Global Patterns of Species Diversity

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Global Patterns of Species Diversity

• Biology 120
• 3 December 2001

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Biodiversity

• What are global patterns of biodiversity?
• Where are the most diverse areas on Earth?
• What taxa contain the greatest levels of
  diversity?
• What factors contribute to these patterns?

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Components of species richness

• Point diversity
• species at any point in space (what we're doing
  in lab)
• Alpha richness
• species in a small, homogenous area
• within-habitat diversity
• e.g. of species of plants in coastal sage scrub
  in Los Angeles County
• Beta-richness
• rate of change in species composition across
  habitats
• between-habitat diversity
• change in species richness from Malibu to the top
  of Mt. Wilson to bottom of Death Valley)
• Gamma-richness
• rate of change in species composition across
  larger landscape gradients
• how does bat species richness change from the tip
  of Baja California to Northern California?

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Alpha richness

• Characterized by widespread, nonrandom patterns
• Patterns in diversity correlated with
  environmental variables

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Pattern 1

• More species in tropical regions than in
  temperate and high-latitude regions
• Examples
• Tunicates
• Bivalve molluscs (overhead)
• Terrestrial birds, trees, mammals in North America

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Tunicate Species Richness

• 100 Arctic spp.
• 400 temperate spp.
• 600 tropical spp.

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Bivalve molluscs

• species, genera, and families peak equatorially

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Diversity of some taxa in North America
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Exceptions to greater diversity in tropics

• marine algae, reach max. richness 20-40 N and S)
• penguins
• salamanders
• bees
• waterfowl

Batrachoseps gabrielli, Mario Garcia-Paris
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Erwins collection techniquehttp//www.sp.uconn.
edu/bi102vc/102f99/terry/bugbomb.html
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Pattern 2 Species richness positively
correlated with habitat structural complexity

• Open ocean, grasslands, cold deserts have fewer
  species
• Complex communities, like forests and coral
  reefs, have more species
• E.g. MacArthur and MacArthur 1961

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Bird species diversity correlated with foliage
structureMacArthur and MacArthur 1961
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Pattern 3

• Species richness correlates with increasing
  primary production

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Species richness and primary production
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Pattern 4 species diversity lower on islands and
other isolated areas