Data from: Fuzzy boundaries: Color and gene flow patterns among parapatric lineages of the Western shovel-nosed snake and taxonomic implication

Accurate delineation of lineage diversity is increasingly important, as
species distributions are becoming more reduced and threatened. During the
last century, the subspecies category was often used to denote phenotypic
variation within a species range and to provide a framework for
understanding lineage differentiation, often considered incipient
speciation. While this category has largely fallen into disuse, previously
recognized subspecies often serve as important units for conservation
policy and management when other information is lacking. In this study, we
evaluated phenotypic subspecies hypotheses within shovel-nosed snakes on
the basis of genetic data and considered how evolutionary processes such
as gene flow influenced possible incongruence between phenotypic and
genetic patterns. We used both traditional phylogenetic and Bayesian
clustering analyses to infer range-wide genetic structure and spatially
explicit analyses to detect possible boundary locations of lineage
contact. Multilocus analyses supported three historically isolated groups
with low to moderate levels of contemporary gene exchange. Genetic data
did not support phenotypic subspecies as exclusive groups, and we detected
patterns of discordance in areas where three subspecies are presumed to be
in contact. Based on genetic and phenotypic evidence, we suggested that
species-level diversity is underestimated in this group and we proposed
that two species be recognized, Chionactis occipitalis and C. annulata. In
addition, we recommend retention of two subspecific designations within C.
annulata (C. a. annulata and C. a. klauberi) that reflect regional shifts
in both genetic and phenotypic variation within the species. Our results
highlight the difficultly in validating taxonomic boundaries within
lineages that are evolving under a time-dependent, continuous process.