Conclusions and future studies
This study showed that maternal effects manifested as gene expression differences in interspecific hybrids of the coral A.tenuis and A. loripes . We also showed that maternal effects can persist to at least seven months of age in coral and were likely responsible for the phenotypes of F1 hybrids. However, exposure to elevated temperature and p CO2 conditions did not result in differential coral gene expression. Although the composition of bacterial and microalgal endosymbiont communities of these corals was similar under ambient and elevated conditions and between hybrids and purebreds (Chan et al., 2019), these microbes may have expressed different genes and contributed to holobiont phenotypic differences. Other less studied members of the coral holobiont, such as viruses and fungi (that were not examined), may also have contributed to coral survival and size differences. Further, post-transcriptional and epigenetic regulation (e.g., DNA methylation) may have varied between treatments and hybrid and purebreds and may have resulted in phenotypic differences (Dimond et al., 2017). Future studies will benefit from adopting a multi-omics approach and assessing other members of the coral-associated microbiome to explore other mechanisms that underpin the phenotype of the coral holobiont.