Geography, environment and organismal traits in the diversification of a major tropical herbaceous angiosperm radiation

Abstract

The terrestrial bromeliads are a diverse group of plants native to the Americas. In this article, the distributions of 564 species are analysed to answer key questions about plant–environment interactions. Contrasting biological characteristics can explain the occurrence of different species in different climatic zones, and species native to arid zones appear to be particularly specialized. Species which are more tolerant of a range of climates tend to occur across larger geographical ranges, and closely related species in large genera tend to show differentiation in their climatic preferences.

Abstract

The generation of plant diversity involves complex interactions between geography, environment and organismal traits. Many macroevolutionary processes and emergent patterns have been identified in different plant groups through the study of spatial data, but rarely in the context of a large radiation of tropical herbaceous angiosperms. A powerful system for testing interrelated biogeographical hypotheses is provided by the terrestrial bromeliads, a Neotropical group of extensive ecological diversity and importance. In this investigation, distributional data for 564 species of terrestrial bromeliads were used to estimate variation in the position and width of species-level hydrological habitat occupancy and test six core hypotheses linking geography, environment and organismal traits. Taxonomic groups and functional types differed in hydrological habitat occupancy, modulated by convergent and divergent trait evolution, and with contrasting interactions with precipitation abundance and seasonality. Plant traits in the Bromeliaceae are intimately associated with bioclimatic differentiation, which is in turn strongly associated with variation in geographical range size and species richness. These results emphasize the ecological relevance of structural-functional innovation in a major plant radiation.