Taxonomy of the Carex flava complex (Cyperaceae) in North America and northern Eurasia. II. Taxonomic treatment

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Abstract
The taxonomy of the Carex flava complex (section Ceratocystis) in North America and northern Eurasia is revised. Three species are recognized in this complex (C. flava L., C. cryptolepis Mack., and C. viridula Michx.). Carex viridula contains six infraspecific taxa, which are differentiated on the basis of differences in inflorescence structure, degree of perigynium curvature, leaf and bract morphology, chromosome number, and ecological preference. Three nomenclatural changes are required: C. viridula ssp. brachyrrhyncha (Celak.) B. Schmid var. elatior (Schlecht.) Crins, comb.nov. [C. flava var. elatior]; C. viridula ssp. brachyrrhyncha var. nevadensis (Boiss. and Reuter) Crins, comb.nov. [C. neva densis]; C. viridula ssp. brachyrrhyncha var. saxilittoralis (Robertson) Crins, comb. et stat. nov. [C. saxilittoralis]. This classification reflects the results of morphological, ecological, and cytological studies, and is also consistent with the hypothesized phylogenetic history of the section as a whole. A key is provided for all of the North American and northern Eurasian members of section Ceratocystis. Descriptions and distribution maps for members of the C. flava complex are also provided.