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.

Should characteristics of a regional flora reflect the relative abundance of a soil type over the region’s evolutionary history?

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)

Central European Scenario

Central European Scenario

Ewald (in press) cites:

Dominance of calcium-rich environs around the time of the last glaciations

Recent environmental bottleneck

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.

Southeastern USA Scenario

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.

Average number of species in 100-plot segments along a pH gradient

Southeastern USA Scenario

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

Species pool for a pH range calculated as the total number of species occurring in a set of 10,000 species occurrences

Genus pool for a pH range calculated as the total number of species occurring in a set of 10,000 species occurrences

Family pool for a pH range calculated as the total number of species occurring in a set of 10,000 species occurrences

Southeastern USA Scenario

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

Species accumulation along the pH gradient based upon the total pH range of observed occurrences

Species accumulation along the pH gradient based upon the total pH range of observed occurrences

Species accumulation along the pH gradient based upon the total pH range of observed occurrences

Cumulative species occurrences and cumulative species median positions encountered when moving across the pH gradient

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

Acknowledgements