Genetic Diversity and Connectivity in the Threatened Staghorn Coral (Acropora cervicornis) in Florida

Abstract

Over the past three decades, populations of the dominant shallow water Caribbean corals, Acropora cervicornis and A. palmata, have been devastated by white-band disease (WBD), resulting in the listing of both species as threatened under the U.S. Endangered Species Act. A key to conserving these threatened corals is understanding how their populations are genetically interconnected throughout the greater Caribbean. Genetic research has demonstrated that gene flow is regionally restricted across the Caribbean in both species. Yet, despite being an important site of coral reef research, little genetic data has been available for the Florida Acropora, especially for the staghorn coral, A. cervicornis. In this study, we present new mitochondrial DNA sequence data from 52 A. cervicornis individuals from 22 sites spread across the upper and lower Florida Keys, which suggest that Florida's A. cervicornis populations are highly genetically interconnected (FST = −0.081). Comparison between Florida and existing mtDNA data from six regional Caribbean populations indicates that Florida possesses high levels of standing genetic diversity (h = 0.824) relative to the rest of the greater Caribbean (h = 0.701±0.043). We find that the contemporary level of gene flow across the greater Caribbean, including Florida, is restricted ( = 0.117), but evidence from shared haplotypes suggests the Western Caribbean has historically been a source of genetic variation for Florida. Despite the current patchiness of A. cervicornis in Florida, the relatively high genetic diversity and connectivity within Florida suggest that this population may have sufficient genetic variation to be viable and resilient to environmental perturbation and disease. Limited genetic exchange across regional populations of the greater Caribbean, including Florida, indicates that conservation efforts for A. cervicornis should focus on maintaining and managing populations locally rather than relying on larval inputs from elsewhere.

Potential Habitat of Acropora spp. on Reefs of Florida, Puerto Rico, and the US Virgin Islands

“…Additionally, gene flow between populations has been found to be restricted, negatively contributing to the influence of WBD on many populations (Baums et al, 2010;Hemond and Vollmer, 2010;Vollmer and Palumbi, 2007). As in many locations, the losses of these two reef-building species have had lasting and widespread effects on reefs throughout Florida, Puerto Rico, and the US Virgin Islands (Rogers et al, 2008a,b).…”

Caribbean acroporid coral hybrids are viable across life history stages

“…This suggests that unidirectional low frequency gene flow occurs from A. palmata to A. cervicornis. Further mole cular studies discovered that unidirectional gene flow varies among loci and across geographic sites (Vollmer & Palumbi 2002, Hemond & Vollmer 2010. For example, the percent of the total A. cervicornis sequences found to be introgressed with A. palmata haplotypes varied across the Carib bean, e.g.…”

“…For example, the percent of the total A. cervicornis sequences found to be introgressed with A. palmata haplotypes varied across the Carib bean, e.g. 0% in Belize, 27% in Puerto Rico, 60% in Panama, and 68% in the Upper Florida Keys (Vollmer & Palumbi 2007, Hemond & Vollmer 2010. The lack of F2 hybrids and differential introgression across 4 sampled loci led Vollmer & Palumbi (2002) to speculate that postzygotic selection limits unidirectional introgression into A. cervicornis, albeit at different strengths across loci.…”

“…hybrid sterility, hybrid inviability, and hybrid breakdown) remain unclear. Based on molecular evidence of unidirectional introgression (Vollmer & Palumbi 2002, Hemond & Vollmer 2010, hybrids mate with A. cervicornis to form a backcross generation providing a conduit for genes to flow from A. palmata to A. cervicornis. Thus hybrid sterility can be ruled out, but the other two potential postzygotic barriers of hybrid inviability and breakdown have yet to be explored.…”

Genetic diversity of the Caribbean spiny lobster virus, Panulirus argus virus 1 (PaV1), and the ­discovery of PaV1 in lobster postlarvae

“…Parentage analysis using micro satellite markers, for example, has been performed in a variety of marine species, including oysters (Xiao et al 2011), clownfish (Planes et al 2009), sunfish (MacKiewicz et al 2002, and dolphins (Krützen et al 2004). Recent investigations of genetic diversity and connectivity between Florida and Carib bean staghorn coral Acropora cervicornis found shared mtDNA haplotypes between the western Caribbean and Florida despite the fact that the planktonic larval duration of A. cervicornis is only about 4 d (Hemond & Vollmer 2010). Potential sources of PaV1 to the Florida Keys include areas considered 'upstream' by current larval dispersal models .…”