Rehmannieae or Rehmanniaceae? Evidence from plastome sequences and floral morphology

Abstract

Rehmannia and Triaenophora form a clade and are widely accepted as being closely allied with Orobanchaceae in Lamiales. However, the taxonomic rank of this clade and its geographical origins are understudied and poorly known. The genera have together been recognized as Orobanchaceae tribe Rehmannieae or Rehmanniaceae. To re-evaluate the taxonomy and systematic position and affinities of these genera, we reconstructed a phylogenety using complete plastid genomes (plastomes) and performed an analysis of comparative floral development. Additionally, we investigated the geographical distributions of Rehmannia and Triaenophora to determine the centre of diversity and origin. The phylogenetic analyses showed that Rehmannia and Triaenophora formed a clade that is sister to all other Orobanchaceae. This relationship was also supported by fruit and floral morphological traits, such as capsules partly or half exserted from the persistent calyx tubes, reticulate testa of seeds, cochlear ascending corolla (rhinanthoid aestivation), late sympetalous corolla tube and axile placentation. In addition, the loss of the adaxial stamen leaving a gap at its expected initiation site and two lateral bracteoles in Rehmannia and Triaenophora may be derived or represent a phylogenetic transitional form in Lamiales. We suggest that Rehmannia and Triaenophora clade should be treated as Orobanchaceae tribe Rehmannieae rather than as a distinct family of Lamiales. The distribution pattern of Rehmannia and Triaenophora indicate that the Shennongjia-Wushan region in central China represents the geographical origin and centre of diversification of the genera.

Herbarium phylogenomics: Resolving the generic status of the enigmatic Pseudobartsia (Orobanchaceae)

“…Topological incongruence was found in the placement of the tribes Buchnereae and Brandisieae between the two MSC analyses using 84 genes and 17 functional groups, respectively. The 84‐gene MSC phylogeny supported a sister relationship between Buchnereae and Cymbarieae with moderate PP, which is congruent with the relationship in the supermatrix tree in this study, as well as that reported by Xia et al (2021). Among the 84 gene trees, there were 14 gene trees supporting this relationship and BS values higher than 70% were found in the petA , petB , petD , rpoC1 , ycf1 , and ycf2 gene trees, but only four gene trees ( accD , atpA , matK , and ndhB ) supported the sister relationship between Buchnereae and Orobanchaceae with poor support values (BS ≤ 50%).…”

“…In this study, the species tree using the 17 functional group genes recovered the tribe Cymbarieae sister to the remaining six tribes/groups. In contrast, phylogenies inferred from three supermatrixes and a species tree inferred using 84 genes found that tribes Cymbarieae and Buchnereae formed a well‐supported clade (also see Xia et al, 2021), that itself was sister to the remainder of parasitic Orobanchaceae. In some phylogenies, Buchnereae was reported as sister to Orobancheae (Yu et al, 2018), or Pedicularideae (McNeal et al, 2013; Fu et al, 2017; Li et al, 2019), or Rhinantheae (Li et al, 2019).…”

Complete chloroplast genomes of hemiparasitic genus Cymbaria: Insights into comparative analysis, development of molecular markers, and phylogenetic relationships

“…The results of our study indicated that C. mongolica lost genes (ndh I, ndh J) and that C. daurica contained pseudogenes (ndh F,ndh H) and lost genes (ndh A, ndh C, ndh E,ndh G, ndh I), indicating that these two species are in the initial phase of the autotroph-to-heterotroph transition. A previous study has confirmed that a hemiparasitic lifestyle can lead to an increase in the pseudogenization/loss of ndh genes (Xin Li et al, 2021). This can be explained to some extent by the facultative root hemiparasitic lifestyle of the two Cymbaria species.…”

“…Traditional Orobanchaceae has been merged with all hemiparasitic genera as well as a few holoparasitic genera formerly placed in Scrophulariaceae (Bennett & Mathews, 2006;dePamphilis, Young, & Wolfe, 1997;Fischer, 2004;McNeal et al, 2013;Wolfe, Randle, Liu, & Steiner, 2005;Young, Steiner, & dePamphilis, 1999) and the three autotrophic genera previously considered as sister taxa to Orobanchaceae (Schneeweiss, 2013;Xia, Li, Wen, & Wang, 2021). Moreover, the two new tribes Brandisieae and Pterygielleae have been proposed (Jiang et al, 2022;Yu et al, 2018).…”

Complete chloroplast genomes of the hemiparasitic genus Cymbaria: Insights into comparative analysis, development of molecular markers, and phylogenetic relationships

“…Traditional Orobanchaceae has been merged with all hemiparasitic genera as well as a few holoparasitic genera formerly placed in Scrophulariaceae (Bennett & Mathews, 2006 ; dePamphilis et al., 1997 ; McNeal et al., 2013 ; Wolfe et al., 2005 ; Young et al., 1999 ) and the three autotrophic genera previously considered as sister taxa to Orobanchaceae (Schneeweiss, 2013 ; Xia et al., 2021 ). Moreover, the two new tribes Brandisieae and Pterygielleae have been proposed (Jiang et al., 2022 ; Yu et al., 2018 ).…”