Morphological, geographical, and ecological differentiation in the Carex willdenowii complex (Cyperaceae).

Field studies as well as principal components analysis and analyses of variance of specimen measurements revealed morphologic variation within Carex willdenowii correlated with differences in geographical distribution and habitat characteristics. C. willdenowii is actually a complex of three species, C. basiantha Steudel, C. willdenowii Willdenow, and C. superata Naczi, Reznicek, & B.A. Ford, sp. nov. Carex basiantha is a calciphile of moist forests in the southern United States. It has relatively long culms and terminal spikes with long staminate portions. Carex willdenowii is a calcifuge of dry forests in the northeastern United States and immediately adjacent Canada. It has relatively long culms and terminal spikes with short staminate portions. Carex superata is a facultative calciphile of moist to dry forests of the southeastern United States. It has relatively short culms and terminal spikes with long staminate portions. Synonymies, typifications, descriptions, and citations of representative specimens are provided for each species, along with an identification key. The recognition of previously unsuspected diversity in a species from a region with a relatively well-known flora suggests the systematics of other common, widespread, and morphologically divergent species should be investigated.