Bot. Rev. (2011) 77:381–425 DOI 10.1007/s12229-011-9084-x Species Diversity and Growth Forms in Tropical American Palm Communities Henrik Balslev1,4 & Francis Kahn2 & Betty Millan3 & Jens-Christian Svenning1 & Thea Kristiansen1 & Finn Borchsenius1 & Dennis Pedersen1 & Wolf L. Eiserhardt1 1 Ecoinformatics and Biodiversity Group, Department of Biological Sciences, Aarhus University, Building 1540, Ny Munkegade 114, DK-8000 Aarhus C, Denmark 2 Institut de Recherche pour le Développement (IRD, UMR DIADE/DYNADIV), Montpellier, France 3 Universidad Nacional Mayor de San Marcos, Lima, Peru 4 Author for Correspondence; e-mail:
[email protected] Published online: 30 June 2011 # The New York Botanical Garden 2011 Abstract To advance our understanding of the processes that govern the assembly of palm communities and the local coexistence of numerous palm species, we here synthesize available information in the literature on species diversity and growth-form composition in palm communities across the Americas. American palm communities surveyed had 4–48 (median 16) species in study plots covering 0.09–7.2 ha. Climate, soils, hydrology, and topography are the main factors determining palm community species richness. Tropical lowland terra firme rain forests are the most species-rich whereas forests that are inundated or grow on sandy soils or in areas with seasonal climate have much fewer species. Palm communities in the central-western Amazon and in Central America are significantly richer than the average region and those in the Caribbean significantly poorer in species. As for branching, the 789 species of tropical American palms belong to Corner’s model (solitary, 268 species, 33%), Tomlinsons model (cespitose, 521 species, 66%) and Schoute’s model (dichotomous branching, three species, <1%).