Canadian Forest Service Publications
Evidence for a substantial host use bottleneck following the invasion of an exotic, polyphagous weevil. 2015. Moise, E.; Forbes, G.B.H.; Morrison, A.; Sweeney, J.D.; Hillier, N.K.; Johns, R.C. Ecological Entomology 40: 796–804.
Issued by: Atlantic Forestry Centre
Catalog ID: 36409
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- The successful establishment of novel plant–insect interactions may depend on the availability of suitable hosts, which itself is influenced by the inherent flexibility of the herbivore for the native plants in its new range. The polyphagous beech leaf mining weevil, Orchestes fagi L., is a recent invader to eastern Canada, and while beech is a primary host, it remains unclear the extent to which it might also utilise co-occurring secondary hosts, as has been observed in its native European range.
- A combination of field and laboratory feeding trials were used to quantify weevil secondary host use. Based on its expansive native host range in Europe, it was predicted that American beech (Fagus grandifolia Ehrh.), as well as several additional plant species, would be susceptible to weevil damage.
- Contrary to this prediction, weevil feeding was almost entirely exclusive to beech in both the field and laboratory feeding trials. This result is further supported by field observations that revealed an absence of weevils and eggs on species other than beech. In general, the lack of pre-diapause feeding on any alternate host species represented an extreme departure from feeding habits observed within the native range.
- Overall, this host-use bottleneck suggests that the adoption of a novel primary host by O. fagi, in this case American beech, may remove the normal requirement or secondary hosts and suggests a significant departure from native feeding habits with possible consequences for related life-history parameters such as overwintering survival and fecundity.
Plain Language Summary
The beech leaf mining weevil, Orchestes fagi L., is a recent invader to eastern Canada, and although beech is a primary host, it remains unclear whether it also utilizes co-occurring secondary hosts, as has been observed in its native European range. Using a combination of observational, sleeve cage, and lab feeding assays, we found that feeding was restricted almost entirely to American beech. Additionally, although weevil offspring are known to feed prior to overwintering in Europe, our study demonstrated that they fed on nothing at all. Overall, our results suggest that weevil host use is highly restricted in eastern Canada, although whether this reflects a limitation or adaptation remains to be determined. Coupled with the lack of feeding observed in the offspring, these changes will have important implications for processes such as reproduction and overwintering survival. From an applied perspective, this also suggests that timber sources other than American beech are unlikely to be greatly impacted by weevil damage.