Geographical vs. ecological diversification inCarexsectionPhacocystis(Cyperaceae): Patterns hidden behind a twisted taxonomy

Abstract

Carex section Phacocystis (Cyperaceae) is one of the most diverse and taxonomically complex groups of sedges (between 116 and 147 species), with a worldwide distribution in a wide array of biomes. It has a very complicated taxonomic history, with numerous disagreements among different treatments. We studied the biogeography and niche evolution in a phylogenetic framework to unveil the relative contribution of geographical and ecological drivers to diversification of the group. We used a large species sampling of the section (82% of extant species) to build a phylogeny based on four DNA regions, constrained with a phylogenomic HybSeq tree and dated with six fossil calibrations. Our phylogenetic results recovered section Phacocystis s.s. (core Phacocystis) as sister to section Praelongae. Ancestral area reconstruction points toward the N Pacific as the cradle for the crown diversification of section Phacocystis during the Middle Miocene. Wide distributions were recurrently inferred across deep nodes. Large Northern Hemisphere lineages with geographical congruence were retrieved, pointing toward the importance of allopatric divergence at deep phylogenetic levels, whereas withinarea speciation emerges as the predominant pattern at shallow phylogenetic level. The Southern Hemisphere (Neotropics, SW Pacific) was colonized several times from the Northern Hemisphere. The global expansion of Carex section Phacocystis did not entail major ecological changes along the inner branches of the phylogeny. Nevertheless, ecological differentiation seems to gain importance toward recent times.

A framework infrageneric classification ofCarex(Cyperaceae) and its organizing principles

“…Scitae , excluding the type of the section ( C. scita ) that is placed in sect. Phacocystis (see also Benítez‐Benítez et al, 2021). It also accommodates several species previously placed in sects.…”

“…Additional relevant literature Faulkner (1972), Chater (1980), Cayouette & Morisset (1985), Cayouette (1987), Standley (1987, 1990), Volkova et al (2008), Dragon & Barrington (2009), Korpelainen et al (2010), Jiménez‐Mejías et al (2011, 2012a, 2014b), Nowak et al (2020), Benítez‐Benítez et al (2021), and Pender et al (2021).…”

“…All of them are medium‐to‐large plants from aquatic or wet habitats, with the only obvious synapomorphy being sheathless bracts. Clades VI.L.IS1–4 below consist of single species or pairs of species whose placements are highly problematic, even unstable between different phylogenetic reconstructions (see placement of the species in Benítez‐Benítez et al, 2021).…”

“…Some phylogenetic hypotheses have placed Carex prasina as sister to the Microchaeta Clade ( VI.L.6), but others have shown that the placement of this species is quite unstable and needs further study (Benítez‐Benítez et al, 2021). This species has been traditionally placed in sect.…”

Revisiting of Carex sect. Confertiflorae s.l. (Cyperaceae): New data from molecular and morphological evidence and first insights on Carex biogeography in East Asia

“…Non-natural groups defined by morphological data are known all over Cyperaceae family due to the effect of homoplasy or symplesiomorphy (e.g., Larridon et al, 2011;Léveillé-Bourret et al, 2020;Starr et al, 2021), with remarkable examples within the tribe Cariceae and the megadiverse Carex (Global Carex Group, 2015;Jiménez-Mejías et al, 2016). The combination of molecular data and morphological evidence is now supporting new taxonomic rearrangements in sedges (e.g., Míguez et al, 2018;Oda et al, 2019;Benítez-Benítez et al, 2021;Jiménez-Mejías et al, 2021;Larridon et al, 2021;Roalson et al, 2021). In addition, while relatively little with other sources of data, morphological and micromorphological characters of nutlets have successfully been employed in Carex taxonomy.…”