Climate change causes species range expansions to higher latitudes and altitudes. It is expected that, due to differences in dispersal abilities between plants and soil biota, range-expanding plant species will become associated with a partly new belowground community in their expanded range. Theory on biological invasions predicts that outside their native range, range-expanding plant species may be released from specialist natural enemies, leading to the evolution of enhanced defence against generalist enemies. Here we tested the hypothesis that expanded range populations of the range-expanding plant species Centaurea stoebe accumulate fewer root-feeding nematodes than populations from the original range. Moreover, we examined whether Centaurea stoebe accumulates fewer root-feeding nematodes in expanded range soil than in original range soil. We grew plants from three expanded range and three original range populations of C. stoebe in soil from the original and from the new range. We compared nematode communities of C. stoebe with those of C. jacea, a congeneric species native to both ranges. Our results show that expanded range populations of C. stoebe did not accumulate fewer root-feeding nematodes than populations from the original range, but that C. stoebe, unlike C. jacea, accumulated fewest root-feeding nematodes in expanded range soil. Moreover, when we examined other nematode feeding groups, we found intra-specific plant population effects on all these groups. We conclude that range-expanding plant populations from the expanded range were not better defended against root-feeding nematodes than populations from the original range, but that C. stoebe might experience partial belowground enemy release.

气候变化导致物种范围扩展到更高的纬度和海拔。可以预期，由于植物和土壤生物群之间的分散能力不同，范围扩大的植物物种将在其扩大范围内与部分新的地下群落有关。关于生物入侵的理论预测，扩大范围的植物物种可能会从专门的天敌中释放出来，从而导致增强的对多面手敌人的防御能力的演变。在这里，我们检验了以下假设：与原始范围的种群相比，范围扩大的植物Centaurea的范围扩大的种群积累的食根线虫较少。此外，我们检查了矢车菊与原始范围土壤相比，扩大范围土壤中累积的根系食根线虫更少。我们从原始范围和新范围中的三个扩展范围和三个原始范围的斯托氏梭菌种群开始在土壤中种植植物。我们比较的线虫群落C. stoebe与那些C. jacea，一个同类品种，原产于两个范围。我们的结果表明，与原始范围的种群相比，stoebe。stoebe的扩大范围种群积累的食根线虫数量没有减少，但是stoebe。C. stoebe与C. jacea不同，在扩大范围的土壤中积累的根生食线虫最少。此外，当我们检查其他线虫摄食组时，我们发现种内植物种群对所有这些组的影响。我们得出的结论是，扩大范围的植物种群比原始范围的种群不能更好地防御食根线虫的侵害，但是斯托氏梭菌可能会在地下被部分敌人释放。