The open bar is closed: restructuration of a native parasitoid community following successful control of an invasive pest

The rise of the Asian chestnut gall waspDryocosmus kuriphilusin France has benefited the native community of parasitoids originally associated with oak gall wasps by becoming an additional trophic subsidy and therefore perturbing population dynamics of local parasitoids. However, the successful biological control of this pest has then led to significant decreases in its population densities. Here we investigate how the invasion of the Asian chestnut gall waspDryocosmus kuriphilusin France and its subsequent control by the exotic parasitoidTorymus sinensishas impacted the local community of native parasitoids.

We explored 5 years of native community dynamics within 26 locations during the rise and fall of the invasive pest. In an attempt to understand how mechanisms such as local extinction or competition come into play, we analyzed how the patterns of co-occurrence between the different native parasitoid species changed through time.

Our results demonstrate that native parasitoid communities experienced increased competition as theD. kuriphiluslevels of infestation decreased. During the last year of the survey, two alternative patterns were observed depending on the sampled location: either native parasitoid communities were represented by an extremely limited number of species occurring at low densities, in some cases no native parasitoid species at all, or they were dominated by one main parasitoid:Mesopolobus sericeus. These two patterns seemed to correlate with the habitat type,M. sericeusbeing more abundant in semi-natural habitats compared to agricultural lands, the former known to be natural reservoirs for native parasitoids. These results highlight how the “boom-and-bust” dynamics of an invasive pest followed by successful biological control can deeply alter the structure of native communities of natural enemies.

This article has been peer-reviewed and recommended byPeer Community in Zoology<ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://doi.org/10.24072/pci.zool.100004">https://doi.org/10.24072/pci.zool.100004</ext-link>