Botanical Journal of the Linnean Society, 2005, 149, 457–464. With 19 figures © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 149, 457–464 457 Blackwell Science, LtdOxford, UKBOJBotanical Journal of the Lin- nean Society0024-4074The Linnean Society of London, 2005? 2005 149? 457464 Original Article REDUCTION OF CHROMOSOME NUMBER IN ELEOCHARIS C. R. M. DA SILVA Et al. *Corresponding author. E-mail: andrevanzela@uel.br Reduction of chromosome number in Eleocharis subarticulata (Cyperaceae) by multiple translocations CARLOS R. M. DA SILVA 1 , M. SOCORRO GONZÁLEZ-ELIZONDO 2 and ANDRÉ L. L. VANZELA 1 * 1 Laboratório de Biodiversidade e Restauração de Ecossistemas, Departamento de Biologia Geral, CCB, Universidade Estadual de Londrina, 86051-970, Londrina, PR, Brazil 2 Instituto Politécnico Nacional CIIDIR, Durango, Dgo. 34000, Mexico Received March 2005; accepted for publication May 2005 Eleocharis subarticulata is recorded as the third species of Cyperaceae with a reduced chromosome number (n = 3), following reports on Rhynchospora tenuis (n = 2) and Fimbristylis umbellaris (n = 3). For Eleocharis, the numbers recorded to date vary from 2n = 10 to 2n = c. 196, with x = 5 as the possible basic number. The karyotype of E. subarticulata was studied using conventional staining (mitosis and meiosis), C-CMA 3 /DAPI banding, and FISH with 45S rDNA and telomere probes. The chromosomes showed no primary constrictions, as expected in the holo- centric chromosomes of Cyperaceae. The meiotic behaviour was abnormal, with a single multivalent ring of six chro- mosomes at metaphase I, resulting from multiple translocations. At anaphase I six chromatids migrated to each pole, evidencing the inverted meiosis, and these groups were also visible at metaphase II. The C-CMA 3 /DAPI banding technique showed only four terminal GC-rich blocks. FISH with 45S rDNA probes revealed four terminal signals, probably associated with GC-rich blocks. The telomeric probe located terminal signals in all the chromosomes, besides a hybridization site in the middle of the large pair. The occurrence of ectopic telomeric sites has not been described previously for plants with holokinetic karyotypes and with reduced chromosome numbers. These data reinforce the hypothesis of the reduction in chromosome number by multiple translocations. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 149, 457–464. ADDITIONAL KEYWORDS: chromosome banding – FISH – holocentric chromosomes – rDNA – telomere. INTRODUCTION Eleocharis subarticulata (Nees) Boeckl. is a small spe- cies in the Cyperaceae characterized by short, filiform and opaque culms (5–15 cm), purple sheaths with usu- ally obtuse subinflated apex; spikelets fusiform to lan- ceolate, achene trigonous to almost planoconvex, narrowly obovate, shining olivaceous, deeply reticu- late, style-base narrow, subulate, grey, a third to a quarter as long as the achene body, and bristles light brown, shorter than or exceeding the achene (Svenson, 1929). Svenson (1929) considered the position of E. subarticulata in the genus Eleocharis to be uncer- tain. Menapace (1993) included this species in the series Palustriformes based on the micromorphology of the achenes. The Palustriformes group is part of the subseries Eleocharis, in the subgenus Eleocharis (Strandhede, 1967; González-Elizondo & Peterson, 1997). Eleocharis subarticulata differs from other members of the subseries Eleocharis in several morphological traits and its taxonomic position in the genus remains unclear. Some cytogenetic peculiarities confirm the tax- onomic uniqueness of this species. Species of Eleocharis as well as other representatives of the Cyperaceae fam- ily possess holocentric chromosomes, post-reductional meiosis, and lack tetrads (see Faulkner, 1972). The chromosome numbers previously recorded for Eleo- charis ranged from 2n = 10 (Wulff, 1937 and Levitski, 1940, both cited by Strandhede, 1965a, b, c, d, 1966, 1967, 1973; Lewis, Stripling & Ross, 1962) to 2n = c. 196 in E. kuroguwai (Hoshino, 1987). The predomi- nance of numbers that are multiples of n = 5 (2n = 10, 20, 30, 40, 50), suggests that x = 5 is the probable basic