Genetic diversity of endangered Acropora spp. corals in Bonaire: implications for restoration and gene banking

Species restoration is a valuable tool to combat biodiversity loss. However, maintaining genetic diversity in species restoration is challenging, particularly for species that can reproduce asexually, such as plants and corals, because a seemingly diverse collection of individuals could be composed of many clones of a few genotypes. Caribbean elkhorn and staghorn corals (Acropora palmata, A. cervicornis) are critically endangered reef-building corals that are a major target for restoration. To better understand the genetic diversity of an Acropora spp. restoration program and interpret local population genetic structure, we conducted microsatellite genotyping on the gene banks of 35 A. palmata lineages and 25 A. cervicornis lineages maintained by Reef Renewal Foundation Bonaire (RRFB) in the Caribbean Netherlands. We found that RRFB had high genotypic richness for A. palmata (0.971) and A. cervicornis (1.0) and estimated that they captured 88.9% and 74.7% of Bonaires microsatellite asymptotic allelic diversity, respectively. Compared to populations of Acropora spp. studied in other locations across the Caribbean, A. palmata in Bonaire had relatively low expected heterozygosity, while A. cervicornis was greater than approximately half of other populations. Across Bonaire and for both coral species, we did not find evidence for genetic structuring among spatially separated subpopulations, indicating that both species are likely well-connected around the island. Together, these results demonstrate the effectiveness of RRFBs strategies to capture high genetic diversity and can be used to inform future initiatives on coral sexual breeding and assisted gene flow beyond Bonaire.