Data from: Systematics of the giant sedges of Carex sect. Rhynchocystis (Cyperaceae) in Macaronesia with description of two new species

<p>Populations of <i>Carex </i>sect.<i> Rhynchocystis</i> (Cyperaceae) from the Macaronesian archipelagos (Azores and Madeira) have traditionally been treated either as a variety of the widely distributed Western Palearctic <i>C. pendula</i>, or directly synonymized under it. However, recent phylogenetic studies have shown that Azorean populations of <i>C. pendula</i> display a certain degree of differentiation from mainland plants, while the phylogenetic relationships of Madeiran populations remain unclear. Here we perform an integrated systematic study focused on the Macaronesian populations of <i>Carex</i> sect. <i>Rhynchocystis</i> to elucidate their phylogenetic relationships and taxonomic status. We reconstructed a molecular phylogeny based on five DNA regions and conducted a multivariate morphological analysis. Divergence time estimates show that the Macaronesian populations can be traced back to a Plio-Pleistocene origin. Our results suggest that these island populations of <i>C. pendula</i> are better treated as two distinct species within <i>Carex </i>sect. <i>Rhynchocystis</i> (i.e., <i>C. leviosa</i> from the Azores and <i>C. sequeirae</i><i> </i>from Madeira). We provide morphological characters to differentiate the new species from <i>C. pendula</i> s.str., detailed descriptions of the three taxa, a revised key for the entire section, as well as detailed analytical drawings of the two newly described species. We also perform a critical evaluation of the taxonomic diversity of <i>Carex</i> in the Azores and Madeira. Finally, we assessed the conservation status of the new species at a global scale under IUCN categories and criteria, resulting in the proposal of the categories "Least Concern" for <i>C. leviosa</i> and "Critically Endangered" for <i>C. sequeirae</i></p>