Water availability alters the tri-trophic consequences of a plant-fungal symbiosis

Abstract

Plant-microbe protection symbioses occur when a symbiont defends its host against enemies (e.g., insect herbivores); these interactions can have important influences on arthropod abundance and composition. Understanding factors that generate context-dependency in protection symbioses will improve predictions on when and where symbionts are most likely to affect the ecology and evolution of host species and their associated communities. Of particular relevance are changes in abiotic contexts that are projected to accompany global warming. For example, increased drought stress can enhance the benefits of fungal symbiosis in plants, which may have multi-trophic consequences for plant-associated arthropods. Here, we tracked colonization of fungal endophyte-symbiotic and aposymbiotic Poa autumnalis (autumn bluegrass) by Rhopalosiphum padi (bird-cherry-oat aphids) and their parasitoids (Aphelinus sp.) following manipulations of soil water levels. Endophyte symbiosis significantly reduced plant colonization by aphids. Under low water, symbiotic plants also supported a significantly higher proportion of aphids that were parasitized by Aphelinus and had higher aboveground biomass than aposymbiotic plants, but these endophyte-mediated effects disappeared under high water. Thus, the multi-trophic consequences of plant-endophyte symbiosis were contingent on the abiotic context, suggesting the potential for complex responses in the arthropod community under future climate shifts.

Currencies of Mutualisms: Sources of Alkaloid Genes in Vertically Transmitted Epichloae

“…Such a situation is expected to select for mutualism because the fitness of a vertically transmitted symbiont links positively to host fitness [41,42]. A common benefit conferred by epichloae to their hosts is the production of protective alkaloids that can deter, impair or even kill invertebrate and vertebrate herbivores [1,3,4,22,43,44,45,46,47,48,49,50,51,52,53]. Whenever a hybrid forms, its fitness may depend on the alkaloid biosynthesis capabilities that it has obtained from its ancestors.…”

Pathogen resistant advantage of endophyte-infected over endophyte-free Leymus chinensis is strengthened by pre-drought treatment

“…The relevance of drought as regulator for plant-microbe interactions has been demonstrated for fungal endophytes (Miranda et al 2011;Vesterlund et al 2011;Yule et al 2011). For instance, Yule et al (2011) found that a moderate water-stress treatment strengthened the positive effect of endophytes on plant biomass and aphid incidence, which was lost under a highwatering regime.…”

“…For instance, Yule et al (2011) found that a moderate water-stress treatment strengthened the positive effect of endophytes on plant biomass and aphid incidence, which was lost under a highwatering regime. In our present study, we found that endophyte could enhance pathogen resistance of the host, and this endophytic advantage over E-plants was strengthened by pre-drought treatment.…”

Consequences of simultaneous interactions of fungal endophytes and arbuscular mycorrhizal fungi with a shared host grass

“…Simultaneous interactions with multiple symbionts make up an important component of the environment in which plant–symbiont interactions takes place (Stanton 2003). Research is increasingly appreciating the role of the community context in the dynamic nature of plant–microbe interactions (Hartley and Gange 2009, Yule et al 2011).…”