Extraordinarily rapid life-history divergence between Cryptasterina sea star species |
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Authors: | Jonathan B Puritz Carson C Keever Jason A Addison Maria Byrne Michael W Hart Richard K Grosberg Robert J Toonen |
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Institution: | Hawai'i Institute of Marine Biology, University of Hawai'i, , PO Box 1346, Kāne'ohe, HI 96744, USA, Department of Biological Sciences, Simon Fraser University, , Burnaby, British Columbia, Canada , V5A 1S6, Center for Population Biology, College of Biological Sciences, University of California at Davis, , Davis, CA 95616, USA, Department of Biology, University of New Brunswick, , Fredericton, New Brunswick, Canada , E3B 5A3, Schools of Medical and Biological Sciences, University of Sydney, , New South Wales 2006, Australia. |
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Abstract: | Life history plays a critical role in governing microevolutionary processes such as gene flow and adaptation, as well as macroevolutionary processes such speciation. Here, we use multilocus phylogeographic analyses to examine a speciation event involving spectacular life-history differences between sister species of sea stars. Cryptasterina hystera has evolved a suite of derived life-history traits (including internal self-fertilization and brood protection) that differ from its sister species Cryptasterina pentagona, a gonochoric broadcast spawner. We show that these species have only been reproductively isolated for approximately 6000 years (95% highest posterior density of 905-22 628), and that this life-history change may be responsible for dramatic genetic consequences, including low nucleotide diversity, zero heterozygosity and no gene flow. The rapid divergence of these species rules out some mechanisms of isolation such as adaptation to microhabitats in sympatry, or slow divergence by genetic drift during prolonged isolation. We hypothesize that the large phenotypic differences between species relative to the short divergence time suggests that the life-history differences observed may be direct responses to disruptive selection between populations. We speculate that local environmental or demographic differences at the southern range margin are possible mechanisms of selection driving one of the fastest known marine speciation events. |
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Keywords: | brooding self-fertilization isolation-with-migration ecological speciation |
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