Differentiation and evolution in two groups of closely related Phyllotreta species (Coleoptera: Chrysomelidae)

This thesis studies differentiation and evolution within several closely related Phyllotreta species (Coleoptera: Chrysomelidae). Population genetics, morphology and systematics of two groups of closely related species are studied: the Phyllotreta tetrastigma complex (4 species) and the Phyllotreta cruciferae complex (6 species).; Part 1 of the thesis (7 chapters) concerns the P. tetrastigma complex. First the type material is studied. Subsequently two colour forms of one of the species are studied for genetic isolation using allozyme electrophoresis (PAGE) and isoelectric focusing of general proteins (IEF) and for morphological differences using biometric research. Finally we study the genetic and morphological relations between the four species of the complex.; Part 2 (5 chapters) concerns the P. cruciferae complex. Again the same topics are studied using identical techniques. In addition a phylogeny based on the morphological characters is constructed.; Part 3 contains two chapters in which all species belonging to both complexes are studied. First the niche-width variation hypothesis is tested for four monophagous and six oligophagous Phyllotreta species. This hypothesis predicts that oligophagous species should be genetically more variable than monophagous species, but is rejected for the Phyllotreta species studied. Finally morphology of eggs and larvae of all species of both complexes is discussed.