Lab of Environmental Change and Community Ecology

When total stressor intensity is allowed to vary with stressor richness (circles), increasing stressor richness degrades ecosystem functioning and community composition. However, when keeping total stressor intensity constant (triangles), stressor richness alone yields different effects on community variables than may be expected intuitively, with ecosystem functioning and compositional resistance to stress improving with stressor richness. This effect can be attributed to the differences in how species are affected, here measured using the stressor coefficient of variation.

Communities are composed of multiple interacting species inhabiting different locations. These are often affected by stressors altering the species’ population dynamics. We are studying the effects of such stressors on the feasibility and stability of those communities, which is complicated by their interaction structure, the different direct effects that the stressors have on different species, and the community’s spatial distribution. Panel a of the figure shows the relative effect of one stressor on isolated species of a given community. Panel b shows the actual effect of the stressor on community composition, obtained by numerical simulations.

Understanding how ecosystems overcome disturbances is a central question in ecology. To answer this question, ecologists try to determine the link between ecosystem complexity and stability. These properties can be measured in various ways, leading to a plethora of complexity-stability relationships. The figure shows how to disentangle the relationships between three complexity (in blue) and three stability (in red) properties of ecosystems. It highlights that, for example, while the number of interactions between the species increases robustness, it decreases local stability of ecosystems. These relationships are based on mathematical modelling of ecosystem and on empirical data. Completing this diagram should provide a better understanding of ecosystem complexity and its impact on their stability.

Myrmecophiles are fascinating arthropods that strictly live in ant nests. A very diverse community of myrmecophiles can be found in the organic mound nests of red wood ants. Myrmecophiles differ in their trophic ecology, including detritus feeders, scavengers steal ant brood and collected prey and predatory species that hunt for other myrmecophiles. We study the dynamics and drivers of this spatial network of food webs (meta food web) using field studies and lab experiments. The obtained empirical data are used to parameterize a spatial network model of a natural community of interacting symbionts.

The number of species within trophic levels contributes to horizontal diversity, while the number of trophic levels is called vertical diversity. We try to understand how both kinds of diversity contribute to the stability of large networks.

Niche and fitness differences allow positioning each species in the niche and fitness differences map (N-F map). The map extends in all four directions to infinity and is divided into different regions by five lines (black text). The diagonal line is the persistence line, below which species are assumed to persist, and above which species may go extinct. The other four lines divide both niche and fitness differences into three qualitative different sections each (blue text), leading to a total of nine different regions in the N-F map.