Discovery of cryptic diversity in phytophagous gall midges (Diptera: Cecidomyiidae) associated with different ecotypes of the perennial herb Cimicifuga simplex

Studying the diversification patterns of species-rich phytophagous insect taxa can help us understand the factors that cause species diversification. We conducted a molecular phylogenetic analysis of the mitochondrial COI gene of larvae of gall midges (Diptera: Cecidomyiidae) using three genetically differentiated morphs of Cimicifuga simplex plants and found that the gall midges could be divided into five major clades. Gall midges collected from morph I of C. simplex belonged to four Schizomyia clades. Gall midges collected from morph II of C. simplex belonged to one of the four Schizomyia clades collected from morph I. Gall midges collected from morph III belonged one Contarinia clade. On morphs I and II of C. simplex, the Schizomyia species induced galls on the flower bud, whereas on morph III of C. simplex, the Contarinia species was collected from normal fruits (not gall inducer); thus, morph III plants were used differently by gall midges than plants of morphs I and II. These results indicate that the cryptic diversity of these phytophagous insects correspond to that of plant ecotypes, and suggests that the diversification of the host plant contributed to parallel diversification of the phytophagous gall midges.