Banded or striped? Significant colour dimorphism of a bridal snake in Borneo

Abstract

Stripes and bands are common colour patterns in snakes. Some species are known to exhibit colour polymorphism and that includes expressing it in the bands and stripes. Bridal snake, Dryocalamus is a medium‐sized arboreal snake in South to Southeast Asia and most species of the genus are banded, but including two striped species. In Borneo, banded D. subannulatus and striped D. tristrigatus occur sympatrically and the two species are similar morphologically except for their colour patterns. We hypothesized the two species in Borneo exhibit a significant colour dimorphism of one species and conducted morphological and genetical analysis to test the hypothesis. Morphological examinations revealed that D. subannulatus and D. tristrigatus are not distinguishable in Borneo by scalation. Mitochondrial phylogenetic analysis and nuclear SNP analysis showed D. subannulatus and D. tristrigatus from Borneo formed clades or clusters by region not by species. Dryocalamus subannulatus and D. tristrigatus in Borneo are morphologically and genetically indistinguishable and Bornean D. subannulatus should be treated as a colour morph of D. tristrigatus. This is a rare example of sympatrically distinct banded/striped dimorphism in snakes. Relative abundance of banded/striped morph of the genus is probably different depending on region, and any ecological factor may contribute to it.