A restoration genetics guide for coral reef conservation

Abstract

Worldwide degradation of coral reef communities has prompted a surge in restoration efforts. They proceed largely without considering genetic factors because traditionally, coral populations have been regarded as open over large areas with little potential for local adaptation. Since, biophysical and molecular studies indicated that most populations are closed over shorter time and smaller spatial scales. Thus, it is justified to re-examine the potential for site adaptation in corals. There is ample evidence for differentiated populations, inbreeding, asexual reproduction and the occurrence of ecotypes, factors that may facilitate local adaptation. Discovery of widespread local adaptation would influence coral restoration projects mainly with regard to the physical and evolutionary distance from the source wild and/or captive bred propagules may be moved without causing a loss of fitness in the restored population. Proposed causes for loss of fitness as a result of (plant) restoration efforts include founder effects, genetic swamping, inbreeding and/or outbreeding depression. Direct evidence for any of these processes is scarce in reef corals due to a lack of model species that allow for testing over multiple generations and the separation of the relative contributions of algal symbionts and their coral hosts to the overall performance of the coral colony. This gap in our knowledge may be closed by employing novel population genetic and genomics approaches. The use of molecular tools may aid managers in the selection of appropriate propagule sources, guide spatial arrangement of transplants, and help in assessing the success of coral restoration projects by tracking the performance of transplants, thereby generating important data for future coral reef conservation and restoration projects.

Genetic variation in responses to a settlement cue and elevated temperature in the reef-building coral Acropora millepora

“…Diverse thermal tolerances are observed among genotypes of the symbiotic zooxanthellae (Robison & Warner 2006), and this variance has a profound impact on the thermal tolerance of corals associated with particular symbiont types (Rowan 2004, Berkelmans & van Oppen 2006. Despite this historical focus on symbionts, it is increasingly clear that thermal responses of corals are affected by both coral-and symbiont-specific factors (Abrego et al 2008), and data on both partners in the symbiosis will be required for effective modeling and management of coral populations (Baums 2008, Day et al 2008, Maynard et al 2008). …”

Alternate benthic assemblages on reef restoration structures and cascading effects on coral settlement

“…Recent advances in culture capacity and rescued 'caches' of coral material in the southern Florida region have increased interest in coral restocking. Such interest has raised additional management concerns, such as diluting potential small-scale genetic adaptation (Baums 2008) or the potential for introduction of harmful microbes to the natural reef environment, requiring directed research for accurate risk assessment.…”

Regional genetic differentiation among populations of Cladocora caespitosa in the Western Mediterranean

“…To improve our knowledge on the recovery potential of this bioconstructive species, a better understanding of the resilience of its populations is needed. Population genetic studies enable the estimation of the structure and connectivity of populations and the identification of associated processes, such as self-recruitment, barriers to gene flow, introgression, isolation, and fragmentation of populations (Baums 2008). It should be noted that these features are linked to species' life history traits, such as species' dispersal capacity at each stage of its life cycle, and their interaction with associated biotic and abiotic factors (DiBacco et al 2006).…”