Distinct routes to parallel adaptation in a mountain plant.

It is a common observation that distinct lineages adapt to similar environments through similar 'parallel' changes in phenotype. Less clear is whether parallel phenotypic change evolves through genetic variation in the same or distinct genes. This question of redundancy-the number of genetic answers to the same evolutionary problem-is an important yet poorly-understood feature of adaptive traits, and is a major hurdle in our transition from understanding evolutionary responses to predicting them. In this issue of Molecular Ecology, Szukala, Lovegrove-Walsh, et al., (2022) examine the redundancy of local adaptation in montane and alpine ecotypes that has occurred in the flowering plant Heliosperma pusillum. By comparing gene expression in each of four montane or alpine-adapted H. pusillum population pairs, the authors observe distinct genetic responses underlying each case of parallel local adaptation.