This is a continuation of our Orchid Bees blog post from last week. If you missed it, you can catch up here. We were reporting on two species of magnificent orchid bees and the fact that they are master chemists, perfumers and alchemists.

Associate professor Santiago Ramirez at UC Davis Department of Evolution and Ecology in California, along with his colleagues, analyzed the genomes of the two species E. viridissima and E. dilemma.

They honed-in on certain differences in a cluster of olfaction-related genes and determined that olfactory receptor gene 41 (OR41) was different when comparing the two species.

Enjoy this stunning NatGeoWild 3:59-minute video of the orchid bee and the orchid, and how each helps the other survive. Marvel at the intelligence of both...

In orchid bees, these genes express through their antennae, so they can detect airborne molecules and scents. Ramirez explained that this particular gene has gathered many changes between the two species, and that implies that those changes are responsible for collecting specific different perfume compounds. As these olfactory genes further evolve and accumulate new mutations, they allow the bees to collect or not collect certain compounds as they are more sensitive to diverse molecules.

According to Philipp Brand, recent Ph.D. from Population Biology Graduate Group, it is very rare to find such differences in a single gene. He explained that what are called divergent genetic regions or ‘genomic islands of divergence’ can include anywhere from tens to hundreds of genes. It can be a challenge to pinpoint the gene under selection.

Ramirez and Brand used the fruit fly (Drosophila melanogaster), another airborne insect, to figure out which molecules the two orchid bee species detect using OR41.  

Ramirez recounted that by creating transgenic flies that express orchid bee genes, it was an ideal setup to dissect exactly what the function of gene OR41 is. Their team then tested the variant OR41 variant gene against single odors and blends of odors that are found in the environment of each of the two species of orchid bees.

E. viridissima's OR41 variant responded to perfume blends found in waxes used by females for brood cell construction as well as to the scent of several medium to long-chain fatty-acids that are commonly found in waxes. This variant did not respond to individual odors.

E. dilemma's OR41 variant repeatedly responded to the species-specific HNDB compound and E. dilemma perfume mixtures that contain HNDB. Brand assesses that the OR41 variant in E. dilemma has evolved to become a highly specific receptor that responds only to its own major species-specific perfume compound. Brand finds it plausible that E. dilemma gained the ability to discriminate HNDB from other chemicals because of this.

This 4:08-minute Smithsonian Channel video is all about our master perfumer, the male orchid bee.

Brand continues to explore insect chemo-sensory systems as a postdoctoral researcher in the lab of Associate Professor Vanessa Ruta at The Rockefeller University. His work is geared towards identifying key genetic and neural mechanisms that underlie the evolution of behavior.

Brand explains that his target is reproductive behaviors such as courtship and mating and how they evolve and contribute to the origin and maintenance of novel species. He believes that fully integrating the traditionally separated fields of neurobiology and evolutionary biology is the next big step in learning how behaviors diverge, and novel species emerge.

At a research facility on the University of Florida’s Ft. Lauderdale campus, Ramirez has established the first-ever breeding population of orchid bees. He hopes to continue studying bee behaviors at this facility to see if orchid bees are a viable option for deeper research into chemical communication, animal behavior and pollination biology.

Thanks to these two pioneers for bringing us insights into the beauty and uniqueness of the orchid bee and the fascinating role that scent plays in their survival.