Between Friends and Foes: Evolutionary Diversification in Mutualistic-Antagonistic Networks

Biotic interactions can drive evolutionary diversification, but the underlying mechanisms differ depending on the type of interaction. For instance, Ehrlich and Raven's escape-and-radiate coevolution provides a pathway of diversification in antagonistic interactions, whereas in mutualistic networks, coevolution is hypothesized to result in trait convergence rather than diversification. The combined effect of mutualism and antagonism on diversification remains unclear, even though organisms naturally engage in multiple types of interactions simultaneously. Using an eco-evolutionary simulation model, we investigate diversification in tripartite ecological networks such as plant-pollinator-herbivore networks. We find that diversification patterns vary according to the way mutualism and antagonism are connected on the trait level. If the two interactions are governed by uncorrelated plant traits, we observe little diversification in the mutualistic and substantial diversification in the antagonistic subnetwork. By contrast, if the same plant trait mediates both mutualism and antagonism (an example of 'ecological pleiotropy'), diversification rates in all guilds become interdependent. In this case, even the mutualistic guild diversifies considerably when antagonism is strong, while strong mutualism restricts diversification also in the antagonistic guild. Our study underlines that the inclusion of multiple interaction types is necessary to advance our understanding of evolutionary dynamics in ecological networks. ### Competing Interest Statement The authors have declared no competing interest. Deutsche Forschungsgemeinschaft, https://ror.org/018mejw64, AL 2563/3‑1 German National Academic Foundation

Many weak and few strong links: the importance of link strength distributions for stabilising patterns in competition networks - Theoretical Ecology

Ecological networks tend to contain many weak and only a few strong links. Furthermore, link strengths are often patterned within a network in ways that enhance system stability considerably, increasing the ability of the system to return to equilibrium after a perturbation. However, little attention has been given to the relation between the skewed “many weak and few strong links” distribution and the stabilising effect of patterning. Here, we focus on the stabilising effect of a hierarchical patterning in bryozoan competition networks and demonstrate that this stabilising effect critically depends on a skewed distribution of link strengths. We first show that, in line with many other ecological networks, the empirically derived link strengths in these competition networks were characterised by a high level of skewness, with many weak and few strong links. Then, we analysed the relationship between the link strength distributions, hierarchy and stability by comparing theoretical competition matrices with different distributions of link strengths. We found that the full stabilising effect of hierarchy only appeared when we used skewed link strengths produced by a gamma distribution, but not in matrices built with uniform or half-normal distributions. This has important methodological implications, since theoretical studies often assume normal or uniform distributions to investigate ecological stability, and therefore might overlook stabilising mechanisms. These implications are relevant for theory on the relation between structure and stability of ecological networks in general, since skewed link strengths are also a common feature of food webs and mutualistic systems.

Models in Population Dynamics, Ecology and Evolution 2026

MPDEE26 Conference

The Silent Impact: How Roads Are Eroding Europe’s Food Webs | Current Conservation

Current Conservation The Silent Impact: How Roads Are Eroding Europe’s Food Webs

The Silent Impact: How Roads Are Eroding Europe’s Food Webs | Current Conservation

Current Conservation The Silent Impact: How Roads Are Eroding Europe’s Food Webs

The domino effect of roads on biodiversity: How the impacts of wildlife-vehicle collisions propagate through food webs — Transport Ecology

Our study reveals that roads and traffic not only cause direct wildlife mortality but also destabilise entire ecological networks by altering predator-prey interactions. By mapping high-risk areas for disrupted predator-prey interactions across Europe, we highlight the urgent need for tailored measu

GfÖ Annual Meeting 2025 September 01 to 05, 2025 in Würzburg, Germany