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The settlement of coral larvae is an important process which contributes to the success and longevity of coral reefs. Coral larvae often recruit to benthic structures covered with crustose coralline algae (CCA) which produce cues that promote settlement and metamorphosis. The PeysonneliaceaeRamicrustaspp. are red-brown encrusting alga that have recently become abundant on shallow Caribbean reefs, replacing CCA habitat, overgrowing corals and potentially threatening coral recruitment. In order to assess the threat ofRamicrustato coral recruitment, we compared the survival and settlement ofPorites astreoidesandFavia fragumlarvae to 0.5 – 2 mg ml-1solutions ofRamicrustasp. or CCA as well as sterile seawater (control). In all cases larval mortality was extremely high in theRamicrustatreatments compared to the CCA and control treatments. We found 96% (± 8.9% standard deviation, SD) mortality ofP. astreoideslarvae when exposed to solutions ofRamicrustaand 0 - 4% (± 0 - 8.9% SD) mortality in the CCA treatments. We observed 100%F. fragumlarval mortality when exposed toRamicrustaand 5 – 10% (± 10 – 20% SD) mortality in the CCA treatments. Settlement or surface interaction of larvae in the CCA treatments was 40 - 68% (± 22 - 37% SD) forP. astreoidesand 65 - 75% (± 10 - 19% SD) forF. fragum. TwoP. astreoideslarva that survivedRamicrustaexposure did settle/surface interact, suggesting that some larvae may be tolerant toRamicrusta. These results suggest thatRamicrustais a lethal threat to Caribbean coral recruitment.
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Brooding and parthenogenesis enhance the success of the coral Porites astreoides relative to Orbicella annularis
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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- Award ID(s):
- 2019992
- PAR ID:
- 10593603
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology
- Volume:
- 106
- Issue:
- 5
- ISSN:
- 0012-9658
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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