Acroglochin, Schrader, 1822

Iamonico, Duilio, 2018, Nomenclatural and taxonomic notes on Acroglochin and its position in Chenopodiaceae s. str., Phytotaxa 383 (2), pp. 197-205 : 198

Acroglochin in Chenopodiaceae

The genus Acroglochin was formerly included in subfam. Betoideae by various authors (e.g., Volkens 1892, Ulbrich 1934, Kühn et al. 1993).

An analysis of the chloroplast markers matK / trnK and ndhF by Kadereit et al. (2006: 16) showed that Acroglochin is included in a clade with Corispermoideae / Chenopodioideae and Beteae/Hablitzieae, respectively. These data partly indicate that Acroglochin might be transferred to subfam. Corispermoideae (a rather unexpected position, for which morphological justification is hardly available now) or Chenopodioideae .

More recently, the molecular study on Chenopodiaceae s.str. by Kadereit et al. (2012: 3307) indicated that Acroglochin is an ancient lineage basal to the remaining Betoideae and phylogenetically isolated from all currently accepted subfamilies (see also Hohmann 2006, and Müller & Borsch 2005, Romeira et al. 2016). Acroglochin and Betoideae form, in turn, the early-branching (basal) group sister to all other clades of Chenopodiaceae (subfamilies in Kadereit et al. l.c.). In addition, this genus is separated from both chorological (Central Asia, from Pakistan to China, see Zhu et al. 2003) and morphological points of view: the terminal branches of inflorescences are needle-like and lack flowers, while tepals are sparsely covered with hairs. Probably in view of the above considerations, Hernández-Ledesma et al. (2015: 333) suggested that Acroglochin could be treated at subfamily rank (“The genus was formerly included in Betoideae and should probably be classified as a subfamily of its own”).

On the basis of the mentioned data on chloroplast markers, which are in conflict with each other, and the lack of other important data such as those based on nuclear markers, the taxonomic position of Acroglochin remains uncertain and establishment of a new subfamily at present is premature. Studies of nuclear markers could be useful for revealing (or confirming?) the real position of Acroglochin in Chenopodiaceae s.str., and, pending further results, I accept here this genus in subfam. Betoideae .