Climate-change-induced species redistribution has the potential to bring isolated species into contact, leading to increased rates of hybridization. While interspecific hybridization may be seen as a risk to local population identities, it can also lead to outcomes whereby hybrid offspring have novel features that can maximize their survival under global change. Transgressive phenotypes — in which offspring have extreme features that are stronger or weaker than either parent — have been studied extensively in crop breeding contexts, but remain largely unexplored in wild populations.
Lindsey Schwartz from the University of South Carolina, USA, and colleagues from the USA and UK, investigated gene expression plasticity — the ability to alter gene expression in response to environmental change — in blue mussel parental species and hybrids under a warming regime. They find that 50% of genes show expression plasticity similar to one of the two parental species, and just 2% are classified as intermediate. However, 26% of genes show transgressive expression plasticity that is either greater or lesser than either parent species. While further experimentation is needed to verify these changes at the phenotype and fitness levels, such transgressive expression could lead to better or worse tolerance to stress.
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