Taxonomic Observations Within Stellaria (Caryophyllaceae): Insights from Ecology, Geography, Morphology, and Phylogeny Suggest Widespread Parallelism in Starworts and Erode Previous Infrageneric Classifications

Abstract

Abstract—Recent phylogenetic analysis circumscribes the bounds of a core genus of Stellaria comprising five major extant clades and around 112 species. Some finer scale phylogenetic relationships emerging from that study are interpreted here. The Larbreae and Petiolares clades are the main foci, as they comprise the bulk of Stellaria diversity. In particular, I address the implications of our phylogenetic work on some widespread and morphologically complex lineages of starworts, including the Stellaria borealis, Stellaria cuspidata, Stellaria longipes, and Stellaria media groups, and also briefly discuss other subclades within the Larbreae and Petiolares clades. Based on phylogenetic evidence, Stellaria sitchana is here recognized as a distinct species from Stellaria borealis rather than as Stellaria borealis subsp. sitchana, and this lineage is furthermore reported from the southern hemisphere for the first time. Other newly discovered lineages that require revised nomenclatural concepts pending future work also are briefly treated. Overall, a picture of widespread evolutionary parallelism emerges within Stellaria, and this parallelism is largely responsible for the non-monophyletic nature of most previous subdivisions of the genus.

Evolution of apetaly in the cosmopolitan genus Stellaria

“…The BEAST phylogeny was inferred from an alignment comprising 80,676 nucleotides (48.9% missing data) and included 92% of 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the S. longipes group; for further discussion, see Sharples, 2019; Sharples and Tripp, 2019a; M. Sharples and E. Tripp, unpublished data). 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).…”

“…Our outgroup sample of Cerastium was coded as petalous given that all or nearly all members of the sister group of Stellaria to which Cerastium belongs bear petals (including our sample), and given that Greenberg and Donoghue (2011) reconstructed all members of this clade, as well as the entire rest of the tribe Alsineae, as petalous. Taxonomic concepts and clade names follow Sharples and Tripp (2019a) and Sharples (2019), and species trait codings are provided in Appendix 1.…”

“…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).…”

A new subspecies of Stellaria alsine (Caryophyllaceae) from Yakushima, Japan

“…( Kadota 2017 ), but S. uliginosa is generally treated as a synonym of S. alsine , which is widely distributed in Europe, Asia, and eastern North America ( Chen and Rabeler 2001 ). A recent molecular phylogenetic study ( Sharples 2019 ) proposed that S. alsine is polyphyletic and included two unrelated lineages: one lineage from European Russia belongs to the Nitentes clade, and another one from eastern Asia and eastern North America form the Uliginosae clade. Stellaria alsine was described from Europe ( Grimm 1767 ), but Sharples (2019) cited the material from European Russia as ‘ S. cf.…”

“…A recent molecular phylogenetic study ( Sharples 2019 ) proposed that S. alsine is polyphyletic and included two unrelated lineages: one lineage from European Russia belongs to the Nitentes clade, and another one from eastern Asia and eastern North America form the Uliginosae clade. Stellaria alsine was described from Europe ( Grimm 1767 ), but Sharples (2019) cited the material from European Russia as ‘ S. cf. alsine ’, while those from N America and E Asia as ‘ S. alsine ’.…”