LAUSR

Insects are able to detect a plethora of olfactory cues in the environment using a divergent family of odorant receptors (ORs). Despite the divergent nature of this family, related species frequently express several evolutionarily conserved OR orthologues. In Coleoptera, it remains unknown whether OR orthologues have conserved or divergent functions in different species. We addressed this question through functional characterization of two groups of OR orthologues in three species of the Curculionidae (weevil) family, the conifer-feeding bark beetles Ips typographus (‘Ityp’) and Dendroctonus ponderosae (‘Dpon’) (both in subfamily Scolytinae), and the pine weevil Hylobius abietis (‘Habi’; Molytinae). The ORs of H. abietis were annotated from antennal transcriptomes. Results show highly conserved response specificities, with one group of orthologues (HabiOR3/DponOR8/ItypOR6) responding exclusively to 2-phenylethanol (2-PE), and the other group (HabiOR4/DponOR9/ItypOR5) responding to angiosperm green leaf volatile (GLV) alcohols. Both groups of orthologues belong to the major coleopteran OR group 2B, and share a common ancestor with OR5 in the cerambycid Megacyllene caryae, also tuned to 2-PE, suggesting a shared evolutionary history of 2-PE receptors across two beetle superfamilies. The detected compounds are ecologically relevant for conifer-feeding curculionids, and are probably linked to fitness, with GLVs being used to avoid angiosperm non-host plants, and 2-PE being important for intraspecific communication and/or playing a putative role in beetle-microbe symbioses. To our knowledge, this study is the first to reveal evolutionary conservation of OR functions across several beetle species and hence sheds new light on the functional evolution of beetle ORs.