Megastigmus parasitism of North American Cupressaceae. Candau, J. (Canadian Forest Service, Canada).
2014
Boivin, Thomas | Candau, Jean-Noël
The plasticity of a pest species is one of the most important criteria to consider when assessing its capacity to invade new territory. Megastigmus species (Hymenoptera: Torymidae) are generally considered host specific, but extra-genus switches have been observed in mixed forest stands. For example, M. pinsapini sand M. schimitscheki, two species generally associated with the genus Cedruscan also infest Abies seeds in mixed stands in the South-East of France. This level of plasticity would suggest that, with the increase of seed trade worldwide and the related increased risk of seed pest introduction, there is much more scope for invasion than previously expected. Worldwide, 15 species of Megastigmus are known to feed on Cupressaceaeseeds. Interestingly, only one species is reported in the Neartic(i.e., Megastigmus thyoides) on only one host (i.e., Chamaecyparisthyoides) although a quarter (33 out of 133) of the Cupressaceae species are native of this region. In addition, host switching among Cupressaceae species seems to occur in Europe, as described for M. amicorum commonly found on Juniperusin France but also on Cupressus species introduced from California. However, host switching has never been reported in North America. These observations prompted us to better investigate Megastigmus parasitism of Cupressaceae in the Neartic.
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