Identifying potential keystone species from field data – an example from temporary ponds

Identifying keystone species is essential for understanding community dynamics and preserving species richness. However, few studies have used quantitative, a priori methods to identify potential keystone species. Species known to act as keystones in North Carolina (NC) temporary ponds ( Notophthalmus viridescens , eastern newt, and Siren intermedia , lesser siren) were tested to see whether they played the same role in similar habitats in South Carolina (SC). Newts and sirens had no effect on anuran species richness in SC. Instead, another salamander ( Ambystoma talpoideum , mole salamander) absent from the NC ponds was identified as a strong keystone in SC. It functioned independently of environmental factors and the densities of other predators. Larval dragonflies ( Tramea carolina , Carolina saddlebag) were identified as weak, context-dependent keystones in SC, supporting anuran richness in isolated ponds with very low pH. The results suggest that the identity of keystone species varies, even in similar habitats within a physiographic region.