A comprehensive appraisal of evolutionary diversity in venomous Asian coralsnakes of the genus Sinomicrurus (Serpentes: Elapidae) using Bayesian coalescent inference and supervised machine learning

Abstract

While species boundaries between conspicuously divergent populations of the medically important snake genus Sinomicrurus are well established, instances of erratic chromatic and meristic variation continue to confound taxonomists, since the mid-1800s. This predicament can be attributed to an inadequate molecular phylogenetic framework and the lack of a comprehensive taxonomic representation of geographic variants. Here, we revisit lineage delineation in this genus, drawing cohesive evidence from a plurality of data and analysis types, including a promising, yet taxonomically under-utilized, supervised machine learning algorithm (random forest). Overall, this study incorporates data generated by molecular analyses as well as morphometrics and comparative anatomy based on 236 specimens from 28 different natural history collections examined by us, and an additional 161 records from 47 other sources. Our results indicate several very divergent evolutionary lineages concealed as subspecies. Thus, to better reflect this phylogenetic diversity, we raise S. macclellandi iwasakii from the southern Ryukyus and S. m. swinhoei from Taiwan to full species, and resurrect S. annularis. We highlight the need to distinguish at species level the current subspecies of S. japonicus, namely as, S. japonicus and S. boettgeri, and provide diagnostic characters to that end. On the other hand, given unpersuasive support of lineage independence, we sink Taiwanese S. hatori into S. sauteri and S. nigriventer into S. macclellandi. We also meticulously redescribe S. peinani from mainland China and Vietnam based on a substantial number of additional specimens, while synonymizing the recently described S. houi under S. kelloggi. We conclude with a discussion on the role of regional biogeography as a primary driver of cladogenesis in the genus.