Genetic structure of a remnant Acropora cervicornis population

Abstract

Amongst the global decline of coral reefs, hope spots such as Cordelia Bank in Honduras, have been identified. This site contains dense, remnant thickets of the endangered species Acropora cervicornis, which local managers and conservation organizations view as a potential source population for coral restoration projects. The aim of this study was to determine the genetic diversity of colonies across three banks within the protected area. We identified low genetic diversity (F_ST = 0.02) across the three banks, and genetic similarity of colonies ranged from 91.3 to 95.8% between the banks. Clonality rates were approximately 30% across the three banks, however, each genotype identified was unique to each bank. Despite the low genetic diversity, subtle genetic differences within and among banks were demonstrated, and these dense thickets were shown not to be comprised of a single or a few genotypes. The presence of multiple genotypes suggests A. cervicornis colonies from these banks could be used to maintain and enhance genetic diversity in restoration projects. Management of hope spots, such as Cordelia Bank, and the incorporation of genetic information into restoration projects to ensure genetic diversity within out-planted populations, will be critical in the ongoing challenge of conserving and preserving coral reefs.

Figure 1

Map of the Honduran north shore, highlighting the location of Cordelia Bank Site of Special Importance to Wildlife, and the three banks with dense thickets of Acropora cervicornis, BC—Big Cay, CS—Cordelia Shoal, SB—Smith Bank, approximate sampling locations are indicated by red stars. Maps were created with R Studio version 1.2.1335 using satellite images provided by Google Maps.

Figure 2

Depth profiles of sampled Acropora cervicornis colonies and location of clones within the three banks of Cordelia Bank Site of Special Importance to Wildlife, each letter represents a unique ramet (clonal genotype).

Figure 3

STRUCTURE outputs for all genotypes (K = 2), mean of 10 permutations, for each colony within each of the banks (a); and the mean cluster classifications of all colonies within Big Cay (b); Cordelia Shoal (c); and Smith Bank (d). Blue—Cluster 1; and Orange—Cluster 2.