A gall mite, Aceria rhodiolae (Acari: Eriophyidae), altering the phytochemistry of a medicinal plant, Rhodiola rosea (Crassulaceae), in the Canadian Arctic

Abstract

ABSTRACTThe eriophyid mite Aceria rhodiolae (G. Canestrini) is known to induce galls on the flowers and leaves of roseroot, Rhodiola rosea L., in subarctic and alpine regions of Europe. After discovering galls on the inflorescences of roseroot in Nunavik (Québec), northeastern Canada, we examined the mites extracted from the galls and compared them with specimens of A. rhodiolae from Europe. Through morphological analyses, we demonstrate that the mites from galls in Nunavik are conspecific with A. rhodiolae from Europe. We then provide a detailed redescription of the mite species based on the morphology of adult females and males from Canada and Europe, using a combination of standard light microscopy, confocal microscopy and scanning electron microscopy. Because roseroot is well-known for its medicinal properties, we tested the hypothesis that roseroot galled by the mite had altered phytochemistry, by using salidroside and rosavins as indicators. Our results show a significant reduction of almost half in salidroside content (45.8%), but not in rosavins. Moreover, because the mite sometimes affects most or all of the inflorescence of R. rosea, it can considerably reduce the production of seeds. We also show that A. rhodiolae is widespread along the Ungava Bay (Nunavik), with 31.5% of 92 sites surveyed having at least a few to numerous plants galled. Given the importance of roseroot as a crop for Inuit communities and as medicinal products used by them and other Canadians, and also in view of the commonness of A. rhodiolae in the Canadian Arctic and its broad distribution in Europe, the impact of the mite and its relationship with roseroot should be examined further in Nunavik and elsewhere.