Topography drives tree–habitat association and functional and phylogenetic structure in the northernmost tropical dry forest of the Americas

Abstract

ABSTRACT Background Plant species composition and structural attributes are related to physiographic factors such as slope orientation and topographic position. This relationship is accentuated with increasing seasonality in temperature and precipitation. Aims We quantified the relationship between topography and the taxonomic, functional and phylogenetic community composition of woody species at the northernmost distribution of seasonally dry tropical forests (STDF) in the Americas. Methods We related slope orientation (north-facing vs. south-facing) and position (upper slope vs. lower slope) to the distribution of species, assessed their habitat preference by life stage (juvenile vs. adult) and compared the observed phylogenetic distance of species against random species assemblages. Results Our results showed the segregation of two species groups in both life stages is related to slope orientation, but not to topographic position. We found a strong habitat association for 68% of the species with both juveniles and adults similarly associated with the same habitat. Slope orientation was related to taxonomic, functional and phylogenetic structure, but it differed in the two life stages. Conclusions The functional and evolutionary segregation of species between north-facing vs. south-facing habitats indicates that species are non-randomly distributed; suggesting that deterministic mechanisms (e.g. topographic habitat specialisation) are operating at a local scale.