How range-expanding plants plug their roots in native belowground food webs

Rutger Wilschut (Invited speaker)

Activity: Talk or presentationAcademic

Description

Due to recent climate change, many plants and associated aboveground and belowground organisms expand their range to higher latitudes and altitudes. Because of different range expansion rates, co-evolved plant-soil interactions can become disrupted. In newly colonized areas, range-expanding plant species enter the local soil food web, thereby establishing new, often non-coevolved interactions. As native soil organisms might not be adapted to secondary root metabolites of the new plant species, interactions between range-expanders and native soil organisms might have different outcomes than with native plants. In turn, these altered interactions might influence the performance of the range-expanders. We studied interactions of root-feeding nematodes with range-expanding plant species and congeneric native plant species. A previous experiment showed that multi-trophic plant-microbe-nematode interactions are established differently in the rhizospheres of range-expanding plant species compared to related natives. Here, we tested the hypotheses that 1) native root-feeding nematodes are more strongly attracted to native plant species than to congeneric range-expanders, 2) root-feeding nematodes multiply better on native plant species than on congeneric range-expanders and 3) in the presence of root-feeding nematodes, range-expanding plant species will have a competitive advantage over related natives. We examined nematode preference by performing choice experiments with 2 native root-feeding nematode species, using 3 pairs of range-expanding and congeneric native plant species. We also examined nematode reproduction on all 6 plant species, and studied competition between native and range-expanding plants with and without nematodes. To explain differences in nematode attraction, we also analyzed root metabolite composition of all 6 plant species. Our results show that in two plant pairs the nematodes preferred the native plant species over the related-range expanders. Preference corresponded well with reproduction on natives vs range expanders. In one pair there was no consistent nematode preference, and nematode reproduction was slightly higher on the range-expander. The range-expanding plant species with the most novel root chemistry repelled nematodes, had lowest nematode reproduction, and highest performance in competition in the presence of root-feeding nematodes. The root chemistries of the other two range-expanders only slightly differed from the natives and both range-expanders did not gain a competitive benefit over the natives in the presence of nematodes. We conclude that in new ranges, range-expanding plant species can benefit from naïve natural enemies as these favor native plants over range-expanders, especially when the latter have strongly differing root chemistries. These results can help explain abundance of range-expanding plant species in their new range.
Period09 Aug 2016