Hybridization: a 'double-edged sword' for Neotropical plant diversity

Hybridization can facilitate both evolutionary diversification and extinction and has had a critical role in plant evolution, with c. 25% of species known to hybridize in some temperate floras. However, in the species-rich Neotropical flora, the role of hybridization in the evolution of diversity remains unclear. Our review examines studies of hybridization in seed plants from across the Neotropics and explores its outcomes on Neotropical plant evolution. We review studies on a per-biome basis and a spectrum of evolutionary outcomes from hybridization are evident across Neotropical biomes and taxa. These range from short-term impacts, such as the broadening of ecological amplitude in hybrid progeny with transgressive phenotypes and genetic swamping, through to long term impacts, such as the generation of new lineages. Among these studies certain themes emerge, such as the pervasive hybridization among species-rich plant radiations from the Andean paramos, suggesting a role for hybridization in rapid diversification events. Finally, we highlight that hybridization is relatively understudied in the Neotropical flora, despite its remarkable species richness. The advent of genomic techniques can facilitate the study of hybridization and its effects in understudied biomes and plant groups. The increasing availability of genomic resources will eventually allow comparisons between tropical and temperate floras and therefore shed light on the evolutionary impacts of hybridization across the latitudinal biodiversity gradient.