title: Ecological conditions determine extinction risk in co-evolving bacteria-phage populations.
abstract: Antagonistic coevolution between bacteria and their viral parasites, phage, drives continual evolution of resistance and infectivity traits through recurrent cycles of adaptation and counter-adaptation. Both partners are vulnerable to extinction through failure of adaptation. Environmental conditions may impose unequal abiotic selection pressures on each partner, destabilising the coevolutionary relationship and increasing the extinction risk of one partner. In this study we explore how the degree of population mixing and resource supply affect coevolution-induced extinction risk by coevolving replicate populations of Pseudomonas fluorescens SBW25 with its associated lytic phage SBW25Ф2 under four treatment regimens incorporating low and high resource availability with mixed or static growth conditions.
  
  
  
  We observed an increased risk of phage extinction under population mixing, and in low resource conditions. High levels of evolved bacterial resistance promoted phage extinction at low resources under both mixed and static conditions, whereas phage populations could survive when phage susceptible bacterial genotypes rose to high frequency.
  
  
  
  These findings demonstrate that phage extinction risk is influenced by multiple abiotic conditions, which together act to destabilise the bacteria-phage coevolutionary relationship. The risk of coevolution-induced extinction is therefore dependent on the ecological context.
authors: Department of Biology, University of York, York, YO10 5DD, UK. rctw500@york.ac.uk.
authors: Rosanna C T
authors: RC
authors: Wright
authors: Department of Biology, University of York, York, YO10 5DD, UK.
authors: Michael A
authors: MA
authors: Brockhurst
authors: Department of Biology, University of York, York, YO10 5DD, UK.
authors: Ellie
authors: E
authors: Harrison
mesh_terms: D005075:Biological Evolution; D004463:Ecology; D053476:Extinction, Biological; D005838:Genotype; D010641:Phenotype; D017105:Pseudomonas Phages / Q000235:genetics*; D011551:Pseudomonas fluorescens / Q000235:genetics* / Q000821:virology*; D012307:Risk Factors; D013997:Time Factors
keywords: Antagonistic coevolution; Bacteriophage; Experimental evolution; Extinction; Pseudomonas fluorescens; Species interaction