Theory suggests that relatives will cooperate more, and compete less, because of an increased benefit for shared genes. In symbiotic partnerships, hosts may benefit from interacting with highly related symbionts because there is less conflict among the symbionts. This has been difficult to test empirically. We used the arbuscular mycorrhizal symbiosis to study the effects of fungal relatedness on host and fungal benefits, creating fungal networks varying in relatedness between two hosts, both in soil and in-vitro. To determine how fungal relatedness affected overall transfer of nutrients, we fluorescently tagged phosphorus and quantified resource distribution between two root systems. We found that colonization by less-related fungi was associated with increased fungal growth, lower transport of nutrients across the network, and lower plant benefit - likely an outcome of increased fungal competition. More generally, we demonstrate how symbiont relatedness can mediate benefits of symbioses.
Bibliographical noteFunding Information:
The research was supported by European Research Council ERC 335542 (to E.T.K), Ammodo Foundation (to E.T.K) and HFSP grant RGP 0029 (to E.T.K and T.S.S.). We thank M. Whiteside for help in developing the quantum‐dot technique, and Lukasz Istel for help with culture cultivation the cultures. We thank four reviewers for their constructive feedback.
© 2021 The Authors. Ecology Letters published by John Wiley & Sons Ltd.