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Abstract The abundance of many Caribbean corals has declined over the past few decades, yet nowPorites astreoidesis more common on many shallow reefs than in the 1980s and shows evidence of local adaptation. We compare the small‐scale (1–8000 m) genetic structure of this brooding species and the broadcasting coralOrbicella annularison reefs (<14 m depth) in St. John, US Virgin Islands, to examine how larval dispersal and asexual propagation contribute to the retention of genotypes within reefs. Populations ofP. astreoideshave genetic structure across reefs separated by a few 100 m, increased relatedness within reefs, and parthenogenetic larval propagation confirmed by parent–offspring genotyping. Within reefs,P. astreoidescolonies <1 m apart are more related, independent of clonal reproduction, than corals at greater distances. In contrast,O. annularislacks across‐reef genetic structure, has low relatedness within and among reefs, and does not produce asexual larvae. Small‐scale genetic structure and high relatedness inP. astreoidesare evident even without considering asexual propagation, but asexual reproduction enhances these differences. Neither species shows the genetic signature of inbreeding or reduced genotypic diversity despite the high within‐site relatedness ofP. astreoides. Monitoring on these reefs from 1987 indicates thatPoriteshas increased in abundance whileOrbicellahas decreased in abundance. The success ofPoritesis due to greatly increased settlement and recruitment compared withOrbicella. Together these results indicate that high numbers of locally retained and successful genotypes might explain the relative success ofPoriteson shallow, present‐day reefs in the Caribbean.
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Small‐scale genetic structure of coral populations in Palau based on whole mitochondrial genomes: Implications for future coral resilience
Abstract The ability of local populations to adapt to future climate conditions is facilitated by a balance between short range dispersal allowing local buildup of adaptively beneficial alleles, and longer dispersal moving these alleles throughout the species range. Reef building corals have relatively low dispersal larvae, but most population genetic studies show differentiation only over 100s of km. Here, we report full mitochondrial genome sequences from 284 tabletop corals (Acropora hyacinthus) from 39 patch reefs in Palau, and show two signals of genetic structure across reef scales from 1 to 55 km. First, divergent mitochondrial DNA haplotypes exist in different proportions from reef to reef, causing PhiSTvalues of 0.02 (p = 0.02). Second, closely related sequences of mitochondrial Haplogroups are more likely to be co‐located on the same reefs than expected by chance alone. We also compared these sequences to prior data on 155 colonies from American Samoa. In these comparisons, many Haplogroups in Palau were disproportionately represented or absent in American Samoa, and inter‐regional PhiST = 0.259. However, we saw three instances of identical mitochondrial genomes between locations. Together, these data sets suggest two features of coral dispersal revealed by occurrence patterns in highly similar mitochondrial genomes. First, the Palau‐American Samoa data suggest that long distance dispersal in corals is rare, as expected, but that it is common enough to deliver identical mitochondrial genomes across the Pacific. Second, higher than expected co‐occurrence of Haplogroups on the same Palau reefs suggests greater retention of coral larvae on local reefs than predicted by many current oceanographic models of larval movement. Increased attention to local scales of coral genetic structure, dispersal, and selection may help increase the accuracy of models of future adaptation of corals and of assisted migration as a reef resilience intervention.
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- Award ID(s):
- 1736736
- PAR ID:
- 10477043
- Publisher / Repository:
- Evol. Applications
- Date Published:
- Journal Name:
- Evolutionary Applications
- Volume:
- 16
- Issue:
- 2
- ISSN:
- 1752-4571
- Page Range / eLocation ID:
- 518 to 529
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/eva.13509
