A taxonomic revision of the New Zealand species ofAsplenium

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Abstract
A taxonomic revision of the fern genus Asplenium in the New Zealand region has been carried out. Fourteen species and four subspecies are recognised. One species, A. terrestre, and three subspecies, A. obtusatum subsp. northlandicum, A. flaccidum subsp. hauraklense, and A. terrestre subsp. maritimum, are described for the first time. Typification, synonymy. range of morphological variation, chromosome number, habitat. and distribution are described for each taxon. A dichotomous key to the species is presented. The origin and development of the New Zealand Asplenium flora is briefly discussed. It has its closest affinities with that of temperate Australia from where most of the species have probably been derived. However, some species such as A. trichomanes, A. polyodon, and A. obtusatum have affinities with Northern Hemisphere, tropical, or South American floras and have therefore ultimately reached New Zealand from much further afield. The genus displays a higher mean level of ploidy (5.9) in this country than in any other area for which records exist; of the 18 sexually reproducing cytotypes, 9 are tetraploid. 1 is hexaplold, and 8 are octoploid. Most of the tetraploid species have distributions extending outside New Zealand and they are therefore considered ancestral. The higher polypoids are almost all endemic and are thought to have originated within New Zealand from the tetraploid taxa.

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