Eriophorum crinigerum (Scirpeae, Cyperaceae) has been placed in either the genus Scirpus (club-rushes) or Eriophorum (cottograsses), but a unique combination of bristle and inflorescence features suggests that it could represent a new generic lineage. In addition, prior field studies and initial analyses suggested that E. crinigerum could consist of two species. Using molecular, morphological, anatomical, embryological and geographical data, I examine relationships within the hyperdiverse Cariceae + Dulichieae + Scirpeae clade (ca. 2055 species)to which E. crinigerum belongs and I explore whether this species could contain undocumented species diversity. Results demonstrate not only that E. crinigerum represents a new genus within Cyperaceae, here called Calliscirpus, but it can be divided into two allopatric species, C. criniger and C. brachythrix sp. nov. Calliscirpus brachythrix is confined to the Sierra Nevada Mountains and C. criniger is confined to the Klamath-Siskiyou and North Coastal Mountains; all three mountain ranges are found within the California Floristic Province (USA) which is well known for its high generic and species endemism. My results suggest that Calliscirpus is distantly related to Eriophorum, but that it could be most closely related to the Cariceae, a osmopolitan clade representing almost 40% of all Cyperaceae diversity.

Eriophorum crinigerum (Scirpeae, Cyperaceae) has been placed in either the genus Scirpus (club-rushes) or Eriophorum (cottograsses), but a unique combination of bristle and inflorescence features suggests that it could represent a new generic lineage. In addition, prior field studies and initial analyses suggested that E. crinigerum could consist of two species. Using molecular, morphological, anatomical, embryological and geographical data, I examine relationships within the hyperdiverse Cariceae + Dulichieae + Scirpeae clade (ca. 2055 species)to which E. crinigerum belongs and I explore whether this species could contain undocumented species diversity. Results demonstrate not only that E. crinigerum represents a new genus within Cyperaceae, here called Calliscirpus, but it can be divided into two allopatric species, C. criniger and C. brachythrix sp. nov. Calliscirpus brachythrix is confined to the Sierra Nevada Mountains and C. criniger is confined to the Klamath-Siskiyou and North Coastal Mountains; all three mountain ranges are found within the California Floristic Province (USA) which is well known for its high generic and species endemism. My results suggest that Calliscirpus is distantly related to Eriophorum, but that it could be most closely related to the Cariceae, a osmopolitan clade representing almost 40% of all Cyperaceae diversity.