The cytology of Brachycome lineariloba. 9. Chromosomal heterogeneity in natural populations of cytodeme C (2n = 16)

Ten natural populations of B. lineariloba cytodeme C (2n = 16) were analysed cytologically. The plant is annual, ephemeral, and self-compatible. Two subdemes, C1 and C2, which are geographically separate, include about 40 kinds of karyological variants. These are of three principal kinds; namely, translocation products, hybrids, and monosomic or polysomic products of such hybrids. Cytodeme C is found to overlap extensively with cytodeme B (2n = 12) and with B. dichromosomatica (2n = 4). A considerable number of hybrids or hybrid derivatives were found between cytodemes B and C. They are fertile and able to produce viable progenies. In contrast, cytodeme C is well isolated from B. dichromosomatica reproductively, although the two are sympatric in many localities. Interchanges are maintained almost entirely in the homozygous condition in variants with a relatively high frequency of occurrence.Key words: Brachycome, karyotype, polymorphism, annual, inbreeding.