Rhodoscirpus (Cyperaceae: Scirpeae), a new South American sedge genus supported by molecular, morphological, anatomical and embryological data

Abstract

In its broadest sense, Scirpus consists of a heterogeneous assemblage of up to 250 species, but modern circumscriptions suggest that only 40–50 species are part of the genus. Despite a narrower definition of the genus, atypical species continue to be segregated from Scirpus with a common pattern being the removal of Southern Hemisphere taxa to other genera and tribes. In South America, the morphology of remaining Scirpus species also suggests that they are not closely related to Scirpus s.str., but most of these taxa are only known from their types, making a detailed analysis of their generic affinities difficult. One notable exception is Scirpus asper, a species that is relatively common in the mountains and adjacent lowlands of Peru south to Argentina. Although this species possesses features used in the circumscription of Scirpus, such as cauline leaves, flat leaf blades and anthelate inflorescences, it is known to differ from Scirpus s.str. by its Schoenus‐type embryo, and most of its presumed allies are now placed in different genera (e.g., Scirpus analecti ≡ Cypringlea analecta; Scirpus giganteus ≡ Androtrichum giganteum). In this study, we use DNA sequence data from the plastid (matK, ndhF) and nuclear (ETS‐1f) genomes to demonstrate that Scirpus asper is not closely related to Scirpus s.str., but sister to Phylloscirpus within the predominantly South American Zameioscirpus clade (Amphiscirpus, Phylloscirpus, Zameioscirpus). When combined with morphological, anatomical and embryological data, results indicate that S. asper is best treated as the sole species of a new monotypic genus, Rhodoscirpus. The implications of these results on the taxonomy of tribe Scirpeae are discussed.

Resolving Rapid Radiations Within Angiosperm Families Using Anchored Phylogenomics

“…With 16 genera and over 2,200 species, this cosmopolitan clade is of considerable evolutionary interest due to its habitat variety (deserts to rain forests), biogeographic patterns (e.g., bipolar, Gondwanan, Amphiatlantic; Croizat 140 1952), and unique cytology (n = 6 to 56) promoted by agmatoploid chromosomal fusion and fragmentation (Hipp et al 2009). Previous phylogenies of CDS have identified seven major lineages using the traditional combination of plastid and nrDNA markers (Muasya et al 2009;Léveillé-Bourret et al 2014;Léveillé-Bourret et al 2015). However, like many plant groups, the backbone of the tree remains unresolved possibly due to a relatively old crown age (>40 Ma) and 9/52 an early radiation that occurred over just 10 million years (Escudero et al 2013;Spalink et al 2016).…”

“…genes matK and ndhF(Gimour et al 2013), as well as the nrDNA region ETS-1f, were obtained from Genbank for the same species as those used in phylogenomics analysis (but replacing the outgroup Eleocharis obtusa with E. acicularis and including only one Scirpus atrovirens 345 accession). Five sequences were newly obtained by PCR and Sanger-sequencing following the procotols inLéveillé-Bourret et al (2015). Genbank accession numbers and voucher information are available in Appendix 2.…”

A tale of worldwide success: Behind the scenes of Carex (Cyperaceae) biogeography and diversification

“…The origin and worldwide diversification of Carex have been discussed in relation to chromosome evolution and adaptation to colder climates (Escudero et al, ; Gebauer et al, ; Hoffmann et al, ), as well as fine‐scale partitioning of niche and distributional ranges of individual species within continents (Waterway et al, ; Gebauer et al, ; Pender, ; Spalink et al, 2016a, 2016b, ; Benítez‐Benítez et al, ). While Cyperaceae have been inferred to have arisen in South America at the late Cretaceous, it was the migration of the ancestors of Carex to the Northern Hemisphere that was the catalyst for the major diversification of this lineage (Léveillé‐Bourret et al, , , 2018a, 2018c; Spalink et al, ). Recent phylogenetic studies have discovered that several early‐diverged lineages of Carex and its closest living relatives are Southeast (SE) Asian (Starr & Ford, 2009; Waterway et al, ; Starr et al, ; Léveillé‐Bourret et al, 2018b), supporting the long‐held view that the genus originated in SE Asia (Nelmes, 1951; Raymond, 1955, 1959; Koyama, 1957; Ball, 1990).…”

Molecular and morphological data reveal three new tribes within the Scirpo‐Caricoid Clade (Cyperoideae, Cyperaceae)

“…Tribal classifications thus continued to use a broad circumscription for the tribe, mainly out of convenience (Koyama, , , ; Schultze‐Motel, , ; Schuyler, ). Accumulation of morphological and embryological evidence eventually resulted in the transfer of the most atypical Scirpus species to other genera, and the most distinctive genera to other tribes, leaving only ~ 50 species in Scirpus and splitting Scirpeae into six tribes in modern classifications (Wilson, ; Bruhl, ; Goetghebeur, ; Govaerts & al., ; Muasya & al., ; Léveillé‐Bourret & al., ) (Table ). Nonetheless, the current circumscription of tribe Scirpeae (10 genera, ~ 79 spp.)…”

“…As expected on the basis of morphological characters, early molecular phylogenetic analyses of the family invariably suggested Scirpeae was paraphyletic with respect to other SCC lineages, but limited species sampling, inconsistent tree topologies and low branch support prevented a new tribal circumscription from being proposed (Muasya & al., , ; Simpson & al., , ; Jung & Choi, ; Gilmour & al., ). Recent studies incorporating broader taxonomic sampling and more informative molecular markers have shown Dulichieae and Khaosokia to form two isolated, early‐diverged lineages, and have suggested Scirpeae to be composed of four distinct clades forming a grade relative to a monophyletic Cariceae (Léveillé‐Bourret & al., , ). However, relationships among these seven lineages were unsupported due to the short branches forming the backbone of the SCC phylogeny, representing a rapid radiation that occurred in less than 15 million years (Escudero & Hipp, ; Spalink & al., b; Léveillé‐Bourret & al., ).…”