Molecular phylogenetics and morphology support two new genera (Memoremea and Nihon) of Boraginaceae s.s.

Abstract

Omphalodes (Boraginaceae s.s., Cynoglosseae s.l.) comprises ca. 29 species of annual and perennial plants distributed in three main disjunct areas: Western Palearctic, Japan and SW of North America. This paper uses micromorphological and DNA data to re-assess the monophyly and taxonomy of the genus. Morphological characters of 15 species of Omphalodes and four closely-related genera were analysed using SEM. A total of 82 ITS and 68 trnL-trnF sequences were newly sequenced, including 14 species of Omphalodes and three genera of the tribe Cynoglosseae. Phylogenetic analyses of 57 genera (186 species) of Boraginaceae indicated that Omphalodes as currently circumscribed is formed by three independent lineages, which were supported by morphological characters of the fruit. As a result, and in the interest of a more natural classification, two new genera are described to accommodate Omphalodes scorpioides (Memoremea) from Europe and the Japanese species (Nihon). Memoremea is distinguished from all the other species previously included in Omphalodes by the apical attachment scar and the hollow nutlet margin. Nihon is easily discriminated by the abrupt change of margin ornamentation towards the nutlet aperture. We also provided a taxonomic treatment that proposes the lowest number of nomenclature changes, although six new combinations are required.

The borage family (Boraginaceae s.str.): A revised infrafamilial classification based on new phylogenetic evidence, with emphasis on the placement of some enigmatic genera

“…The close relationship between Bothriospermum and Thyrocarpus was expected, as Thyrocarpus has been considered a close relative of Bothriospermum since its description (e.g., Hance, 1862;Johnston, 1924;Zhu & al., 1995;. Our results agree with Otero & al. (2014), who found another species of Bothriospermum (i.e., B. secundum Maxim.…”

“…A close relationship with Nihon akiensis and N. japonicum (formerly in Omphalodes), which in our tree are deeply embedded in the Bothriospermum-clade (Fig. 5), also fits with the results of Otero & al. (2014), where Bothriospermum and Thyrocarpus form a clade with the same Nihon species.…”

“…Memoremea scorpioides is also morphologically distinct compared to species of Omphalodes (where it has been placed for a long time as O. scorpioides (Haenke) Schrank), and has scorpioid cymes subtended by bracts, strongly curved embryos, and opposite lower leaves, which are atypical characters in the Cynoglosseae (Brand, 1921). These apomorphies led Johnston (1924) to conclude that O. scorpioides might be segregated in its own genus and hence Otero & al. (2014) described the monospecific Memoremea, distinguished by the apical attachment scar, the incurved nutlet with an air chamber, and the presence of trichomes on the nutlet.…”

“…Interestingly, many genera, such as Omphalodes Moench and Cynoglossum L., were retrieved as either poly-or paraphyletic, indicating that the morphological characters used in traditional taxonomic classifications are highly homoplasious (Weigend & al., 2013). Some of the taxonomic problems arising from the polyphyly of Omphalodes have been addressed by Otero & al. (2014), who created the genera Memoremea A.…”

Worldwide long‐distance dispersal favored by epizoochorous traits in the biogeographic history of Omphalodeae (Boraginaceae)

“…In addition, the nuclear ribosomal DNA ITS (Internal Transcribed Spacer) was chosen based on considerable phylogenetic signal found in previous studies of Boraginaceae (Weigend et al, 2013;Chacón et al, 2017;Chacón et al, 2016). Primers for the ITS and trnL-trnF regions followed those of Otero et al (2014). For the rps16 region, we used the primers described in Otero et al (2019).…”