When the shoe doesn't fit: applying conservation unit concepts to western painted turtles at their northern periphery

As biodiversity continues to be lost at an alarming rate, strategies for prioritizing populations for conservation have become increasingly important. Maintaining intraspecific genetic diversity is of particular importance for preserving evolutionary history and the potential for future adaptation. In order to effectively protect this diversity, units below the species level need to be defined. However, delineation of such units is subject to many challenges, with no one strategy applying universally across taxa. In this study we carried out the first genetic assessment of the western painted turtle (Chrysemys picta bellii) at its northern periphery in British Columbia (BC), Canada, using mitochondrial DNA haplotypic and microsatellite genotypic data to examine population structure and demographic history. We compared the application of evolutionarily significant unit and management unit criteria with Canadian designatable unit guidelines to determine appropriate conservation units. Our results show that BC western painted turtles form a single evolutionarily significant unit, with each occupied site constituting a separate management unit. In contrast, there is evidence for six discrete designatable units. Patterns of genetic variation in BC western painted turtles indicate that the conservation of each region is important to maintaining regional diversity and evolutionary novelty in this widespread species.