Genus Taraxacum (Asteraceae), having ∼60 sections and 2,800 species, is known for its complicated evolutionary relationships and taxonomy due to processes like frequent hybridization, polyploidization, asexual reproduction, clonality and low structural morphological variability. Various taxonomical concepts and approaches are reviewed, evaluated and discussed from point of view of their ability to deal with such a complicated genera as is Taraxacum. Various processes responsible for the complicated situation within Taraxacum are discussed and reviewed. Section Dioszegia, comprising T.
Institute of Botany, Czech Academy of Sciences
Diploid populations of Valeriana officinalis L. (Valerianaceae) in Central Europe exhibit an extensive variation, with two conspicuous morphotypes. One, corresponding to the lectotype of V. officinalis, is larger, with broader, distinctly dentate leaflets, the other is in many respects similar to V. pratensis Dierb. and V. stolonifera Czern., but is glabrous, with narrow, usually entire leaflets. The two forms also differ in their ecological optimum and in geographical distribution, but are linked with numerous intermediates.
The Taraxacum flora of the West Himalaya represents one of the dandelion diversity hotspots, with at least 17 sections and about 150 known species. A number of names published from that region were referred to T. sect. Orientalia Handel-Mazzetti in the literature. All these names are revised and newly interpreted, with emphasis on plants erroneously determined as T. stenolepium. The revision is based on both older herbarium collections and a new material from expeditions of the late L. Klimeš. A new section, T. sect.
There has been a decrease in the ability of biologists to identify their material correctly, particu- larly plants of complicated genera with common agamospermy, where old clonal entities are accorded the rank of species (microspecies). Agamospermous microspecies are taxonomic enti- ties recognizable from one another by a set of minute morphological features. The knowledge of microspecies is confined to a few specialists. Specialists usemicrospecies names but there could be inconsistencies in the taxonomic concepts used by different, geographically remote experts.
The coexistence of agamospermy and sexuality characterizes most of the ~60 sections of the genus Taraxacum. Section Dioszegia, comprising T. serotinum and its allies, are an exception because only sexuals are reported for all the members of this group.