Divergence time shapes gene reuse during repeated adaptation.

Repeated adaptation, also known as parallel or convergent evolution, occurs when different lineages successfully respond to similar environmental challenges. If the same genes are used by independent lineages during repeated adaptation ('gene reuse'), the genetic basis of adaptation might be predictable. Recent genomic studies have highlighted that there is variability in the extent of gene reuse among lineages experiencing repeated adaptation. Divergence time is a promising factor influencing variation in gene reuse in repeated adaptation, as it drives the diversification of shared genetic variation, genome structure, and gene functions among lineages. Genomic studies of repeated adaptation support the idea that gene reuse decreases with increasing divergence time. However, the relationship is complex, emphasizing the need for additional research to better understand evolutionary repeatability. When diverse lineages repeatedly adapt to similar environmental challenges, the extent to which the same genes are involved (gene reuse) varies across systems. We propose that divergence time among lineages is a key factor driving this variability: as lineages diverge, the extent of gene reuse should decrease due to reductions in allele sharing, functional differentiation among genes, and restructuring of genome architecture. Indeed, we show that many genomic studies of repeated adaptation find that more recently diverged lineages exhibit higher gene reuse during repeated adaptation, but the relationship becomes less clear at older divergence time scales. Thus, future research should explore the factors shaping gene reuse and their interplay across broad divergence time scales for a deeper understanding of evolutionary repeatability. [ABSTRACT FROM AUTHOR]