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

2. Amphibians
Lizards
Snakes

3. Moss

4. Bivalves
Ants

5. Lizards
Birds

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

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

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

10. a. ENERGY – DIVERSITY HYPOTHESIS

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

12. "Bottom-Up" - more Energy, more sp.
- qualitative effects: energy increasing types of diversity
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.

13. 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.

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

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

16. "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.

17. "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.
IF species diversify more rapidly in the tropics, THEN tropical species pairs should have a more recent common ancestor.
RESULTS: Temperate pairs of birds and mammals had MORE RECENT divergence times than pairs of tropical species.

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

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

20. Andes, Equator
Rockies, 60 N

22. V. Biodiversity: Patterns and Processes
The Species-Area Relationship
The Latitudinal Trend in Diversity
The patterns
Potential Causes
a. energy-diversity hypothesis
b. habitat heterogeneity – diversity hypothesis
c. Species – Area effects

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

24. V. Biodiversity: Patterns and Processes
The Species-Area Relationship
The Latitudinal Trend in Diversity
The patterns
Potential Causes
a. energy-diversity hypothesis
b. habitat heterogeneity – diversity hypothesis
c. Species – Area Effects
d. Intermediate disturbance hypothesis

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

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

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

28. - 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

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

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

31. end of last glacial - 10,000 years ago

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

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

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

41. 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 RATE
LOWER EXTINCTION RATE

42. 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

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

44. Cradle or museum?
David Jablonski, Kaustuv Roy, James W. Valentine Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314:
Looked at the origin of bivalve taxa (genera) in tropics and beyond
Genera first appearing in the Pliocene (5 mya)

45. Cradle or museum?
David Jablonski, Kaustuv Roy, James W. Valentine Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314:
Looked at the origin of bivalve taxa (genera) in tropics and beyond
Genera first appearing in the Miocene (23 mya)

46. 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?

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

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

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

50. Geological Time
Patterns in Tetrapod Diversity

51. Geological Time
Patterns in Plant Diversity

52. - 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…

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

54. 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…

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

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

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

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