Ecology and nesting biology of the wood-boring bee Trichothurgus laticeps (Hymenoptera: Megachilidae) in a Monte desert reserve in mid-western Argentina

Abstract

-Studying bee nests can enlighten our understanding of feeding specialization and phylogenetic relationships of bees. We studied the nesting and feeding habits of Trichothurgus laticeps in the Monte desert ecosystem. Our results show that T. laticeps is attracted to pre-existing cavities in wood (trap nests), which were further excavated for nest construction; nest cells are unlined and provisioned almost exclusively with pollen of the cactus Opuntia sulphurea . The species overwinters inside a hard cocoon. Our results reinforce the hypothesis previously proposed by other authors that the unworked pollen mass and oligolecty are plesiomorphic characters in the Megachilidae, and that the wood-boring behavior for nest construction indicates convergent evolution with the Xylocopinae. We also propose that the cocoon structure might represent an evolutionary novelty for the Lithurginae.host-plant specialization / Lithurginae / nesting behavior and structure / phylogenetic relationships / solitary bees

Phenological mismatches and the demography of solitary bees

“…Yet, these results make sense in light of the natural history of our study species. Trichothurgus laticeps uses almost exclusively the cactus Opuntia sulphurea as a source of pollen [35]. Megachile leucographa uses the shrubs Larrea spp.…”

“…One species, T. laticeps , lacks organized brood cells, as females lay bare eggs amidst a pollen mass [35]. In turn, in some nests of X. atamisquensis adults emerged in the field before we could count the number of brood cells, and although some nests bore clear marks of the former brood cell divisions, in other nests the marks were less clear.…”

“…We identified pollen to the lowest possible taxonomic resolution: species in most cases, genus in a few cases with several species in the same genus, and morphospecies in a few rare pollen grains that we could not identify. We conducted pollen identification by light microscopy using the natural method [33,34], in comparison with a reference collection that included all flowering plant species recorded in our study plots [35]. We kept some emerged adults of each nest for identification and returned the remaining individuals to their site of origin in the field.…”