Biology subjects

Thebault, E.

Publications and source records attributed to Thebault, E..

2 recordsLinked to original sources

bioRxiv2018

Impact of nutrient cycling on food web stability

AO_SCPLOWBSTRACTC_SCPLOWNutrient cycling is fundamental to ecosystem functioning. Despite recent major advances in the understanding of complex food web dynamics, food web models have so far generally ignored nutrient cycling. However, nutrient cycling is expected to strongly impact food web stability and functioning. To make up for this gap, we built an allometric and size structured food web model including nutrient cycling. By releasing mineral nutrients, recycling increases the availability of limiting resources for primary producers and links each trophic level to the bottom of food webs. We found that nutrient cycling can provide a significant part of the total nutrient supply of the food web, leading to a strong enrichment effect that promotes species persistence in nutrient poor ecosystems but leads to a paradox of enrichment at high nutrient inputs. The presence of recycling loops linking each trophic level to the basal resources weakly affects species biomass temporal variability in the food web. Recycling loops tend to slightly dampen the destabilising effect of nutrient enrichment on consumer temporal variability while they have opposite effects for primary producers. By considering nutrient cycling, this new model improves our understanding of the response of food webs to nutrient availability and opens perspectives to better link studies on food web dynamics and ecosystem functioning.

ecology↗

bioRxiv2017

Selective effects of temperature on body mass depend on trophic interactions and network position

Body mass is a key trait constraining interspecific interactions in food webs through changes in metabolic requirements. Because climate warming affects metabolic rates, it creates direct selective effects on body mass. Many empirical studies suggest that body mass decreases under warming, although important exceptions have been noted. We first analyze the evolution of body mass in a simple consumer-resource model to provide conditions under which a body mass increase or decrease may be expected. We then extend our model to a multi-trophic food web context that allows for the coevolution of body mass and of feeding preferences. We focus here on how the trophic position of a consumer influences its evolutionary response to warming under different scenarios for the temperature dependence of attack rates. We observe that body masses can remain constant or increase with temperature when attack rates are constant or increasing with temperature, while body mass reductions in response to warming are only expected when attack rates have a thermal optimum and populations are initially locally adapted. We also found that body masses at lower trophic levels vary less under warming than body masses at higher trophic levels, which may be explained by decreasing levels of stabilizing selection along food chains.

ecology↗