The American naturalist vol:170 issue:5 pages:800-805
Populations often face changes in environmental conditions at a relatively short timescale, which may lead to micro-evolution of traits to cope with these changing selective pressures. Here, we demonstrate micro-evolution of a physiological trait in a natural population of the water flea Daphnia magna. Levels of the stress protein Hsp60 showed genetic variation, indicating in situ evolutionary potential, and increased through time. The observed micro-evolutionary increase did not fit the historically documented changes in fish predation pressure in this pond, but paralleled an increase in load of infective stages of epibionts through time. In line with this, the locally most abundant epibiont caused an induction of Hsp60. As stress proteins show evolutionary potential and protect organisms against a wide array of environmental factors, micro-evolution of stress proteins in natural populations is likely to be common.