Plastron Pigmentation Variation in a Coastal Turtle Species of Conservation Concern (Malaclemys terrapin)

Abstract

Abstract Malaclemys terrapin inhabits salt marshes of the coastal United States and has been historically divided into seven subspecies. Two of the described subspecies, M. t. pileata and M. t. littoralis, occur along the western and eastern coastlines of Louisiana, respectively. To better understand potential boundaries of these two subspecies, we documented pigmentation variation of the plastron along the coast of Louisiana where the subspecies supposedly intergrade. Photographs of the plastron were taken of captured individuals and we quantified pigment with a photoprocessing software (ImageJ). We found pigmentation differences between sexes, with females having lighter plastrons than males. The plastron pigmentation of females decreased with increasing plastron length, whereas that of males varied by site but not length. Plastron pigmentation did not correlate with longitude in either sex, indicating that there is no geographical cline in this trait. We suggest that large females might be released fro...