Abstract
Increases in local and global stressors have led to major declines in coral populations throughout the western Atlantic. While abundances of other species have declined, however, the relative abundance of the mustard hill coral, Porites astreoides, has increased. Porites astreoides is relatively resilient to some stressors, and because of its mixed reproductive strategies, its populations often recover quickly following disturbances. The ability for P. astreoides to continue as a potential “winner” in western Atlantic reefs relies on maintaining sufficient genetic variation within populations to support acclimatization and adaptation to current and future environmental change. Without high genetic diversity and gene flow within the population, it would have limited capacity for adaptation and the species’ competitive advantages could be short-lived. In this study, we determined the genetic relatedness of 37 P. astreoides colonies at four shallow reefs along the offshore Florida Keys Reef Tract (FKRT), a region particularly hard-hit by recent disturbances. Using previously designed microsatellite markers, we determined the genetic diversity and connectivity of individuals among and between sites. Our results suggest that the FKRT likely contains a single, well-mixed genetic population of P. astreoides, with high levels of gene flow and evidence for larval migration throughout the region. This suggests that regional populations of P. astreoides likely have a higher chance of maintaining resilience than many other western Atlantic species as they face current and future disturbances.
Highlights
Coral reefs provide a variety of important ecosystem services including supporting marine biodiversity (Harborne et al 2006; Pratchett et al 2014; Fisher et al 2015), engineering habitat for marine organisms (Mumby et al 2008; Pratchett et al 2014), and transferring energy through trophic levels (Moberg and Folke 1999; Woodhead et al 2019)
Met this threshold in all but one pairwise comparison: Fowey Rocks and Pulaski Shoal. Comparisons between these two populations may be underpowered and not fully represent the potential genetic diversity and variation that is present. These results suggest that despite the relatively low sample size in our study, we had sufficient power to make general inferences about the genetic structure of populations of P. astreoides in the Florida Keys
We found that all loci in our P. astreoides samples conformed to Hardy–Weinberg Equilibrium (HWE), indicating that the major assumptions of the Hardy–Weinberg principle—a large population size, random mating, no net mutations, no migration between populations, and no net selection (Chen 2010)—have been met for this population
Summary
Coral reefs provide a variety of important ecosystem services including supporting marine biodiversity (Harborne et al 2006; Pratchett et al 2014; Fisher et al 2015), engineering habitat for marine organisms (Mumby et al 2008; Pratchett et al 2014), and transferring energy through trophic levels (Moberg and Folke 1999; Woodhead et al 2019). Mānoa 96744, USA 5 Sea Grant College Program, University of Hawai’i At Mānoa, coral reefs create complex, coastal geological structures (Moberg and Folke 1999; Spalding et al 2014; Kuffner and Toth 2016) that can reduce wave energy and decrease erosion and storm damage on reef-lined coasts (Spalding et al 2014; Storlazzi et al 2019). In the western Atlantic, there have been major shifts in reef composition from dominance of large, reef-building corals, such as Orbicella and Acropora spp., to small nonreef-building “weedy” corals (Darling et al 2012; sensu Knowlton, 2001) such as P. astreoides (González-Barrios and Álvarez-Filip 2018; Toth et al 2019; Courtney et al 2020) and other non-calcifying, benthic-dwelling organisms (Ruzicka et al 2013; Lenz et al 2015). There is evidence that shifts from reefs dominated by Acropora and Orbicella to weedy taxa can result in significant losses in communitywide calcification and reef rugosity (Alvarez-Filip et al. Vol.:(0123456789)
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