Phylogenetics, subspecies, and conservation of the eastern pinesnake

Abstract

Whether or where to draw subspecies' taxonomic boundaries is much more than an esoteric argument. Subspecific taxonomies and associated geographic ranges have important conservation and management implications because the Endangered Species Act (ESA) protects distinct populations segments below the species level. Genomic data can help resolve taxonomic disputes and assist with conservation policy; however, because subspecific lineages often exhibit gene flow, genomic lineages for subspecific taxa are rarely distinct. We used genomic data from the eastern pinesnake (Pituophis melanoleucus) to determine the geographic range of the morphologically variable Florida pinesnake (P. m. mugitus), which is petitioned for listing under the ESA. The overall genomic pattern of the eastern pinesnake is one of admixture, and there are gradual differences over the wide range of the species. But there still are discernable areas of genetic differentiation that correspond to the morphologically defined Florida pinesnake, and other subspecies. This pattern of admixture should be expected for subspecies. We propose that boundaries for the Florida pinesnake should maximize the species redundancy, resilience, and representation based on genomic data. We also propose best practices for managers and policymakers interpreting genomic data of subspecies, given that the genomic cutoffs will rarely be truly distinct.