Quantifying amphibian range fragmentation in the southeastern United States

Catherine E Newman,Christopher C Austin

doi:10.21425/f5fbg37772

Abstract

Author(s): Newman, Catherine E.; Austin, Christopher C. | Abstract: The southeastern United States is home to the highest amphibian species richness in North America. An often overlooked component of research on factors that drive amphibian geographic distributions is description of species range shape. Broad-scale range disjunction has implications for phylogeography, ecology, and conservation, but descriptions of fragmentation are usually based on subjective visual assessment of range maps. Here, we describe a method for objectively quantifying range fragmentation and use this method to describe the patterns of amphibian species range shapes in the Southeast. Species ranges varied widely in degree of fragmentation, from completely contiguous to highly fragmented, and degree of isolation of range fragments. Incorporating ecological niche models added information about fine-scale habitat fragmentation. Although 12 species had ranges with either high or moderate fragmentation, the only area where range fragments of more than two of the 12 species overlapped was the Appalachian Highlands, suggesting that range fragmentation in the Southeast is driven by multiple biogeographic processes.

Highlights

Geographic ranges of species are fundamental to the study of biogeography
Phylogeographic studies that use ecological niche modeling and paleodistribution modeling to explore species distribution shifts through time generally rely on qualitative visual assessment of model differences and would benefit from objective measurement of distribution shape (e.g., Newman and Austin 2015)
If the county-based range map consists of multiple patches, the Ecological niche models (ENMs) is clipped to the extent of the minimum convex polygon encompassing all patches of the range

Summary

Introduction

Geographic ranges of species are fundamental to the study of biogeography. The size and shape of species ranges are related to the biotic and abiotic factors and historical processes that influence the distribution and abundance of organisms (Brown et al 1996). When comparing fragmentation metrics using both a county-based range map and an ENM for a given species, it is important to minimize overprediction of the ENM into areas where the species probably does not occur due to various factors other than climate.

Results

Conclusion