title: Evolutionary asymmetry in the arbuscular mycorrhizal symbiosis: conservatism in fungal morphology does not predict host plant growth.
abstract: Although arbuscular mycorrhizal (AM) fungi are obligate symbionts that can influence plant growth, the magnitude and direction of these effects are highly variable within fungal genera and even among isolates within species, as well as among plant taxa. To determine whether variability in AM fungal morphology and growth is correlated with AM fungal effects on plant growth, we established a common garden experiment with 56 AM fungal isolates comprising 17 genera and six families growing with three plant host species. Arbuscular mycorrhizal fungal morphology and growth was highly conserved among isolates of the same species and among species within a family. By contrast, plant growth response to fungal inoculation was highly variable, with the majority of variation occurring among different isolates of the same AM fungal species. Our findings show that host performance cannot be predicted from AM fungal morphology and growth traits. Divergent effects on plant growth among isolates within an AM fungal species may be caused by coevolution between co-occurring fungal and plant populations.
authors.affiliation: Department of Biology, University of British Columbia, Okanagan Campus, Kelowna, BC, V1V 1V7, Canada.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Koch
authors.affiliation: Department of Biology, Algoma University, Sault Ste. Marie, ON, P6B 2G4, Canada.
authors.forename: Pedro M
authors.initials: PM
authors.lastname: Antunes
authors.affiliation: Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada.
authors.forename: Hafiz
authors.initials: H
authors.lastname: Maherali
authors.affiliation: Department of Biology, University of British Columbia, Okanagan Campus, Kelowna, BC, V1V 1V7, Canada.
authors.forename: Miranda M
authors.initials: MM
authors.lastname: Hart
authors.affiliation: Department of Biology, University of British Columbia, Okanagan Campus, Kelowna, BC, V1V 1V7, Canada.
authors.forename: John N
authors.initials: JN
authors.lastname: Klironomos
mesh_terms: D005075:Biological Evolution; D055137:Glomeromycota / Q000166:cytology*; D038821:Mycorrhizae / Q000502:physiology*; D010802:Phylogeny; D063245:Plant Development; D010944:Plants / Q000382:microbiology*; D019655:Quantitative Trait, Heritable; D013045:Species Specificity; D013559:Symbiosis
keywords: arbuscular mycorrhiza (AM); asymmetry; coevolution; mutualism; parasitism; phylogenetic conservatism; symbiosis