Author:
Yi Eunnuri,Meng Nova,Wood Corlett W.
Abstract
AbstractMutualistic microbes often increase their host’s susceptibility to parasite infection. We tested two competing hypotheses to identify the cause of this phenomenon. First, mutualist-provided resources could attract antagonists by making hosts more resource-rich. Second, mutualism establishment itself might increase host vulnerability to antagonists. To test which mechanism underlies increased parasite susceptibility, we experimentally decoupled mutualism establishment and mutualist-provided resources in the legume-rhizobia mutualism. We measured parasite load onMedicago truncatulaplants infected with root-knot nematodes in a full-factorial design, in which we independently manipulated rhizobia nodulation (mutualism establishment) and nitrogen availability (mutualist-provided resources). We found little effect of mutualism establishment on susceptibility, as nodulation without nitrogen fixation did not significantly increase parasite infection. By contrast, nitrogen did increase parasite infection, but with non-linear effects not fully explained by nitrogen assimilation into tissues. Our results suggest that mutualist-provided resources are an important but complex driver of indirect ecological costs of mutualism.
Publisher
Cold Spring Harbor Laboratory
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