The carnivorous plant described as Sarracenia alata contains two cryptic species

Modern methods for species delimitation provide biologists with the power to detect cryptic diversity in nearly any system. To illustrate the application of such methods, we collected data (21 sequence loci) from a carnivorous plant in southeastern North America and applied several recently developed methods (Gaussian clustering, Structurama, BPP, spedeSTEM). The pale pitcher plant Sarracenia alata inhabits the southeastern USA along the northern coast of the Gulf of Mexico. Sarracenia alata populations are separated by the Mississippi River and Atchafalaya Basin, a known biogeographical barrier in this region, but the cohesiveness of S. alata as currently classified has not been tested rigorously. Multiple analytical approaches (including allelic clustering and species trees methods) suggest that S. alata comprises two cryptic lineages that correspond to the eastern and western portions of the plant's distribution. That such clear genetic evidence for cryptic diversity exists within S. alata and is in conflict with other sources of data (e.g. morphology, environmental differentiation) illustrates a conundrum faced by those who investigate species boundaries: genetic data are often the first type of data to accumulate evidence of differentiation, but most existing taxonomic treatments are based on nongenetic data. Our results suggest that S. alata as currently described contains two cryptic species, and we recommend the elevation of the western populations to species status.