Ecology and evolution of perfumes in recently established island populations of orchid bees.

• Applicant: Dr. Jonas Henske
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 556613301

Male orchid bees collect volatiles from various sources, including orchids, to concoct complex perfumes. Females select males based on these perfumes, which function as intersexual signals that convey the sender’s availability as a mate. However, what additional information is encoded in the signal and which chemical components are behaviorally relevant remains unknown. Furthermore, the origin of several major, possibly essential perfume compounds remains elusive. Orchid bee perfumes are species-specific, yet intraspecific variation exists, suggesting that perfumes are fitness indicators shaped by female choice. My project aims to clarify the function and origin of male perfumes by studying island populations of the Central American orchid bee Euglossa dilemma. Neurophysiological studies indicate that E. dilemma’s major perfume compound, 2-Hydroxy-6-Nona-1,3-Dienylbenzaldehyd (HNDB), is a key signal feature, either for species-recognition or as an indicator of male quality, or both. E. dilemma was recently introduced to the Bahamas, Hispaniola, and the Florida Keys. Males of these island populations, inhabiting simpler environments, likely possess less complex perfumes. This provides unique opportunities to disentangle signal components contained in complex perfumes, verify essential chemical compounds, and identify their sources. The proposed project is structured around four milestones: (1) Retrace the colonization events that led to the current distribution of E. dilemma across the Caribbean by conducting population genetic analyses. (2) Examine the role of E. dilemma’s major perfume compound HNDB by sampling and chemically analyzing perfumes from all introduced populations. I hypothesize that HNDB is present in all populations, whereas other compounds are more variable. (3) Identify the sources of HNDB and other major perfume compounds by combining chemical analyses with DNA metabarcoding. I predict that fungi are the main sources of perfumes, as many key components have not yet been found in flowers. (4.1) Test the attractiveness of different perfume “dialects” on mate choice in cage experiments by applying perfumes derived from different island populations on lab-bred males to conduct mate-choice experiments. I hypothesize that females will prefer certain perfumes over others, for instance, perfumes that are more complex or contain a higher proportion of HNDB. (4.2) Measure the reproductive success of artificially introduced, perfume-enhanced males in a field experiment by tracing marker genes in the recipient island population. I hypothesize, that perfume-enhanced males will have a higher fitness and achieve more copulations.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Santiago Ramírez, Ph.D.