Species Delimitation on Eastern Pinesnakes

Population structure of Eastern pinesnake complex

The classification of the eastern Pinesnake (Pituophis melanoleucus) has long been a subject of debate in the scientific community. This species, found throughout the eastern United States, was traditionally divided into three subspecies based on geography and scale coloration: the northern Pinesnake (P. m. melanoleucus), the Florida Pinesnake (P. m. mugitus), and the Black Pinesnake (P. m. lodingi). This project aimed to test the validity of these subspecies using modern genomic data and powerful statistical methods.

At left, The colors of the tips represent current subspecific designations: Black represents the outgroup, red corresponds to Pituophis melanoleucus melanoleucus (Northern Pinesnake), blue corresponds to Pituophis melanoleucus mugitus (Florida Pinesnake), and green corresponds to Pituophis melanoleucus lodingi (Black Pinesnake). The values on the nodes represent the posterior probabilities of the corresponding clade. At right, the colors correspond to designations from BPP and the DAPC analysis. Nodes represented by circles are nodes where DAPC and BPP agree that the clade is distinct. Nodes represented by stars are clades where BPP considers the clade a separate species, but DAPC does not.

Our findings strongly refute the traditional three-subspecies classification. We discovered that the evolutionary history of these snakes is shaped not by superficial color patterns, but by major geographic barriers like river systems and human-caused habitat fragmentation. Our analyses suggested the existence of significant population structure that may represent as many as eight evolutionarily diverging groups within what was formerly considered a single species complex.

This work was published in the Bulletin of the Society of Systematic Biologists.

Khakurel, B., Nikolakis, Z. L., Crother, B. I., & Wright, A. M. (2023). Species Delimitation of Eastern Pinesnake complex (Pituophis melanoleucus). Bulletin of the Society of Systematic Biologists. DOI: https://doi.org/10.18061/bssb.v2i1.9423