Calliscirpus, a new genus for two narrow endemics of the California Floristic Province, C. criniger and C. brachythrix sp. nov. (Cyperaceae)

Although the polyphyletic genus Scirpus L. s.l. (formerly > 200 species) has been divided into more than 50 separate genera and now consists of only 64 species, its circumscription remains problematical. Three new genera have been segregated from Scirpus s.s. in the past decade, and the delimitation of Scirpus from its possible sister genus Eriophorum L. (c. 18 species) is still unresolved. The primary character used to delimit Eriophorum from Scirpus is ≥ 10 smooth, elongate perianth bristles vs ≤ 6 short, serrulate bristles or a lack of bristles, but some species display character combinations that make it difficult to place them in either genus. Eriophorum crinigerum (A. Gray) Beetle (= Scirpus criniger A. Gray), endemic to the California Floristic Province, USA, is one such species, possessing a unique combination of bristle and inflorescence features that suggest affinities with both Scirpus and Eriophorum. In this study we use molecular (matK, ndhF), morphological, and embryological data to demonstrate that E. crinigerum is not closely related to either Scirpus or Eriophorum, but represents a new generic lineage, here named Calliscirpus C. N. Gilmour, J. R. Starr & Naczi (tribe Scirpeae). Within the genus, molecular (matK, ETS 1f) and morphological data strongly support the recognition of two species, each of which is restricted to a distinct region of high endemism. Calliscirpus criniger (A. Gray) C. N. Gilmour, J. R. Starr & Naczi comb. nov. is common to the Klamath-Siskiyou and North Coast mountain ranges of Oregon and California, whereas a new species, Calliscirpus brachythrix C. N. Gilmour, J. R. Starr & Naczi, is unique to the Sierra Nevada mountain range of California. Scirpus maximowiczii C. B. Clarke, another transitional species that has blurred the limits of Scirpus and Eriophorum, and has been cited as morphologically similar to Calliscirpus species in the past, is strongly placed within a Scirpus s.s. + Eriophorum s.s. clade (100% bootstrap) on the basis of molecular and embryological data. Tree support and taxonomic sampling are not sufficient to resolve the delimitation of Eriophorum s.s. from Scirpus s.s.