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Comparing directions of Acropora coral adaptive response to environmental gradients
  • Sofia Beskid,
  • Mikhail Matz
Sofia Beskid
The University of Texas at Austin

Corresponding Author:[email protected]

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Mikhail Matz
The University of Texas at Austin
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Abstract

As climate change progresses, reef-building corals face multiple environmental stressors that they must adapt to. Can corals adapt to all these stressors at the same time, or would some adaptations exclude others (i.e., a genetic tradeoff)? Here, we reanalyzed RNA-seq and Tag-seq data from four studies that compared gene expression in corals from tidal pools of different daily heat stress levels, with varying proximity to a CO2 seep, containing different kinds of algal symbionts, and separated by 15 degrees of latitude. We computed both the genetic divergence (FST) and log-fold expression change per gene for each contrast, and then compared these results to see whether the same genes were involved in adaptation and/or acclimatization to different environmental gradients. We find that genetic divergence patterns are entirely independent from each other (with the exception of just two shared FST outliers between the two cases of CO2 adaptation), while at the gene expression level there is significant overlap in up- and down-regulated genes among multiple environmental contrasts. These results suggest that coral populations maximize their local fitness predominantly via gene expression plasticity (involving similar pathways) rather than through selection-driven genetic divergence. Still, there remains the possibility of highly polygenic adaptation with extensive redundancy (many alternative genetic ways to achieve the same phenotype). Regardless of the mechanism, the overall lack of tradeoffs that we observed here suggests that corals have substantial capacity to withstand multiple simultaneous stressors.