The utility of plastron shape for uncovering cryptic diversity in Hermann's tortoise

Abstract

© 2019 The Zoological Society of London Although a significant unexploited potential of the geometric morphometrics in taxonomy and systematics has been documented, only a few studies so far have focused on the utility of this method in the detection of population genetic structure in turtles. For the first time, we employed geometric morphometrics to explicitly analyse whether populations possessing divergent haplotypes evolved different patterns of plastral shape in any Testudo species using the Greek populations of Hermann's tortoise as a case study. To molecularly characterize the Greek populations of Testudo hermanni boettgeri used for plastron shape analyses, 12s rRNA gene of tortoises sampled from seven localities in Greece was sequenced. Three divergent haplotypes were observed, regionally corresponding to the north-western (HI), south-western (HII) and Peloponnese (HIII) areas of Greece. In both females and males, haplotypes HI and HII showed the lack of plastral shape divergence, but were both statistically significantly different relative to HIII found in Peloponnese. The Peloponnesian populations (HIII) had longer bridges and the wider and shorter anterior part of the plastron, relative to populations from the mainland Greece (HI and HII). Hence, both morphological and molecular markers suggested Peloponnese as a distinct lineage in relation to mainland populations. Finally, we consider geometric morphometrics as an efficient method to detect and characterize subtle interpopulation differences. Findings in this study have conservation applications as well, implying the presence of cryptic genetic and taxonomic diversity, and, thus, filling the crucial gap in the assessment of the conservation status of T. hermanni.