Relationships within the CDS Clade (Cariceae-Dulichieae-Scirpeae): New tribes, new genera and new species

LEMMON A.; SPALINK D.; THI KIM THAN N.; GILMOUR C. N.; STARR J. R.; SYTSMA K.; ANH TÀI V.; NACZI R.; LÉVEILLÉ-BOURRET E.; MORIARTY LEMMON E.; BINGHUA C.; DONADÍO S.; FORD B.

Shenzhen

Congreso; XIX International Botanical Congress; 2017

Botanical Society of China

With approximately 40% of all sedge species (>2,050), the Cariceae-Dulichieae-Scirpeae (CDS) clade is a cosmopolitan lineage that is found in habitats ranging from deserts to tundra and from temperate wetlands to tropical rain forests. Although comprised of three tribes, the CDS clade is dominated by the Cariceae, a monotypic tribe for Carex. Long recognised as one of the world´s largest plant genera, this taxon´s diverse biogeography (e.g. amphiatlantic, bipolar, Gondwanan), intriguing cytology (holocentric chromosomes: n=6 to 56), and morphological singularity have made it an ideal model for studying speciation, ecology and biogeography. Despite many significant advances in our knowledge of relationships within Carex, our understanding of its relationships within the CDS clade remain unclear, a fact that affects the conclusions drawn in all Carex studies since outgroup relationships have a significant impact on homology assessment, character polarisation and biogeographical analyses. Over the past decade, we have focused our research on the relationships of Cariceae to the approximately 86 species and infraspecific taxa in tribes Scirpeae and Dulichieae that make up the remaining members of the CDS clade. Using representatives for all 18 genera currently recognised in CDS and ca. two thirds of the species that comprise tribes Scirpeae and Dulichieae, our five marker DNA sequence dataset (matK, ndhF, rps16, ETS 1f, ITS), in conjunction with morphological, anatomical and embryological data, suggest there are seven well supported major lineages within the CDS clade with Dulichieae and Khaosokia successively sister to a clade containing the previously recognised Cariceae, Trichophorum, Calliscirpus, Zameioscirpus and Scirpus+Eriophorum Clades. Although the backbone of our previous phylogenetic analyses has often been weak or unresolved due to a rapid radiation among CDS lineages (10 million years), we have since employed universal flowering plant enrichment probes for a subset of key taxa to generate a matrix of 461 nuclear genes using next generation sequencing technology. The results of these phylogenomic analyses are fully congruent with our Sanger-sequence datasets and morphology, but we now have unprecedented support for backbone nodes (100% BS) that were previously unsupported (