Seasonal variation on DNA methylation patterns in the staghorn coral Acropora cervicornis in Culebra Island, PR.

Seasonal cues can have profound effects on organism’s physiology and transcriptional outcomes. DNA methylation has been proposed to mediate responses to environmental change in a wide range of organisms. However, we are still far from understanding the dynamicity of this mechanism in natural conditions, the correlation (or lack off) with different environmental factors, and the resulting transcriptional outcomes. This is particularly critical for the study of the response of stony corals to the effects of climate change. Corals have experienced dramatic declines worldwide and there is an urgent need to understand their capacity to respond and acclimate to these stressors. Here, we evaluate DNA methylation changes in the staghorn coral (Acropora cervicornis) during a 17-month field experiment in Culebra Island, PR. Two hundred fragments rescued after Sep 2017 hurricanes were stabilized by direct outplanting in 4 experimental sites (two reefs, two depth) maintaining replicated genotypes in all sites. DNA methylation was assessed through Methyl Sensitive Amplification Polymorphism (MSAP) in samples collected through the experiment and analyzed in relationship with site- and time-specific environmental parameters (temperature, light, etc.) constantly measured. Our results indicate the presence of a marked seasonal patterns of DNA methylation across sites. Such changes are primarily driven by temperature and, in a lower extent, by light. We observed no influence of the genotype, the outplant site or source reef of the fragments in the methylation loci showing seasonal variation. These results evidence the importance of defining a baseline of natural variation in DNA methylation in order to be able to apply these techniques to identify threats and predict ecological outcomes in natural populations of this species.