INTRASPECIFIC VARIATION OF PLOIDY IN ANGIOSPERMS AND ITS TAXONOMICAL TREATMENT
He intraspecific variation of ploidy in angiosperms was found a bit more than a hundred years ago. Soon after the discovery of this phenomenon some authors supposed that the cytotypes of different ploidy (chromosome races) should be treated as separate species, especially when they differ morphologically and geographically. However, other authors were of opposite opinion. According to some modern estimates 12-16 % of angiosperm species include cytotypes of different ploidy. In this paper, we review the history of discovery and studies of cytotypes within some mixed-ploidy species with different approaches and methods, changes in their taxonomic treatment, as well as the reasons pro et contra specific status of cytotypes, suggested by some authors who in short or at large discussed this issue (J. Clausen, K. B. Blackburn, A. Muntzing, A. Love, H. L. Lewis, D. E. Soltis and others). The number of the cytotypes named as distinct species and accepted by taxonomists is not large, and they usually concern species with restricted distribution ranges and the cytotypes having distinct geographic ranges. More often the cytotypes are treated as subspecies. Modern studies of the species with rather wide distribution throughout most of their range often show complexed patterns of morphological, geographical, ecological and other differences between cytotypes, and this does not allow to separate them taxonomically. Usually allopolyploid origin of the cytotype of higher ploidy was considered as an evidence of its specific status, but not autopolyploid origin. But nowadays it is clear that autopolyploid cytotypes occur more often that it was assumed previously, and ten years ago several authors suggested to describe autopolyploid cytotypes as distinct species. Nevertheless, few cytotypes were named as species for the past time, though several were suggested to. However, lately it was shown that the cytotypes in some species differ not in morphological characters but in other ones, not used in specific descriptions yet, but very important in the existence of the species, such as time of flowering, fragrance and secondary metabolites, adaptation to soil, light, drought and other ecological factors, invasiveness, interactions with other organisms - pollinators, herbivores, mycorrhizal fungi and other. As a result, first attempts were made to use such characters in the description of species on the base of cytotype, in absence of morphological differences.