A Research Review of Interventions to Increase the Persistence and Resilience of Coral Reefs (2019) / Chapter Skim
Currently Skimming:
4 Coral Population and Community Interventions
4 Coral Population and Community Interventions
Pages 119-142
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From page 119... ...
. Assisted gene flow supports the expansion of resilient genotypes within a coral's current range.
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From page 120... ...
As a result, managing coral communities is more than just managing corals: Though corals play a fundamental role, management of other species is also important. Maintaining ecological processes and community dynamics has been identified as an important factor in facilitating coral restoration success (Ladd et al., 2018; Shaver et al., 2018)
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From page 121... ...
. Assisted gene flow typically focuses on the relocation of individuals with genotypes that confer higher stress tolerance, which requires that populations exhibit genetically-based variation in stress tolerance across locations with different historical levels of stress exposure.
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. Assisted migration (also called assisted colonization)
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In addition to the two overarching goals that can apply to all relocations, proximate goals vary with relocation type. For assisted gene flow, a key proximate goal is to enhance the spread of stress-tolerant alleles and their transmission into the next generation.
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. For introduction to new areas, a key proximate goal is to enhance stress tolerance of the local reef assemblage by adding species at the recipient location.
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. The Decision to Translocate Managed relocation is relevant when limited dispersal, slow population growth, small populations, or fragmented habitat distribution impede natural movement responses to climate change or other such stressors (Hewitt et al., 2011)
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, genetic drift (random loss of genetic diversity at low population sizes) , and inbreeding (exposure of deleterious recessive alleles in small populations)
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is reversed. Relocations to advance the gene flow of adaptive alleles into a healthy population with fewer local stressors, lower algal cover, and more abundant and diverse herbivore communities may be more successful.
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. For assisted migration, coral morphology can also be an indicator of major coral taxa that generally show high stress tolerance or susceptibility.
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. How to Identify Source and Target Locations The target location depends on the relocation type and goal.
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A further consideration is connectivity between sites. Promoting range shifts through assisted gene flow or assisted migration relies on connectivity between reefs and therefore might focus on target locations that confer connectivity to downstream reefs (e.g., across environmental gradients)
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Specifically, new restoration projects taking place at highly degraded sites, which are increasing in the Caribbean (Young et al., 2012) , might present unique opportunities to engage in all types of managed relocation by focusing on sources from either more stress-tolerant populations or with a diversity of stress tolerances or stress histories (Broadhurst et al., 2008; Rice and Emery, 2003; Sgrò et al., 2011)
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From page 132... ...
. The cost and complexity will inevitably increase with the project scale in terms of distance transport, number of colonies moved, and number of repeated transports, such that we expect the feasibility of assisted gene flow and assisted migration to be significantly less than that of introduction to new areas (as depicted in Figure 4.1)
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From page 133... ...
Identification of dispersal-limited species, an indicator of both climate vulnerability and the relevance of managed relocation, through genetic data and/or oceanographic models of larval dispersal is feasible but requires investment. For identifying species with low thermal tolerance, dispersal limitation, or other such indicators of vulnerability, the Coral Traits Database (coraltraits.org; Madin et al., 2016)
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. Second, while stress tolerances such as thermal tolerance and disease resistance are holobiont properties that arise from a combination of the coral host, symbiotic zooxanthellae, and microbiome, their relative contributions are typically unresolved.
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. Typically the distinction between relocation types is based on the spatial scale of a species range, but many coral species' boundaries span entire (and sometimes multiple)
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The value of active relocation is also dependent on the stress tolerance (for assisted gene flow) and natural dispersal capabilities of these organisms.
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, means that local-scale movement has the potential to enhance disease spread. Compared to invasiveness of associated organisms and diseases, invasiveness of the translocated coral type or species might pose less of a risk for coral reefs.
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Relocation of zooxanthellae and the microbiome associated with a coral host might be a component of managed relocation goals given that stress tolerance and disease resistance are holobiont properties (Baker, 2003; Baker et al., 2004; Berkelmans and van Oppen, 2006; Teplitski and Ritchie, 2009; Ziegler et al., 2017) , but spread of these associated organisms to other corals in the target location might alter the co-evolutionary relationships between corals and their symbionts.
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From page 139... ...
. First, assisted gene flow to the wrong place or at the wrong time might incur "gene swamping," where the input of translocated maladapted genes may dominate over existing better-adapted genes, with a decline in total genetic variation across locations.
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From page 140... ...
. Using local eggs with nonlocal sperm in assisted gene flow would eliminate the risk of accidentally introducing diseases or invasive species from associated organisms, as well as reduce the risks of gene swamping and disruption of local adaptation to nonclimatic factors.
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From page 141... ...
or knowledge availability (e.g., increased knowledge of relative plastic and genetic, and relative coral, zooxanthellae, and microbiome contribution to thermal tolerance can reduce the likelihood of no conference of stress tolerance between source and target locations) , while others are irreducible (e.g., storm events following relocation)
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From page 142... ...
Beyond the technical infrastructure, additional requirements arise from gathering the data necessary for the managed relocation decisionmaking process and monitoring. Aspects of the decision-making process that require site, system, or species-specific data include identification of target species, locations, and timing of relocation as well as assessment of risks such as accidentally invasive species and pathogens.
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