Abstract Summary
The contemporary distribution of Acropora cervicornis includes dispersed, isolated colonies and very dense interlocking assemblages called thickets that may cover hectares of the bottom. The density of thickets and sessile nature of corals creates the opportunity for ongoing interactions between genets which occur across a range of potential relatedness values. This type of interaction influences resistance, resilience and associated community function in other ecosystems. Using next generation sequencing data and field observations we document a positive relationship between genetic diversity and coral cover. This pattern does not appear to relate to growth, but may be due to changes in fragmentation mortality or disturbance response. In the Florida Keys, one thicket with observations during the 2015 bleaching event fared better than outplanted corals on the same reef and discrete colonies monitored as part of a region-wide survey (FRRP). Thickets (n=4) observed in Florida and The Dominican Republic contained between 13 and 30 genotypes, with clones distributed from 0-12m across the substrate, however some observed areas were nearly monoclonal. These data highlight the natural patterns of thickets which may be replicated during restoration in an attempt to gain added biomass or stress resistance from emergent properties of high-density assemblages.
