Ecological Load and Balancing Selection in Circumboreal Barnacles.

Affiliation

Nunez JCB(1), Rong S(1)(2), Damian-Serrano A(3), Burley JT(1)(4), Elyanow RG(2), Ferranti DA(1), Neil KB(1), Glenner H(5), Rosenblad MA(6), Blomberg A(6), Johannesson K(7), Rand DM(1)(2).
Author information:
(1)Department of Ecology and Evolutionary Biology, Brown University, Providence, RI.
(2)Center for Computational Molecular Biology, Brown University, Providence, RI.
(3)Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT.
(4)Institute at Brown for Environment and Society, Brown University, Providence, RI.
(5)Department of Biological Sciences, University of Bergen, Bergen, Norway.
(6)Department of Chemistry and Molecular Biology, University of Gothenburg, Lundberg Laboratory, Göteborg, Sweden.
(7)Department of Marine Sciences, University of Gothenburg, Tjärnö Marine Laboratory, Strömstad, Sweden.

Abstract

Acorn barnacle adults experience environmental heterogeneity at various spatial scales of their circumboreal habitat, raising the question of how adaptation to high environmental variability is maintained in the face of strong juvenile dispersal and mortality. Here, we show that 4% of genes in the barnacle genome experience balancing selection across the entire range of the species. Many of these genes harbor mutations maintained across 2 My of evolution between the Pacific and Atlantic oceans. These genes are involved in ion regulation, pain reception, and heat tolerance, functions which are essential in highly variable ecosystems. The data also reveal complex population structure within and between basins, driven by the trans-Arctic interchange and the last glaciation. Divergence between Atlantic and Pacific populations is high, foreshadowing the onset of allopatric speciation, and suggesting that balancing selection is strong enough to maintain functional variation for millions of years in the face of complex demography.

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