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Optimal foraging predicts the ecology but not the evolution of host specialization in bacteriophages.

Guyader S, Burch CL - PLoS ONE (2008)

Bottom Line: Although generalist phiX174 populations evolved even broader diets at low host density, they did not show a tendency to evolve the predicted specialist foraging strategy at high host density.Similarly, specialist G4 populations were unable to evolve the predicted generalist foraging strategy at low host density.These results demonstrate that optimal foraging models developed to explain the behaviorally determined diets of predators may have only limited success predicting the genetically determined diets of bacteriophage, and that optimal foraging probably plays a smaller role than genetic constraints in the evolution of host specialization in bacteriophages.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America.

ABSTRACT
We explore the ability of optimal foraging theory to explain the observation among marine bacteriophages that host range appears to be negatively correlated with host abundance in the local marine environment. We modified Charnov's classic diet composition model to describe the ecological dynamics of the related generalist and specialist bacteriophages phiX174 and G4, and confirmed that specialist phages are ecologically favored only at high host densities. Our modified model accurately predicted the ecological dynamics of phage populations in laboratory microcosms, but had only limited success predicting evolutionary dynamics. We monitored evolution of attachment rate, the phenotype that governs diet breadth, in phage populations adapting to both low and high host density microcosms. Although generalist phiX174 populations evolved even broader diets at low host density, they did not show a tendency to evolve the predicted specialist foraging strategy at high host density. Similarly, specialist G4 populations were unable to evolve the predicted generalist foraging strategy at low host density. These results demonstrate that optimal foraging models developed to explain the behaviorally determined diets of predators may have only limited success predicting the genetically determined diets of bacteriophage, and that optimal foraging probably plays a smaller role than genetic constraints in the evolution of host specialization in bacteriophages.

Show MeSH
The generalist phenotype of φX174 is costly at high host density (108 bacteria/mL) but advantageous at low host density (106 bacteria/mL).Data are the differences between ln(growth rate) in mixed host cultures containing E. coli and S. typhimurium (ES) and ln(growth rate) in pure host cultures containing only E. coli (E). The dotted line represents equal growth in both host composition treatments. Each data point represents the mean of 5 replicates±95% confidence intervals.
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pone-0001946-g003: The generalist phenotype of φX174 is costly at high host density (108 bacteria/mL) but advantageous at low host density (106 bacteria/mL).Data are the differences between ln(growth rate) in mixed host cultures containing E. coli and S. typhimurium (ES) and ln(growth rate) in pure host cultures containing only E. coli (E). The dotted line represents equal growth in both host composition treatments. Each data point represents the mean of 5 replicates±95% confidence intervals.

Mentions: In figure 3, we illustrated the nature of this interaction effect by plotting the differences between ln(growth rate) in mixed host cultures containing E. coli and S. typhimurium and ln(growth rate) in pure host cultures containing only E. coli. For the generalist phage φX174, the presence of S. typhimurium (the less profitable host) in experimental microcosms significantly decreased growth rate at high host density, but significantly increased growth rate at low density. In contrast, host composition had no significant effect on the growth rate of G4 at either host density.


Optimal foraging predicts the ecology but not the evolution of host specialization in bacteriophages.

Guyader S, Burch CL - PLoS ONE (2008)

The generalist phenotype of φX174 is costly at high host density (108 bacteria/mL) but advantageous at low host density (106 bacteria/mL).Data are the differences between ln(growth rate) in mixed host cultures containing E. coli and S. typhimurium (ES) and ln(growth rate) in pure host cultures containing only E. coli (E). The dotted line represents equal growth in both host composition treatments. Each data point represents the mean of 5 replicates±95% confidence intervals.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2279161&req=5

pone-0001946-g003: The generalist phenotype of φX174 is costly at high host density (108 bacteria/mL) but advantageous at low host density (106 bacteria/mL).Data are the differences between ln(growth rate) in mixed host cultures containing E. coli and S. typhimurium (ES) and ln(growth rate) in pure host cultures containing only E. coli (E). The dotted line represents equal growth in both host composition treatments. Each data point represents the mean of 5 replicates±95% confidence intervals.
Mentions: In figure 3, we illustrated the nature of this interaction effect by plotting the differences between ln(growth rate) in mixed host cultures containing E. coli and S. typhimurium and ln(growth rate) in pure host cultures containing only E. coli. For the generalist phage φX174, the presence of S. typhimurium (the less profitable host) in experimental microcosms significantly decreased growth rate at high host density, but significantly increased growth rate at low density. In contrast, host composition had no significant effect on the growth rate of G4 at either host density.

Bottom Line: Although generalist phiX174 populations evolved even broader diets at low host density, they did not show a tendency to evolve the predicted specialist foraging strategy at high host density.Similarly, specialist G4 populations were unable to evolve the predicted generalist foraging strategy at low host density.These results demonstrate that optimal foraging models developed to explain the behaviorally determined diets of predators may have only limited success predicting the genetically determined diets of bacteriophage, and that optimal foraging probably plays a smaller role than genetic constraints in the evolution of host specialization in bacteriophages.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America.

ABSTRACT
We explore the ability of optimal foraging theory to explain the observation among marine bacteriophages that host range appears to be negatively correlated with host abundance in the local marine environment. We modified Charnov's classic diet composition model to describe the ecological dynamics of the related generalist and specialist bacteriophages phiX174 and G4, and confirmed that specialist phages are ecologically favored only at high host densities. Our modified model accurately predicted the ecological dynamics of phage populations in laboratory microcosms, but had only limited success predicting evolutionary dynamics. We monitored evolution of attachment rate, the phenotype that governs diet breadth, in phage populations adapting to both low and high host density microcosms. Although generalist phiX174 populations evolved even broader diets at low host density, they did not show a tendency to evolve the predicted specialist foraging strategy at high host density. Similarly, specialist G4 populations were unable to evolve the predicted generalist foraging strategy at low host density. These results demonstrate that optimal foraging models developed to explain the behaviorally determined diets of predators may have only limited success predicting the genetically determined diets of bacteriophage, and that optimal foraging probably plays a smaller role than genetic constraints in the evolution of host specialization in bacteriophages.

Show MeSH