Genotypic variation of seedlings of wild populations of Cordyline australis (Lomandraceae)

W Harris; RE Beever


Observations were made on seedlings grown under uniform conditions of 28 wild populations of Cordyline australis (cabbage tree, ti kouka) from a wide latitudinal range in New Zealand and single populations each of C. banksii and C. indivisa. There were highly significant differences in leaf size and shape and in seedling colour between the populations of C. australis. Seedling leaves ofresembled in shape those of the four C. australis populations north of Auckland and one in north-west Nelson, suggestive of possible introgression. C. indivisa seedlings differed markedly in leaf size and shape from the other species. The main trend in the genotypic variation of C. australis was clinal along a north-to-south latitudinal gradient with seedling leaves becoming longer, narrower, and having a higher frequency of red-brown coloration the further south the origin of the population. There were populations that deviated significantly from this latitudinal trend, and their locations suggest geographical foci of variation of C. australis independent of latitude, the distinction of which may have been blurred by disturbances associated with human activity. The adaptive function of the characters measured and how they may function in maintaining the patterns of genotypic variation of C. australis are discussed.

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