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- PublicationRestriction temporaireEnvironmental gradients and the evolution of tri‐trophic interactionsLong‐standing theory predicts herbivores and predators should drive selection for increased plant defences, such as the specific production of volatile organic compounds for attracting predators near the site of damage. Along elevation gradients, a general pattern is that herbivores and predators are abundant at low elevation and progressively diminish at higher elevations. To determine whether plant adaptation along such a gradient influences top‐down control of herbivores, we manipulated soil predatory nematodes, root herbivore pressure and plant ecotypes in a reciprocal transplant experiment. Plant survival was significantly higher for low‐elevation plants, but only when in the presence of predatory nematodes. Using olfactometer bioassays, we showed correlated differential nematode attraction and plant ecotype‐specific variation in volatile production. This study not only provides an assessment of how elevation gradients modulate the strength of trophic cascades, but also demonstrates how habitat specialisation drives variation in the expression of indirect plant defences.
- PublicationAccès libreTritrophic interactions follow phylogenetic escalation and climatic adaptation
- PublicationAccès librePlant physical and chemical traits associated with herbivory in situ and under a warming treatment
- PublicationMétadonnées seulementEnvironmental gradients and the evolution of tri‐trophic interactions
- PublicationMétadonnées seulementGrowth‐competition‐herbivore resistance trade‐offs and the responses of alpine plant communities to climate change
- PublicationAccès libreEarthworms affect plant growth and resistance against herbivores: A meta-analysis1. Subterranean detritivores such as earthworms can increase soil nutrient availability through their burrowing and casting activities. A number of recent studies have explored whether these changes caused by earthworms may in turn affect plant performance and resistance to herbivores, but no formal synthesis of this literature has been conducted to date. 2. We tested for the effects of earthworms on plant growth, resistance and chemical defences against insect herbivores by performing a meta-analysis of the existing literature up to 2016. We also explored ecological factors that might explain among-studies variation in the magnitude of the earthworm effects on plant growth and resistance. 3. We found that earthworm presence increases plant growth (by 20%) and nitrogen content (by 11%). Overall, earthworms did not affect plant resistance against chewing herbivores (caterpillars, slugs and rootworms), and even led to a 22% decrease in plant resistance against phloem-feeding herbivores (aphids). However, earthworm presence increased production of chemical defences by 31% when plants where attacked by cell-feeders (thrips), and resulted in an 81% increase in resistance against thrips. The magnitude of earthworm effects was stronger when earthworm inoculations consisted of a mix of species and ecological types, and when densities of earthworms were high. 4. These results suggest that earthworm presence is an important factor underlying natural variation in plant defences against erbivores, and call for a better integration of the soil fauna in the studies of plant-herbivore interaction, both for applied and fundamental research.
- PublicationAccès libreRelative contribution of high and low elevation soil microbes and nematodes to ecosystem functioningEcosystem productivity is largely dependent on soil nutrient cycling which, in turn, is driven by decomposition rates governed by locally adapted below-ground microbial and soil communities. How climate change will impact soil biota and the associated ecosystem functioning, however, remains largely an open question. To address this gap, we first characterized differences in soil microbial and nematode communities as well as functional characteristics from soils collected from the foothills or in sub-alpine elevations of the Alps. We next performed a full-factorial reciprocal transplant common garden experiment at two elevations, and asked whether elevation-related functional and taxonomic differences are maintained or can be altered depending on the local climatic conditions. For this, we separately transplanted soil microbial and nematode communities from low and high elevation in their home or opposite elevation in pots added with a common plant community. We found evidence for taxonomic and functional differentiation of the microbial and nematode communities when collected at high or low elevation. Specifically, we observed a decrease in microbial diversity and activity at high elevation, and additionally, through nematodes' functional characterization, we found increased fungal-dominated energy channels at high elevation. Moreover, according to the reciprocal transplant experiment, while we found little effect of soil biodiversity change based on elevation of origin on plant growth and plant community composition, soils inoculated with microbes originating from low elevation respired more than those originating from high elevation, particularly when at low elevation. This observation correlates well with the observed faster carbon degradation rates by the low elevation microbial communities. Climate change can reshuffle soil communities depending on organism-specific variation in range expansion, ultimately affecting soil fertility and carbon-cycle dynamics.
- PublicationMétadonnées seulementThe abundance, diversity and metabolic footprint of soil nematodes is highest in high elevation alpine grasslands
- PublicationAccès libreNovel trophic interactions under climate change promote alpine plant coexistence