title: Recent rapid speciation and ecomorph divergence in Indo-Australian sea snakes.
abstract: The viviparous sea snakes (Hydrophiinae) are a young radiation of at least 62 species that display spectacular morphological diversity and high levels of local sympatry. To shed light on the mechanisms underlying sea snake diversification, we investigated recent speciation and eco-morphological differentiation in a clade of four nominal species with overlapping ranges in Southeast Asia and Australia. Analyses of morphology and stomach contents identified the presence of two distinct ecomorphs: a 'macrocephalic' ecomorph that reaches >2 m in length, has a large head and feeds on crevice-dwelling eels and gobies; and a 'microcephalic' ecomorph that rarely exceeds 1 m in length, has a small head and narrow fore-body and hunts snake eels in burrows. Mitochondrial sequences show a lack of reciprocal monophyly between ecomorphs and among putative species. However, individual assignment based on newly developed microsatellites separated co-distributed specimens into four significantly differentiated clusters corresponding to morphological species designations, indicating limited recent gene flow and progress towards speciation. A coalescent species tree (based on mitochondrial and nuclear sequences) and isolation-migration model (mitochondrial and microsatellite markers) suggest between one and three transitions between ecomorphs within the last approximately 1.2 million to approximately 840,000 years. In particular, the macrocephalic 'eastern' population of Hydrophis cyanocinctus and microcephalic H. melanocephalus appear to have diverged very recently and rapidly, resulting in major phenotypic differences and restriction of gene flow in sympatry. These results highlight the viviparous sea snakes as a promising system for speciation studies in the marine environment.
authors.affiliation: School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA, Australia. kate.sanders@adelaide.edu.au
authors.forename: Kate L
authors.initials: KL
authors.lastname: Sanders
authors.forename: Arne R
authors.initials: AR
authors.lastname: Rasmussen
authors.lastname: Mumpuni
authors.forename: Johan
authors.initials: J
authors.lastname: Elmberg
authors.forename: Anslem
authors.initials: A
authors.lastname: de Silva
authors.forename: Michael L
authors.initials: ML
authors.lastname: Guinea
authors.forename: Michael S Y
authors.initials: MS
authors.lastname: Lee
mesh_terms: D000818:Animals; D001210:Asia, Southeastern; D001315:Australia; D001483:Base Sequence; D001499:Bayes Theorem; D017931:DNA Primers / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D017815:Elapidae / Q000033:anatomy & histology* / Q000235:genetics* / Q000502:physiology; D005247:Feeding Behavior / Q000502:physiology; D005766:Gastrointestinal Contents / Q000737:chemistry; D051456:Gene Flow / Q000235:genetics; D049810:Genetic Speciation; D005828:Genetics, Population; D006257:Head / Q000033:anatomy & histology*; D018895:Microsatellite Repeats / Q000235:genetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D017931:DNA Primers; D004272:DNA, Mitochondrial