Decreased mycorrhizal colonization of Conyza canadensis (L.) Cronquist in invaded range does not affect fungal abundance in native plants

If we are to fight against plant invasions, we need to know the invasion mechanisms of particular neophytes. Conyza canadensis is a successful invader that is native to North America and expanding to human-made as well as natural habitats. Arbuscular mycorrhizal fungi (AMF) are obligate symbionts of a large majority of land plants, and they seem to play significant roles in a number of plant invasions. Although C. canadensis hosts AMF, their role in its invasion remains to be addressed. This survey’s aim was to test the interactions of C. canadensis with AMF in its native (North America) and invaded (Europe) range and the effect of its invasion on the AMF in roots of native plants within the invaded range. We compared AMF colonization of C. canadensis in both ranges, as well as AMF colonization of three native plant species of not yet invaded and invaded sites within the invaded range. Although this survey proved the colonization of C. canadensis with arbuscules and decreased AMF colonization of C. canadensis in the invaded versus its native range, AMF colonization of native plants was not affected by the invasion of C. canadensis. We presume there to be decreased dependence of C. canadensis on mycorrhiza in the invaded range and that another mechanism supports the successful invasions of this plant species. Nevertheless, this is the first time that the impact of C. canadensis on the abundance of AMF in roots of native plants has been assessed.