The Evolutionary Legacy of Al Gentry: Uniting Patterns and Processes of Neotropical Rainforest Evolution

Abstract

Alwyn Gentry had unique insights into the diversity of Neotropical rainforests. He observed plant diversity with incredible detail and used the data he and colleagues collected to answer questions on the distribution, ecology, and evolutionary origins of tropical rainforest diversity. Leaning on patterns of species distributions accumulated from intense fieldwork, Gentry discussed numerous ideas and proposed important hypotheses on the evolution of Neotropical rainforests. However, he never advanced these evolutionary ideas in a unified and consistent framework across all scales he treated. For instance, comparing intercontinental differences in rainforest taxa, he suggested Neotropical forests to be “uniquely and phenomenally enriched” compared to other rainforests. This he attributed, among other factors, to increased speciation especially in Andean-centered taxa, linked both directly and indirectly to the uplift of the northern Andes. Even at the smallest scales, he put forward specific hypotheses on the processes of speciation in the Neotropics, ranging from specialization to edaphic conditions in Amazonia to founder-effect–mediated speciation in the Andes. The ensemble of hypotheses and ideas proposed by Gentry on tropical and Neotropical plant evolution, his evolutionary legacy, remains relevant even today. Despite this, many of his contributions may not have received the attention they rightly deserve. Overall, those hypotheses put forward by Gentry that have been tested are well supported, in particular the ones concerning regional and intercontinental scale processes. However, many of his smaller-scale hypotheses have not been tested to our knowledge, or remain inconclusive, highlighting significant knowledge gaps in our understanding of tropical rainforest diversity and evolution. Furthermore, his work and thinking, 30 years on, emphasize significant biases in our current understanding, that being concentrated on large woody plants and specific taxa. Contrary to this, Gentry’s perspective is refreshingly encompassing, not being limited to specific taxa or growth forms. To consolidate and underline his important contributions to tropical plant evolution, we summarize and assemble Al Gentry’s evolutionary ideas and hypotheses here. Leveraging his comprehensive view of tropical rainforest diversity, his ideas provide succinct starting points for future research across disciplines on the ecology and evolution of tropical rainforests.