title: Genetic surfing, not allopatric divergence, explains spatial sorting of mitochondrial haplotypes in venomous coralsnakes.
abstract: 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.
authors.affiliation: Department of Life Sciences, The Natural History Museum, London, United Kingdom.|Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona.|Department of Biology, University of Texas at Arlington, Arlington, Texas.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Streicher
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona.|Department of Biology, University of Florida, Gainesville, Florida.
authors.forename: Jay P
authors.initials: JP
authors.lastname: McEntee
authors.affiliation: Department of Biology, University of Texas at Arlington, Arlington, Texas.
authors.forename: Laura C
authors.initials: LC
authors.lastname: Drzich
authors.affiliation: Department of Biology, University of Texas at Arlington, Arlington, Texas.
authors.forename: Daren C
authors.initials: DC
authors.lastname: Card
authors.affiliation: Department of Biology, University of Texas at Arlington, Arlington, Texas.
authors.forename: Drew R
authors.initials: DR
authors.lastname: Schield
authors.affiliation: Department of Biology, University of Texas at Arlington, Arlington, Texas.
authors.forename: Utpal
authors.initials: U
authors.lastname: Smart
authors.affiliation: Department of Biology, University of Central Florida, Orlando, Florida.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Parkinson
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona.
authors.forename: Tereza
authors.initials: T
authors.lastname: Jezkova
authors.affiliation: Department of Biology, University of Texas at Arlington, Arlington, Texas.
authors.forename: Eric N
authors.initials: EN
authors.lastname: Smith
authors.affiliation: Department of Biology, University of Texas at Arlington, Arlington, Texas. todd.castoe@uta.edu.
authors.forename: Todd A
authors.initials: TA
authors.lastname: Castoe
mesh_terms: D000818:Animals; D004272:DNA, Mitochondrial / Q000235:genetics*; D017815:Elapidae / Q000235:genetics*; D019143:Evolution, Molecular; D051456:Gene Flow; D006239:Haplotypes; D008800:Mexico; D010802:Phylogeny; D014481:United States
chemical_list: D004272:DNA, Mitochondrial
keywords: Directionality index psi; Elapidae; RADseq; heterozygosity; mitonuclear discordance; private alleles; serial founder effect