New sea urchin phylogeography reveals latitudinal shifts associated with speciation


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Authors: Hart, MW
Year: 2012
Journal: Molecular Ecology 21: 26-27   Article Link (DOI)
Title: New sea urchin phylogeography reveals latitudinal shifts associated with speciation
Abstract: Where do new species arise? When do they form and how do they diverge from a common ancestor? A new comprehensive study of Arbacia sea urchins provides surprising answers to these questions. By combining mtDNA phylogeographic markers with a nuclear locus (encoding the sperm acrosomal protein bindin) known to be susceptible to high rates of adaptive codon evolution, Lessios (2012) show that new species and lineages arose relatively recently, most often in association with latitudinal shifts between the temperate zones and the tropics, and in one case, in association with a significant geological barrier to gene flow (the rise of the Isthmus of Panama). In addition to the where and when of Arbacia speciation, these new data resolve an important question about whoArbacia species are by revealing extensive allele sharing at both loci between a pair of broadly sympatric nominal species (that should perhaps be considered a single taxon). HowArbacia diverge from each other is less easily resolved: there is no evidence for reinforcement (via selection on bindin) as an important source of divergence between nominal species, and there are few other data to decide among the alternative hypotheses to explain Arbacia speciation.
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