TY  - JOUR
AB  - To cope with abiotic and biotic stressors, plants have developed mutualistic associations with beneficial soil microbes, but little is known about how extreme abiotic conditions impact on microbe-induce resistance to insect herbivores. Extreme temperatures are often accompanied by extremes in plant water availability, which together reduce plant growth and change plant physiology. There are potential consequences for increasing plant susceptibility to biotic stresses, and this poses a real challenge for plant productivity. We evaluated how the effects of beneficial soil bacteria (Acidovorax radicis N35e) on barley plant growth and resultant resistance against aphid infestation (Sitobion avenae) were impacted by a single heatwave event across a plant water availability gradient. We also tested if timing of bacterial inoculation (before or after the temperature treatment) affected bacteria-plant interactions on aphids. We found that heatwaves affected plant biomass allocation from above-ground to below-ground tissues. Inoculation with A. radicis led to reduction of aphid numbers, but depended on timing of inoculation, and led to stronger resistance when inoculations occurred closer to aphid infestation. Remarkably, microbe-induced resistance against aphids was consistent across heatwave and water availability treatments. This study provides evidence that beneficial plant-bacteria interactions may represent a potential solution for sustainable agricultural practices to enhance plant growth and response to insect pests under climate change. Future field trials should investigate the consistency of beneficial effects reported here for a better understanding of multispecies interactions in the context of global change. Read the free Plain Language Summary for this article on the Journal blog.
AU  - Sanchez-Mahecha, O.*
AU  - Klink, S.
AU  - Rothballer, M.
AU  - Sturm, S.*
AU  - Weisser, W.W.*
AU  - Zytynska, S.E.*
AU  - Heinen, R.*
C1  - 70067
C2  - 55407
CY  - 111 River St, Hoboken 07030-5774, Nj Usa
SP  - 848–860
TI  - Microbe-induced plant resistance against insect pests depends on timing of inoculation but is consistent across climatic conditions.
JO  - Funct. Ecol.
VL  - 38
PB  - Wiley
PY  - 2024
SN  - 0269-8463
ER  - 

TY  - JOUR
AB  - Plants harbour a wide range of leaf-feeding insects whose survival and fitness are influenced by both energy-rich molecules and phytochemicals in the host foliage. Yet, how leaf host chemical diversity and insect microbiota—key factors in ecological and physiological processes—impact insect nutrition and fitness are still poorly understood. To study the effects of leaf metabolic composition on insect herbivory resistance and performance, we fed the larvae of the specialist herbivory Tortrix viridana with leaves of susceptible and resistant Quercus robur trees that are characterized by contrasting metabolomes. We analysed the larval performance and mortality, the metabolomes in plant leaves, and in the insects' saliva and faeces by non-targeted metabolomics. Using chemometrics, mass difference network analysis and metabarcoding, we show the metabolome changes and chemical reactions associated with the different diets as well as their impact on insect fitness and gut microbiota. In the saliva and faeces of larvae, plant secondary metabolites (e.g. flavonoids) persisted more the insect digestion while compounds from primary metabolism were more depleted. In addition, metabolic reactions within the larvae indicated different degradation pathways used on the two plant metabolic types (syn. metabotypes), including sulfation and sulfonation. We show that feeding insects with resistant oak leaves, enriched in secondary metabolites and depleted in primary metabolites, impaired insect performance and mortality. Although the insects' gut microbiota was slightly different upon the contrasting diets, overall, it was fairly stable. Despite the impact of host chemicals on herbivores, larvae were generally highly efficient in nutrient assimilation (feed conversion ratios of 3.3–3.6) and able to minimize plant defences (78% of secondary metabolites were converted, broken down or sequestrated). The comparison of the oak metabotypes showed how the foliar composition of resistant oaks affected insect fitness by influencing their digestion. Herbivores feeding on resistant oaks were less efficient due to their lower ability to metabolize and detoxify higher levels of host phytochemicals, whereas those on susceptible oaks were more efficient as they could degrade the host metabolome. This study highlights the importance of the oak leaf chemical composition to insect digestion and fitness of a specialized herbivore. Read the free Plain Language Summary for this article on the Journal blog.
AU  - Bertic, M.
AU  - Orgel, F.*
AU  - Gschwendtner, S.
AU  - Schloter, M.
AU  - Moritz, F.
AU  - Schmitt-Kopplin, P.
AU  - Zimmer, I.
AU  - Fladung, M.*
AU  - Schnitzler, J.-P.
AU  - Schroeder, H.*
AU  - Ghirardo, A.
C1  - 68599
C2  - 53573
CY  - 111 River St, Hoboken 07030-5774, Nj Usa
SP  - 1476-1491
TI  - European oak metabolites shape digestion and fitness of the herbivore Tortrix viridana.
JO  - Funct. Ecol.
VL  - 37
IS  - 5
PB  - Wiley
PY  - 2023
SN  - 0269-8463
ER  - 

TY  - JOUR
AB  - 1.Cascading effects in ecological systems acting across three or more trophic levels can be either of a resource‐based (bottom‐up) or natural enemy‐based (top‐down) nature. But, due to their complexity these effects are often considered separately and their relative strength, acting simultaneously, remains unknown. 2.In a semi‐natural field experiment using tansy (Tanacetum vulgare L.) and the specialised tansy aphid Metopeurum fuscoviride Stroyan as a model system, we compared the effects of four distinct plant chemotypes (i.e. bottom‐up), defined by the bouquet of their volatile terpenoids, on aphid population dynamics by manipulating the presence/absence of mutualistic ants and presence/absence of naturally‐occurring predators (i.e. top‐down). 3.Predators reduced aphid abundance and colony survival but did not reduce initial growth rate due to a time lag until predators arrived on the plants. Ants directly benefited initial aphid growth rates and abundance, even in the absence of predators, but not the number of days an aphid colony persisted on the plant. 4.Plant chemotype directly affected aphid growth rate and final abundances across the different plants and indirectly affected the abundances of tending ants and predators through effects on aphids. We found that tending ants were more abundant on one plant chemotype. Although ant abundance did not affect aphid population development, it became clear that ants had a preference towards aphids on certain chemotypes. However, a higher number of predators led to a lower number of aphids. 5.The results confirm the importance of plant chemical variation, acting through multiple effects on many species in arthropod communities, and support results from field studies. In a natural population, with a diverse selection of host‐plant variants, aphid populations and their interacting species can therefore be structured at the level of an individual plant. Specialist aphids on patchily‐distributed host plants can exhibit metacommunity dynamics at very local scales. Plant within‐species variation within a local population is often ignored in metacommunity ecology, yet our work shows that this can have strong effects on insect‐ant‐natural enemy dynamics and therefore future research should incorporate this into current theory and experimental studies.
AU  - Senft, M.*
AU  - Clancy, M.V.
AU  - Weisser, W.W.*
AU  - Schnitzler, J.-P.
AU  - Zytynska, S.E.*
C1  - 54605
C2  - 45689
CY  - 111 River St, Hoboken 07030-5774, Nj Usa
SP  - 139-151
TI  - Additive effects of plant chemotype, mutualistic ants and predators on aphid performance and survival.
JO  - Funct. Ecol.
VL  - 33
IS  - 1
PB  - Wiley
PY  - 2019
SN  - 0269-8463
ER  - 

TY  - JOUR
AB  - Phenology-induced changes in carbon assimilation by trees may affect carbon stored in fine roots and as a consequence, alter carbon allocated to ectomycorrhizal fungi. Two competing models exist to explain carbon mobilization by ectomycorrhizal fungi. Under the 'saprotrophy model', decreased allocation of carbon may induce saprotrophic behaviour in ectomycorrhizal fungi, resulting in the decomposition of organic matter to mobilize carbon. Alternatively, under the 'nutrient acquisition model', decomposition may instead be driven by the acquisition of nutrients locked within soil organic matter compounds, with carbon mobilization a secondary process. We tested whether phenology-induced shifts in carbon reserves of fine roots of aspen (Populus tremuloides) affect potential activity of four carbon-compound degrading enzymes, β-glucuronidase, β-glucosidase, N-acetylglucosaminidase and laccase, by ectomycorrhizal fungi. Ectomycorrhizal roots from mature aspen were collected across eight stands in north-eastern Alberta, Canada, and analysed during tree dormancy, leaf flush, full leaf expansion and leaf abscission. We predicted potential extracellular enzyme activity to be highest when root carbon reserves were lowest, should host phenology induce saprotrophism. Further, we anticipated enzyme activity to be mediated by invertase, a plant-derived enzyme which makes carbon available to fungal symbionts in the plant-fungus interface. Root carbon reserves were positively correlated with invertase, suggesting phenology may affect carbon allocation to ectomycorrhizal fungi. However, of the four enzymes, host phenology had the largest effect on β-glucuronidase, but activity of this enzyme was not correlated with root carbon reserves or invertase. Low-biomass ectomycorrhizas had greater potential laccase activity than high-biomass ectomycorrhizas, highlighting discrete functional traits in fungi for litter decomposition. Our results suggest that the decomposition of organic matter may be driven by foraging by fungi for nutrients locked within organic compounds rather than for mobilizing carbon. Furthermore, the potential ability to degrade lignin was more common in low-biomass ectomycorrhizas when compared to high-biomass ectomycorrhizas.
AU  - Hupperts, S.F.*
AU  - Karst, J.*
AU  - Pritsch, K.
AU  - Landhäusser, S.M.*
C1  - 49119
C2  - 41661
CY  - Hoboken
SP  - 116-126
TI  - Host phenology and potential saprotrophism of ectomycorrhizal fungi in the boreal forest.
JO  - Funct. Ecol.
VL  - 31
IS  - 1
PB  - Wiley-blackwell
PY  - 2017
SN  - 0269-8463
ER  -