Contrasting patterns of species, functional and phylogenetic bird diversities in two Tropical dry vegetation types

Abstract The main objective of this study was to analyse the changes of taxonomic, functional and phylogenetic diversities shown by bird assemblages at two contrasting vegetational types in Southern Mexico. Our main hypothesis was that we would find a higher diversity in Tropical Dry Forest (TDF) than in Oak Woodland (OW) due to a monotonic decrease in diversity with altitude. During eleven months, we surveyed both vegetation types to record bird species and abundances. We established points and simultaneously carried out 5-minutes count and soundscape recordings. We quantified our sampling effort by means of the sample coverage and calculated Hill numbers to express alpha and beta diversities. Contrary to our expectations, in terms of alpha taxonomic and functional diversities, the OW had consistently higher values than the TDF. After accounting for abundance data, we found a marked decrease in phylogenetic and taxonomic beta diversity, but an increase in functional diversity compared to the presence/absence matrix. The low beta phylogenetic diversity combined with the high beta functional diversity suggests that a small set of closely related species could have evolved in the dry slopes of the area, and by the action of niche differentiation developed different functional traits. The high functional beta diversity indicates a high complementarity between the avifaunas of each vegetation type, which is relevant in terms of conservation.