The Laboratory as an Altered Habitat: Phenotypic and Genetic Consequences of Colonization

Abstract

Colonization of insects can cause dramatic changes in both phenotypes and genotypes. Phenotypic changes have been reported to occur in host plant acceptability, pheromonal responses, and reproductive parameters. Genetic alterations can include loss of genes, decreases in heterozygosity, and shifts in allele frequencies. The latter may be caused by random genetic drift, founder effects, nonrandom mating, and selection. Monitoring of laboratory quality can be accomplished by extensive record keeping on performance but a more efficient way is starch gel electrophoresis. Examples of this method applied to a soybean looper (Pseudoplusia includens) (Walker) laboratory colony and several fall armyworm (Spodoptera frugiperda (J. E. Smith)) populations are presented. Soybean looper heterozygosity decreased from 0.216 to 0.083 after two years of colonization. Fall armyworm colonies exhibited more variable heterozygosity levels and, in general, genetic distances were higher among colonies than field populations.