Biotic and abiotic factors in promoting the starting point of hybridization in the Neotropical flora: implications for conservation in a changing world

Abstract

Abstract Coevolution between floral traits and specific pollination behaviour is a significant evolutionary force in angiosperm diversification. However, hybridization is also reported to occur between plants with specialist pollination syndromes. Understanding the role of pollinators in plant diversification is crucial, especially in megadiverse regions, such as the Neotropics. In this review, we examine plant hybridization studies in the Neotropics with the aim of providing a perspective on biotic and abiotic factors starting hybrid zone formation. The Pleistocene was the most widely cited time for the occurrence of hybridization facilitated by geographical range shifts, but time-calibrated analyses are needed to recover a more realistic scenario. Our synthesis of hybridization and pollination systems suggested that specialist and generalist pollinators were associated with the starting point of hybridization in the Neotropical flora. Bees and hummingbirds are most likely to be the primary vectors of interspecific gene flow, and even sporadic visits by bees or other generalist pollinators could allow the formation of a new hybrid zone. We highlight that seed and pollen dispersal vectors should be included in an integrative discussion on hybridization in the Neotropical flora. We also provide a preliminary map of hybrid zones in the Neotropics, including Brazilian vegetation cover and losses in the last 30 years, with the aim of encouraging research into human-driven anthropogenic changes and formation and/or shift of hybrid zones through time.