Effects of warming conditions in eastern North American forests on red-backed salamander morphology

Several studies have reported climate-associated changes in phenotypically plastic traits of amphibians, yet it remains unknown whether amphibians can manifest an evolutionary response to global climate change at the rate and magnitude that it is occurring. To assess this issue, we examined temporal change in the morphology of the red-backed salamander (Plethodon cinereus), a small, abundant woodland salamander distributed widely in eastern North America with two distinct morphotypes: striped individuals associated with cooler microclimates and unstriped individuals associated with warmer microclimates. We compiled morph frequencies for 50,960 individual salamanders from 558 sites as recorded in the published literature and in unpublished field notes of herpetologists between 1908 and 2004. We observed that striping probability increased with increasing latitude, longitude, and elevation and decreased (from 80% to 74% range wide) with time. The combined forces of regional climate warming and, particularly, forest disturbance have evidently been sufficient to cause morphological evolution in this amphibian over the last century.