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Byline: Okihito Yano (1), Teruo Katsuyama (2), Hiromi Tsubota (3), Takuji Hoshino (1) Keywords: Chromosomal evolution; Cyperaceae; Diffuse centromeric chromosome; Eleocharis; ITS phylogeny; Karyotype Abstract: ITS sequence data were used to estimate the phylogeny of 24 Japanese Eleocharis species and to make karyomorphological observations on 19 of these taxa. Two major clades were identified in Japanese Eleocharis molecular phylogenetic trees: (1) one including all species of section Limnochloa, and (2) another comprising two sections, Pauciflorae and Eleocharis. Phylogenetic analysis including both Japanese and North American species also shows strong support for monophyly of the Mutatae/Limnochloa clade. The width of the spikelets in the species Mutatae/Limnochloa is the same as that of the culms, indicating that the relative widths of spikelets and culms are useful characteristics for classification. Two major clades were supported by karyomorphological data. All taxa of section Limnochloa had very small chromosomes, while sections Pauciflorae and Eleocharis had large chromosomes. The basic chromosome number of sections Eleocharis and Pauciflorae is thought to be x=5. Chromosomal evolution in the genus Eleocharis with diffuse centromeric chromosomes may be caused by both aneuploidization and polyploidization. Our data suggest that a 3-bp insertion near the 3 end of the 5.8S gene is useful for intrageneric delimitations of the genus Eleocharis. Author Affiliation: (1) Department of Biosphere-Geosphere System Science, Graduate School of Informatics, Okayama University of Science, 1-1 Ridaicho, Okayama 700-0005, Japan (2) Kanagawa Prefectural Museum of Natural History, Kanagawa, Japan (3) Department of Biological Science, Graduate School of Science, Hiroshima University, Hiroshima, Japan Article History: Registration Date: 13/08/2004 Received Date: 30/06/2004 Accepted Date: 09/08/2004 Online Date: 15/09/2004

Carex section Acrocystis (Cyperaceae) traditionally has included ca. 45 species. Recent studies have suggested that a 'core' group of Acrocystis species forms a monophyletic group, while other species are more closely related to other sections. This core group includes all North American Acrocystis species and some but not all Eurasian members. Taxonomists have recognized several species complexes in North American Acrocystis, with several 'orphan' species not delt with in these species complexes. The complexes that have been defined include the 'Carex pensylvanica complex,' the 'Carex nigromarginata complex,' the 'Carex deflexa complex,' and the 'Carex umbellata complex'. Taxa not included in these complexes are Carex novae-angliae, C. turbinata, C. leucodonta, C. communis, C. globosa, C. brainerdii, and C. serpenticola. How these complexes and orphan species are related has not been addressed explicitly, and none of the North American species have been explicitly compared with Eurasian or South American members of Acrocystis, with few exceptions. The study presented here explores relationships within North American members of Carex section Acrocystis and related Eurasian species and addresses biogeographic patterns of diversification using nuclear Adh genic regions and the nrDNA ITS region.