EVOLUTION OF PREY SPECIFICITY VIA 3 STEPS

Comparative experiments with two extant sister-species of Chrysopa pro vide the first demonstration of mechanisms whereby a general predator (e.g., a C. quadripunctata-like ancestor) may have given rise to a spe cialist (C. slossonae). First, the generalist expresses characteristic s (e.g., phenotypic plasticity in larval and adult behaviour, defence- related morphology) that promote establishment on the specialist's ant -tended prey. Second, the patterns of variation among populations of t he generalist suggest heritability and repeatability in traits that in fluence survival and reproduction on the specialist's prey - a require ment for evolutionary adaptation to the specific prey. Third, sympatri c populations of the generalist and specialist have evolved reproducti ve isolation, thus maintaining prey fidelity. This descriptive model a ppears broadly applicable to predacious as well as herbacious insects.