Considerations for maximizing the adaptive potential of restored coral populations in the western Atlantic

Abstract

Active coral restoration typically involves two interventions: crossing gametes to facilitate sexual larval propagation; and fragmenting, growing, and outplanting adult colonies to enhance asexual propagation. From an evolutionary perspective, the goal of these efforts is to establish self-sustaining, sexually reproducing coral populations that have sufficient genetic and phenotypic variation to adapt to changing environments. Here, we provide concrete guidelines to help restoration practitioners meet this goal for most Caribbean species of interest. To enable the persistence of coral populations exposed to severe selection pressure from many stressors, a mixed provenance strategy is suggested: genetically unique colonies (genets) should be sourced both locally as well as from more distant, environmentally distinct sites. Sourcing three to four genets per reef along environmental gradients should be sufficient to capture a majority of intraspecies genetic diversity. It is best for practitioners to propagate genets with one or more phenotypic traits that are predicted to be valuable in the future, such as low partial mortality, high wound healing rate, high skeletal growth rate, bleaching resilience, infectious disease resilience, and high sexual reproductive output. Some effort should also be reserved for underperforming genets because colonies that grow poorly in nurseries sometimes thrive once returned to the reef and may harbor genetic variants with as yet unrecognized value. Outplants should be clustered in groups of four to six genets to enable successful fertilization upon maturation. Current evidence indicates that translocating genets among distant reefs is unlikely to be problematic from a population genetic perspective but will likely provide substantial adaptive benefits. Similarly, inbreeding depression is not a concern given that current practices only raise first-generation offspring. Thus, proceeding with the proposed management strategies even in the absence of a detailed population genetic analysis of the focal species at sites targeted for restoration is the best course of action. These basic guidelines should help maximize the adaptive potential of reef-building corals facing a rapidly changing environment.

Coral bleaching patterns are the outcome of complex biological and environmental networking

“…(e.g., Camp, Schoepf, & Suggett, ). Developing tools that can identify coral populations with enhanced stress tolerance (Baums et al, ; Morikawa & Palumbi, ) or indeed the complex environmental networks that precondition enhanced survival (Camp, Schoepf, Mumby, et al, ) are undoubtedly a priority. Using knowledge of site‐specific differences in thermal histories has indeed proven central in the success of propagating coral populations more resistant to thermally induced bleaching (Morikawa & Palumbi, ), but how this can further scale to include other factors moderating bleaching severity will require more advanced environmental assessment capability.…”

Molecular tools for coral reef restoration: beyond biomarker discovery

“…Furthermore, given the substantial progress being made in the field of coral ecological genomics, additional candidates could be identified through a larger meta-analysis of currently published studies which quantify both '-omics' markers and phenotypes of interest. Such an analysis would be facilitated by establishing a broader genotype/phenotype database, similar to those currently available for model organisms (Gramates et al 2016) and planned for Acropora cervicornis and other Caribbean corals (Baums et al 2018). Because discovery is relatively easy and inexpensive, it should be viewed as an initial step in any biomarker project with application goals, not an end goal.…”

“…van Oppen et al 2015). One impediment to achieving this goal is the challenge of determining what readily quantifiable phenotypes are most indicative of resilience, and we refer readers to our companion review for more detailed consideration (Baums et al 2018). These restoration priorities have also spurred renewed interest in the development of simplistic assays, such as biomarkers (Box 1), which could provide managers with additional information to aid in outplant design.…”

Molecular tools for coral reef restoration: Beyond biomarker discovery

“…Growth and survival of outplants is highly variable, both among genotypes and reef sites (Bowden-Kerby, 2008;Drury, Manzello, & Lirman, 2017;Lirman et al, 2014), and practitioners currently have no way of reliably matching source corals with their optimum outplant destinations. Moreover, outplanting success does not necessarily equate to restoration of ecological function (Ladd, Burkepile, & Shantz, 2019) Although maximizing genetic diversity of restored coral populations is paramount (Baums et al, 2019), there is also a growing desire to identify and outplant the most resilient corals, such as those less susceptible to disease outbreaks or more tolerant of temperature stress (e.g., van Oppen, Oliver, Putnam, & Gates, 2015). One impediment to achieving this goal is determining what readily quantifiable phenotypes are most indicative of resilience (for more detailed consideration, see Baums et al, 2019).…”

“…Moreover, outplanting success does not necessarily equate to restoration of ecological function (Ladd, Burkepile, & Shantz, 2019) Although maximizing genetic diversity of restored coral populations is paramount (Baums et al, 2019), there is also a growing desire to identify and outplant the most resilient corals, such as those less susceptible to disease outbreaks or more tolerant of temperature stress (e.g., van Oppen, Oliver, Putnam, & Gates, 2015). One impediment to achieving this goal is determining what readily quantifiable phenotypes are most indicative of resilience (for more detailed consideration, see Baums et al, 2019). These restoration priorities have also spurred renewed interest in the development of simplistic assays, such as biomarkers (Box 1), which could provide managers with additional information to aid in outplant design.…”