We investigated twenty-six strains of Xanthidium antilopaeum Kütz. and seven strains of X. cristatum Ralfs isolated from various European localities or obtained from public culture collections. A combination of molecular, geometric morphometric, and morphological data were used to reveal the patterns of the phylogenetic and morphological differentiation of these taxonomically very compli-cated desmid taxa. The molecular data based on trnG(ucc) and ITS rDNA sequences illustrated the monophyly of both the complexes, which indicated that their traditional morphology-based discriminative criteria, such as the different number of spines, may generally continue to be considered relevant. The single exception was X. antilopaeum var. basiornatum B. Eichler et Raciborski, which was positioned outside the X. antilopaeum/cristatum clade. The independent status of this taxon was also confirmed on the basis of the geometric morphometric data, so that we concluded that it probably represents a separate species. Within X. cristatum complex, the traditional varieties X. cristatum var. cristatum Ralfs, X. cristatum var. uncinatum Ralfs, and X. cristatum var. scrobiculatum Scott et Grönblad turned out to be separate taxa. Conversely, X. cristatum var. bituberculatum Lowe lacked any taxonomical value. Our data on X. antilopaeum illustrated extensive phylogenetic as well as phenotypic variability within this species complex. However, our data did not result in any unambiguous pattern that would allow sound taxonomic classification. Finally, we also found out that the morphologically peculiar Staurastrum tumidum Ralfs belongs to the genus Xanthidium based on the combined rbcL + cox III data set. Consequently, this species was formally transferred to this genus.

• Klíčová slova
• Desmidiales, Xanthidium, geometric morphometrics, molecular phylogeny, taxonomy,
• Publikační typ
• časopisecké články MeSH

The genus Viola (Violaceae) is among the 40-50 largest genera among angiosperms, yet its taxonomy has not been revised for nearly a century. In the most recent revision, by Wilhelm Becker in 1925, the then-known 400 species were distributed among 14 sections and numerous unranked groups. Here, we provide an updated, comprehensive classification of the genus, based on data from phylogeny, morphology, chromosome counts, and ploidy, and based on modern principles of monophyly. The revision is presented as an annotated global checklist of accepted species of Viola, an updated multigene phylogenetic network and an ITS phylogeny with denser taxon sampling, a brief summary of the taxonomic changes from Becker's classification and their justification, a morphological binary key to the accepted subgenera, sections and subsections, and an account of each infrageneric subdivision with justifications for delimitation and rank including a description, a list of apomorphies, molecular phylogenies where possible or relevant, a distribution map, and a list of included species. We distribute the 664 species accepted by us into 2 subgenera, 31 sections, and 20 subsections. We erect one new subgenus of Viola (subg. Neoandinium, a replacement name for the illegitimate subg. Andinium), six new sections (sect. Abyssinium, sect. Himalayum, sect. Melvio, sect. Nematocaulon, sect. Spathulidium, sect. Xanthidium), and seven new subsections (subsect. Australasiaticae, subsect. Bulbosae, subsect. Clausenianae, subsect. Cleistogamae, subsect. Dispares, subsect. Formosanae, subsect. Pseudorupestres). Evolution within the genus is discussed in light of biogeography, the fossil record, morphology, and particular traits. Viola is among very few temperate and widespread genera that originated in South America. The biggest identified knowledge gaps for Viola concern the South American taxa, for which basic knowledge from phylogeny, chromosome counts, and fossil data is virtually absent. Viola has also never been subject to comprehensive anatomical study. Studies into seed anatomy and morphology are required to understand the fossil record of the genus.

• Klíčová slova
• Viola, Violaceae, fossils, monophyletic, morphology, nomenclature, phylogeny, polyploidy, taxonomic revision,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH