Phylogenetic Relationships Within and Delimitation of the Cosmopolitan Flowering Plant Genus Stellaria L. (Caryophyllaceae): Core Stars and Fallen Stars

Abstract

Abstract—Stellaria (Caryophyllaceae, tribe Alsineae) is a cosmopolitan genus of herbaceous plants that heretofore has lacked a stable estimate of total number of species. Here, we attempted to sample all species currently recognized under the name Stellaria to determine which belong to a core Stellaria genus versus which are masquerading under this name and are instead more closely related to one of several outgroup lineages. Phylogenetic relationships inferred with RAD loci were recovered with generally high levels of support, regardless of age of specimens (here up to 98 yr) utilized for molecular work. Analyses resolved a monophyletic, core radiation of Stellaria that is sister to Cerastium and others. Within core Stellaria, of which we sampled ca. 87% of species, we recovered five primary lineages. However, current infrageneric hypotheses are incongruous with phylogenomic data, and most morphology-based infrageneric hypotheses break down in light of these results. Outside of core Stellaria we recovered numerous other species currently ascribed to Stellaria that are in need of revised generic placement. Based on current results, however, we propose several new taxonomic and nomenclatural renovations within core Stellaria and external to this group as contribution towards stabilization of generic boundaries in Alsineae. These modifications include description of a new genus of Caryophyllaceae from eastern Asia, Nubelaria, as well description of a new genus, Rabelera, to accommodate the lineage previously and more widely known as Stellaria holostea. Nine new combinations are proposed in the genera Adenonema, Cerastium, Mesostemma, Nubelaria, Rabelera, and core Stellaria. Additionally, one new status, one new synonymy, and lectotypes for four species are proposed. We estimate core Stellaria to consist of approximately 112 species, a decrease from many other published species counts. Our results lay a robust foundation for future evolutionary, phylogenetic, and morphological comparisons within Stellaria and among relatives.

Evolution of apetaly in the cosmopolitan genus Stellaria

“…Sharples and E. Tripp, unpublished data). Phylogenetic relationships in this MCC tree were generally congruent with relationships in previously published trees based on a maximum likelihood approach including far more loci than included here (i.e., all major clades were recovered, but with some variation in relationships within clades; Sharples and Tripp, 2019a).…”

“…Total ovules (5-) 13 (-22); n = 218 (11-) 26 (-38); n = 220 Control SS (0. samples newly sequenced for the present study. These data are robust to genus-and family-wide phylogenomic inference across the Caryophyllaceae and other lineages (e.g., Rubin et al, 2012;Hipp et al, 2014;Díaz-Arce et al, 2016;Nieto-Montes de Oca et al, 2017;Tripp et al, 2017;Paetzold et al, 2019;Sharples & Tripp, 2019a, 2019b. New species of Stellaria that have not previously been used in RADseq phylogenetic analysis were S. fontana, S. himalayensis, "S. parviflora" of South America (as opposed to Oceania), S. reticulivena, and S. weberbaueri.…”

“…New species of Stellaria that have not previously been used in RADseq phylogenetic analysis were S. fontana, S. himalayensis, "S. parviflora" of South America (as opposed to Oceania), S. reticulivena, and S. weberbaueri. Library generation of new samples followed Sharples and Tripp (2019a). In contrast with our prior work, phylogenomic analyses conducted for the present study targeted only one accession per species.…”

“…Our current data set is not suitable for better interpretation of instances of re-evolution of petaly from apetaly, owing to poor support and rogue taxa associated with a predominantly Asian clade (i.e., clade 10; Fig. 5; Appendix S1; see also Sharples and Tripp, 2019a). This clade has radiated into nearly one-third of all species diversity in Stellaria within the Pleistocene (M. Sharples and E. Tripp, unpublished data), and greater infraspecific sampling of species combined with analyses that better account for phenomena such as ILS and introgression are needed for a clearer understanding of relationships and thus character evolution within this clade.…”

“…taxonomic diversity in Stellaria. Posterior probabilities in the MCC tree were generally high across nodes (Appendix S1), with relatively strong support across the backbone but some areas of poor support toward the tips (particularly in the main Pan-Himalaya group, the S. cuspidata group, and the S. longipes group; for further discussion, see Sharples, 2019;Sharples and Tripp, 2019a;M. Sharples and E. Tripp, unpublished data).…”