KARYOLOGICAL VARIATION IN THE GROUP OF MYOSOTIS-ALPESTRIS (BORAGINACEAE)

A total of 6 population samples of Myosotis stenophylla KNAF, a rare s pecies showing great ecological disjunction in its distribution, were examined to clarify the present status of its karyological variation. In order to elucidate relationships between lowland tetraploid populat ions of M. stenophylla and diploid and tetraploid montane populations of M. alpestris F.W. SCHMIDT, four population samples of M. alpestris were also examined. The karyotypes of all populations of M. alpestris s.l. studied were highly asymmetrical and heterogeneous, being compose d of metacentric, submetacentric, subtelocentric and satellited acroce ntric chromosomes. The karyotype formula for haploid chromosome set wa s established: n = x = 12 = 6m + 2sm + 3st + It(SAT) Multivariate anal ysis based on chromosome length and shape showed significant differenc es between diploid and tetraploid forms of M. alpestris s.l. Four nume rical parameters, used to characterize the karyotype of M. stenophylla , revealed significant differences between populations on serpentine a nd on non-serpentine substrates. In addition, the noticeable affinity of the karyotype of non-serpentine populations to that of M. alpestris tetraploids has been shown by means of discriminant analysis. These d ata suggest that the unique features of serpentine play an important r ole in the origin of karyotypic differentiation within populations of M. stenophylla.