Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession V. Biodiversity: Patterns and Processes A.The Species-Area Relationship B.The Latitudinal Trend in Diversity 1. The patterns

AmphibiansLizardsSnakes

Moss

BivalvesAnts

LizardsBirds

Marine Gastropods

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession V. Biodiversity: Patterns and Processes A.The Species-Area Relationship B.The Latitudinal Trend in Diversity 1.The patterns 2.Potential Causes a. energy-diversity hypothesis

"Bottom-Up" - more Energy, more sp. - quantitative effects

"Bottom-Up" - more Energy, more sp. - quantitative effects

a. ENERGY – DIVERSITY HYPOTHESIS

PET = amount of water that a plant would lose to the environment; increases with radiation and decreases with increasing humidity.

The tropics not only have MORE productivity, they have more KINDS of productivity – more types of plants, allowing greater specialization by more types of animals. We tend to see this diversity evolving by sister species using slightly different resources. This should make sense; sister species are probably very similar, and so they would have to partition some important resources in order to coexist without competitive exclusion. "Bottom-Up" - more Energy, more sp. - qualitative effects: energy increasing types of diversity

This diversity evolves by sister species using slightly different resources. This should make sense; sister species are probably very similar, and so they would have to partition some important resources in order to coexist without competitive exclusion.

"Bottom-Up" - more Energy, more sp. "Top-Down" – more energy, more predators, less, competitive exclusion at each trophic level.

"Bottom-Up" - more Energy, more sp. "Top-Down" - more predators, less competitive exclusion. "Faster Evolution" and speciation

Rohde, K Latitudinal Gradients in Species Diversity: The Search for the Primary Cause. Oikos 65: 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.

"Faster Evolution" and speciation Weir, JT, and D Schluter The Latitudinal Gradient in Recent Speciation and Extinction Rates of Birds and Mammals. Science 315: 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.

BIRDSMAMMALS Time since divergence of species pairs. Age of intraspecific haplotype variation. Age of deepest phylogroup splits all relationships are strongly significant (p < 0.001)....

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession V. Biodiversity: Patterns and Processes A.The Species-Area Relationship B.The Latitudinal Trend in Diversity 1.The patterns 2.Potential Causes a. energy-diversity hypothesis b. habitat heterogeneity – diversity hypothesis

Andes, Equator Rockies, 60 N

- Area Effect - the tropics have more area than ecosystems at higher latitudes.

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession V. Biodiversity: Patterns and Processes A.The Species-Area Relationship B.The Latitudinal Trend in Diversity 1.The patterns 2.Potential Causes a. energy-diversity hypothesis b. habitat heterogeneity – diversity hypothesis c. Intermediate disturbance hypothesis

Diversity is Maximized at Intermediate Disturbance (Connell, 1978). Diversity Disturbance

- "Disturbance" is removal of biomass... - frequency - intensity - areal extent Diversity Disturbance

- Why is diversity maximized in the middle? Diversity Disturbance Competitive exclusion in very stable habitats

- Why is diversity maximized in the middle? Diversity Disturbance No competitive exclusion because disturbance keeps populations low, but doesn't cause extinctions.... lots of colonists coexist...

- Why is diversity maximized in the middle? Diversity Disturbance Environment is too harsh; only species that can survive the disturbance persist...

V. Biodiversity: Patterns and Processes A.The Species-Area Relationship B.The Latitudinal Trend in Diversity 1.The patterns 2.Potential Causes a. energy-diversity hypothesis b. habitat heterogeneity – diversity hypothesis c. Intermediate disturbance hypothesis d. Environmental stability hypothesis

end of last glacial - 10,000 years ago

So temperate regions have not had enough time to exploit all the available niches opened by glacial retreat.

- BUT.. still a global impact on climate...

V. Biodiversity: Patterns and Processes A.The Species-Area Relationship B.The Latitudinal Trend in Diversity 1.The patterns 2.Potential Causes a. energy-diversity hypothesis b. habitat heterogeneity – diversity hypothesis c. Intermediate disturbance hypothesis d. Environmental stability hypothesis 3. Cradle or Museum?

Cradle or museum? David Jablonski, Kaustuv Roy, James W. Valentine Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314: Diversity is a function of speciation rate, extinction rate, and immigration rate (range expansion into that region). HIGHER SPECIATION RATELOWER EXTINCTION RATE

Cradle or museum? David Jablonski, Kaustuv Roy, James W. Valentine Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314: Diversity is a function of speciation rate, extinction rate, and immigration rate (range expansion into that region). "Out of the tropics" model

Cradle or museum? David Jablonski, Kaustuv Roy, James W. Valentine Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314: Genera first appearing in the Pleistocene (2mya) Looked at the origin of bivalve taxa (genera) in tropics and beyond

Cradle or museum? David Jablonski, Kaustuv Roy, James W. Valentine Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314: Genera first appearing in the Pliocene (5 mya)

Cradle or museum? David Jablonski, Kaustuv Roy, James W. Valentine Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314: Genera first appearing in the Miocene (23 mya)

Cradle or museum? David Jablonski, Kaustuv Roy, James W. Valentine Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314: SO: The tropics may be both cradle and museum. And that begs the question regarding divergence rates... could pairs of species in temperate zone with recent common ancestors have a tropical origin?

V. Biodiversity: Patterns and Processes A.The Species-Area Relationship B.The Latitudinal Trend in Diversity C.Trend in Diversity over Geological Time

Geological Time - diversity increases through time - there are periodic mass extinctions, followed by faunal recovery

Geological Time Patterns in Fish Diversity Competitive replacement seems likely, as do adaptive radiations of competitively successful group.

Geological Time Patterns in Tetrapod Diversity

Geological Time Patterns in Plant Diversity

- innovation: new “adaptive zone” colonized - radiation – explosion of species colonizing new areas and exploiting new environments in this new way - competitive contraction? – winners exclude others…

Mechanisms: - How/why is a new adaptive zone colonized?

Mechanisms: - How/why is a new adaptive zone colonized? 1. Evolve a new way of life that allows the organism to use new resources, or old resources in a new way (adaptations to land… adaptations for flight…) 2. Colonize an uninhabited area (islands) – these are “ecological vacuums”, too… 3. Be released from competition by mass extinction of competitors…

Geological Time But predation has been important, too. These are Cnidarians - stinging predators This is Spriggia, thought to be a soft-bodied arthropod precursor. Animals of the Vendian Period: mya

Geological Time But predation has been important, too. Animals of the Cambrian Period: mya Hard parts evolve... leading to a burst in preserved specimens Predation - selects for anti-predator traits in prey

Geological Time Mutualisms are important, too Cretaceous Flowering Plants (Angiosperms) and Insect Pollinators beetles Ants, bees, wasps flies Butterflies and moths

Conclusion: There are a range of factors that probably contribute differentially depending on the taxon. Climate Trophic Relationships Evolutionary Processes DIVERSITY History