Morpholigical and genetic diversity of the fern genus Polystichum Roth (Dryopteridaceae) in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Biology at Massey University, Palmerston North, New Zealand
Two morphologically variable taxa in the fern genus Polystichum Roth (Dryopteridaceae) from New Zealand were investigated using a combination of morphological, cytological, and molecular (AFLP DNA-fingerprinting) analyses to test the null hypothesis that each constituted only a single evolutionary lineage. In this study, lineages for which there was prospective evidence (looking to the future; eg. inference of Specific Mate Recognition System, or SMRS, differentiation) of assortative fertilisation were recognised as distinct species. Lineages for which there was only retrospective evidence (looking to the past; eg. character state variation) of assortative fertilisation were recognised at the subspecific level. Polystichum richardii (Hook.) J. Smith was shown to be an allopolyploid complex of four evolutionary lineages, with two tetraploid and two allo-octoploid lineages. The new combination P. wawranum (Szyszyl. in Wawra) comb. nov. is proposed for one of the tetraploids, with the name P. oculatum (Hook.) J.B. Armstr. reinstated for the other. The two octoploids. which are allopatric, are recognised as separate subspecies under the reinstated name P. neozelandicum Fée, of which the name P. richardii is a later synonym. The new combination P. neozelandicum subsp. zerophyllum (Colenso) comb. et slat. nov. is proposed for the southern octoploid lineage. The same methodology confirmed that P. silvaticum (Colenso) Diels and P. vestitum (G. Forst.) C. Presl should be recognised as separate species, but did not indicate that morphologically 'divergent' plants from the Chatham Islands comprise a separate lineage from the remainder of P. vestitum. Consequently, P. vestitum is retained as a single, albeit morphologically variable species. Also investigated was the genetic relationship of the New Zealand species of Polystichum to their geographically closest congeners from Australia and Lord Howe Island using AFLP DNA-fingerprinting and DNA sequences from the chloroplast. These data are consistent with the hypothesis that the ecologically diverse New Zealand species of Polystichum were derived from a single trans-Tasman disjunction event (between New Zealand, and Australia/Lord Howe Island), with long-distance dispersal implicated rather than vicariance.
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Perrie, L. R., Lockhart, P. J., Brownsey, P. J., & Large, M. F. (2000). Morphological and molecular concordance for the recognition of two species in the new zealand polystichum richardii (hook.) J. smith complex. Plant Systematics and Evolution, 224(1-2), 97-107
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