Chromosome Numbers for Species of Characeae from Southern Illinois

Abstract

Chromosome numbers were determined for five species of Nitella and five species of Chara representing 27 naturally occurring populations. Chromosome counts were as follows: Nitella mirabilis, n=6; N. flexilis, n=12; N. acuminata, n=18; N. axillaris, n=18; N. oligospira, n=18; Chara braunji, n=14; C. contraria, n=42; C. globularis, n = 28; C. foliosa, n = 14; and C. haitensis, n = 42. Relationships among these and similar forms reported from elsewhere in North America are discussed. INTRODUCTION Several authors have reported dhromosome numbers for species of Characeae in North America (Hotchkiss, 1958, 1963; Tindall and Sawa, 1964; Griffin and Proctor, 1964; Tindall et al., 1965; Sawa, 1965, 1966; Tindall, 1966, 1967, 1970; Proctor, 1970, 1971a, 1971b; Proctor and Wiman, 1971; Proctor et at., 1971; Grant and Proctor, 1972). Reports of chromosome numbersfor species of Characeae occurring in other countries are reviewed by Guerlesquin (1966) and Corillion and Guerlesquin (1972). The importance of polyploidy, intraspecific barriers to gene flow, minor ecological differences and geographical distribution in relation to speciation in the Characeae are stressed in several of the above reports. These studies have shown that knowledge of chromosome number is quite useful in resolving taxonomic problems and in clarifying distribution patterns for some species complexes. The present study was carried out to determine relationships between species occurring in southern Illinois and those previously reported from elsewhere in North America. Previous work on the taxonomy of the Characeae of Illinois was reviewed by Stotler (1968). MATERIALS AND METHODS Twenty-seven naturally occurring populations of Characeae in southern Illinois were examined. These populations represented five species of Nitella and five species of Chara. All collections consisted of cvtological sDecimens and voucher specimens. Cytological material for Nitella flexilis was obtained from culture of the field collection. Cytological material was fixed in an absolute ethanol-glacial acetic acid (i3: 1) solution for '24 h. Following fixation, cytological specimens were stored in 70% ethanol at 5 C until examined. Antheridial filaments were dissected from immature antheridia and were squashed and stained with aceto-carmine. No attempt was made to standardize the fixing and staining procedure for determining chromosome morL Current address: School of Medicine, Southern Illinois University, Carbondale 62901.