Aim: Genetic connectivity is a key component of species resilience to climate change in terms of recovery capacity following disturbance and capacity to disperse to novel locations as the climate warms and isotherms shift poleward. We aimed to strengthen our understanding of resilience in this context by characterizing patterns of connectivity and genetic diversity in a broadcast spawning coral across a tropical-temperate transition zone. We hypothesize genetic differentiation between tropical and temperate populations and decreasing genetic diversity with higher latitudes. Location: Western Australia (WA). Taxon: Turbinaria species complex. Turbinaria reniformis Oken, 1815 (Dendrophylliidae). Methods: Samples from 930 target corals were collected from ten locations between 13 - 32 o latitude spanning a 9° C mean temperature range. In-situ species identification of T. reniformis is hindered by morphological plasticity and homoplasy with sister species. We combined Sanger sequencing of two mitochondrial DNA markers and high-throughput genotyping by sequencing (GBS) to isolate a single genetic Turbinaria lineage from our dataset through which patterns of genetic flow and diversity along the WA coastline could be explored using population- and individual-based analyses. Results: Mitochondrial DNA sequence variation was low among Turbinaria samples and could not resolve individual species. Using GBS, we identified three genetically distinct lineages. Subsequent analyses within one of these lineages revealed strong spatial subdivision with 2-3 genetic clusters. While temperate populations were genetically diverged from more tropical sites, we did not observe declines in genetic diversity with latitude. Main Conclusions: Temperate coral populations in Western Australia are genetically isolated from their tropical counterparts. Tropical populations of T. ‘reniformis’ exhibit adequate connectivity. Shark Bay represents the current southern limit of the tropical population of T. ‘reniformis’. Interestingly, temperate T. ‘reniformis’ in this study exhibit some genetic resilience due to their relatively high genetic diversity, yet the strong patterns of genetic subdivision for this widely dispersing coral species potentially limit their resilience to future climate scenarios.
|Date made available||2021|