Karyological studies of three species of Cladophora (Cladophorales,Chlorophyta) from Bermuda

Abstract

Chromosome numbers for three species of Cladophora from Bermuda are presented. C. laetevirens (Dillw.) Kuetz., C. prolifera (Roth) Kuetz., and C. conferta Crouan frat. ex Schramm & Maze were found to have similar karyotypes with 1 N = 2 X = 12 chromosomes belonging to size class III (0.8–2.2 μm). Correlations between each species' karyotype and its morphology and phytogeographic affinity are discussed. Estimates of the basic genome (1 X) for these and other Cladophora species indicate that nuclear DNA content, which shows a threefold variation in the genus, occurs in discontinuous increments. These findings are discussed in relation to reports of large scale, discontinuous DNA variation in vascular plant genera.