TY - JOUR

T1 - Effects of grassland management, endophytic fungi and predators on aphid abundance in two distinct regions

AU - Börschig, Carmen

AU - Klein, Alexandra-Maria

AU - Krauss, Jochen

PY - 2014/10

Y1 - 2014/10

N2 - Aims Fungal endophytes of cool-season grass species produce alkaloids toxic to herbivores, affecting food webs in agricultural and natural ecosystems. Field studies about the effects of endophytes on herbivores are rare and show contradictory results, leading to uncertain conclusions about the nature of endophyte-grass symbiosis. We asked whether the environmental contexts of local and regional scales and predation could modify the effects of endophytes on herbivores. Methods In a full factorial field experiment, we quantified the abundance of the aphid species Rhopalosiphum padi on the potted host grass Lolium perenne, which was either infected or uninfected with the endophytic fungus Neotyphodium lolii. Predators were either excluded or had free access to the pots with the aphids. One hundred and sixty grass pots were located in two regions on altogether 40 grassland sites, half of the sites intensively and half extensively managed. We tested the importance of endophyte infection, study region, management intensity of grasslands, predation and all two-way interactions on aphid abundance. Important Findings Endophyte infection reduced aphid abundance significantly in one study region only. In both regions, we found that the impacts of aphidophagous predators and grassland management intensity on aphid abundance were substantially stronger and more consistent than that of endophytes on aphid abundance. Pots excluding predators and pots placed on extensive grasslands contained higher aphid abundance. The impact of predators and management on aphid abundance were not modified by the endophyte. We conclude that the effect of endophytes on herbivores can be weak in field experiments and depends on environmental context at a regional scale. Hence, more field research efforts are necessary to detect the relative importance of endophytes and the environmental context on biotic interactions in ecosystems.

AB - Aims Fungal endophytes of cool-season grass species produce alkaloids toxic to herbivores, affecting food webs in agricultural and natural ecosystems. Field studies about the effects of endophytes on herbivores are rare and show contradictory results, leading to uncertain conclusions about the nature of endophyte-grass symbiosis. We asked whether the environmental contexts of local and regional scales and predation could modify the effects of endophytes on herbivores. Methods In a full factorial field experiment, we quantified the abundance of the aphid species Rhopalosiphum padi on the potted host grass Lolium perenne, which was either infected or uninfected with the endophytic fungus Neotyphodium lolii. Predators were either excluded or had free access to the pots with the aphids. One hundred and sixty grass pots were located in two regions on altogether 40 grassland sites, half of the sites intensively and half extensively managed. We tested the importance of endophyte infection, study region, management intensity of grasslands, predation and all two-way interactions on aphid abundance. Important Findings Endophyte infection reduced aphid abundance significantly in one study region only. In both regions, we found that the impacts of aphidophagous predators and grassland management intensity on aphid abundance were substantially stronger and more consistent than that of endophytes on aphid abundance. Pots excluding predators and pots placed on extensive grasslands contained higher aphid abundance. The impact of predators and management on aphid abundance were not modified by the endophyte. We conclude that the effect of endophytes on herbivores can be weak in field experiments and depends on environmental context at a regional scale. Hence, more field research efforts are necessary to detect the relative importance of endophytes and the environmental context on biotic interactions in ecosystems.

KW - Biology

KW - bottom-up control

KW - microorganisms

KW - multi-trophic interactionedator exclosure, top-down control

KW - bottom-up control

KW - microorganism

KW - multi-trophic

KW - interaction

KW - predator exclosure

KW - top-down control

KW - Ecosystems Research

UR - http://www.scopus.com/inward/record.url?scp=84942325568&partnerID=8YFLogxK

U2 - 10.1093/jpe/rtt047

DO - 10.1093/jpe/rtt047

M3 - Journal articles

VL - 7

SP - 490

EP - 498

JO - Journal of Plant Ecology

JF - Journal of Plant Ecology

SN - 1752-9921

IS - 5

ER -