title: Reciprocal rewards stabilize cooperation in the mycorrhizal symbiosis.
abstract: Plants and their arbuscular mycorrhizal fungal symbionts interact in complex underground networks involving multiple partners. This increases the potential for exploitation and defection by individuals, raising the question of how partners maintain a fair, two-way transfer of resources. We manipulated cooperation in plants and fungal partners to show that plants can detect, discriminate, and reward the best fungal partners with more carbohydrates. In turn, their fungal partners enforce cooperation by increasing nutrient transfer only to those roots providing more carbohydrates. On the basis of these observations we conclude that, unlike many other mutualisms, the symbiont cannot be "enslaved." Rather, the mutualism is evolutionarily stable because control is bidirectional, and partners offering the best rate of exchange are rewarded.
authors.affiliation: Institute of Ecological Science, Vrije Universiteit, 1081 HV Amsterdam, Netherlands. toby.kiers@vu.nl
authors.forename: E Toby
authors.initials: ET
authors.lastname: Kiers
authors.forename: Marie
authors.initials: M
authors.lastname: Duhamel
authors.forename: Yugandhar
authors.initials: Y
authors.lastname: Beesetty
authors.forename: Jerry A
authors.initials: JA
authors.lastname: Mensah
authors.forename: Oscar
authors.initials: O
authors.lastname: Franken
authors.forename: Erik
authors.initials: E
authors.lastname: Verbruggen
authors.forename: Carl R
authors.initials: CR
authors.lastname: Fellbaum
authors.forename: George A
authors.initials: GA
authors.lastname: Kowalchuk
authors.forename: Miranda M
authors.initials: MM
authors.lastname: Hart
authors.forename: Alberto
authors.initials: A
authors.lastname: Bago
authors.forename: Todd M
authors.initials: TM
authors.lastname: Palmer
authors.forename: Stuart A
authors.initials: SA
authors.lastname: West
authors.forename: Philippe
authors.initials: P
authors.lastname: Vandenkoornhuyse
authors.forename: Jan
authors.initials: J
authors.lastname: Jansa
authors.forename: Heike
authors.initials: H
authors.lastname: Bücking
mesh_terms: D005075:Biological Evolution; D050260:Carbohydrate Metabolism; D002244:Carbon / Q000378:metabolism; D055137:Glomeromycota / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D046913:Medicago truncatula / Q000382:microbiology* / Q000502:physiology*; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D010758:Phosphorus / Q000378:metabolism; D018517:Plant Roots / Q000382:microbiology* / Q000502:physiology; D012331:RNA, Fungal / Q000378:metabolism; D013045:Species Specificity; D013559:Symbiosis
chemical_list: D012331:RNA, Fungal; D010758:Phosphorus; D002244:Carbon