title: The evolution of a pleiotropic fitness tradeoff in Pseudomonas fluorescens.
abstract: The evolution of ecological specialization is expected to carry a cost, due to either antagonistic pleiotropy or mutation accumulation. In general, it has been difficult to distinguish between these two possibilities. Here, we demonstrate that the experimental evolution of niche-specialist genotypes of the bacterium Pseudomonas fluorescens that colonize the air-broth interface of spatially structured microcosms is accompanied by pleiotropic fitness costs in terms of reduced carbon catabolism. Prolonged selection in spatially structured microcosms caused the cost of specialization to decline without loss of the benefits associated with specialization. The decline in the cost of specialization can be explained by either compensatory adaptation within specialist lineages or clonal competition among specialist lineages. These results provide a possible explanation of conflicting accounts for the cost of specialization.
authors.affiliation: Department of Biology, McGill University, 1205 Avenue Docteur Penfield, Montreal, QC, Canada H3A 1B1. rmacle2@po-box.mcgill.ca
authors.forename: R Craig
authors.initials: RC
authors.lastname: MacLean
authors.forename: Graham
authors.initials: G
authors.lastname: Bell
authors.forename: Paul B
authors.initials: PB
authors.lastname: Rainey
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D005075:Biological Evolution; D005838:Genotype; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D011551:Pseudomonas fluorescens / Q000235:genetics* / Q000378:metabolism*; D012641:Selection, Genetic