Reproductive versatility of kelps in changing oceans

Kelp forests underpin enormous ecological, eco-nomic, and cultural values on temperate reefs glob-ally, yet are declining in many places (Krumhanslet al. 2016). Among the most prevalent cause ofdecline is climate-induced thermal stress, which isresulting in loss and range contractions for manykelp species (e.g., Verges et al. 2016, Wernberget al. 2016, Arafeh-Dalmau et al. 2019). While wehave an emerging understanding of how theseevents impact the macroscopic sporophyte stage,knowledge of how gametophytes perform underheat stress and how this varies across their range isscant (Harley et al. 2012, Muth et al. 2019) despitethis stage being critical to kelp persistence. One ofthe primary drivers of performance of natural popu-lations under stress is genetic diversity (Wernberget al. 2018), which is partly mediated by reproduc-tive traits such as inbreeding. Inbreeding can resultin reduced genetic diversity, adaptive capacity, andfitness. As such, many organisms have evolved mech-anisms to avoid mating with related individuals.