54.4 Saturday, Jan. 5 Understanding Connectivity of Acropora Corals Across Remote Islands Using Genetics and Biophysical Modeling DAVIES, S/W*; TREML, E; KENKEL, C/D; MATZ, M/V; University of Texas at Austin; The University of Queensland; University of Texas at Austin; University of Texas at Austin email@example.com
Many Indo-Pacific Acropora corals have species ranges that exceed thousands of kilometers. These ranges seem to contradict the growing consensus that dispersal distances of many marine species are less than previously assumed. Understanding larval dispersal is imperative to predicting population level responses to climate change. Few studies have looked into the connectivity among isolated reefs across large geographical scales. Knowledge of source-sink dynamics between remote reefs is important as they occur as discrete stepping-stones across large expanses, and extinctions of individual populations may have far-reaching demographic effects. Here we employ a spatially explicit biophysical model to predict larval dispersal between Micronesian islands. These predictions were then evaluated against genetic data and coalescent models of gene flow in two Acropora species. We analyzed twelve SSR loci across nearly 2000 individuals to determine connectivity patterns and the distribution of genetic diversity in Acropora hyacinthus and A. digitifera in Micronesia at different spatial scales, with samples from 22 reef sites across 9 island groups. Due to westerly equatorial Pacific Ocean currents, we hypothesized that genotypic diversity would decrease from west to east across Palau, the Caroline Islands and into the Marshall Islands, and that migration would predominantly be west to east. We observed strong genetic structure across Micronesia for both species with highly significant FST and isolation by distance signatures. However, dispersal routes modeled by the coalescent approach and the biophysical model are more complex than the simple isolation by distance model, which might help explain the extensive ranges of Acropora.