Evolutionary diversity in tropical tree communities peaks at intermediate precipitation
Danilo M. Neves, Kyle G. Dexter, Timothy R. Baker, Fernanda Coelho de Souza, Ary Teixeira de Oliveira‐Filho, Luciano Paganucci de Queiroz, Haroldo C. de Lima, Marcelo Fragomeni Simon, Gwilym P. Lewis, Ricardo A. Segovia, Luzmila Arroyo, Carlos Reynel, José Luís Marcelo Peña, Isau Huamantupa‐Chuquimaco, Daniel Villarroel, Germaine Alexander Parada, Aniceto Daza, Reynaldo Linares‐Palomino, Leandro Valle Ferreira, Rafael P. Salomão, Geovane Souza Siqueira, Marcelo Trindade Nascimento, Cláudio Nicoletti de Fraga, R. Toby Pennington
Abstract
Global patterns of species and evolutionary diversity in plants are primarily determined by a temperature gradient, but precipitation gradients may be more important within the tropics, where plant species richness is positively associated with the amount of rainfall. The impact of precipitation on the distribution of evolutionary diversity, however, is largely unexplored. Here we detail how evolutionary diversity varies along precipitation gradients by bringing together a comprehensive database on the composition of angiosperm tree communities across lowland tropical South America (2,025 inventories from wet to arid biomes), and a new, large-scale phylogenetic hypothesis for the genera that occur in these ecosystems. We find a marked reduction in the evolutionary diversity of communities at low precipitation. However, unlike species richness, evolutionary diversity does not continually increase with rainfall. Rather, our results show that the greatest evolutionary diversity is found in intermediate precipitation regimes, and that there is a decline in evolutionary diversity above 1,490 mm of mean annual rainfall. If conservation is to prioritise evolutionary diversity, areas of intermediate precipitation that are found in the South American 'arc of deforestation', but which have been neglected in the design of protected area networks in the tropics, merit increased conservation attention.