Research at University of California – Davis indicates that a single gene for scent reception separates these two species.
Male orchid bees collect chemicals to create their own signature perfumes, unique to their specific species. Researchers are now linking the orchid bee’s sexual signaling to a single gene that identifies the species’ perfume preferences.
Have you ever seen how stunning the male orchid bee is? Zipping and buzzing its way around the rainforest, it flashes iridescent green amid an emerald green backdrop. The bee is on a quest, not for nectar and pollen necessarily, but it stops at various flowers, dead trees and fungi to collect fragrant particles. Storing them in its hind legs, it perches on a tree trunk, then flits about, dispersing a wafting aroma into the air by using its wings.
The purpose is to attract a mate.
Associate professor Santiago Ramirez at UC Davis Department of Evolution and Ecology explains that while most animals produce pheromones by way of a metabolic pathway, the orchid bee is unique in collecting most of their pheromones from plants and such sources as fungi.
This stunning short 2:16-minute video narrated by David Attenborough shows the vibrant colors of these male orchid bees and of the rain forest itself, but it comes to an abrupt ending.
Ramirez and recent Ph.D. graduate student Philipp Brand, Population Biology Graduate Group, have studied orchid bee mating behaviors, especially the complex chemicals that lead to successful procreation. This research has given them insight that the driver of divergence when it comes to formation of new species is environmental perfumes. Orchid bees are master perfumers and the perfumes they concoct are unique to their specific species.
Brand pointed out that for the orchid bee, perfume is a communication system and that the male perfume chemistry and the female preference for the perfume chemistry can evolve at the same time via changes in a single receptor gene. Say your ancestral species communicated with each other using certain compounds in a chemical communication channel, but then the chemical communication channel split into 2 channels. This allows two separate species to form.
There are 250 species of orchid bees, but Ramirez and Brand focused their research on two species that are almost indistinguishable genetically and physically and were previously classified under a single scientific name: Euglossa viridissima and Euglossa dilemma. They diverged about 150,000 years ago, one living in Central America and the other in South America with an overlap in the Yucatan area, Mexico. It reveals that the variants are not just due to geographic variation, because they remain distinctly separate species even when they coexist despite experiencing hybridization in the recent past. What distinguishes them is their unique niche in chemical space.
Here is a 4-minute long Nat Geo Wild video with more specific information about the magnificent green orchid bee:
Gas chromatography and mass spectrometry helped the researchers separate and analyze each chemical compound in a male orchid bee’s enticing perfume. The difference boiled down to just two molecules. For E. viridissima the molecule is 2-hydroxy-6-nona-1,3-dienylbenzaldehyde HNDB and for E. dilemma it is a lactone called L97, suggesting each is a separate species of orchid bee. Ramirez says this indicates these pheromone-like perfumes aren’t just different between the species but actually influenced their original divergence. This means an orchid bee with one chemical signal won’t mate with an orchid bee with a different signal, so this helps keep the species separate from each other.
If you enjoyed this blog post, stay tuned for Part 2, coming soon.