Root chemistry determines the outcome of novel plant-nematode interactions of range-expanding plant species

Due to recent climate change, many plants and associated aboveground and belowground organisms expand their range to higher latitudes and altitudes. During this process, co-evolved plant-soil interactions can become disrupted, because of different range expansion rates. In newly colonized areas, range-expanding plant species establish new, often non-coevolved interactions. As the native soil organisms might not be adapted to the root chemistries of these range-expanding plant species, plant-soil interactions of range-expanders might have different outcomes than those of native plants. We studied plant-nematode interactions of 3 range-expanding plant species and their native congeners. We tested the hypotheses that 1) native root-feeding nematodes are more strongly attracted to native plant species than to congeneric range-expanders and that 2) root-feeding nematodes multiply better on native plant species than on congeneric range-expanders. We examined nematode preference in choice experiments with 2 native root-feeding nematode species. We also examined nematode reproduction on all 6 plant species. To explain differences in nematode attraction and reproduction, we analyzed root volatile composition of all 6 plant species. We found that in two plant pairs the nematodes preferred the native plant species over the related-range expanders, which corresponded well with nematode reproduction patterns. In one pair there was no consistent nematode preference for either the native or range-expander, and nematode reproduction was higher on the range-expander. The range-expanding plant species with the most novel root chemistry repelled nematodes and had lowest nematode reproduction. The root chemistry of the other two range-expanders did not strongly differ from the natives. We conclude that in new ranges, especially range-expanding plant species with strongly different root chemistries might benefit indirectly from exposure to naïve natural enemies as these preferentially attack native species. These results can help explain differences in abundance between range-expanding plant species in their new range.