title: Increasing antagonistic interactions cause bacterial communities to collapse at high diversity.
abstract: Biodiversity is a major determinant of ecosystem functioning. Species-rich communities often use resources more efficiently thereby improving community performance. However, high competition within diverse communities may also reduce community functioning. We manipulated the genotypic diversity of Pseudomonas fluorescens communities, a plant mutualistic species inhibiting pathogens. We measured antagonistic interactions in vitro, and related these interactions to bacterial community productivity (root colonisation) and ecosystem service (host plant protection). Antagonistic interactions increased disproportionally with species richness. Mutual poisoning between competitors lead to a 'negative complementarity effect', causing a decrease in bacterial density by up to 98% in diverse communities and a complete loss of plant protection. The results emphasize that antagonistic interactions may determine community functioning and cause negative biodiversity-ecosystem functioning relationships. Interference competition may thus be an additional key for predicting the dynamics and performance of natural assemblages and needs to be implemented in future biodiversity models.
authors.affiliation: J.F. Blumenbach Institute for Zoology and Anthropology, Georg August University Göttingen, Berliner Str. 28, 37073 Göttingen, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Becker
authors.forename: Nico
authors.initials: N
authors.lastname: Eisenhauer
authors.forename: Stefan
authors.initials: S
authors.lastname: Scheu
authors.forename: Alexandre
authors.initials: A
authors.lastname: Jousset
mesh_terms: D000898:Antibiosis; D001419:Bacteria / Q000235:genetics; D018407:Bacterial Physiological Phenomena; D044822:Biodiversity; D005838:Genotype; D000455:Medicago sativa / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology; D011775:Pythium / Q000502:physiology