Genome size and chromosome number in the New Zealand species of Schoenus (Cyperaceae)

Abstract

Schoenus (Cyperaceae) has holocentric chromosomes. Chromosome numbers were counted and nuclear DNA amounts were measured for all the New Zealand species of the genus. Chromosome numbers ranged from 2n = 8 to c .2 n = 90. Two chromosome races, with 2n = 28 and 2n = 56, were found in S. pauciflorus. Flow cytometry using propidium iodide-stained nuclei was used to measure genome size. A 14.8-fold variation in 2C DNA content was found, with values ranging from 1.33 to 19.71 pg/2C nucleus. Phylogenetic trees based on sequence variation in the internal transcribed spacer (ITS) region of the 45S ribosomal DNA locus were constructed using several phylogenetic models to reveal possible evolutionary relationships among the New Zealand Schoenus spp. and a sample of Australian Schoenus spp. Analysis revealed heterogeneity of chromosome number, size and DNA C value within clades. Meiosis in four species showed only bivalent formation at metaphase I. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 555–564. ADDITIONAL KEYWORDS: flow cytometry – holocentric chromosomes – ITS phylogeny.