Sexual and Seasonal Dimorphism in the Cumberland Plateau Woodland Salamander, Plethodon kentucki (Caudata: Plethodontidae)

Abstract

Previous studies revealed sexual dimorphism in terrestrial plethodontid salamanders of the genus Plethodon for greater snout–vent length (SVL) at first reproduction and maximum SVL in females, presence of a mental gland in males, larger vomeronasal organ (VNO) in males, and greater internarial width in males. Here I describe additional sexual dimorphism as well as seasonal (i.e., breeding versus non-breeding) dimorphism in Plethodon kentucki. I measured morphological variables on preserved specimens of adult individuals that were collected from Wise Co., Virginia during the breeding season (n = 26 females and 30 males) and non-breeding season (n = 29 females and 30 males). Residuals from regressions of morphological variables on SVL (all log10-transformed) and a principal component analysis on the residuals demonstrate that body mass, trunk length, and tail width are greater in females. These female features may be associated with selection for greater fecundity and increased fat storage to enhance reproductive success. The head is relatively larger in males and has a longer snout with a broader tip (i.e., greater orbitonarial distance and internarial width). Such dimorphism for the snout increases during the breeding season. Sexually dimorphic features in males may be associated with selection for increased mating success in terms of finding reproductive females (i.e., the enlarged snout may be related to a larger VNO and enhanced chemosensory function) and increased competitive ability during competition for mating opportunities (i.e., the larger head may result from selection for better fighting ability). An increase in vent length for both sexes may facilitate the indirect transfer of sperm during the breeding season.