Premium
REVERSE EVOLUTION: SELECTION AGAINST COSTLY RESISTANCE IN DISEASE‐FREE MICROCOSM POPULATIONS OF PARAMECIUM CAUDATUM
Author(s) -
Duncan Alison B.,
Fellous Simon,
Kaltz Oliver
Publication year - 2011
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/j.1558-5646.2011.01388.x
Subject(s) - biology , paramecium caudatum , resistance (ecology) , asexual reproduction , reproduction , parasite hosting , genetic fitness , experimental evolution , selection (genetic algorithm) , zoology , ecology , genetics , paramecium , gene , biochemistry , artificial intelligence , world wide web , computer science
Evolutionary costs of parasite resistance arise if genes conferring resistance reduce fitness in the absence of parasites. Thus, parasite‐mediated selection may lead to increased resistance and a correlated decrease in fitness, whereas relaxed parasite‐mediated selection may lead to reverse evolution of increased fitness and a correlated decrease in resistance. We tested this idea in experimental populations of the protozoan Paramecium caudatum and the parasitic bacterium Holospora undulata . After eight years, resistance to infection and asexual reproduction were compared among paramecia from (1) “infected” populations, (2) uninfected “naive” populations, and (3) previously infected, parasite‐free “recovered” populations. Paramecia from “infected” populations were more resistant (+12%), but had lower reproduction (–15%) than “naive” paramecia, indicating an evolutionary trade‐off between resistance and fitness. Recovered populations showed similar reproduction to naive populations; however, resistance of recently (<3 years) recovered populations was similar to paramecia from infected populations, whereas longer (>3 years) recovered populations were as susceptible as naive populations. This suggests a weak, convex trade‐off between resistance and fitness, allowing recovery of fitness, without complete loss of resistance, favoring the maintenance of a generalist strategy of intermediate fitness and resistance. Our results indicate that (co)evolution with parasites can leave a genetic signature in disease‐free populations.