Allozyme and Other Aspects of Variation in the Genus Bulbinella in New Zealand

Abstract

This thesis examines some aspects of morphological, cytogenetic and allozyme variation in the six species of the genus Bulbinella in New Zealand. Because evidence was found suggesting that fragmentation and reduction of the habitat of some species of the study genus had occurred, aspects of the conservation status of Bulbinella were also investigated. Some of the morphological characters described and used by Moore (1964) to separate the species were employed in this study as well as other characters recorded by the author in actively glowing plants. Generally, the seven taxa could be successfully distinguished using selected morphological characters, although in some species or populations a range of morphological forms was observed. Increased human land use (mainly mining, farming and associated activities) has reduced some populations of Bulbinella to low numbers by destroying large areas of habitat. In some cases once vast areas of Bulbinella have been reduced to fragments or probably exterminated. The karyotypes of five of the seven taxa were determined and these were all consistent with published data. G-banding was achieved in only one slide from one plant. A total of four bands (restricted to two pairs of chromosomes) was observed in the entire chromosome complement of 14. Each band was located on a separate chromosome. Inflorescence material from 61 natural populations of Bulbinella in New Zealand was examined for enzyme activity using starch gel electrophoresis. Activity was detected for eight of a total of 43 enzyme stains. Three monomorphic and 11 polymorphic loci were resolved. While no completely fixed differences between all the taxa could be demonstrated, four almost fixed differences were found. In some instances where populations belonging to different species were not geographically separated by great distances (<50km) shared alleles between species were demonstrated, indicating that introgression had occurred and may still be taking place. Overall, the genetic distance (Nei 1978) within taxa was less than that between taxa. The dendrogram resulting from cluster analysis of Nei's unbiased genetic distances divided the genus into four groups, three of which corresponded to three currently recognised taxa. The other group contained the remaining four taxa. Although the component taxa of this cluster could be readily separated using morphological characters, they could not be distinguished using allozyme data. The endemic distribution of B. rossii (Campbell Island and Auckland Island Group) and fixed morphological differences justify its remaining a separate taxon. The formal raising of B. gibbsii var. gibbsii to a separate specific status is subject to the analysis of further samples of this taxon. B. angustifolia, B, talbotii, and B. gibbsii vat. balanifera also remain separate taxa, with B. gibbsii var. balanifera being raised to a separate specific status. B. modesta, which is genetically closely related to B. hookeri, becomes a sub-species of this taxon.