Distribution patterns of orchid bees in xeric and mesic habitats on a tropical mountaintop

1. Most studies evaluating insect communities along climatic gradients in mountain regions have overlooked the relevance of the contrasting effects of xeric and mesic habitats on species distribution and richness. Mesic zones located in the xeric ecosystems represent drastic climate changes that can provide more favourable conditions for some insect maintenance, particularly for orchid bees (Apidae, Euglossini), which are known to be speciose in humid tropical forests. 2. For the first time, we sought to understand the distribution of orchid bees in xeric and mesic habitats in dry and wet seasons along an elevational gradient in Espinhaco mountains, southeastern Brazil. 3. Overall, 4873 individuals belonging to three genera and 15 species of orchid bees were collected. Species richness decreased with increased elevation, regardless of habitat type and season. Otherwise, lower bee richness and abundance were recorded in xeric habitats compared to mesic habitats in the dry season but not in the wet season. Bee richness and abundance did not differ between the dry and wet seasons for mesic habitats, while lower richness and abundance were recorded in the dry season for xeric habitats. Species turnover was the main component of beta-diversity among elevations and between seasons, while nestedness was the main component of beta-diversity from mesic to xeric. 4. Orchid bees require high temperatures, although they cannot withstand the water stress of xeric habitats during the dry season, reinforcing the importance of mesic habitats for the maintenance of these pollinators of great relevance to ecosystems in savannic and mountainous regions.