The identity of the Javan Krait, Bungarus javanicus Kopstein, 1932 (Squamata: Elapidae): evidence from mitochondrial and nuclear DNA sequence analyses and morphology

Abstract

The Javan Krait (Bungarus javanicus Kopstein, 1932) was described on the basis of a single specimen that had been discovered subsequent to its delivery of lethal bites to two sleeping people in a rice field hut. Until 1936, only two additional specimens were found in the vicinity of the type locality near Cirebon on the north coast of West Java province, Indonesia. The taxonomic status of B. javanicus has remained doubtful due to its great similarity to the common and widely distributed Malayan Krait (Bungarus candidus), from which it was distinguished only by its black (vs. black-andwhite banded) colouration. We rediscovered B. javanicus near its type locality in 1993 and obtained substantial series of black kraits in West and Central Java provinces in 1996 and 1998. We provide a detailed redescription of the type specimen and the two other specimens of B. javanicus available to Kopstein. We then use nucleotide sequences of the mitochondrial cytochrome b gene to estimate relationships among 27 black and black-and-white banded kraits from Java and Bali. In addition, we use exon-primed intron-crossing primers to analyze a sequence segment of the alpha-bungarotoxin (A31) gene from ten black and black-and-white banded kraits from these islands. Four mitochondrial haplotypes were identified which exhibited minimal sequence divergence and no correlation to colouration. In particular, both external phenotypes were found in the same genealogical lineage near Indramayu, where black kraits and black-and-white banded B. candidus occur in syntopy. Neither the nucleotide sequence of intron 2 nor partial exon 2 and 3 sequences of the alphabungarotoxin (A31) gene exhibited variation within the sample from Java and Bali. Intron 2 sequence divergence between the Javan kraits and the closely related Bungarus multicinctus is 1.1%. Morphological examination of specimens of B. javanicus and B. candidus from Java revealed no differences beyond colouration. The combined evidence identifies the locally strong populations of black kraits in Java as conspecific with local B. candidus. Their regional dichromatism includes two fundamentally different patterns for predator avoidance, and is interpreted as the result of increased genetic fixation of mutations in one or several instable genes (which can cause similar pattern abnormalities in various species of Bungarus), in the course of the colonization of the alluvial plains of northern Java. These plains are of very recent origin and likely offered selective pressures different from those in older parts of the island, rendering both black and black-and-white banded phenotypes successful in predator avoidance.