Pollination of euglossinophylic epiphytic orchids in agroecosystems and forest fragments in southeast Mexico

Abstract

To determine the reproductive status of the native orchids of the biodiversity “hotspot”, Biological Corridor Tacaná-Boquerón, in theregion of Soconusco, southeast Mexico, which are suffering the effects of habitat degradation, unsustainable exploitation and potentially,climate change, we analysed the species richness, abundance, habitat and abiotic preferences, pollinaria transport and relation to orchidpopulations, of male Euglossine bees (Hymenoptera: Apidea: Euglossini) in agroecosystems and forest fragments within the region. Usingvolatile baits we trapped 2,480 bees, consisting of 14 species, during a total of 256 hours, of which 284 individuals (11.5%) had pollinariaof 18 orchid species adhered to their bodies. Three species of Eufriesia (E. caerulescens, E. mexicana, E. rugosa) and one species of Euglossa(E. villosa) were recorded for the first time. We report Eulaema meriana as the pollinator of the recently rediscovered Plectrophora alata.We did not detect habitat preferences for the species of Euglossini captured, and they were frequent, or even more frequent, in intensivecoffee plantations, as are many of the orchid species, which can be classified as a disturbed habitat. Bees tended to be more abundantwith increasing light intensity and decreasing humidity at each site. There was little indication of pollinator specificity and the position ofthe pollinaria of each orchid species on the bodies of the bees was also variable. We did not recover any pollinaria from various euglossinophylic,epiphytic orchid species present in the region and three bee species showed signs of population decline. However, our resultsindicate that many species of orchids with this pollination syndrome are receiving pollination service within an increasingly fragmentedand disturbed environment, suggesting that both the orchids and the bees are adapting to the changes.