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Branchlets with fruit, bract and bracteoles of Thesium ramosum (a), Thesium linophyllon (b), Thesium alpinum (c) and Thesium ebracteatum (d).
Source publication
Two species of the genus Thesium (T. ebracteatum and T. linophyllon) are constantly recognized as members of the flora of Lithuania. However, the study on plants currently occurring in Lithuania and usually identified as T. linophyllon revealed that in fact they belong to T. ramosum. The analysis of all available data on the occurrence of T. linoph...
Contexts in source publication
Context 1
... ramosum, newly reported in Lithuania, is eas- ily distinguishable from T. ebracteatum by the pres- ence of two bracteoles (Fig. 2, a), several to numerous stems growing from the rootstock and usually much branched inflorescence. T. ebracteatum is character- ized by the absence of bracteoles (Fig. 2, d), solitary shoots growing from underground rhizomes and usu- ally unbranched stem and inflorescence (if the stem is branched, then lateral branches usually are sterile ...
Context 2
... ramosum, newly reported in Lithuania, is eas- ily distinguishable from T. ebracteatum by the pres- ence of two bracteoles (Fig. 2, a), several to numerous stems growing from the rootstock and usually much branched inflorescence. T. ebracteatum is character- ized by the absence of bracteoles (Fig. 2, d), solitary shoots growing from underground rhizomes and usu- ally unbranched stem and inflorescence (if the stem is branched, then lateral branches usually are sterile and grow from the lower part of the stem). T. ramosum differs from T. linophyllon by the type of the inflo- rescence. Inflorescence of T. linophyllon is a pani- cle ...
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... (if the stem is branched, then lateral branches usually are sterile and grow from the lower part of the stem). T. ramosum differs from T. linophyllon by the type of the inflo- rescence. Inflorescence of T. linophyllon is a pani- cle composed of dichasia, i.e., the lower and middle part of the inflorescence is composed of multifloral branchlets (Fig. 2, b). The inflorescence of T. ramo- sum is branched below; however, all branchlets in the inflorescence are with one flower. T. ramosum also differs from T. linophyllon and T. bavarum Schrank (=T. linophyllon subsp. montanum (Schrad.) Čelak.) by the length of bracts. Bracts of T. ramosum are distinctly longer than flowers (only occasionally ...
Context 4
... are with one flower. T. ramosum also differs from T. linophyllon and T. bavarum Schrank (=T. linophyllon subsp. montanum (Schrad.) Čelak.) by the length of bracts. Bracts of T. ramosum are distinctly longer than flowers (only occasionally sub- equal), whereas bracts of T. linophyllon are equal with flowers and later become shorter than fruit (Fig. 2, b). It should be noted that T. linophyllon is a rhizoma- tous plant, whereas T. ramosum and T. bavarum have no rhizomes, and stems usually grow from rootstock. Another species quite similar to T. ramosum is T. al- pinum. T. ramosum from this species is easily distin- guished by flowers with five perianth lobes, whereas flowers of T. ...
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... pinum. T. ramosum from this species is easily distin- guished by flowers with five perianth lobes, whereas flowers of T. alpinum are predominantly with four perianth lobes. Another important and reliable charac- ter is the length of persistent perianth, which is about twice shorter than nut in T. ramosum and 2-3 times as long as nut in T. alpinum (Fig. 2, c). It should be noted that stem ridges, especially in the upper part, leaves and pedicels of all studied plants of T. ramosum from Lithuania, Ukraine and the Caucasus are quite dense- ly covered by almost translucent short (0.1-0.2 mm) papillae, whereas the studied specimens of T. lino- phyllon from the Czech Republic and T. alpinum from ...
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Citations
... The confusion of the species with T. linophyllon in the original North Dakota and Montana specimen identifications probably derived from the lack of available reference floras and descriptions. Thesium linophyllon differs from T. ramosum in having rhizomes, a dichasium inflorescence, and comparatively short bracts (Gudžinskas and Žalnervičius 2017). All of the North American occurrences have been mapped in the United States Department of Agriculture weed risk assessment (PPQ 2019) and in the United States on a county level, by the Biota of North America Program (BONAP 2015). ...
Field Thesium (Thesium ramosum Hayne; Thesiaceae/Santalaceae) is an alien species in Canada, previously misidentified as Thesium arvense Horvátovszky or Flaxleaf (Thesium linophyllon L.). It is a hemiparasitic herb characterized by its many 25–50 cm long aerial stems that grow indeterminately from a caudex. Its narrow leaves extend along each aerial stem from their base into the paniculate inflorescence. The flowers are white, 4–5 mm wide, with five corolla lobes; they are perfect and occur singly, subtended by a three-parted bract at the tip of a narrow pedicel, with 60–90 such flowers along each inflorescence. Its roots develop profuse haustoria that attach to host plant roots. Thesium ramosum is compared to the related native genera, Comandra and Geocaulon (placed in Comandraceae or Santalaceae), which share features but differ by having determinate growth and being unbranched. Thesium ramosum is widespread from western Europe to western China, but in North America it is known from only three western states and Alberta, where it has established in Fish Creek Provincial Park and elsewhere in Calgary. Worldwide, many species in the genus Thesium are notable invasives and T. ramosum has the potential to be a high risk invasive in North America. Observations in the park show that it can spread rapidly and parasitize many host species. It does not have federal or provincial control status in Canada, but because it is parasitic and has potential to become widespread, it is regulated in the USA by the United States Department of Agriculture.
... Since the 1980s, several checklists and floras have been published that contain regional treatments of Thesium; e.g., for Iran (Polatschek, 1982), Egypt (Sa'ad, 1983, Pakistan (Nasir, 1984), Central Africa (Lawalrée, 1985), Ethiopia (Miller, 1989), South Tropical Africa (Hilliard, 1991(Hilliard, , 2006, China (Xia & Gilbert, 2003), Crimea (Romo & al., 2004), Tropical East Africa (Polhill, 2005), Madagascar (Rogers & al., 2008), Nigeria (Hutchinson & al., 2014), Lithuania (Gudžinskas & Žalneravičius, 2017) and Zimbabwe (Hyde & al., 2017). In addition, Mashego & Le Roux (2018) published a short communication on the southern African taxa. ...
Recent phylogenetic hypotheses reveal that Thesium (Santalaceae) is paraphyletic with respect to Austroamericium, Chrysothesium, Kunkeliella and Thesidium, suggesting the need for generic realignment. In addition, existing subgeneric and sectional classifications of this large genus lack a phylogenetic basis, thus compromising their predictive value. Using an expanded taxon sampling and a combination of nuclear (ITS) and chloroplast (matK, rpl32-trnL, trnL-F) DNA sequence data, we therefore re-assessed the phylogenetic relationships of Thesium and used these as the basis of a new subgeneric classification of the genus. Our phylogeny confirms the need to sink the four segregate genera to render Thesium monophyletic. In addition, it resolves five well-supported major clades within Thesium that we recognize as subgenera. Within Thesium, the South African endemic subgenus Hagnothesium is sister to the Eurasian subgenus Thesium (including Kunkeliella and Mauritanica). The subgenus Psilothesium, occurring in tropical South America (formerly genus Austroamericium) and tropical Africa, is sister to the rest of the subgenera, which are all confined to South Africa. Within the latter, the subgenus Discothesium consists of subtropical and temperate species, whereas subgenus Frisea, comprising the previously recognized sections Annulata, Barbata, Frisea, Imberbia and Penicillata, is entirely of the Greater Cape Floristic Region. To facilitate identification of subgenera, we identify morphological ancestral characters and present an identification key, brief diagnoses, species assigned, distribution and ecological data
Recent phylogenetic hypotheses reveal that Thesium (Santalaceae) is paraphyletic with respect to Austroamericium, Chrysothesium, Kunkeliella and Thesidium, suggesting the need for generic realignment. In addition, existing subgeneric and sectional classifications of this large genus lack a phylogenetic basis, thus compromising their predictive value. Using an expanded taxon sampling and a combination of nuclear (ITS) and chloroplast (matK, rpl32-trnL, trnL-F) DNA sequence data, we therefore re-assessed the phylogenetic relationships of Thesium and used these as the basis of a new subgeneric classification of the genus. Our phylogeny confirms the need to sink the four segregate genera to render Thesium monophyletic. In addition, it resolves five well-supported major clades within Thesium that we recognize as subgenera. Within Thesium, the South African endemic subgenus Hagnothesium is sister to the Eurasian subgenus Thesium (including Kunkeliella and Mauritanica). The subgenus Psilothesium, occurring in tropical South America (formerly genus Austroamericium) and tropical Africa, is sister to the rest of the subgenera, which are all confined to South Africa. Within the latter, the subgenus Discothesium consists of subtropical and temperate species, whereas subgenus Frisea, comprising the previously recognized sections Annulata, Barbata, Frisea, Imberbia and Penicillata, is entirely of the Greater Cape Floristic Region. To facilitate identification of subgenera, we identify morphological ancestral characters and present an identification key, brief diagnoses, species assigned, distribution and ecological data.
