Comparison of Semi-aquatic Snake Communities Associated with the Khorat Basin, Thailand

Abstract

The Khorat Basin is a prominent geographic feature of Indochina, potentially important in the ecology and evolution of semi-aquatic snake communities. We compared community structure and population characteristics of semi-aquatic snakes (taxonomic focus on homalopsine snakes) from localities located in the Khorat Basin, on the mountainous rim of the Khorat Basin, and at lower elevation sites located outside of the Khorat Basin. Species richness of semi-aquatic snakes assemblages was comparable in and outside of the Khorat Basin (8 species). There was a high degree of species overlap between assemblages found in and out of the basin (coefficient of similarity = 0.88), but species diversity was higher in the Khorat Basin (evenness = 0.694). Enhydris enhydris was the strong dominant at sites located outside of the basin (evenness = 0.334). Homalopsine snakes were absent from the Khorat Basin rim sites. Snakes were over twice as abundant at sites located outside of the Khorat Basin compared to sites in the basin. We found size sexual dimorphism for E. enhydris outside of the Khorat Basin, but not in the basin. Female snakes (E. enhydris and E. plumbea) from sites outside the Khorat Basin were larger and heavier in comparison to Khorat Basin populations. We discuss historical, biogeographical, biotic, and abiotic factors that may contribute to the observed differences.