Karyotype analysis of marine and freshwater populations of Bangia (Bangiales, Rhodophyta) in Italy

A detailed karyotype analysis was carried out on several populations of Ban gia atropurpurea (Roth) C. Agardh from marine and freshwater habitats in It aly. All the populations studied had a constant somatic chromosome number o f n = 3. A statistical analysis of chromosomal dimensions allowed the recog nition of a consistent difference in the size of chromosome 3. Neither mari ne nor freshwater populations showed significant interpopulation variation in chromosome size and shape; however, comparison of karyotypes between mar ine and freshwater thalli revealed significant differences. Chromosome 3 of freshwater specimens is significantly shorter than the same chromosome fro m marine populations, and is possibly meta-centric. The results of this stu dy suggest that the proposed conspecificity of marine and freshwater popula tions of Bangia is questionable.