The Asplenium aethiopicum complex in South Africa

Members of the complex in South Africa form an extensive polyploid series with three sexual and two apomictic cytotypes. The sexual tetraploid (n = 72), octoploid (n = 144) and dodecaploid (n = 216) are described as Asplenium aethiopicum subsp. tripinnatum, A. aethiopicum subsp. aethiopicum and A. aethiopicum subsp. dodecaploideum respectively, and the apomictic octoploids (2n = 288) and decaploid (2n = 360) as A. aethiopicum subsp. filare, which is subdivided into apomicts pseudqfilare (8X), transvaalense (8 X) and capense (10 X). Comparison of their ecology and distribution suggests there is an increased tolerance to drier and cooler conditions with increase in level of polyploidy among the sexual subspecies and that the apomicts are tolerant of even more extreme conditions. The natural hexaploid hybrid between A. aethiopicum subsp. aethiopicum and A. aethiopicum subsp. tripinnatum is described and its meiotic pairing analysed. The numerical structure of the polyploid series in Africa generally suggests the complex represents a secondary polyploid cycle based on a genome of 72 chromosomes, and the unequivocal antosyndesis between the genomes of A. aethiopicum subsp. aethiopicum shown by the chromosome pairing in the hexaploid hybrids suggests the octoploid is either a segmental allopolyploid or autopolyploid. While it can be concluded from the morphology and cytology of A aethiopicum subsp. filare that the apomicts have arisen more than once, their precise mode of origin is unknown, although there is good evidence in at least one case for suggesting a hybrid origin.