Links between host-plant type and site of feeding as revealed by the evolution of Palaearctic Eriococcidae (Sternorrhyncha: Coccoidea)

This work is an assessment of the biogeographical, taxonomic, biological and phylogenetic knowledge of the poorly defined family Eriococcidae. The study of its geographical diversity shows the richness of the Palearctic fauna on which the present analysis focuses. The numerous systems dealing with the taxonomy of Eriococcidae are detailed, and the specific taxonomical status of the genus Eriococcus, which contains 155 out of the 175 known Palearctic species is reevaluated. The phylogeny of the palaearctic members of the scale insect family Eriococcidae is reconstructed, using 9 genera and 52 species. Three more scale insect species belonging to 3 families were used as outgroups. The cladistic analysis of 130 morphological characters of the adults resulted in 10 most parsimonious trees, placing Eriococcus buxi as the sister-group of all other sampled Eriococcidae. The genera Acanthococcus, Rhizococcus, Greenisca and Anophococcus appear as para- or polyphyletic, but the weakness of most of the clades does not allow to denounce strictly the monophyly of these genera. However, some clades are supported with high confidence, like (Kaweckia + Neokaweckia), (Anophococcus parvispinus(Anophococcus inermis+Greenisca placida) and (Gossyparia spuria+Acanthococcus aceris). Concerning host-plant relationships, the phylogeny supports an evolutionary scenario whereby the ancestor of the family Eriococcidae fed originally on woody plants, and more typically on leaves. The switch observed from Poaceae to other herbaceous plants is correlated to the switch from leaves as preferred site of nutrition to branches and stems. The supported scenario shows another switch, back from other herbs to Poaceae, associated to the choice of leaves as nutrition site.