Abrupt decrease in the diversity of Euglossini bees (Hymenoptera: Apidae) in a montane rainforest

Euglossini bees are more diverse in tropical and subtropical rainforests in the Neotropics and their distribution may have a strong influence of altitude. These bees are considered important pollinators being able to cross long distances in continuous forests. Euglossini males collect fragrances, mainly from orchids, used as precursors for sex pheromones, a fact that allows the use of synthesized compounds for their capture. The aim of this study was to evaluate the occurrence of Euglossini males in elevated sites of a montane rainforest (from 960 to 1,200 m) in southeastern Brazil (Atlantic Forest). Scent traps were distributed at three locations in different altitudes on one day per month over 19 months. Six traps with different baits were distributed at each location. Overall, the male Euglossini community presented a low number of species (seven) and individuals (110). Moreover, we detected a drastic decay in Euglossini species richness and abundance with increasing altitude, which suggests a limit for the occurrence of Euglossini populations around 1100 m in the study area. This community presented a high dominance degree with a single dominant species (Euglossa annectans). In addition, only one species of perfume orchid was abundant and flowered in the study area during our sampling period. The distribution of this orchid species corresponds to the occurrence of Euglossini males in the study area. Our results indicate that pollinator scarcity may compromise the establishment of perfume orchid populations at higher altitudes in the Atlantic Forest.