Gall mite molecular phylogeny and its relationship to the evolution of plant host specificity

The phylogenetic relationships of all seven known species of Cecidophyopsis mites (Acari: Eriophyidae) with Ribes hosts have been inferred from riboso mal DNA sequences. This analysis found groups of closely related mites. The five gall-forming species, four of which are monophagous and one which has two hosts, were found in two groups. Another group consisted of the two no n gall-forming species, one of which has two hosts, while the other is mono phagous. The molecular phylogeny of their known Ribes host plants was calcu lated using the equivalent ribosomal regions as the mites. The structure of the two trees (mites vs hosts) was clearly different, implying that mite s peciation did not closely follow speciation events in the plant hosts. Inst ead, the three groups of Ribes-infesting Cecidophyopsis mites have derived from a common galling ancestor millions of years ago. Each mite group has r ecently diversified onto different primary hosts. One group of mites has al so lost the galling habit. The results have implications for host range cha nges and the durability of mite-resistance genes in cultivated Ribes.