Species richness and species pool size variation across pH gradients in Southern Blue Ridge Forests

1
Species richness and species pool size variation
across pH gradients in Southern Blue Ridge Forests
Joel M. Gramling, Robert K. Peet, Jason D.
Fridley, and Thomas R. Wentworth.
2
Should characteristics of a regional flora
reflect the relative abundance of a soil type
over the regions evolutionary history?
3
Central European Scenario

• High pH specialists in the flora of Central
  Europe
• Richness and edaphic characteristics vary
  according to the evolutionary centers of a
  regional flora (Pärtel 2002)

4
Central European Scenario

• Ewald (in press) cites
• Dominance of calcium-rich environs around the
  time of the last glaciations
• Recent environmental bottleneck

5
Southeastern USA Scenario

• How might these hypotheses be applied to the
  Southeastern USA?
• Southern Blue Ridge Mountains have always had
  primarily acidic soils.
• The flora of the Southern Blue Ridge would be
  expected to be acidophilic.

6
Southeastern USA Scenario

• Does the Southern Blue Ridge exhibit a negative
  relationship between pH and species richness as
  implied by the findings of Pärtel and Ewald?
• No.

7
Average number of species in 100-plot segments
along a pH gradient
8
Southeastern USA Scenario

• How is the flora of the Southern Blue Ridge
  distributed across the pH gradient?

9
Species pool for a pH range calculated as the
total number of species occurring in a set of
10,000 species occurrences
10
Genus pool for a pH range calculated as the total
number of species occurring in a set of 10,000
species occurrences
11
Family pool for a pH range calculated as the
total number of species occurring in a set of
10,000 species occurrences
12
Southeastern USA Scenario

• How specialized is the flora of the Southern Blue
  Ridge across the pH gradient?

13
Species accumulation along the pH gradient based
upon the total pH range of observed occurrences
14
Species accumulation along the pH gradient based
upon the total pH range of observed occurrences
15
Species accumulation along the pH gradient based
upon the total pH range of observed occurrences
16
Cumulative species occurrences and cumulative
species median positions encountered when moving
across the pH gradient
17
Conclusions

• Southern Blue Ridge diversity at the species,
  genus and family level is positively correlated
  to soil pH
• Observed species pool is biased toward basic
  soils
• Lack of high pH specialists in Southern Blue
  Ridge flora

18
Acknowledgements