Chromosome evolution in Bulbine glauca (Asphodelaceae or Xanthorrhoeaceae subfam. Asphodeloideae) indicates six species, not one

摘要

The genus Bulbine Wolf has similar to 130 species in Africa and only seven species in Australia. Base chromosome numbers in African and Australian Bulbine are x = 7 and x = 12, respectively. This raises the possibility of Australian Bulbine being of polyploidy origin or, alternatively African Bulbine may have evolved through dysploid reduction. Previous chromosome counts in Bulbine glauca (Raf.) E.M. Watson were predominantly 2n = 46, with aneuploid numbers of 2n = 45, 44, 48, 47, 40 and 41 also being encountered within and between populations. Novel chromosome counts are presented here for a wide sample of populations of B. glauca, occurring on volcanic and granite outcrops along the New South Wales and Victorian tablelands and on granite outcrops in Tasmania. Chromosome numbers for Bulbine crassa D.I. Morris and Duretto is 2n = 26. The modal chromosome count for B. glauca is confirmed as 2n = 46 with no evidence of aneuploidy. The species complex shows a variable asymmetric karyotype across its distribution, indicating karyotypic evolution involving structural rearrangements. There appear to be six distinctive groups within the complex based on karyomorphology. Evolutionary changes in both B. glauca s. lat. and B. crassa appear to have not involved recent polyploidy. Variation in chromosome morphology across the B. glauca complex is consistent with our morphological evidence of more than one species.