUD FOREST IN VENEZUELA (Rancho Grande)
Number of plant species in equatorial forests
(after Primack i Corlett, 2005)
Region
Neotropics
Number of
species
93500
Africa (land)
16000
Madagascar
4000
Africa total
20000
Malaysia
45000
Indochina etc.
10000
S. India
4000
Sri Lanka
1000
Australia
700
Pacific Islands
Total Asia and Pacific
Total
Area forested (mln ha)
400
180
1000
61700
250
175200
830
Number of tree species per ha
in rain forests of different continents
Primack i Corlett 2005
Other data
Gentry 1988: 580 trees of 283 species/ha
(Amazon, border of Venezuela and Brasil)
Region
West Indies, Mexico, Central and
South America
No. sp.
2233
North America, North of Mexico
USA
Europe
Africa (sub-saharan)
Asia (parts of this region)
585
400
429
2500
2080
New Guinea, New Britian and New
Ireland
Australia
New Zealand
Polynesia
TOTAL
275
1100
23
42
9667
Species
diversity of
ants in
various
regions
From Holldobler
and Wilson
(1991) and
Groombridge
(1992).
Number of coral genera in frelation to surface
temperature of the see (Fraser & Currie 1996)
DIFFICULTIES WITH
BIODIVERSITY MEASUREMENT
• How to measure species number with
regard to area? (ecoregions, latitudinal
zones, longitudinal belts, meridian, maps
with species density contours)
• The majority of tropical species are not
known yet!
Okapi (Okapia johnstoni)
Giraffidae
discovered in Congo in 1900
Pseudoryx nghetinhensis
1992
wstawić przyrost l. gat. ptaków (jak w podręczniku)
odkrywane ostatnio gatunki (liczby, przykłady, antylopa
z Wietnamu, ośmiornice głębinowe
Wollemia nobilis Anonymus 1999
(Araukariaceae);
discovered in Australia : 1994
T.L.Erwin
ERWIN’S ESTIMATE OF THE TOTAL SPECIES RICHNESS
19 trees Luehea seemani (Panama) fumigated
species of beetles collected .................................1200
Assumption 1: Average specifity of beetles = 13.5%
ergo: No. of specialised species .............................163
Assumption 2: 50000 tree species in rein forests, on each specialised
species of beetles
ergo: total No. of species specialised .......... 8150000
Assumption 3: Beetles make up 40% spesies of arthropods
ergo: No. of arthropod species ................... 20000000
Assumption 4: 2 × more species in tree canopies than on forest floor
ergo: total No. of species in rain forest ............ 30 mln
Problems:
• Clinal variation of biotic diversity on Earth
• Hypotheses explaining species richness in
the tropics
• Adaptive strategies of tropical biota
LATITUDINAL BIODIVERSITY GRADIENTS
ARE UNIVERSAL
Hillebrand, 2004:
meta-analysys of 600 data sets confirms gradient properties:
• at regional scale are stronger and steeper than at
local one;
• strength and steepness increases with body size of
the group studied;
• strength increases with trophic level;
• taxonomic effect (poikilo- vs. homeotherms);
• in freshwater environments weaker than in marine
and terrestrial ones;
• differs between continents and environments;
• hemispheres (S or N) do not matter.
HISTORY OF THE RESEARCH CONCERNING THE
GEOGRAPHY OF SPECIES DIFERSITY
•
•
•
•
•
•
Wallace 1878
Dobzhanski 1950
Hutchinson 1959
MacArthur (et all.) 1965, 1969, 1972
Pianka 1966
RECENT REVIEWS (WITH NEW HYPOTHESES)
– Rosenzweig 1992
– Brown 1988
– Currie 1991
– Rohde 1992
– Wright, Currie & Maurer 1993
– Turner, Lennon & Greenwood 1996
– Fraser & Currie 1996
– Rohde 1999
– Kaspari et al. 2000
– Willig et al. 2003
– Turner 2004
– Mittelbach et al. 2007
SPECIATION
LIMBO
EXTINCTION
evolutionary
time scale
history = randomness
SPECIES
POOL
dispersal limitation
environmental filtering
interactions
LOCAL
COMMUNITY
Continental spatial scale
„ASSEMBLY
RULES”
SUCCESSION
ecological
time scale
MAJOR APPROACHES AND
CONTROVERSIES
• Neutral theories (MacArthur & Wilson, Hubbell)
• Niche-based theories (competition,
specialization)
• Equilibrium vs. Non-equilibrum communities
GROUPS OF
HYPOTHESES
ECOLOGICAL FACTORS
(carrying capacity)
VARIOUS RATE OF
SPECIES
DIFFERENTIATION
(speciation and extinction)
MORE TIME FOR
DIFFERENTIATION IN
THE TROPICS
Mittelbach et al. 2007
EVOLUTIONARY HYPOTHESES CONC.
BIODIVERSITY GRADIENT
Differentiation rate similar, but more time in the tropics:
1. Tropical environments are older, many extant clades originated there
2. Clade dispersal from the tropics is limited and only recent
Differentiation rate in the tropics is higher...
...because speciation is faster
1. Genetic drift in small populations
2. Climatic changes accelerate speciation
3. Higher likeness of para- and sympatric speciation
4. Larger area of the tropics – more chances for isolation
5. Narrower physiological tolerance of tropical biota
6. Higher temperature accelerates evolution
7. Stronger interactions – narrower specialisation and faster speciation
...because extinction rate is lower
1. Stable climate
2. Larger area – more numerous populations – lower risk of extinction
Most important hypotheses explaining
geographical biodiversity gradient
•
•
•
•
•
•
•
•
Geographical area
History
Productivity
Environmental energy
Rapoport’s rule
The rate of evolution
Geometric limitation
Continuous disturbance
Geographical area
(Terborgh; Rosenzweig)
• The geometry of the globe implies that the
area of equatorial zone is the largest;
• This area is thermally most uniform and
stable;
• The number of species increases with
area;
• Large area has more diverse habitats.
Rosenzweig 1995
SPECIES RICHNESS (S) IN RELATION
TO THE SURFACE AREA (A)
S = cAz
log S = log c + z log A
NUMBER OF TREE SPECIES
IN RELATION TO ISLAND AREA (AUSTRALIA)
LARGER AREAS OF RAIN FORESTS MAINTAINT MORE
PRIMATE SPECIES
Primack i Corlett 2005)
NUMBER OF PRIMATE SPECIES CORRELATES ALSO
WITH RAINFALL (EXCEPT FOR ASIA)
Primack i Corlett 2005
THE EFFECT OF LATITUDE UPON
„species-area” RELATION
Lyons & Willig 2002
• data: marsupials and bats of Americas
• relation: S = C Az
where S = species number, A = area
C, z = parameters
log S
1
2
3
C1 > C2
z2 > z3
log A
pasami
kwadratami
1. A clear latitudinal gradient of z (Lyons & Willig 2002)
1. A clear latitudinal gradient of C (Lyons & Willig 2002)
Conclusions:
• Biotic diversity in the tropics is higher but
less dependent on area;
• This effect should be taken into account at
any comparisons;
log S
tropics
other
log A
HISTORY
(Rosenzweig)
• Tropical area was not subjected to deep
climatic changes during a long time;
• Climatic changes caused fragmentation of
typical tropical environments (rain forests)
and enhanced speciation;
• In the tropics the number of species
increases with time (many old taxons).
The extent of recent glaciation, 18000 y. ago
CHANGES OF THE RAIN FOREST EXTENT
IN SOUTH AMERICA
DURING PEISTOCENE
RECENTLY
HISTORY: thermal maximum in eocene,
maximum extent of tropical environments
Mittelbach et al. 2007
Average age of avian taxa
in relation to latitude
log (av. age of taxon)
Stebbins: „cradle or museum?”
latitude
Weiner 2003
from Gaston & Blackburne 1996
Productivity
• Higher primary production (Pp) enables to
maintain more species populations (S)
(Hutchinson 1959, „Santa Rozalia”)
• S correlates (in large spatial scale) with Pp
and AET
• No correlation of Pp i S in small scale
• No explanation of the mechanism
Daniel Simberloff: „Santa Rozalia was a goat”
Environmental energy
(Turner)
• Thermal conditions in the tropics are close
to thermoneutrum and stable
• Individual energy budget is less loaded
enabling more expensive specialisations
• Temperature and PET correlate with S
Rapoport’s rule
•
•
•
•
Species ranges close to equator are smaller
Species ranges at low elevations are smaller
„Mountains in the tropics are higher” (Janzen)
Mechanism: seasonal climate suports broader
adaptations, enabling greater geographical
ranges
• Stronger endemism in tropical climate
• Critics: contradictory examples, no evidence for
the mechanism postulated
Sea molluscs
Trees
Fishes
Reptiles and amphibians
Rapoport’s rule
Ranges of the taxons
with the centres distant
from equator are larger.
Mammals
from Stevens 1989; Weiner 2003
Trees in Costarica
Rapoport’s rule
on elevation gradient
Mammals in Colorado
Vertical ranges of species are
larger if their centre is located
at higher elevation a.s.l.;
With increasing elevation the
diversity decreases.
Birds in Venezuela
Stevens 1992; Weiner 2003
The rate of evolution
• The rate of speciation is supposed to
increase with temperature:
– shorter generation time,
– higher mutation rate,
– stronger selection pressure
(Rohde 1992)
• Critics: The evidence not convincing
Geometric limitation
• Ranges randomly distributed over a large
but limited area make up a gradient of
local diversities because of purely
„mechanical” reasons.
Intermediate Disturbance Hypothesis
(Connel)
•
•
•
•
Rain forest: non-equilibrium;
„Gaps” continuously colonized (succesion)
Coral reef: non-equilibrium
Intermedite disturbances (hurricanes) and
continuous succesion
Classic text to read:
Joseph H. Connel, 1978:
Diversity in Tropical Rain Forests
and Coral Reefs
Science, V. 199, 4335: 1302-1310
FUNCTIONAL SIGNIFICANCE OF
BIODIVERSITY
IN THE TROPICS
•
•
•
•
Global carbon balance
Global water circulation
Local trophic cascade
Local biogeochemical balance
Tree biodiveersity efect upon
biomass carbon accumulation in
equatorial forest (Panama)
Bunker et al. 2005; SCIENCE 310:1029-1031
• Mid column: average and c.v.
• Number of tree species: 1 ... 126
• Carbon accumulation: Mg/ha
• Simulated sequence of spiecies loss:
• random
• large-statured first
• low density
‘’
• high density
‘’
• slow-growing
‘’
• drought sensitive
‘’
• endemic
‘’
• widespread ‘’
Species richness
The effuct of mammals and birds upon
herbivores, soil fauna and phosphorus
balance (Dunham, 2008)
[exclusion experiment]
• Study
area: equatorial rain forest
(Ivory Coast, W. Africa)
• Mammals and birds excluded from study plots;
• Studied were:
• plant consumption
• faunal composotion
• decomposition rate
• phosphorus balance
Microfaunal sbundance drops, macrofaunal (earthworms)
(Dunham, 2008)
inceases on the plots void of mammale and birds
Percent loss of leaf biomass and morality of seedlings in he plots
without mammals and birds
(Dunham, 2008)
Changes in the amount of
the available inorganic
phosphorus (P) and
nitrogen (N) in the soil
depending on the presence
of mammals and birds,
after 8 month of exclusion.
(Dunham, 2008)
Trophic cascade in the rain forest
positive effects
negative efects
(Dunham, 2008)