Plants are expanding their range: does this affect their association with arbuscular mycorrhizal fungi?

Current climate warming has brought about range expansion of plants, animals, and microorganisms to higher altitudes and latitudes. Range shifts of plant species are well documented, but we know little about the ecological consequences of this expansion. As plants disperse faster than soil organisms, range-expanding plants may in their new range be released from their natural enemies, but also from symbionts and decomposer organisms. To test this expectation, we characterized fungal communities (targeting the ITS region) associated to range expanding plant species (Centaurea stoebe, Solanum nigrum, Rorippa sylvestris) in their original and new range. We detected differences in fungal community composition associated to these plants in the two ranges. Fungal community dynamics, focusing on arbuscular mycorrhizal fungi, will be discussed in the presentation. With time, soil organisms may also disperse over long distances and expand their ranges but the effects of this possible event has never been tested. We established a greenhouse experiment to examine how range expansion of soil organisms influences the establishment of range expanding plants in the new range. Eight plant individuals, consisting of plants from distinctive ecological strategies (range-expanding plants, native plant species, and their combination), were grown in mesocosms, which were inoculated with different soil communities (sterile soil, soil community from original range, new range, or a mixture of original and new range). Our results show that the range-expanding plant species, which do not have closely related plant species in native plant communities, suppress the growth of native plants, whereas range-expanders with closely related species in the native plant community have no negative effect. Interestingly, the effect of soil communities differed also between these two types of range-expanding plants, being clearly distinctive between plants that commonly form arbuscular mycorrhizas and plants that do not.