Pheromones of three ambrosia beetles in the Euwallacea fornicatus species complex: ratios and preferences
- Published
- Accepted
- Subject Areas
- Agricultural Science, Entomology
- Keywords
- pheromone, polyphagous shot hole borer, tea shot hole borer, repellent, attractant, Kuroshio shot hole borer, quercivorol, kairomone, chemical ecology
- Copyright
- © 2017 Cooperband et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2017. Pheromones of three ambrosia beetles in the Euwallacea fornicatus species complex: ratios and preferences. PeerJ Preprints 5:e3175v1 https://doi.org/10.7287/peerj.preprints.3175v1
Abstract
Three cryptic species in the Euwallacea fornicatus species complex were reared in laboratory colonies and investigated for the presence of pheromones. Collections of volatiles from combinations of diet, fungus, beetles, and galleries from polyphagous shot hole borer (Euwallacea sp. #1) revealed the presence of 2-heneicosanone and 2-tricosanone only in the presence of beetles, regardless of sex. Subsequent examination of volatiles from the other two species, tea shot hole borer (Euwallacea sp. #2) and Kuroshio shot hole borer (Euwallacea sp. #5), revealed these two ketones were present in all three species but in different ratios. In dual choice olfactometer behavioral bioassays, mature mated females were strongly attracted to a synthetic binary blend of ketones matching their own natural ratios. However, females in each species were repelled by ketone blends in ratios corresponding to the other two species. Males of each species responded similarly to females when presented with ratios matching their own or the other two species. The presence of these compounds in the three beetle species, in ratios unique to each species, and their strong species-specific attraction and repellency, suggests they are pheromones. The ecological function of these pheromones is discussed. In addition to the pheromones, the previously known attractant (1S,4R)-p-menth-2-en-1-ol (also known as quercivorol) was discovered in the presence of the fungal symbionts, but not in association with the beetles. Quercivorol was tested in a dual-choice olfactometer and was strongly attractive to all three species. This evidence suggests quercivorol functions as a kairomone for members of the E. fornicatus species complex, likely produced by the symbiotic fungi.
Author Comment
This is a submission to PeerJ for review.
Supplemental Information
Collecting PSHB volatiles using different approaches in search of possible pheromones
The frequency that compounds were detected in collections (% of samples that were positive) are shown. Media are listed as either SPME fibers exposed to still air head space of the odor source, volatile collection of head space air flowing through a trap that was subsequently eluted into a solvent, or a direct solvent rinse or extract of the odor source. Odors were contained in and collected from various receptacles, consisting of either the rearing tube or a jar, a Pasteur pipette, within the beetle gallery in the colonized diet, or by touching the SPME fiber to the odor source.
List of volatile collections conducted in search of possible pheromones
In exploratory volatile collections, for each sample the contents of the sample, approach used, and GCMS peak areas for the three compounds of interest are listed.
Ketone ratio comparisons between species
For each extraction of beetles in the quantitative analysis using an internal standard, the amount of each ketone (ng) per beetle was used to compare ratios between species.