Karyotype morphology and cytogeography in Brunnera and Cynoglottis (Boraginaceae)

A comparative study of karyotype morphology and heterochromatin patterns in Brunnera and Cynoglottis (Boraginaceae) was carried out with traditional m ethods and Giemsa C-banding. Two polymorphic species of Cynoglottis, each w ith two subspecies, and two of Brunnera were investigated using native popu lation samples from the central-eastern Mediterranean and Middle East. Poll en size of these samples was measured to investigate relationships with plo idy level. C. barrelieri subsp. barrelieri and subsp. serpentinicola are ch aracterized by 2n = 18 and smaller pollen grains in contrast to C. chetikia na subsp. chetikiana and subsp. paphlagonica, which are fundamentally tetra ploid with 2n = 36. The occurrence of cytotypes with 2n = 12 and 2n = 24 in both subspecies of C. chetikiana, however, would suggest x = 6 as the orig inal haploid number and x = 9 as a derived one. Furthermore, the finding of a hypoploid cytotype with 2n = 16 in C. barrelieri ssp. barrelieri was con sistent with previous reports and suggested relationships with Anchusa. Kar yoevolutionary processes possibly associated with such a wide chromosome va riation in Cynoglottis are discussed. Brunnera macrophylla and B. orientali s share a complement of 2n = 12 and an apparently identical karyotype, whic h differs from Cynoglottis in terms of asymmetry, chromosome size and morph ology. A basic C-banding style was present in Brunnera and Cynoglottis, but heterochromatin content increased from the former to the latter. The paral lel 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. (C) 2001 The Linnean Society of London.