The quantitative genetics of polyphagy in an insect herbivore. I. Genotype-environment interaction in larval performance on different host plant species.

Abstract

Within a polyphagous species, individuals may either be generalists or be genetically variable in their capabilities on different potential hosts. Using the pest species Liriomyza sativae (Diptera: Agromyzidae), the hypothesis that individuals are generalized was tested by estimating the extent of overall genetic variation and genotype-environment interaction in pupal weight and development time for siblings reared on 2 plant species. Parents of the test larvae were sampled from closely adjacent fields of the 2 crops. The existence of significant genotype-environment interaction for development time within populations suggests that directional or stabilizing selection on either crop separately could lead to differences in the genetic composition of populations, and thus, to the evolution of genetically based host plant specialization at the population level. However, populations originating from the 2 crops differed very little in average responses to the 2 plant species, indicating that population divergence has not occurred. The absence of 'host races' may be due to frequent migration among crops.-from Author