GENOMICS OF LOCAL ADAPTATION IN POPULATIONS OF ACROPORA MILLEPORA FROM THE GREAT BARRIER REEF
Local adaptation of coral populations inhabiting disparate reef environments could be the major source of genetic diversity to fuel rapid adaptation to climate change. To investigate this possibility, we performed genome scans using 2bRAD in populations of Acropora millepora from six locations along the Great Barrier Reef representing a variety of thermal and water quality conditions. We then undertook common garden and reciprocal transplantation experiments to see whether variation at the candidate loci identified by the genome scan were associated with fitness and/or gene expression variation among locations. The clearest genome scan signal, combining both high genetic divergence and elevated linkage disequilibrium, was obtained for two adjacent single-nucleotide polymorphisms (SNPs) located within a cluster of paralogous genes encoding delta-9 desaturases (d9d), enzymes that adjust the fluidity of biological membranes in response to ambient temperature. These SNPs formed a latitudinal gradient of allele frequency and were associated with elevated baseline expression of two d9d genes at a cooler, higher latitude, location. These genes also exhibited gene expression plasticity aligned with this baseline change: they were up-regulated in corals that were transplanted from a warmer to a cooler location. Thus, evolution of elevated baseline expression of these genes at a cooler location may represent a case of genetic assimilation, whereby regulatory adaptation is based on a pre-existing plastic response.
Barfield, S. J., University of Texas, Austin, USA, email@example.com
Kenkel, C. D., Australian Institute of Marine Science , Australia, C.Kenkel@aims.gov.au
Bay, L. K., Australian Institute of Marine Science , Australia, L.Bay@aims.gov.au
Matz, M. V., University of Texas, Austin, USA, firstname.lastname@example.org
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