Restricted Gene Flow in the Caribbean Staghorn Coral Acropora cervicornis: Implications for the Recovery of Endangered Reefs

Abstract

Coral reef conservation requires information about the distance over which healthy reefs can rescue damaged reefs through input of coral larvae. This information is desperately needed in the Caribbean where the 2 dominant shallow water corals Acropora cervicornis and Acropora palmata have suffered unprecedented declines. Here we compare the population genetic structure in the staghorn coral A. cervicornis across the greater Caribbean using DNA sequence data from 1 mitochondrial and 3 nuclear genes. Data from 160 individuals from 22 populations and 9 regions show that A. cervicornis exhibits significant population genetic structure across the greater Caribbean in both the mitochondrial (Phi(st) = 0.130) and nuclear data (Phi(st) = 0.067). The highest population structure was observed in the species' own, native mtDNA haplotypes (Phi(st) = 0.235). Introgressed alleles from A. palmata tempered higher population structure in A. cervicornis over regional scales but in some cases generated highly localized "introgression hot spots" and fine-scale genetic structure among reefs separated by as few as 2 km. These data show that larval dispersal over moderate or long distances (>500 km) is limited for this threatened species and in some cases locally limited as well. Thus, the endangered Caribbean staghorn corals require local source populations for their recovery and targeted conservation efforts over spatial scales much smaller than the hundreds to thousands of kilometers usually proposed for marine reserves.

Patrones a gran escala del reclutamiento de coral en Isla Mona, Puerto Rico: evidencia de una trayectoria transitoria de comunidad después del blanqueamiento y mortalidad coralino masivo

“…Therefore, genetic isolation due to the oceanographic barrier associated to strong surface currents across the Mona Channel between La Hispaniola and Puerto Rico play a critical role in maintaining high genetic structuring and rendering isolated coral reefs to largely rely on remnant colony regrowth, colony fragmentation, and self-recruitment for their natural recovery from disturbance. Long-distance coral larval dispersal is an unusual event (Baums et al, 2005;Vollmer & Palumbi, 2007;García-Reyes & Schizas, 2010;Mège et al, 2014) and suggest the paramount importance of replenishing rapidly declining coral reefs though a combination of novel efforts focused on ecosystem-based approaches (i.e., managing food webs, enhancing herbivory, increasing percent cover CCA, and improving coral reproductive stocks). Replenishment of depleted coral engineer species will require immediate novel efforts (i.e., low-tech coral farming) to rehabilitate their populations.…”

“…Genetic connectivity also plays a critical role in natural coral reef recovery (Zubillaga, Márquez, Cróquer & Bastidas, 2008). But populations for many important coral species, particularly across the Caribbean, show high genetic structuring implying that long-distance larval dispersal is an unusual event (Baums et al, 2005;Vollmer & Palumbi, 2007;García-Reyes & Schizas, 2010;Mège, Schizas, García-Reyes & Hrbek, 2014), rendering isolated coral reefs to largely rely on remnant colony regrowth, colony fragmentation, and self-recruitment for their natural recovery from disturbance. Nonetheless, there is still scarce information regarding remote coral reef natural recovery rates and the trajectory followed by benthic communities impacted from disturbance.…”

Caribbean acroporid coral hybrids are viable across life history stages

“…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.…”

Active adaptive conservation of threatened species in the face of uncertainty

“…Many threatened species now only persist in a small number of relatively isolated subpopulations (Harrison and Bruna 1999) and numerous management programs worldwide distribute resources between subpopulations in an attempt to ensure the persistence of threatened species (e.g., Sumatran tiger, Panthera tigris sumatrae [Linkie et al 2006]; Gunnison's Sage Grouse, Centrocerus minimus [Oyler-McCance et al 2001]; the golden lion tamarin, Leontopithecus rosalia [Pinto and Rylands 1997]; Caribbean staghorn coral, Acropora cervicornis [Vollmer and Palumbi 2007]; and Japanese woodland primula, Primula sieboldii [Washitani et al 2005]). Predictably, the number of subpopulations or areas available to implement management actions affects how learning can take place.…”