Cytoevolutionary Studies in the Genus Bulbine Wolf (Liliaceae) .II. The Australian Annual Taxa (Bulbine semibarbata s.1.)

Abstract

A cytological survey, using root tip mitotic cells and supplemented by some crosses and pollen fertility studies, was carried out on plants of 55 populations of the Australian annual Bulbine sernibarbata s.1. (Liliaceae). There are 4x, 8x and 12.x populations.The 4x forms are almost completely confined to eastern Australia and comprise populations of two kinds: (1) 28-chromosome types, corresponding in morphology to B. alata Baijnath, which to date has had limited taxonomic acceptance; (2) 26-chromosome types with the morphology of B. sernibarbata s. str. The alata form occurs in arid, the sernibarbata in more mesic, areas. The eastern 8x populations are mainly 2n = 54 and are intermediate between the other two taxa in both range and morphology. This suggests an allopolyploid origin based on hybridisation between the alata and sernibarbata types. The western 8x populations are nearly all 2n = 52, with much interpopulation variation in karyotype and a mesic distribution similar to that of the eastern 26-chromosome types. The karyotypic diversity parallels the species richness of other genera in southwestern Australia and indicates that the complex may be older than the corresponding polyploid complex within the perennial B. bulbosa s.1. The 12x (2n =78) populations are confined to arid and transitional rainfall areas of Western Australia. The identification of a distinctive 28-chromosome karyotype for the alata group gives support to the recognition of B. alata Baijnath, and, by providing a logical euploid bridge between the chromosome numbers of the African (2n = 14) and Australian species, strengthens the arguments for treating the two groups as congeneric.