Range limitation of the Peaks of Otter salamander (Plethodon hubrichti) due to competition with the eastern red-backed salamander (Plethodon cinereus) in sympatry

The Peaks of Otter salamander, Plethodon hubrichti, is a montane species found at altitudes above 442 m within a 117 km2 area of the Blue Ridge Mountains in central Virginia, USA. In areas where this species is sympatric with the eastern red-backed salamander (Plethodon cinereus) it seemed likely that P. hubrichti populations were either depressed or eliminated. The habitability of areas beyond the current range boundaries for P. hubrichti is supported by several disjunct populations in areas sympatric with P. cinereus. From 2009 to 2012 we tested whether P. hubrichti was negatively impacted by competition with P. cinereus by removing P. cinereus from treatment plots at three sympatric field locations. The number of surface-active (SA) P. hubrichti increased significantly more on treatment plots than on corresponding reference plots, whereas the number of SA P. cinereus decreased significantly more on treatment plots than on reference plots. The removal of every one P. cinereus from the treatment plots led to an increase of 0.69 P. hubrichti. These results emphasise the importance of conserving mature hardwood forests along the perimeter of the P. hubrichti distribution, where it is sympatric with P. cinereus, so as to prevent future range contraction of this vulnerable species.