On the taxonomic status of the genus Dichodon (Caryophyllaceae: tribe Alsineae): morphological and molecular evidence reassessed

Abstract

The status of the genus Dichodon has long been debated, and its taxonomic position in tribe Alsineae has been changed during the time from a section or subgenus in Cerastium to genus sister to Holosteum. This group comprises important members of wet meadows in alpine and subalpine vegetation of Europe, arctic regions, and SW-Asia plus one species known as a weed in N-America, and a further one occuring in mountains of Taiwan. In order to clarify the taxonomic questions concerning this group and its species delimitation, we constructed phylogenetic trees, selecting several species belonging to tribe Alsineae as representatives of major lineages of this tribe as well as several accessions of Dichodon. Morphological studies focused more intensively on members of Dichodon using herbarium specimens and direct field examinations. The results confirm those of recent molecular phylogenetic studies, indicating Dichodon as a monophyletic genus sister to Holosteum and not Cerastium. In addition, the obtained cladograms support five distinct groups in Dichodon corresponding to five species of this genus we recognize in Iran, the focal area of this study. Seed micromorphology provides strong support for the recognition of Dichodon as a separate genus, but it is not informative at species and subspecies ranks due to constancy of most of seed characters within the genus. As part of this study, a new species—Dichodon alborzensis—is described, D. kotschyi is reported in Iran for the first time, and Cerastium schischkinii is placed in synonymy (new synonymy) under D. kotschyi.

Intergeneric relationships within the tribe Alsineae (Caryophyllaceae) as inferred from nrDNA ITS and cpDNArps16 sequences: A step toward a phylogenetically based generic system

“…Some of the taxa traditionally assigned to this group (see below) are not associated with this clade or with the genera they were originally assigned to. The number of genera within Alsineae has been increasing in recent years through the addition of several newly defined genera, e.g., Hartmaniella (Zhang & al., 2017) and Shivparvatia (Pusalkar & Singh, 2015;Sadeghian & al., 2015), and resurrection of others, e.g., Dichodon (Arabi & al., 2018) and Schizotechium (Pusalkar & Srivastava, 2016), that were described earlier and then synonymized. The phylogenetic analyses performed here provide better resolution of the relationships and delimitation of genera in Alsineae.…”

“…Dichodon , which was previously treated as a subgenus of Cerastium (Möschl, 1988), is another member of clade “Alsineae B”. It includes seven species, ranging from the Arctic over central Europe to Iran (Arabi & al., 2018). According to our phylogenetic data, Dichodon shares a common clade with Holosteum , Moenchia and Cerastium recovered in all trees (Figs.…”

“…Other phylogenetic studies that covered several representatives of Cerastium have shown that C. subg. Dichodon deserved to be recognized as a distinct genus (Greenberg & Donoghue, 2011;Arabi & al., 2018).…”

“…Rchb. from Cerastium was recently confirmed (Arabi & al., 2018). A comprehensive molecular phylogenetic study using selected cpDNA markers identified the main clades within Cerastium (Scheen & al., 2004), but due to poor outgroup sampling, the correct position of Cerastium (ca.…”

“…subg. Dichodon deserved to be recognized as a distinct genus (Greenberg & Donoghue, 2011; Arabi & al., 2018).…”