582.6-cmp KIR ej.1
Kirschner, Jan
A monograph of Taraxacum sect. Palustria [LIB]. -- Pruhonice :
Institute of Botany Academy of Sciences of the Czech Republic, Pruhonice, 1998
The reader expecting spectacular theories ardently advocating our sectional ans species concepts will be disappointed. We limit ourselves to a reference to Kirschner & Stepánek (1996) where basic facts and explanations of the sectional conception in Taraxacum are given. As regards the section, we should repeat a single paragraph of the above work (p. 417): The supraspecific taxonomy in Taraxacum has originally been based amost purely on morphological grounds: evolutionary interpretation of morphological data is mostly speculative and, in the case of many Asian sections, often rested on non-representative material. A number of sections are defined merely by their type species, and their limits or relationships remain unknown. With an increasing mechanisms, polyploidy, gene flow restrictions remain unknown. With an increasing knowledge of biosistematical properties of individual species, it turnsout that reproduction mechanisms, polypolidy, gene flow restrictions and other phenomena are not randomly distributed in the genus. The closely correlate with many of the traditionally recognized boundaries of sections. There is a question whether a section in Taraxacum can be undestood as an evolutionary unit, which potentially forms a progenitor of other taxa. The first argument in favour of the latter concept is the fact of the relative coherence of the Taraxacum sections. The integrity of the section is a result of multiple reticulation of ancestral lineages (soon after the hypothetical original explosion of hibridization). It not only leads to the mosaic distribution of character states in the section but also to the fact that morphological limits of the section are congruent with biological and ecological nature of the group. Another argument for making the section a central concept is that some sections probably gave rise to derivative groups through intersectorial hybridization.
The section Palustria belongs to the Taraxacum groups that are comprised of two basic types of biological entities , as they are evaluated from the viewpoint of variation and the cnsequent taxonomic species concept. The first of the two types is a sexual species with a high level of genetic variation, the other type is an apomictic species, with an agamospermous or a predominantly agamospermous reproduction, and a significantly lower level of variation (see also Chapter 3.4). Both these types of species are treated at the same taxonomic rank of species. However, the reader should bear in mind the principal differences in the behaviour of the two types (population variation, evolution history and evolutionary potential).
There are two sexual species, T. raii and T. tenuifolium; both probably fit the criteria for the biological species. The variation range within populations of T. tenuifolium, in particular, is broader than in any apomitic member of genus. The agamospermous taxa have been delimited primariy on morphological grounds, with reference to their geography, karyology and (rarely) the known character of genentic variation. Botanists conidering any agamospermous taxon as an obscure entity will view our monograph as a work of crazy splitters. The experienced taraxacologist probably will evaluate some of our taxonomic conclusions (particularly in the groups of T. palustre and T. hollnadicum) as an inconsequent lumping. We should like to emphasize that the agamospermous species, as we undestand it here, by no means can be equated with a group of genetically uniform individuals (in spite of the fact that some agamospermous species are almost uniform gentically).
ISBN: 8086188000
1.
TARAXACUM; 2.
PALUSTRIA I.
Stepánek, Jan
(62)
Inv.: 01-015219
S.T.: 582.6-cmp KIR ej.1
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