A framework infrageneric classification of Carex (Cyperaceae) and its organizing principles
2021
Phylogenetic studies of Carex L. (Cyperaceae) have consistently demonstrated that most subgenera and sections are para‐ or polyphyletic. Yet, taxonomists continue to use subgenera and sections in Carex classification. Why? The Global Carex Group (GCG) here takes the position that the historical and continued use of subgenera and sections serves to (i) organize our understanding of lineages in Carex, (ii) create an identification mechanism to break the ~2000 species of Carex into manageable groups and stimulate its study, and (iii) provide a framework to recognize morphologically diagnosable lineages within Carex. Unfortunately, the current understanding of phylogenetic relationships in Carex is not yet sufficient for a global reclassification of the genus within a Linnean infrageneric (sectional) framework. Rather than leaving Carex classification in its current state, which is misleading and confusing, we here take the intermediate steps of implementing the recently revised subgeneric classification and using a combination of informally named clades and formally named sections to reflect the current state of our knowledge. This hybrid classification framework is presented in an order corresponding to a linear arrangement of the clades on a ladderized phylogeny, largely based on the recent phylogenies published by the GCG. It organizes Carex into six subgenera, which are, in turn, subdivided into 62 formally named Linnean sections plus 49 informal groups. This framework will serve as a roadmap for research on Carex phylogeny, enabling further development of a complete reclassification by presenting relevant morphological and geographical information on clades where possible and standardizing the use of formal sectional names.
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