Genotype by environment interactions in coral bleaching

Abstract

Climate-driven reef decline has prompted the development of next-generation coral conservation strategies, many of which hinge on the movement of adaptive variation across genetic and environmental gradients. This process is limited by our understanding of how genetic and genotypic drivers of coral bleaching will manifest in different environmental conditions. We reciprocally transplanted 10 genotypes ofAcropora cervicornisacross eight sites along a 60 km span of the Florida Reef Tract and documented significant genotype × environment interactions in bleaching response during the severe 2015 bleaching event. Performance relative to site mean was significantly different between genotypes and can be mostly explained by ensemble models of correlations with genetic markers. The high explanatory power was driven by significant enrichment of loci associated DNA repair, cell signalling and apoptosis. No genotypes performed above (or below) bleaching average at all sites, so genomic predictors can provide practitioners with ‘confidence intervals' about the chance of success in novel habitats. These data have important implications for assisted gene flow and managed relocation, and their integration with traditional active restoration.

Signatures of Adaptation and Acclimatization to Reef Flat and Slope Habitats in the Coral Pocillopora damicornis

“…Predictions of coral trait-related fitness in time and space require carefully designed field and lab experiments. Here, we show that replicate RTEs might yield differing population-byhabitat interactions, and other replicated experiments have also uncovered variation in physiological performance among sites (e.g., Drury and Lirman, 2021). The physiological differences between the Canyons and Gardens reef sites at Heron Island may be due to local environmental conditions such as hydrodynamic conditions and/or the coral tissue-associated prokaryote community.…”

“…Genetically based variation in fitness is fuel for natural or artificial selection to promote performance under local prevailing conditions. Bleaching tolerance to thermal stress has a strong genetic basis in acroporid corals (Oliver and Palumbi, 2011;Howells et al, 2013;Bay and Palumbi, 2014;Dixon et al, 2015;Drury and Lirman, 2021) and Platygyra sp. (Elder et al, 2020), and here we extend knowledge to a representative of the genus Pocillopora.…”

“…Reciprocal transplantation also revealed adaptive divergence among depth habitats in the coral species Seriatopora hystrix (Bongaerts et al, 2011), as well as the octocoral species Eunicea flexuosa (Prada and Hellberg, 2013) and Briareum asbestinum (West et al, 1993). Most recently, Acropora cervicornis genotypes reciprocally transplanted among numerous replicate reef sites with different thermal regimes in the Florida Reef Tract indicated G × E interactions for bleaching tolerance, where the greatest variability in bleaching tolerance among genotypes was within each site, and no genotype had superior bleaching tolerance in all transplant locations (Drury and Lirman, 2021). Studies of reciprocal transplantation of corals continue to reveal that performance is affected by environmental conditions, but varies significantly by colony, highlighting the need to expand replicate RTEs among small spatial scales to elucidate colony differences.…”

“…Local adaptation is inferred when natives outperform foreign transplants (Blanquart et al, 2013;Savolainen et al, 2013), and acclimatization of a population manifests shifts in performance toward the locals in the novel environment and consequently outperforms its conspecifics that remained at the native environment (Kawecki and Ebert, 2004;Henn et al, 2018). The physiological responses of multiple populations to reciprocal transplantation may be coupled with genetic data to explore genotype-by-environment (G × E) interactions (Blanquart et al, 2013;Drury and Lirman, 2021).…”

Census of heat tolerance among Florida's threatened staghorn corals finds resilient individuals throughout existing nursery populations

“…Overcoming these challenges requires a better understanding of the natural variation in coral heat tolerance, the distribution of heat-tolerant genotypes and phenotypes and the degree to which heat tolerance is determined by a coral's genes, symbiotic interactions and environment. There is extensive variation in coral heat tolerance across latitudinal and environmental gradients [19][20][21][22][23][24][25], with populations from warmer locations having higher tolerance. However, such differences can also occur over reefal scales of just 10s to 100s of metres [26][27][28], indicating strong selection across habitats and microenvironments over small spatial scales, and/or an important role for acclimatization [29,30].…”