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

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.

Differences in cellular structure regulate stem elongation of alpine and prairie ecotypes of Stellaria longipes grown under two contrasting temperature regimes

The objectives of this study were to explore differences in the structural features of stem elongation in alpine and prairie ecotypes of Stellaria longipes Goldie in response to two contrasting temperature regimes. The two ecotypes were grown under warmer, 28 °C (day) – 22 °C (night), and cooler, 10 °C (day) – 4 °C (night) temperatures, and under the same light irradiance (∼120 µmol·m–2·s–1) and photoperiod (16 h). Temperature exerts a significant effect on the stem elongation of alpine and prairie ecotypes of S. longipes. Significant retardation of growth occurred in plants grown in cooler temperatures (10 °C (day) – 4 °C (night)), while growth was profoundly enhanced when plants were grown under warmer conditions (28 °C (day) – 22 °C (night)). The ecotypes exhibited differential responses to temperature (owing to differences in their cellular structure), particularly in cell length, the timing of cell wall thickening, the deposition of phenolic compounds, and the changes in cortical microtubule orientation.