Rates and Patterns of Laboratory Adaptation in (Mostly) Insects

Insects and other invertebrates can readily adapt to a range of environmental conditions and these include conditions used in artificial rearing. This can lead to problems when mass-rearing insects and mites for release as biocontrol agents or in sterile insect control programs, and when using laboratory strains to understand field population dynamics. Laboratory adaptation experiments also help to understand potential rates of trait evolution and repeatability of evolutionary changes. Here, we review evidence for laboratory adaptation across invertebrates, contrasting different taxonomic groups and providing estimates of the rate of evolutionary change across trait classes. These estimates highlight rapid changes in the order of 0.033 (median) haldanes and up to 2.4 haldanes, along with proportional changes in traits of more than 10% per generation in some cases. Traits tended to change in the direction of increased fitness for Coleoptera, Diptera and Hymenoptera, but changes in Lepidoptera were often in the opposite direction. Laboratory- adapted lines tend to be more sensitive to stress, likely reflecting relaxed selection for stress-related traits. Morphological traits show smaller changes under laboratory conditions than other types of traits. Estimates of evolutionary rates slowed as more generations were included in comparisons, perhaps reflecting nonlinear dynamics although such patterns may also reflect variance differences among trait classes. The rapid rate of laboratory adaptation in some cultures reinforces the need to develop guidelines for maintaining quality during mass-rearing and highlights the need for caution when using laboratory lines to represent the performance of species in vulnerability assessments. (author)