Diversity and composition of palm communities (Arecaceae) in Quintana Roo Mexico Arturo Alvarado1, Luz Ma. Calvo1, Rodrigo Duno1, Henrik Balslev2* 1 Unidad de Recursos Naturales, Centro de Investigación Científica de Yucatán A.C., México. 2 Department of Biological Science, Aarhus University, Denmark. * Correspondence: email@example.com Abstract We compared composition and diversity of palm (Arecaceae) communities in three forest types along a gradient from dry deciduous, over intermediate to wet evergreen forest in Quintana Roo, Mexico. In forty-nine 5×500m transects, we counted 52,612 individuals representing 14 species in 11 genera. Within the 49 transects we found monodominance in six. The most abundant palms were Cryosophila stauracantha, Thrinax radiata and Coccothrinax readii and the least abundant were Bactris major and Gaussia maya. Thrinax radiata was the most abundant species in the northern deciduous and central intermediate forests and Cryosophila stauracantha was the most abundant palm in the evergreen rain forest to the south. Chamaedorea seifrizii and Sabal yapa were the most frequent palms in the sample. Combining all individuals in the three forest types 29% were seedlings, 59% juveniles, 1% subadults and 10% were adults. As expected, the Shannon index confirmed that the southern evergreen forest was the most diverse. Because the Yucatan Peninsula has been recognized as biotic province, and palms have ecological and economic importance, our results could be relevant for conservation and contribute to understanding diversity changes along gradients. Both species richness and overall palm abundance increased from north to south, which correlates with higher precipitation, deeper soils, fewer ground rocks and a higher forest cover.