Macroevolution of perfume signalling in orchid bees.

Theory predicts that both stabilising selection and diversifying selection jointly contribute to the evolution of sexual signalling traits by (1) maintaining the integrity of communication signals within species and (2) promoting the diversification of traits among lineages. However, for many important signalling traits, little is known about whether these dynamics translate into predictable macroevolutionary signatures. Here, we test for macroevolutionary patterns consistent with sexual signalling theory in the perfume signals of neotropical orchid bees, a group well studied for their chemical sexual communication.

Olfactory specialization for perfume collection in male orchid bees.

Insects rely on the olfactory system to detect a vast diversity of airborne molecules in their environment. Highly sensitive olfactory tuning is expected to evolve when detection of a particular chemical with great precision is required in the context of foraging and/or finding mates. Male neotropical orchid bees (Euglossini) collect odoriferous substances from multiple sources, store them in specialized tibial pouches and later expose them at display sites, presumably as mating signals to females.

Enantioselective preference and high antennal sensitivity for (-)-Ipsdienol in scent-collecting male orchid bees, Euglossa cyanura.

Male neotropical orchid bees (Euglossini) collect volatile chemicals from their environment, store them in tibial pouches, and later expose their "perfumes" during a courtship display. Here, we showed that enantiomeric selectivity plays an important role in the choice of volatiles by male Euglossa cyanura in southern Mexico, and that behavioral selectivity is linked to antennal sensitivity. In field bioassays with equal concentrations of (+)-ipsdienol, (-)-ipsdienol, and racemate, males preferred the (-)-isomer to the racemate, while neglecting the (+)-isomer.