Orchid bees (Apidae, Euglossini) from Oil Palm Plantations in Eastern Amazon Have Larger but Not Asymmetrical Wings.

Phenotypic variation in both morphology and symmetry of individuals may appear due to environmental stress caused by land-use changes. Here, we evaluated fluctuating asymmetry (FA) and wing size variations of two orchid bee species, Euglossa ignita Smith, 1874 and Eulaema meriana (Olivier, 1789), comparing 11 wing traits. We sampled the individuals from legal reserves (LR), areas of permanent protection (APP), and oil palm plantations (PALM) in Eastern Amazonia. We calculated FA as the absolute difference between the wing measurements made in the right and left wings of specimens and both species' wing size. We corrected each FA measure for possible directional asymmetry bias by subtracting the mean value of the mean FA signed difference to each FA measure. We compared FA and the size of each wing trait of each species between land-use types using one-way ANOVAs. We found no effect of FA between land-use types, but we observed individuals of both species from PALM areas having larger wings than those from LR areas. Our results demonstrate that there seems to be a pressure exerted by land-use change associated with palm oil cultivation favoring individuals with larger wings, although both species had shown substantial permeability of oil palm.

Landscape genomics to the rescue of a tropical bee threatened by habitat loss and climate change.

Habitat degradation and climate change are currently threatening wild pollinators, compromising their ability to provide pollination services to wild and cultivated plants. Landscape genomics offers powerful tools to assess the influence of landscape modifications on genetic diversity and functional connectivity, and to identify adaptations to local environmental conditions that could facilitate future bee survival. Here, we assessed range-wide patterns of genetic structure, genetic diversity, gene flow, and local adaptation in the stingless bee Melipona subnitida, a tropical pollinator of key biological and economic importance inhabiting one of the driest and hottest regions of South America. Our results reveal four genetic clusters across the species' full distribution range. All populations were found to be under a mutation-drift equilibrium, and genetic diversity was not influenced by the amount of reminiscent natural habitats. However, genetic relatedness was spatially autocorrelated and isolation by landscape resistance explained range-wide relatedness patterns better than isolation by geographic distance, contradicting earlier findings for stingless bees. Specifically, gene flow was enhanced by increased thermal stability, higher forest cover, lower elevations, and less corrugated terrains. Finally, we detected genomic signatures of adaptation to temperature, precipitation, and forest cover, spatially distributed in latitudinal and altitudinal patterns. Taken together, our findings shed important light on the life history of M. subnitida and highlight the role of regions with large thermal fluctuations, deforested areas, and mountain ranges as dispersal barriers. Conservation actions such as restricting long-distance colony transportation, preserving local adaptations, and improving the connectivity between highlands and lowlands are likely to assure future pollination services.

Pulsed mass recruitment by a stingless bee, Trigona hyalinata.

Research on bee communication has focused on the ability of the highly social bees, stingless bees (Hymenoptera, Apidae, Meliponini) and honeybees (Apidae, Apini), to communicate food location to nest-mates. Honeybees can communicate food location through the famous waggle dance. Stingless bees are closely related to honeybees and communicate food location through a variety of different mechanisms, many of which are poorly understood. We show that a stingless bee, Trigona hyalinata, uses a pulsed mass-recruitment system that is highly focused in time and space. Foragers produced an ephemeral, polarized, odour trail consisting of mandibular gland secretions. Surprisingly, the odour trail extended only a short distance away from the food source, instead of providing a complete trail between the nest and the food source (as has been described for other stingless bees). This abbreviated trail may represent an intermediate strategy between full-trail marking, found in some stingless bees, and odour marking of the food alone, found in stingless bees and honeybees.

Olfactory eavesdropping by a competitively foraging stingless bee, Trigona spinipes.

Signals that are perceived over long distances or leave extended spatial traces are subject to eavesdropping. Eavesdropping has therefore acted as a selective pressure in the evolution of diverse animal communication systems, perhaps even in the evolution of functionally referential communication. Early work suggested that some species of stingless bees (Hymenoptera, Apidae, Meliponini) may use interceptive olfactory eavesdropping to discover food sources being exploited by competitors, but it is not clear if any stingless bee can be attracted to the odour marks deposited by an interspecific competitor. We show that foragers of the aggressive meliponine bee, Trigona spinipes, can detect and orient towards odour marks deposited by a competitor, Melipona rufiventris, and then rapidly take over the food source, driving away or killing their competitors. When searching for food sources at new locations that they are not already exploiting, T. spinipes foragers strongly prefer M. rufiventris odour marks to odour marks deposited by their own nest-mates, whereas they prefer nest-mate odour marks over M. rufiventris odour marks at a location already occupied by T. spinipes nest-mates. Melipona rufiventris foragers flee from T. spinipes odour marks. This olfactory eavesdropping may have played a role in the evolution of potentially cryptic communication mechanisms such as shortened odour trails, point-source only odour marking and functionally referential communication concealed at the nest.