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Constraints on adaptation of Escherichia coli to mixed‐resource environments increase over time
Author(s) -
Satterwhite Rebecca S.,
Cooper Tim F.
Publication year - 2015
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/evo.12710
Subject(s) - generalist and specialist species , biology , adaptation (eye) , sympatric speciation , local adaptation , experimental evolution , population , resource (disambiguation) , selection (genetic algorithm) , ecology , evolutionary biology , genetic fitness , biological evolution , demography , genetics , habitat , computer science , computer network , neuroscience , artificial intelligence , sociology , gene
Can a population evolved in two resources reach the same fitness in both as specialist populations evolved in each of the individual resources? This question is central to theories of ecological specialization, the maintenance of genetic variation, and sympatric speciation, yet relatively few experiments have examined costs of generalism over long‐term adaptation. We tested whether selection in environments containing two resources limits a population's ability to adapt to the individual resources by comparing the fitness of replicate Escherichia coli populations evolved for 6000 generations in the presence of glucose or lactose alone (specialists), or in varying presentations of glucose and lactose together (generalists). We found that all populations had significant fitness increases in both resources, though the magnitude and rate of these increases differed. For the first 4000 generations, most generalist populations increased in fitness as quickly in the individual resources as the corresponding specialist populations. From 5000 generations, however, a widespread cost of adaptation affected all generalists, indicating a growing constraint on their abilities to adapt to two resources simultaneously. Our results indicate that costs of generalism are prevalent, but may influence evolutionary trajectories only after a period of cost‐free adaptation.