Bursaphelenchus mucronatus kolymensis comb. n. – new definition of the “European type” of B. mucronatus
Keywords: Bursaphelenchus mucronatus, distribution, hybridization, morphology, subspecies, molecular taxonomy
AbstractThe two Bursaphelenchus mucronatus types are proposed to be subspecies. The European type is named B. mucronatus kolymensis comb. n., and the East Asian type is the nominate subspecies B. mucronatus mucronatus. The earlier described Bursaphelenchus kolymensis corresponds to the European type of B. mucronatus in morphological characters. The two subspecies show morphological differences in the shape of female tail, length of mucro, position of excretory pore and also small differences in spicule shape. They can be distinguished by their ITS-RFLP patterns on the basis of restriction fragments obtained with enzymes RsaI and HaeIII. Based on sequence analysis of ribosomal ITS1/2, LSU D2/D3 and mitochondrial COI regions, a clear subdivision of the two isolate groups (subspecies) has been confirmed. The genetic distance between the two subspecies is lower than between species of the xylophilus group, but higher than the distances between various isolates within the subspecies. Successful hybridization of the two subspecies had been shown previously in mating experiments. Bursaphelenchus mucronatus kolymensis comb. n. is widely distributed in Europe and Siberia, whereas B. m. mucronatus is predominant in East Asia. Bursaphelenchus mucronatus kolymensis comb. n. is locally present in the border regions of the northern conifer forests in East Asia and is found scattered in some East Asian countries, but sporadic records of B. m. mucronatus in Europe and Siberia are also known. Spreading of the two subspecies from West to East and vice versa is most likely caused by transport with wood and/or vector beetles.