title: Experimental demonstration of an Allee effect in microbial populations.
abstract: Microbial populations can be dispersal limited. However, microorganisms that successfully disperse into physiologically ideal environments are not guaranteed to establish. This observation contradicts the Baas-Becking tenet: 'Everything is everywhere, but the environment selects'. Allee effects, which manifest in the relationship between initial population density and probability of establishment, could explain this observation. Here, we experimentally demonstrate that small populations of Vibrio fischeri are subject to an intrinsic demographic Allee effect. Populations subjected to predation by the bacterivore Cafeteria roenbergensis display both intrinsic and extrinsic demographic Allee effects. The estimated critical threshold required to escape positive density-dependence is around 5, 20 or 90 cells ml(-1)under conditions of high carbon resources, low carbon resources or low carbon resources with predation, respectively. This work builds on the foundations of modern microbial ecology, demonstrating that mechanisms controlling macroorganisms apply to microorganisms, and provides a statistical method to detect Allee effects in data.
authors.affiliation: Odum School of Ecology, University of Georgia, Athens, GA, USA reni@uga.edu.
authors.forename: RajReni B
authors.identifier: 0000-0003-4820-5972
authors.initials: RB
authors.lastname: Kaul
authors.affiliation: Odum School of Ecology, University of Georgia, Athens, GA, USA.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Kramer
authors.affiliation: Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, VA, USA.
authors.forename: Fred C
authors.initials: FC
authors.lastname: Dobbs
authors.affiliation: Odum School of Ecology, University of Georgia, Athens, GA, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Drake
mesh_terms: D048908:Aliivibrio fischeri / Q000254:growth & development* / Q000502:physiology; D000818:Animals; D002244:Carbon; D017753:Ecosystem; D012623:Seawater / Q000737:chemistry; D058009:Stramenopiles
chemical_list: D002244:Carbon
keywords: Allee effect; microbial; micrososm; positive density-dependence