How fast species’ environmental tolerances can evolve is crucial for their survival prospect under climate change. Phylogenetic information can yield insights into the tempo of niche evolution. Phylogenetic community structure (PCS) complements the more widely used approach of studying niche parameters in a trait evolution framework: it avoids using summary statistics for niche parameters, keeps spatial information - and thus information on niche filling - and separates the effects of niche conservatism and dispersal limitation. We analyse palm assemblages in the Americas, hypothesising: 1) there are centres of in situ-diversification defined by climate and geomorphology. 2) The phylogenetic relatedness of assemblages decreases both with increasing environmental dissimilarity and geographical distance, but a significant part of its variation is explained by environment alone and reflects niche conservatism (not dispersal). 3) The relatedness of species within assemblages correlates with environment in a way that reflects niche conservatism s. str., i.e. transition into extreme environments rarely occurs. We found phylogenetic clustering of assemblages, and centres of diversification that match geomorphology and climate well. A significant independent contribution of environment to explaining the phylogenetic relatedness of assemblages was found, indicating that niches are conserved in evolutionary time. Our results underline the value of the PCS approach to niche evolution.