Karyotype morphology and cytogeography in Brunnera and Cynoglottis (Boraginaceae)

Abstract

A comparative study of karyotype morphology and heterochromatin patterns in Brunnera andCynoglottis (Boraginaceae) was carried out with traditional methods and Giemsa C-banding. Two polymorphic species ofCynoglottis , each with two subspecies, and two of Brunnera were investigated using native population samples from the central-eastern Mediterranean and Middle East. Pollen size of these samples was measured to investigate relationships with ploidy level. C. barrelieri subsp. barrelieri and subsp. serpentinicola are characterized by 2n =18 and smaller pollen grains in contrast to C. chetikiana subsp. chetikiana and subsp.paphlagonica , which are fundamentally tetraploid with 2 n=36. The occurrence of cytotypes with 2n =12 and 2 n=24 in both subspecies of C. chetikiana, however, would suggestx =6 as the original haploid number and x=9 as a derived one. Furthermore, the finding of a hypoploid cytotype with 2 n=16 in C. barrelieri ssp. barrelieri was consistent with previous reports and suggested relationships with Anchusa. Karyoevolutionary processes possibly associated with such a wide chromosome variation in Cynoglottis are discussed. Brunnera macrophylla and B. orientalis share a complement of 2 n=12 and an apparently identical karyotype, which differs from Cynoglottis in terms of asymmetry, chromosome size and morphology. A basic C-banding style was present in Brunnera and Cynoglottis, but heterochromatin content increased from the former to the latter. The parallel increase in chromosome number, heterochromatin content and size of the pollen from Brunnera to Cynoglottis may reflect an evolutionary progression, and is consistent with the supposed ancient origin of Brunnera.