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.

Next‐generation phylogeography of the cockle Cerastoderma glaucum: Highly heterogeneous genetic differentiation in a lagoon species

“…Thus, a great part of genetic variation in C. glaucum seems to be spatially segregated because of the stochastic processes associated with a recent colonization of the Atlantic coast, and this can explain the poor resolution and discordant patterns found in previous studies. Mitochondrial surfing is rarely reported in the literature, but our scenario is similar to the one described by Streicher et al () for the Texas coral snake Micrurus tener . As noticed by the authors, circumstances under which mitochondrial surfing can be detected are rare: Divergent haplotypes need to be maintained in sympatry before range expansion, and the dispersal capability of species has to be limited.…”

Range instability leads to cytonuclear discordance in a morphologically cryptic ground squirrel species complex

“…Here, we provide support for a demographic scenario that would otherwise go undetected if only autosomal markers were analysed, adding to an extensive literature emphasizing the importance of matrilineal‐biased markers in providing windows into ancient events in the past histories of organisms (Cahill et al., ; Currat et al., ; Melo‐Ferreira et al., ; Streicher et al., ; Wilson & Bernatchez, ). Specifically, we document the existence of a distinct Central lineage that now barely exists, but its past presence can be detected because parts of the Central lineage genome (e.g., X‐linked markers, mtDNA) have been “fossilized” (Currat et al., ) or captured by the Southern lineage.…”

Loss of genetic diversity, recovery and allele surfing in a colonizing parasite, Geomydoecus aurei

“…Similarly, the effect of changing geographic distribution on genetic diversity and its structure is an integral component of the field of biogeography (Waters, Fraser, & Hewitt, ) and an important aspect of the global ecological problem of invasive species (Bock et al, ). Finally, genetic consequences of range expansion can be important to systematic studies, because recently established genetic structure of expanding populations may mislead efforts to determine population divergence and complicate efforts to delimit species (Streicher et al, ).…”