Using genomics, morphometrics, and environmental niche modeling to test the validity of a narrow-range endemic snail, Patera nantahala (Gastropoda, Polygyridae)

Abstract

Terrestrial gastropods are among the most imperiled groups of organisms on Earth. Many species have a complex taxonomic history, often including poorly defined subspecies, most of which have not been the focus of modern systematics research. Genomic tools, geometric morphometrics, and environmental niche modeling were used to assess the taxonomic status of Patera clarkii nantahala (Clench & Banks, 1932), a subspecies of high conservation concern with a restricted range of approximately 3.3 km2 in North Carolina, USA. A genome-scale dataset was generated that included individuals with morphologies matching P. c. nantahala, P. c. clarkii, and one individual with an intermediate form between P. c. nantahala and P. c. clarkii that was initially hypothesized as a potential hybrid. Mitochondrial phylogenetics, nuclear species tree inference, and phylogenetic networks were used to assess relationships and gene flow. Differences in shell shape via geometric morphometrics and whether the environmental niches of the two subspecies were significantly different were also examined. Molecular analyses indicated an absence of gene flow among lineages of P. clarkii sensu lato. Analyses rejected our hypothesis that the intermediate shelled form represented a hybrid, but instead indicated that it was a distinct lineage. Environmental niche models indicated significant differences in environmental niche between P. c. clarkii and P. c. nantahala, and geometric morphometrics indicated that P. c. nantahala had a significantly different shell shape. Given multiple lines of evidence, species-level recognition of P. nantahala is warranted.