Meeting Abstract
Recent advances in population genomics have facilitated the discovery of adaptive divergence of marine organisms across contrasting environmental conditions at unexpectedly small geographic scales despite their high potential for gene flow. Acropora hyacinthus, a broadcast spawning reef-building coral, is highly dispersive and can populate environmentally distinct reef zones: the backreef (i.e. greater diel variability in temperature, light, and other factors) and forereef (i.e. proximate to open ocean; more stable environmental conditions). Adaptive genomic divergence across habitats could allow these corals to thrive in both environments. Alternatively, these divergent environments could select for different communities of algal symbionts (Symbiodiniaceae) that influence host performance. Here, we sampled A. hyacinthus colonies at paired backreef-forereef sites off the French Polynesian islands of Moorea (two paired sites) and Tahiti (one paired site). We performed 2b-RAD genome-wide de novo genotyping to examine host genetic divergence and metabarcoding of the ITS-2 locus to characterize symbiont community composition. Our results suggest that while subtle genetic structure exists between islands (Tahiti vs. Moorea), no significant population structure in coral hosts between reef zones was observed. However, our analyses of potential loci under selection in the host genome between reef zones are ongoing. Lastly, algal symbiont community compositions across all sites and reef zones were homogenous. Although our ongoing genomic analyses will provide further insight, our current results suggest that acclimatization may play a more significant role than host genetic structure and algal symbiont communities in coping with divergent reef zones in this dispersive coral species.
