Diversity: Patterns and Processes

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Diversity Patterns and Processes
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude - regardless of the taxon (animal,
plant) - regardless of habitat (aquatic,
terrestrial) - regardless of metabolism
("cold/warm") diversity is higher in the
tropics
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Amphibians
Lizards
Snakes
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Moss
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Bivalves
Ants
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Lizards
Birds
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Marine Gastropods
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude diversity is higher in the
tropics ---------------------
WHY??--------------------------------
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude A. "Bottom-Up" - more Energy, more
sp.
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude A. "Bottom-Up" - more Energy, more
sp. - quantitative effects
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A. "Bottom-Up" - more Energy, more sp. -
quantitative effects
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude A. "Bottom-Up" - more Energy, more
sp. B. "Top-Down" - more predators, less
competitive exclusion at each trophic level.
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude A. "Bottom-Up" - more Energy, more
sp. B. "Top-Down" - more predators, less
competitive exclusion. C. "Faster Evolution" and
speciation
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C. "Faster Evolution" and speciation Rohde, K.
1992. Latitudinal Gradients in Species Diversity
The Search for the Primary Cause. Oikos 65
514-527. Mutation rates are increased by
radiation and heat - so mutation rates should be
higher in the tropics...
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C. "Faster Evolution" and speciation Rohde, K.
1992. Latitudinal Gradients in Species Diversity
The Search for the Primary Cause. Oikos 65
514-527. Mutation rates are increased by
radiation and heat - so mutation rates should be
higher in the tropics...Confirmed
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C. "Faster Evolution" and speciation Rohde, K.
1992. Latitudinal Gradients in Species Diversity
The Search for the Primary Cause. Oikos 65
514-527. Mutation rates are increased by
radiation and heat - so mutation rates should be
higher in the tropics...Confirmed developmental
rate is faster at higher temps, so generation
time should be shorter....
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C. "Faster Evolution" and speciation Rohde, K.
1992. Latitudinal Gradients in Species Diversity
The Search for the Primary Cause. Oikos 65
514-527. Mutation rates are increased by
radiation and heat - so mutation rates should be
higher in the tropics...Confirmed developmental
rate is faster at higher temps, so generation
time should be shorter.... Confirmed
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C. "Faster Evolution" and speciation Rohde, K.
1992. Latitudinal Gradients in Species Diversity
The Search for the Primary Cause. Oikos 65
514-527. Mutation rates are increased by
radiation and heat - so mutation rates should be
higher in the tropics...Confirmed developmental
rate is faster at higher temps, so generation
time should be shorter.... Confirmed So, with
greater variation and more rapid generational
turnover, responses to selection (and other
evolutionary agents) should be more rapid in the
tropics... divergence and speciation should be
more rapid in the tropics.
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C. "Faster Evolution" and speciation Weir, JT,
and D Schluter. 2007. The Latitudinal Gradient in
Recent Speciation and Extinction Rates of Birds
and Mammals. Science 315 1574 - 1576. Compared
pairs of sister bird and mammal taxa in the
tropics and temperate zone. Compared DNA, and
estimated time since divergence for these pairs.
Temperate pairs of birds and mammals had MORE
RECENT divergence times than pairs of tropical
species.
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BIRDS
MAMMALS

Time since divergence of species pairs.
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BIRDS
MAMMALS

Time since divergence of species pairs.
Age of intraspecific haplotype variation
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BIRDS
MAMMALS

Time since divergence of species pairs.
Age of intraspecific haplotype variation.
Age of deepest phylogroup splits
all relationships are strongly significant (p lt
0.001)....
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude D. Habitat Variation....alpha-divers
ity - More plant species allows for more
specialization of animals (notably
insects) qualitative effects
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude D. Habitat Variation....gamma
diversity - From rainforests up the slopes of
tropical mountains, all latitudinal habitats are
present... from rainforest to deciduous forest to
grassland to tundra to glaciers. So all the
animals adapted to these habitats are present at
that latitude, too.
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Andes, Equator
Rockies, 60 N
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude D. Habitat Variation....gamma
diversity - Area Effect - the tropics have more
area than ecosystems at higher latitudes.
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- Area Effect - the tropics have more area than
ecosystems at higher latitudes.
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude E. Evolutionary/Geological Time
- undisturbed by ice ages
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end of last glacial - 10,000 years ago
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(No Transcript)
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So temperate regions have not had enough time to
exploit all the available niches opened by
glacial retreat.
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude E. Evolutionary/Geological Time
- undisturbed by ice ages - BUT.. still a
global impact on climate...
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- BUT.. still a global impact on climate...
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude F. Diversity is Maximized at
Intermediate Disturbance (Connell, 1978).
Diversity
Disturbance
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F. Diversity is Maximized at Intermediate
Disturbance - "Disturbance" is removal of
biomass... - frequency - intensity - areal
extent
Diversity
Disturbance
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F. Diversity is Maximized at Intermediate
Disturbance - Why is diversity maximized in the
middle?
Competitive exclusion in very stable habitats
Diversity
Disturbance
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F. Diversity is Maximized at Intermediate
Disturbance - Why is diversity maximized in the
middle?
No competitive exclusion because disturbance
keeps populations low, but doesn't cause
extinctions.... lots of colonists coexist...
Diversity
Disturbance
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F. Diversity is Maximized at Intermediate
Disturbance - Why is diversity maximized in the
middle?
Environment is too harsh only species that can
survive the disturbance persist...
Diversity
Disturbance
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F. Diversity is Maximized at Intermediate
Disturbance - Why is diversity maximized in the
middle?
Environment is too harsh only species that can
survive the disturbance persist...
any example?
Diversity
Disturbance
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F. Diversity is Maximized at Intermediate
Disturbance - Why is diversity maximized in the
middle?
Tropics storms cause local treefalls and reef
damage
Diversity
Disturbance
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude G. Climatic Stability - With no
winter, the tropics foster divergence all year
round. - Greater climatic variation selects for
generalists with broad niches, not specialists
(thus decreasing diversity).
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude G. Climatic Stability - With no
winter, the tropics foster divergence all year
round. - Greater climatic variation selects for
generalists with broad niches, not specialists
(thus decreasing diversity). - Of course, there
IS seasonality in the tropics (rainy and dry
seasons).
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude H. Spatial Heterogeneity -
Forests provide greater spatial complexity than a
grassland, and allow for greater niche
partitioning.
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude I. Smaller latitudinal ranges in
tropical species - more niche partitioning along
a climate axis - "Rapoport's rule"
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Marine latitudinal diversity gradients Tests of
causal hypotheses Kaustuv Roy, David Jablonski,
James W. Valentine, and Gary Rosenberg. 1998.
PNAS.
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Marine latitudinal diversity gradients Tests of
causal hypotheses Kaustuv Roy, David Jablonski,
James W. Valentine, and Gary Rosenberg. 1998.
PNAS.
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Marine latitudinal diversity gradients Tests of
causal hypotheses Kaustuv Roy, David Jablonski,
James W. Valentine, and Gary Rosenberg. 1998.
PNAS.
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Marine latitudinal diversity gradients Tests of
causal hypotheses Kaustuv Roy, David Jablonski,
James W. Valentine, and Gary Rosenberg. 1998.
PNAS.
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Marine latitudinal diversity gradients Tests of
causal hypotheses Kaustuv Roy, David Jablonski,
James W. Valentine, and Gary Rosenberg. 1998.
PNAS.
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude Summary - Direct Climatic
Causes - Stability in short and long terms -
Partitioning of latitude (Rapoport) -
Evolutionary Rate - Habitat Variation
(topography, area)
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude Summary - Direct Climatic Causes
- Trophic Causes (not primary) - productivity
(qualititative/quantitative) -
competition/niche specialization - predation
- structural complexity
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Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude Summary - Are the tropics a
cradle (birthing species?) - Or a museum (where
species persist longer because of lower
extinction rates?)