Evolutionary dynamics of a rapidly receding southern range boundary in the threatened California Red-Legged Frog (Rana draytonii)
Article first published online: 3 APR 2013
© 2013 The Authors. Evolutionary Applications published by Blackwell Publishing Ltd.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Volume 6, Issue 5, pages 808–822, July 2013
How to Cite
Richmond, J. Q., Barr, K. R., Backlin, A. R., Vandergast, A. G. and Fisher, R. N. (2013), Evolutionary dynamics of a rapidly receding southern range boundary in the threatened California Red-Legged Frog (Rana draytonii). Evolutionary Applications, 6: 808–822. doi: 10.1111/eva.12067
- Issue published online: 17 JUL 2013
- Article first published online: 3 APR 2013
- Manuscript Accepted: 25 FEB 2013
- Manuscript Received: 24 AUG 2012
- USFWS/USGS Science
- USGS Western Ecological Research Center
- conservation genetics;
- ranid frogs;
- range edge - empirical;
- wildlife management
Populations forming the edge of a species range are often imperiled by isolation and low genetic diversity, with proximity to human population centers being a major determinant of edge stability in modern landscapes. Since the 1960s, the California red-legged frog (Rana draytonii) has undergone extensive declines in heavily urbanized southern California, where the range edge has rapidly contracted northward while shifting its cardinal orientation to an east-west trending axis. We studied the genetic structure and diversity of these frontline populations, tested for signatures of contemporary disturbance, specifically fire, and attempted to disentangle these signals from demographic events extending deeper into the past. Consistent with the genetic expectations of the ‘abundant-center’ model, we found that diversity, admixture, and opportunity for random mating increases in populations sampled successively further away from the range boundary. Demographic simulations indicate that bottlenecks in peripheral isolates are associated with processes extending tens to a few hundred generations in the past, despite the demographic collapse of some due to recent fire-flood events. While the effects of recent disturbance have left little genetic imprint on these populations, they likely contribute to an extinction debt that will lead to continued range contraction unless management intervenes to stall or reverse the process.