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|Authors:||Рысс, А. Ю.|
Субботин, С. А.
|Title:||Происхождение и эволюция микотрофных фитопаразитических нематод с циклами, включающими насекомых–переносчиков|
|Other Titles:||The origin and evolution of the mycotrophic plant parasitic nematodes with life cycles including insect vectors|
|Description:||Phylogenetic analyses of the D2-D3 of 28S rRNA, partial 18S rRNA gene sequences, could verify the former classification of the fam. Aphelenchoididae based on the morphological characters. Some characters considered as the supplementary ones are revealed as the good markers cladogram branches. Such characters are to be included into diagnoses of genera and subfamilies. Other characters, formerly considered as taxonomically important, seem to be convergent. They may be used for more deep understanding of the adaptations in host-parasite relations. The most important factor for speciation and the super-species clades formation in evolution of wood nematodes is the genus of insect vector, and not the taxon of the plant host. It is in contradiction with the host-parasite coevolution conception, because in the comparative analysis of life cycles the plant is historically more ancient host in comparison to relatively recent inclusion of the insect vectors. The cause of unequal value of two nematode associates may be the natural selection. The spread of the nematode dauer juveniles by vector is more risk part of life-cycle; it includes a complicated set of behavior, physiological and immune adaptations, comparing to the feeding of the nematode colony of propagative generation in dying infected wood. But in the laboratory experiments of the first author it was proved that the host specificity of aphelenchoidids to plant host does still exist. In addition to the recent host specificity (at plant families' level) there is the “historic” memory of the plant host of the ancestor of the Bursaphelenchus species group. This latent host specificity may lead to the sudden host switch, if the Bursaphelenchus isolate will contact the area of distribution of the new insect vector with different preferences in the target host, for feeding and oviposition (the nematode transfer to intact plant by vector takes places during these two processes). Human economic activity, especially infected wood transportation into the potential vector area, creates conditions for host switch. Forest fires and global warming lead to spread of the insect vector species from the south to north taiga regions with nematode latent refuges. This is why it is necessary to develop a system of the regular tests of local nematode wood parasites, to reveal the latent specificity to the local wood hosts.|
|Appears in Collections:||Современные проблемы теоретической и морской паразитологии / Contemporary problems of theoretical and marine parasitology|
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