Report of chromosome number and karyotype asymmetry inSchizopetalonSims. and related genera from the South American tribe Schizopetalae (Brassicaceae)

Abstract

Schizopetalae is one of the representative South American tribes of Brassicaceae, which has remained poorly studied for cytological data. With a single report existing, no additional cytological information is known for the rest of the species and genera of this tribe (Atacama, Mathewsia and Schizopetalon). The present study reports the chromosome number and karyotype asymmetry for five species of Schizopetalon, two for Mathewsia and the only species of the monotypic genus Atacama. While a constant 2n = 18 is confirmed in all analysed samples, larger interchromosomal asymmetry levels were found in Schizopetalon than Atacama and Mathewsia. Both results suggest different processes of fixation and recombination in chromosome architecture among genera, probably associated to life history strategies maintaining genetic diversity under extreme and unpredicted environmental conditions. The present study represents the first report of chromosome number in any South American Brassicaceae in the last 30 years, revealing the need of more cytological studies to contextualize the diversification of Schizopetalae and other closely related tribes.