A METAANALYSIS OF ADAPTIVE DEME FORMATION IN PHYTOPHAGOUS INSECT POPULATIONS

The adaptive deme formation (ADF) hypothesis predicts that herbivorous insects become locally adapted to their host plants over time. Since its inception, approximately 17 independent studies have tested ADF, a nd they are divided in support and rejection of the hypothesis. This f ield of insect evolutionary ecology has a contentious history, and the contradictory studies obscure our understanding of the general evolut ionary importance of adaptive deme formation in phytophagous insects. We conducted a meta-analysis in an attempt to clarify this issue. Meta -analysis is a statistical method for quantitatively comparing and syn thesizing the results of different studies in a way that is more objec tive than a traditional literature review. Our analysis indicates that local ad aptation is an important phenomenon in diverse insect system s. Contrary to predictions of the original hypothesis, there was no ev idence that insect dispersal ability, and ostensibly gene flow, was as sociated with local adaptive differentiation. There was some indicatio n that breeding (parthenogenetic, haplodiploid, diplodiploid) and feed ing (exophagous, endophagous) modes may influence the evolution of loc ally adapted demes. Our analysis supports the theory of adaptive deme formation and provides guidance for future research directions.