Species Diversity

1
Species Diversity

• Chapter 16

2
Textbook Readings

• Chapter 16 Pp. 371-376 (small scale
  explanations)
• Chapter 22 pp. 517-524 (large scale
  explanations)

3
Intermediate Disturbance Hypothesis (IDH)chapter
16

• Connell Rainforests and Reefs
• We saw model simulation of Eastern Deciduous
  Forest
• Does it apply elsewhere in real life (not just a
  model, but observation)?

4
Experimental evidence of IDH
5
What about Global Patterns?

• Chapter 22 (mostly)

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Plant species diversity vs. latitude
7
Prairie dogs
8
There are exceptions, however
9
Salamanders also reach diversity in temperate
forests
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Biodiversity Hotspots

• Hotspots
• High Diversity
• High Threat by humans
• Need for preservation

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Diversity of Species Latitudinal Changes
Pines and Oaks
Birds
Butterflies
12
Vascular Plant Diversity
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Why? Hypotheses

• 1) Time Since Pertubation
• More time for speciation
• Less frequent perturbation reduces extinction

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Hypothesis 2

• Productivity
• More energymore biomassmore diversity
• For example, coral reefs and rainforests
• However

15
From Chapter 16
16
Rank-Abundance changes due to fertilization
From Chapter 16
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Hypothesis 3 Environmental Heterogeneity

• More heterogenous environments make more
  diversity
• Difficult to prove because of presence of other
  species complicates things
• Species in more diverse environments subdivide
  habitats more finely

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The Tropics The Riches of Niches

• Biological interactions are dominant in tropics
  physical interactions are dominant in high
  latitudes
• Interactions include things like competition,
  predation, parasitism and mutualisms
• Competition is more interspecific (between
  species) than intraspecific (within a species) in
  the tropics

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All of this assumes the following
Speciation in tropics gtgtgt Extinction in tropics
Species in tropics
speciation
extinction
Species in temperate zone
speciation
extinction
Speciation in temperate Zone gt extinction in
Temperate zone
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Niche Possibilities

• Narrower niches in the tropics i.e. more
  specialization
• More niche overlap in tropics

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Or maybe its just far simpler than all this

• Maybe, like we saw in Island Biogeography,
  theres just more land area in the tropics

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The Argument More area in the tropics means

• Tropical species are spread out over a bigger
  area
• A bigger area means species have bigger ranges
  (or thats the claimI personally dont know if
  this is true)
• Bigger ranges means that more allopatric
  speciation can occur leading to.
• MORE SPECIES! (than in temperate areas)

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Maybe its a complex set of reasons why tropics
are more diverse

• Large scale A climate driving less extinction
  and more speciation combined with
• Smaller scale processes such as disturbance leads
  to
• More niches available for species to occupy and
  therefore more species
• And more niches can make more niches!!!