Systematics of Libertia (Iridaceae)
2018-09-17T23:27:00Z (GMT) by
Libertia Spreng. is a genus of monocotyledonous perennial herbs of bicentric distribution, from Australasia and South America. It contains sixteen species, with seven found in South America, seven endemic to New Zealand, one endemic to Australia, and one found in New Zealand, Tasmania, Australia, and New Guinea. Two species, L. flaccidifolia Blanchon and Weaver and L. cranwelliae Blanchon, Murray, and Braggins, are listed as Nationally Critical in New Zealand and L. peregrinans Cockayne and Allan is listed as Nationally Vulnerable. No South American species has been assessed for conservation status. The genus is best defined by its uniform n=19 chromosome count cytologically and 6 paired tepals morphologically.
Polyploidy and hybridization have played a critical role in the development of Libertia as a genus. Polyploidy is extremely common in perennial herbs, particularly the tribe Sisyrinchiae. In Libertia, only two of the eleven studied species are diploid, the remaining nine ranging from tetraploid to dodecaploid. The higher levels of polyploidy are particularly common in New Zealand, with all seven endemics being either hexaploid or dodecaploid. These levels of polyploidy are suggestive of a historic retreat into mountains during New Zealand’s glacial periods, as polyploids are more productive and reproductively successful than diploids in high altitudes.
Further study should include a phylogenetic study of Libertia, necessary to establish clades and relations intragenerically. Future research in Libertia should put a focus on South American studies, in particular the identification of clades within L. chilensis (Molina) Gunckel and the confirmation of chromosome count within the Juan Fernandez Islands group of L. chilensis. Establishment of a united and publicly available species description for the South American species is necessary as well.