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Université de Fribourg

Evidence of climatic niche shift during biological invasion

Broennimann, Olivier ; Treier, Urs A. ; Müller-Schärer, Heinz ; Thuiller, W. ; Peterson, A. T. ; Guisan, Antoine

In: Ecology Letters, 2007, vol. 10, no. 8, p. 701-709

Niche-based models calibrated in the native range by relating species observations to climatic variables are commonly used to predict the potential spatial extent of species’ invasion. This climate matching approach relies on the assumption that invasive species conserve their climatic niche in the invaded ranges. We test this assumption by analysing the climatic niche spaces of Spotted...

Université de Fribourg

A permeable cuticle in Arabidopsis leads to a strong resistance to Botrytis cinerea

Bessire, Michael ; Chassot, Céline ; Jacquat, Anne-Claude ; Humphry, Matt ; Borel, Sandra ; MacDonald-Comber Petétot, Jean ; Métraux, Jean-Pierre ; Nawrath, Christiane

In: The EMBO Journal, 2007, vol. 26, no. 8, p. 2158–2168

The plant cuticle composed of cutin, a lipid-derived polyester, and cuticular waxes covers the aerial portions of plants and constitutes a hydrophobic extracellular matrix layer that protects plants against environmental stresses. The botrytis-resistant 1 (bre1) mutant of Arabidopsis reveals that a permeable cuticle does not facilitate the entry of fungal pathogens in...

Université de Fribourg

Juvenile hormone as a regulator of the trade-off between reproduction and life span in Drosophila melanogaster

Flatt, Thomas ; Kawecki, Tadeusz J.

In: Evolution, 2007, vol. 61, no. 8, p. 1980–1991

Trade-offs between reproduction and life span are ubiquitous, but little is known about their underlying mechanisms. Here we combine treatment with the juvenile hormone analog (JHa) methoprene and experimental evolution in Drosophila melanogaster to study the potential role of juvenile hormone (JH) in mediating such trade-offs at both the physiological and evolutionary level. Exposure to...

Université de Fribourg

Influence of plasticity and learning on evolution under directional selection

Paenke, Ingo ; Sendhoff, Bernhard ; Kawecki, Tadeusz J.

In: American Naturalist, 2007, vol. 170, no. 2, p. E47-E58

Phenotypic plasticity and related processes (learning, developmental noise) have been proposed to both accelerate and slow down genetically based evolutionary change. While both views have been supported by various mathematical models and simulations, no general predictions have been offered as to when these alternative outcomes should occur. Here we propose a general framework to study the...

Université de Fribourg

Experimental evolution of olfactory memory in Drosophila melanogaster

Mery, Frederic ; Pont, Juliette ; Preat, Thomas ; Kawecki, Tadeusz J.

In: Physiological and Biochemical Zoology, 2007, vol. 80, no. 4, p. 399-405

In order to address the nature of genetic variation in learning performance, we investigated the response to classical olfactory conditioning in "high-learning" Drosophila melanogaster lines previously subject to selection for the ability to learn an association between the flavor of an oviposition medium and bitter taste. In a T-maze choice test, the seven high-learning lines were better at...

Université de Fribourg

Evolutionary biology of starvation resistance: what we have learned from Drosophila

Rion, Stéphanie ; Kawecki, Tadeusz J.

In: Journal of Evolutionary Biology, 2007, vol. 20, no. 5, p. 1655-1664

Most animals face periods of food shortage and are thus expected to evolve adaptations enhancing starvation resistance (SR). Most of our knowledge of the genetic and physiological bases of those adaptations, their evolutionary correlates and trade-offs, and patterns of within- and among-population variation, comes from studies on Drosophila. In this review, we attempt to synthesize the...

Université de Fribourg

Natural polymorphism affecting learning and memory in Drosophila

Mery, Frederic ; Belay, Amsale T. ; So, Anthony K.-C. ; Sokolowski, Marla B. ; Kawecki, Tadeusz J.

In: Proceedings of the National Academy of Sciences of the United States of America, 2007, vol. 104, no. 32, p. 13051-13055

Knowing which genes contribute to natural variation in learning and memory would help us understand how differences in these cognitive traits evolve among populations and species. We show that a natural polymorphism at the foraging (for) locus, which encodes a cGMP-dependent protein kinase (PKG), affects associative olfactory learning in Drosophila melanogaster. In an assay...

Université de Fribourg

Genotypic selection in Daphnia populations consisting of inbred sibships

Haag, Christoph ; Hebert, Dieter

In: Journal of Evolutionary Biology, 2007, vol. 20, no. 3, p. 881–891

The genetic basis of fitness reduction associated with inbreeding is still poorly understood. Here we use associations between allozyme genotypes and fitness to investigate the genetic basis of inbreeding depression in experimental outdoor populations of the water flea, Daphnia magna. In Daphnia, a phase of clonal reproduction follows hatching from sexually produced resting eggs,...

Université de Fribourg

Functional responses: a question of alternative prey and predator density

Tschanz, Britta ; Bersier, Louis-Félix ; Bacher, Sven

In: Ecology, 2007, vol. 88, no. 5, p. 1300–1308

Throughout the study of ecology, there has been a growing realization that indirect effects among species cause complexity in food webs. Understanding and predicting the behavior of ecosystems consequently depends on our ability to identify indirect effects and their mechanisms. The present study experimentally investigates indirect interactions arising between two prey species that share a...