Geographic variation in the Pine Barrens Treefrog (Hyla andersonii): concordance of genetic, morphometric and acoustic signal data.

Abstract

Delimiting species is important to every subfield in biology. Templeton's cohesion species concept uses genetic and ecological exchangeability to identify sets of populations that ought to be considered as the same species, and the lack of exchangeability helps determine which populations can be grouped as evolutionarily significant units (ESU) in conservation science. However, previous work assessing genetic and ecological interchangeability among populations has been limited in scope. Here, we provide a method for assessing exchangeability that incorporates multiple, independent lines of multivariate evidence in genetic, behavioural and morphological data. We use this approach to assess exchangeability across three disjunct groups of populations of the Pine Barrens Treefrog (Hyla andersonii) from the eastern United States. This species is considered threatened by each state in which it occurs and conservation management of this taxon requires a clearer understanding of how populations in these three regions may differ from one another. We find a strikingly concordant pattern in which the first axis of variation for each of the three types of data distinguishes populations along a latitudinal gradient and the second axis distinguishes the set of populations occurring in the Carolinas from those occurring in the New Jersey and Florida/Alabama regions. We know of no comparable data set that displays such concordance among different types of data across so large a geographic range. The overlap in trait values (i.e. exchangeability) between neighbouring regions, however, is substantial in all three types of data, which supports continued consideration of this taxon as a single species.