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Université de Fribourg

Increased temperature disrupts the biodiversity–ecosystem functioning relationship

Parain, Elodie C. ; Rohr, Rudolf P. ; Gray, Sarah M. ; Bersier, Louis-Félix

In: The American Naturalist, 2018, vol. 193, no. 2, p. 227–239

Gaining knowledge of how ecosystems provide essential services to humans is of primary importance, especially with the current threat of climate change. Yet little is known about how increased temperature will impact the biodiversity–ecosystem functioning (BEF) relationship. We tackled this subject theoretically and experimentally. We developed a BEF theory based on mechanistic population ...

Université de Fribourg

Understanding negative biodiversity–ecosystem functioning relationship in semi-natural wildflower strips

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

In: Oecologia, 2019, vol. 189, no. 1, p. 185–197

Studies on biodiversity–ecosystem functioning (BEF) in highly controlled experiments often yield results incompatible with observations from natural systems: experimental results often reveal positive relationships between diversity and productivity, while for natural systems, zero or even negative relationships have been reported. The discrepancy may arise due to a limited or closed local...

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

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

Do spiders respond to global change? A study on the phenology of ballooning spiders in Switzerland

Blandenier, Gilles ; Bruggisser, Odile T. ; Bersier, Louis-Félix

In: Écoscience, 2014, vol. 21, no. 1, p. 79–95

We studied ballooning spiders captured weekly over an 11-y period using a 12.2-m- high suction trap in an agricultural landscape of western Switzerland. We analyzed population trends, changes in phenology, and species composition. Yearly trends in population size of the most abundant species were studied with nonparametric correlations. We found that these trends were markedly different for...

Université de Fribourg

Effects of temperature variability on community structure in a natural microbial food web

Zander, Axel ; Bersier, Louis-Félix ; Gray, Sarah M.

In: Global Change Biology, 2017, vol. 23, no. 1, p. 56–67

Climate change research has demonstrated that changing temperatures will have an effect on community-level dynamics by altering species survival rates, shifting species distributions, and ultimately, creating mismatches in community interactions. However, most of this work has focused on increasing temperature, and still little is known about how the variation in temperature extremes will...

Université de Fribourg

Persist or produce: a community trade-off tuned by species evenness

Rohr, Rudolf P. ; Saavedra, Serguei ; Peralta, Guadalupe ; Frost, Carol M. ; Bersier, Louis-Félix ; Bascompte, Jordi ; Tylianakis, Jason M.

In: The American Naturalist, 2016, vol. 188, no. 4, p. 411–422

Understanding the effects of biodiversity on community persistence and productivity is key to managing both natural and production systems. Because rare species face greater danger of extinction, species evenness, a measure of how similar abundances are across species in a community, is seen as a key component of biodiversity. However, previous studies have failed to find a consistent...

Université de Fribourg

Mismatch in microbial food webs: predators but not prey perform better in their local biotic and abiotic conditions

Parain, Elodie C. ; Gravel, Dominique ; Rohr, Rudolf P. ; Bersier, Louis-Félix ; Gray, Sarah M.

In: Ecology and Evolution, 2016, vol. 6, no. 14, p. 4885–4897

Understanding how trophic levels respond to changes in abiotic and biotic conditions is key for predicting how food webs will react to environmental perturbations. Different trophic levels may respond disproportionately to change, with lower levels more likely to react faster, as they typically consist of smaller-bodied species with higher reproductive rates. This response could cause a...