Phylogeography of the smooth greensnake, Opheodrys vernalis (Squamata: Colubridae): divergent lineages and variable demographics in a widely distributed yet enigmatic species

Abstract

Phylogeographic studies can uncover robust details about the population structure, demographics, and diversity of species. The smooth greensnake, Opheodrys vernalis, is a small, cryptic snake occupying mesic grassland and sparsely wooded habitats. Although O. vernalis has a wide geographical range, many metapopulations are patchy and some are declining. We used mitochondrial DNA and double digest restriction-site associated DNA sequencing to construct the first phylogeographic assessment of O. vernalis. Genomic analysis of 119 individuals (mitochondrial DNA) and a subset of another 45 smooth greensnakes (nuclear DNA; N = 3031 single nucleotide polymorphisms) strongly supports two longitudinally separated lineages, with admixture in the Great Lakes region. Post-Pleistocene secondary contact best explains admixture from populations advancing northwards. Overall, populations expressed low heterozygosity, variable inbreeding rates, and moderate to high differentiation. Disjunct populations in the Rocky Mountains and central Great Plains regions might be contracting relicts, whereas northerly populations in more continuous mesic habitats (e.g., Prairie Pothole region, southern Canada) had signals of population expansion. Broadly, conservation management efforts should be focused on local populations, because habitat connectivity may facilitate gene flow and genetic diversity.

First Observations of Smooth Greensnake (Opheodrys vernalis) Communal Oviposition within An Active Ant Nest of Lasius interjectus

“…Opheodrys vernalis (Harlan) (Smooth Greensnake) is a small-bodied, oviparous, grassland-dependent, insectivorous colubrid snake, distributed in the northeastern and midwestern United States, and southern Canada, as well as in disjunct locations in the Black Hills and Rocky Mountains (Blais et al 2021). Smooth Greensnake populations are declining in much of the range, driven by habitat loss and fragmentation (Blais et al 2021) as well as reduced survival of eggs (Sacerdote-Velat and King 2022, Sacerdote-Velat et. al.…”