Evol Ecol Res 9: 959-974 (2007)     Full PDF if your library subscribes.

Inter-specific competitive stress does not affect the magnitude of inbreeding depression

Yvonne Willi,1,2,3* Stefan Dietrich,4 Mark van Kleunen,4,5,6 and Markus Fischer4,6

1Institute of Integrative Biology, ETH Zürich, Universitätstrasse 2, CH-8092 Zürich, Switzerland, 2Centre for Environmental Stress and Adaptation Research CESAR, Zoology Department, University of Melbourne, Melbourne, VIC 3010, Australia,  3Institute of Environmental Sciences, University of Zürich, CH-8057 Zürich, Switzerland,  4Institute of Biochemistry and Biology, University of Potsdam, D-14471 Potsdam, Germany,  5Centre for Invasion Biology, School of Biological and Conservation Sciences, University of KwaZulu-Natal, Pietermaritzburg 3209, South Africa and  6Institute of Plant Sciences, University of Bern, CH-3013 Bern, Switzerland

Author to whom all correspondence should be addressed.
e-mail: yvonne.willi@agrl.ethz.ch


Hypothesis: Stressful inter-specific competition enhances inbreeding depression.

Organisms: Creeping spearwort (Ranunculus reptans L.) and its common competitor, the creeping bentgrass (Agrostis stolonifera L.).

Field site: Outdoor common garden experiment at the University of Potsdam.

Methods: We collected plants of 12 natural populations of R. reptans differing in mean parental inbreeding coefficient (0.01–0.26). We performed within-population crosses for two generations and kept the offspring in a common environment. In the second generation, we raised plants in the presence or absence of the grass competitor A. stolonifera. After 2 months, we assessed survival and growth of two replicate plants per seed family and treatment. To compare our results with those of previous investigations, we compiled a list of studies on inbreeding and competition.

Conclusions: Both population mean inbreeding and inter-specific competition led to a significant reduction in plant performance (survival and growth) and were therefore sources of stress. However, inbreeding and competition did not interact in their effects on plant performance or developmental instability (estimated by within-family coefficient of variation in performance). Inter-specific competition did not enhance inbreeding depression, which is in line with the results of most previous studies.

Keywords: environment dependence, environmental stress, inbreeding depression, inter-specific competition, intra-specific competition.

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