Searching for the sister to sedges ( C arex ): resolving relationships in the C ariceae‐ D ulichieae‐ S cirpeae clade ( C yperaceae)

With approximately 2000 species, tribe C ariceae ( C yperaceae) comprises a morphologically distinctive cosmopolitan clade, with holocentric chromosomes ( N  = 6 to 56), complex biogeographical patterns, and habitat diversity ranging from rainforests to deserts. Such a remarkable combination of characteristics should make C ariceae an ideal model for studying the evolution of biodiversity, although they also obscure their relationships in C yperaceae, complicating attempts to identify the contributing factors to diversity of C ariceae. Recent molecular studies place C ariceae in a strongly supported clade consisting of tribes D ulichieae, S cirpeae s.s , and the enigmatic monotypic genus K haosokia , although relationships in this clade are unresolved. Using the plastid genes mat K and ndh F and a greatly improved taxonomic sampling covering 16 of 17 genera and 55% of the species outside C ariceae, our analyses firmly position D ulichieae and K haosokia (79% and 85% bootstrap support) as successive sisters to a clade consisting of five major lineages ( C alliscirpus , T richophorum  +  O reobolopsis  +  C ypringlea , C ariceae, S cirpus  +  E riophorum , and A mphiscirpus  +  P hylloscirpus  +  Z ameioscirpus ), the first four of which receive good to strong support (> 80% bootstrap support). Cariceae are sister to the T richophorum clade, although topological tests cannot exclude either C alliscirpus or a S cirpus clade +  Z ameioscirpus clade as sister to the tribe. T richophorum appears to be paraphyletic and E riophorum is firmly nested in S cirpus . There appears to be a trend in the increase of chromosome numbers in S cirpus and E riophorum and a trend in the reduction and proliferation of the inflorescence throughout the major C ariceae‐ D ulichieae‐ S cirpeae clades. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society , 2014, 176 , 1–21.