Generalized olfactory detection of floral volatiles in the highly specialized Greya-Lithophragma nursery pollination system

Authors: SCHIESTL, FLORIAN - University Of Zurich; WALLIN, ERIKA - Mid Sweden University; Beck, John; FRIBERG, MAGNA - Mid Sweden University; THOMPSON, JOHN - University Of California Santa Cruz

Submitted to: Arthropod-Plant Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2021
Publication Date: 3/5/2021
Citation: Schiestl, F.P.; Wallin, E.A.; Beck, J.J.; Friberg, M.; Thompson, J.N. Generalized olfactory detection of floral volatiles in the highly specialized Greya lithophragma nursery pollination system. Arthropod Plant Interact. 2021, 15:209-221 https://doi.org/10.1007/s11829-021-09809-5
DOI: https://doi.org/10.1007/s11829-021-09809-5

Interpretive Summary: Odors emitted from plants and microbes play an important role in affecting insect behavior, including insects that pollinate flowers. Greya moths are insects with a particular affinity for certain flowering plants, namely Lithophragma, commonly known as woodland stars. An ARS scientist at the Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL in an international collaboration with scientists from Switzerland, Sweden, and California, investigated the odors emitted from various woodland star species and the odor’s ability to influence Greya moths. Using bioassays with excised Greya moth antennae, the team of researchers identified 23 volatile chemical compounds (odors) that elicited responses from the Greya moth antennae. Analyzing the odors detected, the plant species that emitted the odors, and the odor’s ability to elicit antennal responses, the researchers deduced that there was no pattern of evolutionary connection between the different plant species at varying regions and the Greya moths. Information such as this provides valuable information of how insects evolve with particular plant species and what odors are used attract the insects to that plant. This information can also be used to protect agricultural plants.

Technical Abstract: Volatiles are of key importance for host-plant recognition in insects. In the pollination system of Lithophragma flowers and Greya moths, moths are highly specialized on Lithophragma , in which they oviposit and thereby pollinate the flowers. Floral volatiles in Lithophragma are highly variable between species and populations, and moths prefer to oviposit into Lithophragma flowers from populations of the local host species. Here we used gas chromatography coupled with electroantennographic detection (GCEAD)to tested whether Greya moths detect specific key volatiles or respond broadly to many volatiles of Lithophragma flowers. We also addressed whether olfactory detection in Greya moths varies across populations, consistent with a co-evolutionary scenario. We analyzed flower volatile samples from three different species and five populations of Lithophragma occurring across a 1400 km range in the Western USA, and their sympatric female Greya politella moths. We showed that Greya politella detected a broad range of Lithophragma volatiles, with a total of 23 compounds being EAD active. We chemically identified 15 of these, including the chiral 6,10,14-trimethylpentadecan-2-one (hexahydrofarnesyl acetone), which was not previously detected in Lithophragma . All vestigated Lithophragma species produced the (6R ,10 R )-enantiomer of this compound. We showed that Greya moths detected not only volatiles of their local Lithophragma plants, but also those from allopatric populations/species that they never encounter locally. In conclusion, the generalized detection of volatiles and a lack of co-divergence between volatiles and olfactory detection may be of selective advantage for moths in tracking hosts with rapidly evolving, chemically diverse floral volatiles.