Utpal Smart

Genetic surfing, not allopatric divergence, explains spatial sorting of mitochondrial haplotypes in venomous coralsnakes.

Strong spatial sorting of genetic variation in contiguous populations is often explained by local adaptation or secondary contact following allopatric divergence. A third explanation, spatial sorting by stochastic effects of range expansion, has been considered less often though theoretical models suggest it should be widespread, if ephemeral. In a study designed to delimit species within a clade of venomous coralsnakes, we identified an unusual pattern within the Texas coral snake (Micrurus tener): strong spatial sorting of divergent mitochondrial (mtDNA) lineages over a portion of its range, but weak sorting of these lineages elsewhere. We tested three alternative hypotheses to explain this pattern—local adaptation, secondary contact following allopatric divergence, and range expansion. Collectively, near panmixia of nuclear DNA, the signal of range expansion associated sampling drift, expansion origins in the Gulf Coast of Mexico, and species distribution modeling suggest that the spatial sorting of divergent mtDNA lineages within M. tener has resulted from genetic surfing of standing mtDNA variation—not local adaptation or allopatric divergence. Our findings highlight the potential for the stochastic effects of recent range expansion to mislead estimations of population divergence made from mtDNA, which may be exacerbated in systems with low vagility, ancestral mtDNA polymorphism, and male‐biased dispersal.

A New Genus and Two New Species of Arboreal Toads from the Highlands of Sumatra with a Phylogeny of Sundaland Toad Genera

Abstract: We describe a new genus and two new species of toads from the Sumatran volcanoes Gunung Sorikmarapi and G. Kunyit, in the provinces of Sumatera Utara and Jambi, respectively. The new taxa can be distinguished from other genera, and each other, based on genetic differentiation, morphology, and advertisement call structure. We employ both nuclear and mitochondrial data to provide a phylogenetic hypothesis of relationships for the bufonid genera of the Sunda Shelf. While broadly corroborating previous studies, our results also shed light on the phylogenetic position of Pseudobufo. The new genus, Duttaphrynus, and Pseudobufo are basal to other Sunda Shelf genera in our phylogenies.

A New Species of Long-glanded Coralsnake of the Genus Calliophis (Squamata: Elapidae) from Dinagat Island, with Notes on the Biogeography and Species Diversity of Philippine Calliophis and Hemibungarus

Abstract We describe a new species of coralsnake from northern Dinagat Island, southeastern Philippines. The discovery of this new species comes as a surprise because it is phenotypically distinct from all other Philippine coralsnakes and has a close phylogenetic affinity to the blue coralsnakes of the Sunda Shelf. The new species is distinguished from all Philippine and other Southeast Asian taxa by its large body size and ventral scale counts; its black head and neck; an alternating, broadly banded color pattern of black and off-white; and a bright orange tail. We use DNA sequence data to investigate the phylogenetic placement of the new species and that of several other populations of Philippine coralsnakes with respect to other Southeast Asian and Australasian elapids. Our results corroborate the uniqueness of the new species with respect to all other Philippine and Sundaic taxa, including the species most closely related to it: Calliophis bivirgatus, C. bilineatus, C. philippinus, and C. suluensis. We summarize phylogenetic, biogeographic, and phenotypic character data that substantiate the elevation of Philippine species of Calliophis (formerly considered subspecies of C. intestinalis: C. bilineatus, C. philippinus, and C. suluensis) and Hemibungarus (formerly subspecies of H. calligaster: H. calligaster, H. gemianulis, and H. mcclungi) to the level of full species. The allopatric distributions of these taxa emphasize the systematic and biogeographical significance of the newly discovered taxon: a poorly understood and independent colonization of the Philippine Archipelago by elapid snakes.