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Université de Fribourg

A guideline to study the feasibility domain of multi-trophic and changing ecological communities

Song, Chuliang ; Rohr, Rudolf P. ; Saavedra, Serguei

In: Journal of Theoretical Biology, 2018, vol. 450, p. 30–36

The feasibility domain of an ecological community can be described by the set of environmental abiotic and biotic conditions under which all co-occurring and interacting species in a given site and time can have positive abundances. Mathematically, the feasibility domain corresponds to the parameter space compatible with positive (feasible) solutions at equilibrium for all the state variables...

Université de Fribourg

Towards the integration of niche and network theories

Godoy, Oscar ; Bartomeus, Ignasi ; Rohr, Rudolf P. ; Saavedra, Serguei

In: Trends in Ecology & Evolution, 2018, vol. 33, no. 4, p. 287–300

The quest for understanding how species interactions modulate diversity has progressed by theoretical and empirical advances following niche and network theories. Yet, niche studies have been limited to describe coexistence within tropic levels despite incorporating information about multi-trophic interactions. Network approaches could address this limitation, but they have ignored the...

Université de Fribourg

The feasibility of equilibria in large ecosystems: A primary but neglected concept in the complexity-stability debate

Dougoud, Michaël ; Vinckenbosch, Laura ; Rohr, Rudolf P. ; Bersier, Louis-Félix ; Mazza, Christian

In: PLOS Computational Biology, 2018, vol. 14, no. 2, p. e1005988

The consensus that complexity begets stability in ecosystems was challenged in the seventies, a result recently extended to ecologically-inspired networks. The approaches assume the existence of a feasible equilibrium, i.e. with positive abundances. However, this key assumption has not been tested. We provide analytical results complemented by simulations which show that equilibrium...

Université de Fribourg

Why are some plant–pollinator networks more nested than others?

Song, Chuliang ; Rohr, Rudolf P. ; Saavedra, Serguei

In: Journal of Animal Ecology, 2017, vol. 86, no. 6, p. 1417–1424

Empirical studies have found that the mutualistic interactions forming the structure of plant–pollinator networks are typically more nested than expected by chance alone. Additionally, theoretical studies have shown a positive association between the nested structure of mutualistic networks and community persistence. Yet, it has been shown that some plant–pollinator networks may be more...

Université de Fribourg

Reorganization of interaction networks modulates the persistence of species in late successional stages

Saavedra, Serguei ; Cenci, Simone ; del-Val, Ek ; Boege, Karina ; Rohr, Rudolf P.

In: Journal of Animal Ecology, 2017, vol. 86, no. 5, p. 1136–1146

Ecological interaction networks constantly reorganize as interspecific interactions change across successional stages and environmental gradients. This reorganization can also be associated with the extent to which species change their preference for types of niches available in their local sites. Despite the pervasiveness of these interaction changes, previous studies have revealed that...

Université de Fribourg

The perfect mixing paradox and the logistic equation: Verhulst vs. Lotka

Arditi, Roger ; Bersier, Louis-Félix ; Rohr, Rudolf P.

In: Ecosphere, 2016, vol. 7, no. 11, p. e01599

A theoretical analysis of density-dependent population dynamics in two patches sheds novel light on our understanding of basic ecological parameters. Firstly, as already highlighted in the literature, the use of the traditional r-K parameterization for the logistic equation (due to Lotka and Gause) can lead to paradoxical situations. We show that these problems do not exist with Verhulst's...

Université de Fribourg

The relative contributions of species richness and species composition to ecosystem functioning

Sandau, Nadine ; Fabian, Yvonne ; Bruggisser, Odile T. ; Rohr, Rudolf P. ; Naisbit, Russell E. ; Kehrli, Patrik ; Aebi, Alexandre ; Bersier, Louis-Félix

In: Oikos, 2017, vol. 126, no. 6, p. 782–791

How species diversity influences ecosystem functioning has been the subject of many experiments and remains a key question for ecology and conservation biology. However, the fact that diversity cannot be manipulated without affecting species composition makes this quest methodologically challenging. Here, we evaluate the relative importance of diversity and of composition on biomass...

Université de Fribourg

A structural approach for understanding multispecies coexistence

Saavedra, Serguei ; Rohr, Rudolf P. ; Bascompte, Jordi ; Godoy, Oscar ; Kraft, Nathan J. B. ; Levine, Jonathan M.

In: Ecological Monographs, 2017, p. -

Although observations of species-rich communities have long served as a primary motivation for research on the coexistence of competitors, the majority of our empirical and theoretical understanding comes from two-species systems. How much of the coexistence observed in species rich communities results from indirect effects among competitors that only emerge in diverse systems remains poorly...