Abstract
AbstractSalicornioideae (Amaranthaceae / Chenopodiaceae) comprise 11 genera and ca. 100 species of succulent halophytes distributed worldwide in coastal and inland saline habitats. Most species have peculiar articulated, seemingly leafless stems and spike‐like sessile thyrses with highly reduced flowers hidden by fleshy bracts. We analysed sequence data of four markers (ETS, ITS, atpB‐rbcL, matK‐trnK) from 57 species, 9 subspecies, 1 variety and 2 hybrids representing all curently accepted genera using maximum likelihood, Bayesian analysis, fossil‐calibrated molecular dating and ancestral area analysis. All molecular markers gave similar phylogenetic signals. Salicornioideae probably originated in Eurasia during the late Eocene–early Oligocene. The divergence of the early main clades took place in the middle Oligocene with the separation of Allenrolfea /Heterostachys, Halocnemum /Halopeplis /Halostachys /Kalidium and Arthrocnemum /Microcnemum /Tecticornia /Salicornia/ Sarcocornia lineages. The latter lineage diversified most and comprises ¾ of the species of the subfamily. The Arthrocnemum macrostachyum /Microcnemum lineage diverged at the turn of the Oligocene/Miocene – while the Arthrocnemum subterminale, Tecticornia and Salicornia /Sarcocornia lineages were all present by the middle Miocene. Long‐distance dispersal has taken place several times to the Americas (Allenrolfea /Heterostachys, Arthrocnemum subterminale, Salicornia /Sarcocornia), South Africa (Halopeplis, Salicornia /Sarcocornia) and Australia (Tecticornia, Salicornia /Sarcocornia). Most currently accepted genera were resolved as monophyletic. However, Sarcocornia is paraphyletic in relation to Salicornia, and Arthrocnemum proved to be polyphyletic. In addition, the name Arthrocnemum is a nomenclatural synonym of Salicornia. As a consequence, we propose the merging of Sarcocornia under Salicornia and provide 19 new nomenclatural combinations and one replacement name. For Salicornia (incl. Sarcocornia) we propose a new infrageneric classification to accommodate the four phylogenetically and geographically well‐supported sublineages of the genus. We also propose abandoning the name Arthrocnemum in its current use, and describe two new genera, Arthrocaulon (Eurasia, Africa) and Arthroceras (North America), and provide three new nomenclatural combinations.
Highlights
Arthrocnemum was described as a new genus in the monograph on the Chenopodiaceae family published by Moquin-Tandon (1840:111)
The morphology and taxonomy of this group of halophytes has been discussed in the scientific literature by numerous authors, e.g. Lagasca, 1817; Willkomm, 1862; Ball, 1964; Scott, 1977; Castroviejo & Coello; 1980; Pastor & Valdés, 1986; Castroviejo 1990; Castroviejo & Lago, 1992; Ball, 2003; Shepherd et al, 2005; Alonso & Crespo, 2008; Kadereit et al, 2006; Piirainen et al, 2017. In their in-depth study on Arthrocnemum, Sukhorukov & Nilova (2016) give a detailed description of its vegetative and reproductive characters such as phyllotaxis, nodes, leaves, branches and inflorescences; they do not confirm the presence of lateral staminate flowers –and sterile, as proposed by Kühn (1993), and consider the presence of an indurated pericarp to be unfounded, as stated by Ungern-Sternberg (1866), Scott (1977), Jafri & Rateeb (1978) or Friis & Gilbert (1993)
We propose the new taxon Arthrocaulon meridionalis spec. nova to include the diploid populations distributed in southern Mediterranean halophytic habitats
Summary
Arthrocnemum was described as a new genus in the monograph on the Chenopodiaceae family published by Moquin-Tandon (1840:111). Lagasca, 1817; Willkomm, 1862; Ball, 1964; Scott, 1977; Castroviejo & Coello; 1980; Pastor & Valdés, 1986; Castroviejo 1990; Castroviejo & Lago, 1992; Ball, 2003; Shepherd et al, 2005; Alonso & Crespo, 2008; Kadereit et al, 2006; Piirainen et al, 2017 In their in-depth study on Arthrocnemum, Sukhorukov & Nilova (2016) give a detailed description of its vegetative and reproductive characters such as phyllotaxis, nodes, leaves, branches and inflorescences; they do not confirm the presence of lateral staminate flowers –and sterile, as proposed by Kühn (1993)–, and consider the presence of an indurated pericarp to be unfounded, as stated by Ungern-Sternberg (1866), Scott (1977), Jafri & Rateeb (1978) or Friis & Gilbert (1993). We propose the new taxon Arthrocaulon meridionalis spec. nova to include the diploid populations distributed in southern Mediterranean halophytic habitats
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