Do the benefits of hybridization outweigh the costs under conditions of global change?

Patrick Krapf, Thomas Blankers, Jonna Kulmuni

Global change is predicted to facilitate hybridization but whether the hybrid populations persist and shape biodiversity remains unknown. At the grey zone, before speciation is completed, hybridization is likely leading to simultaneous costs and benefits for hybrid fitness. Whether the benefits outweigh the costs depends on the environment, as hybrid fitness, and potential incompatibilities, can be context dependent. However, hybrid fitness is rarely investigated in environmental conditions that simulate global change. Further knowledge gaps exist in understanding whether adaptive plasticity of hybrids and novel behaviours they may display can facilitate or hinder their persistence under conditions of global change. Previous work has discussed the impact of global change on the erosion of species barriers and persistence of parental lineages, but here we draw attention to the role of hybrids themselves and selective pressures acting on them. We predict that benefits of hybridization can outweigh the costs in scenarios where hybrid incompatibilities can be purged and the environment is sufficiently different from the parental environments. This can give hybrid populations an advantage due to their increased genetic diversity and plasticity to outcompete the parental species or establish in environments where the parental species cannot. Persistence of hybrid lineages over ecological and evolutionary time scales may help to preserve parental genetic diversity, especially in scenarios where parental species would go extinct.