Phylogeny, Species Richness, and Ecological Specialization in Cyperaceae Tribe Cariceae

Abstract

Cyperaceae tribe Cariceae is characterized by both species richness and habitat diversity, making it an ideal system to study ecological specialization and niche differentiation. We present a phylogenetic hypothesis for the tribe based on nuclear and chloroplast DNA sequence comparisons (ETS-1f, ITS, trnL intron, trnL-trnF intergenic spacer) for 140 representative species from five continents, and use this hypothesis to suggest patterns of both niche conservatism and niche differentiation, particularly within the large subgenus Carex. We identify a new major clade, comprising forest species of East Asian Carex section Siderostictae (subgenus Carex) as sister to the rest of tribe Cariceae. Within Carex subgenus Carex, species tolerant of water-saturated habitats occur in only a few, apparently derived groups, with varying species richness. Clades of predominantly wetland species tend to have broad geographic distribution, often with sister species on different continents, suggesting recent dispersal. In contrast, species within several clades are predominantly forest specialists with distinct Asian and North American lineages. Niche segregation along environmental gradients, such as soil moisture or acidity, is quite common among closely related wetland species, but more difficult to demonstrate within upland forest groups. More complete sampling of species within both wetland and forest groups, combined with comparable sampling of environmental preferences and testing against null models, will be needed for more rigorous exploration of the observed patterns.

New Insights into the Systematics of the Schoenoxiphium Clade (Carex, Cyperaceae)

“…Phylogenetic work has shown that this broader circumscribed Carex comprises three strongly supported clades (Siderostictae, Vignea, and Core Carex) and a weak to moderately supported clade, the Caricoid clade, which includes most unispicate and a few multispicate Carex species as well as the remaining genera traditionally considered within the tribe (Cymophyllus, Kobresia, Schoenoxiphium, and Uncinia; Starr et al 1999;Yen and Olmstead 2000;Roalson et al 2001;Waterway and Starr 2007;Waterway et al 2009). Within the Caricoid clade, two well-supported lineages are found: the Schoenoxiphium clade, including the former genus Schoenoxiphium plus two small clades of Carex species (one containing sections Junciformes and Aciculares and the other grouping C. distachya and allies; Gehrke et al 2010;Global Carex Group 2016), and another comprising the polyphyletic genus Kobresia, the monophyletic genus Uncinia, and several clades with mostly unispicate Carex species (Waterway et al 2009).…”

Flora of Guaramacal (Venezuela): Monocotyledons

“…Gehrke et al (2010); Hipp et al (2006); Kükenthal (1909); Reznicek (1990); Starr and Ford (2009);Starr et al (2004Starr et al ( , 2008; Waterway and Starr (2007); Waterway et al (2009).…”

“…Although molecular data (Starr et al, 2004(Starr et al, , 2008Waterway et al, 2009;Gehrke et al, 2010) resolve Uncinia as monophyletic, it is embedded in the very large genus Carex and is a major element in a core unispicate clade (Waterway and Starr, 2007;Starr and Ford, 2009) that also includes Cymophyllus and unispiculate species of Kobresia and Carex. Sister to this core unispicate clade is the Schoenoxiphium clade composed of Schoenoxiphium Nees and species of Carex.…”

Carex concava (Carex sect. Rhomboidales, Cyperaceae), a new species from Hainan, China

“…Psyllophora (Degland 1828:285). This classification was widely followed by most authors (Koyama 1962;Reznicek 1990;Dai 2000Dai , 2010Waterway et al 2007Waterway et al , 2009.…”