Resource use of cavity-nesting bees in Colombia’s tropical savannas

Tropical savannas provide numerous ecosystem services but are increasingly threatened by intensive agriculture and extensive livestock farming. In addition, limited information exists on the pollinators and pollination services from these ecosystems. We studied the nesting phenology and nest architecture of non-social, cavity-nesting bees from gallery forests in the Orinoquia region of Colombia for two consecutive years. Using more than 1,000 trap nests, we documented the nest architecture of 13 bee species, some of which are recorded for the first time for the country. We found that bees used a wide range of trap nest diameters, ranging from 6 to 24 mm. A positive correlation (Pearson = 0.72, P < 0.05) was found between nest diameter and the size of emerged bees, suggesting space optimization within their nests. Bees used several materials to build their nests, including sand, wood particles, oils, detritus, leaves, petals, and resins, with sand being the most frequently used resource. Phylogenetically closer species tended to use similar resources. Except for orchid bees of the genus Euglossa, remaining bees displayed a linear cell arrangement. Closing nest plugs were present in all species, except in the carpenter bee Xylocopa fimbriata. Overall, our findings are similar to studies from other gallery forests in South America, suggesting common ecological drivers and adaptive strategies among bees. This research was funded by VICEIN UMNG IMP CIAS 3740.