Oxybasis glauca

Mosyakin, Sergei L. & De Lange, Peter J., 2018, New combinations for three taxa of the Oxybasis glauca aggregate (Chenopodiaceae) from Australasia, East Asia, and South America, Phytotaxa 350 (3), pp. 259-273 : 260-261

The Oxybasis glauca ( Chenopodium glaucum ) aggregate: underestimated diversity?

The taxonomy of several groups of species in Oxybasis remains problematic. In particular, Sukhorukov (2014) commented that Eurasian taxa of Oxybasis are still very poorly studied; it refers to the aggregate of O. glauca , and especially the O. rubra group [in Russian: “…евраЗийские таксоны рода иЗучены крайне слабо, в частности, круг родства O. glauca и, в особенности, O. rubra ”; see Sukhorukov 2014: 63].

Several geographically isolated and morphologically poorly outlined taxa of the O. glauca group were described; they were usually recognized as varieties or subspecies of Chenopodium glaucum or Oxybasis glauca (see synonymy in Mosyakin 2013).

As mentioned above, Fuentes-Bazan et al. (2012) transferred Chenopodium glaucum to Oxybasis as O. glauca , but they did not make combinations for the Australasian Chenopodium ambiguum R. Brown (1810: 407) , East Asian (Russian Far East) C. amurense Ignatov (1986: 111) , and North American C. salinum Standley (1916: 29) . This prompted Mosyakin (2013) to make combinations at subspecies rank for these taxa in Oxybasis , as O. glauca subsp. ambigua (R. Br.) Mosyakin (2013: 4) , subsp. amurensis (Ignatov) Mosyakin (2013: 4) , and subsp. salina (Standl.) Mosyakin (2013: 5) . In the process Mosyakin (2013: 4) noted that the Oxybasis glauca complex “is rather a species aggregate than a species; it is represented on various continents by several geographically and morphologically more or less distinct entities, which may be treated as subspecies or even species” (see also Aellen 1960–1961, Mosyakin 1993, 1996, Clemants & Mosyakin 2003). When referring to O. glauca subsp. ambigua , he stated that it might be regarded “even as a separate species”.

South American Chenopodium parodii Aellen (1929: 49) [≡ C. glaucum L. subsp. parodii (Aellen) Aellen in Aellen & Just 1943: 60] described from Argentina is another noteworthy taxon belonging or related to the O. glauca species aggregate. Chenopodium marlothianum Murr (1906: 110) [≡ C. glaucum ssp. marlothianum (Murr) Thellung & Aellen in Aellen 1928: 345] described from South Africa also seems to be a member of the same species group, but its taxonomic status yet remains uncertain. Sukhorukov (2014) noted that distribution of Oxybasis glauca is, quite amazingly, still insufficiently known because it was often confused with closely related taxa from North America or South Africa known as Chenopodium mexicanum or C. marlothianum ; they reportedly differ from European plants mainly by characters of the keel on tepals [In Russian: “Распространение Этого вида, как ни странно, выЯснено не до конца, так как он часто смеШивалсЯ с блиЗкими таксонами иЗ Северной Америки или Южной Африки, иЗвестными как С. mexicanum Moq. или С. marlothianum Murr , отличиЯ которых от европейских растений сводЯтсЯ, в частности, к степени выраженности килЯ на листочках околоцветника”; Sukhorukov 2014: 238].

Preliminary results of Feodorova (2017), who did a comparative study of nucleotide sequences of the segment ITS1– 5.8S –ITS2 nrDNA, indicate that even in Europe O. glauca is most probably represented by two or more rather distinct races (cryptic species or subspecies). In particular, Feodorova (2017: 8) reported that “…the sequence belonging to the C. glaucum sample from Moscow clusters with C. rubrum , while those obtained from plants collected from West Europe ( Spain and Italy) and identified as C. glaucum cluster with C. urbicum ”. She further concluded that “…it is logical to assume that the Chenopodium glaucum from West Europe is of an independent hybridogeneous origin. Its genome donors could have been C. rubrum and C. urbicum . The C. glaucum from central European Russia appears to also be of an independent hybridogeneous origin, and one of the genome donors in this case also could have been C. rubrum . To find out which the second donor was, one must study closely related species, such as C. chenopodioides L.”.

The morphological differences of plants of that group (taxa presumably native to different continents and distant regions) are obscured by the almost worldwide synanthropic occurrence of alien populations of O. glauca native to Eurasia ( Clemants & Mosyakin 2003, Mosyakin 2013). Further morphological and especially molecular phylogenetic and phylogeographical studies of members of Oxybasis , and in particular taxa of sect. Glaucae , are needed on a worldwide basis. However, even before such studies, the names (nomenclatural combinations) should be available in Oxybasis for morphologically distinct and geographically isolated taxa earlier accepted in Chenopodium . Here we consider three taxa from Australasia, East Asia, and South America, and propose new species-level combinations for them.