Seasonal drought limits tree species across the Neotropics
Authors: Esquivel‐Muelbert Adriane , Baker Timothy R. , Dexter Kyle G. , Lewis Simon L. , ter Steege Hans , Lopez‐Gonzalez Gabriela , Monteagudo Mendoza Abel , Brienen Roel , Feldpausch Ted R. , Pitman Nigel , Alonso Alfonso , van der Heijden Geertje , Peña‐Claros Marielos , Ahuite Manuel , Alexiaides Miguel , Álvarez Dávila Esteban , Murakami Alejandro Araujo , Arroyo Luzmila , Aulestia Milton , Balslev Henrik , Barroso Jorcely , Boot Rene , Cano Angela , Chama Moscoso Victor , Comiskey James A. , Cornejo Fernando , Dallmeier Francisco , Daly Douglas C. , Dávila Nallarett , Duivenvoorden Joost F. , Duque Montoya Alvaro Javier , Erwin Terry , Di Fiore Anthony , Fredericksen Todd , Fuentes Alfredo , García‐Villacorta Roosevelt , Gonzales Therany , Guevara Andino Juan Ernesto , Honorio Coronado Euridice N. , Huamantupa‐Chuquimaco Isau , Eliana Maria Jiménez Rojas , Killeen Timothy J. , Malhi Yadvinder , Mendoza Casimiro , Mogollón Hugo , Jørgensen Peter Møller , Montero Juan Carlos , Mostacedo Bonifacio , Nauray William , Neill David , Vargas Percy Núñez , Palacios Sonia , Palacios Cuenca Walter , Pallqui Camacho Nadir Carolina , Peacock Julie , Phillips Juan Fernando , Pickavance Georgia , Quesada Carlos Alberto , Ramírez‐Angulo Hirma , Restrepo Zorayda , Reynel Rodriguez Carlos , Paredes Marcos Ríos , Peñuela-Mora Maria Cristina , Sierra Rodrigo , Silveira Marcos , Stevenson Pablo , Stropp Juliana , Terborgh John , Tirado Milton , Toledo Marisol , Torres‐Lezama Armando , Umaña María Natalia , Urrego Ligia Estela , Vasquez Martinez Rodolfo , Gamarra Luis Valenzuela , Vela César I. A. , Vilanova Torre Emilio , Vos Vincent , von Hildebrand Patricio , Vriesendorp Corine , Wang Ophelia , Young Kenneth R. , Zartman Charles Eugene , Phillips Oliver L. 
Published: April 2016

Within the tropics, the species richness of tree communities is strongly and positively associated with precipitation. Previous research has suggested that this macroecological pattern is driven by the negative effect of water‐stress on the physiological processes of most tree species. This implies that the range limits of taxa are defined by their ability to occur under dry conditions, and thus in terms of species distributions predicts a nested pattern of taxa distribution from wet to dry areas. However, this ‘dry‐tolerance’ hypothesis has yet to be adequately tested at large spatial and taxonomic scales. Here, using a dataset of 531 inventory plots of closed canopy forest distributed across the western Neotropics we investigated how precipitation, evaluated both as mean annual precipitation and as the maximum climatological water deficit, influences the distribution of tropical tree species, genera and families. We find that the distributions of tree taxa are indeed nested along precipitation gradients in the western Neotropics. Taxa tolerant to seasonal drought are disproportionally widespread across the precipitation gradient, with most reaching even the wettest climates sampled; however, most taxa analysed are restricted to wet areas. Our results suggest that the ‘dry tolerance' hypothesis has broad applicability in the world's most species‐rich forests. In addition, the large number of species restricted to wetter conditions strongly indicates that an increased frequency of drought could severely threaten biodiversity in this region. Overall, this study establishes a baseline for exploring how tropical forest tree composition may change in response to current and future environmental changes in this region.