No abstract

The tribe Alsineae is a large monophyletic group in the family Caryophyllaceae especially found across Eurasia and the Americas, but with a center of diversity in the Mediterranean region. Several previous molecular phylogenetic studies have focused on the delimitation of genera and tribes of Caryophyllaceae, especially the subfamily Alsinoideae or the tribe Alsineae in a broader sense than now recognized. However, there are still many open questions regarding the subdivision of the tribe and genus delimitation. In the present study, we sampled 191 (148 species) and 149 (125 species) accessions of Alsineae representing almost all (Adenonema and Pseudocerastium were not available to us) recognized genera in the tribe for nuclear DNA internal transcribed spacer (ITS) and plastid marker rps16 sequences, respectively. A combined matrix of 103 species was built for taxa with both sequences available. Maximum parsimony and Bayesian inference analyses retrieved Cerastium and Stellaria (including Myosoton) as the largest monophyletic genera, while other genera were medium‐sized (10–20 spp.) or small (<10 spp.). Our expanded sampling of Pseudostellaria and its relatives suggests a broader circumscription of this genus. Major divergence in morphology, particularly of the seeds, observed in the “Protostellaria”‐clade, allows recognition of some taxonomic changes. A total of 16 genera are recognized in Alsineae including Cerastium, Dichodon, Hartmaniella, Holosteum, Lepyrodiclis, Mesostemma, Moenchia, Nubelaria, Odontostemma, Pseudostellaria, Rabelera, Schizotechium, Shivparvatia, and Stellaria, along with Adenonema and Pseudocerastium that could not be analyzed and are, therefore, kept as distinct genera. A diagnostic key to these genera, as well as notes on their relationships, distribution, and nomenclature, is provided.

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.