Classification and phylogeny of the plant genus Dianella Lam. ex Juss.
AuthorMuscat, Mary Karen
AffiliationSchool of Botany
Document TypePhD thesis
Access StatusThis item is embargoed and will be available on 2019-07-26. This item is currently available to University of Melbourne staff and students only, login required.
© 2017 Dr Mary Karen Muscat
The global distribution of Dianella Lam. ex Juss. (flax lilies, Asphodelaceae, Asparagales) extends from south-eastern Africa, Madagascar and India, to south-east Asia (north to Japan), Australia, Pacific Islands from Micronesia to Tahiti, Pitcairn Islands, New Zealand, New Caledonia, Norfolk Island and Hawaii. It occurs throughout Australia (excluding the central arid region), where there is the greatest diversity of 42 taxa (19 species and 23 varieties) (Australian Plant Census 2016). Of those, three taxa also extend to south-east Asia, and a further 17 species occur outside Australia (Australian Plant Census 2016; Kew World Checklist of Selected Families, compiled by Govaerts et al. 2016). Plants are characterised by two leaf forms: basal strap-like leaves and cauline leaves on aerial stems (+/- extravaginal branching units). The showy flowers have a characteristic struma between the anther and filament, while the fruit is a fleshy berry, typically in shades of purple. The name Dianella is attributed to the Greek goddess Diana, the mythical goddess of the hunt. A cpDNA phylogeny by Wurdack & Dorr (2009) found Dianella to be monophyletic and sister to the monotypic genus Eccremis from South America. However, there has been no comprehensive phylogenetic analysis of taxa within Dianella, which has the potential to reveal not only taxonomic relationships but biogeographic patterns and the evolutionary history of the group, including the role of polyploidy. Furthermore, species delimitations, including complexes of varieties, have been based only on morphology from field observation and herbarium samples and require further study. Using three chloroplast markers (trnQUUG–5'rps16, 3'rps16–5'trnK(UUU) and rpl14– rps8–infA–rpl36) and two nuclear markers, (ITS 4, ITS 5, 18SE-ETS and DIAN-ETS) molecular phylogenetic analyses using Bayesian and Maximum Parsimony are presented (Chapters 2, 3, 4 and 5). Accessions include the majority of Australian and extra-Australian Dianella. The related outgroup genera Eccremis, Stypandra, Thelionema and Herpolirion were also included. The cpDNA and nrDNA phylograms were relatively congruent and a combined data set produced the most resolution. The combined results (Chapter 5) differed from those of Wurdack & Dorr (2009) in showing Stypandra with a sister relationship to Herpolirion + Thelionema. Within Dianella, resolved clades largely related to biogeographic regions, such as the Hawaiian Islands and New Caledonia, Norfolk Island related to New Zealand and Australian bioregions, revealing for example an early divergence between eastern and Western Australian lineages, congruent with the pattern for other Australian biota. Of the four Australian species complexes described by Rodney Henderson in The Flora of Australia, volume 45, the D. caerulea complex was found to be monophyletic except for two varieties that clustered with other far-north Queensland taxa, and two D. caerulea var. caerulea samples that are morphologically distinct when compared to taxa in the complex. Of the other species complexes, D. revoluta, D. pavopennacea and D. longifolia are each polyphyletic. Their relationships indicate biogeographic patterns, such as for D. longifolia accessions, which were resolved in two separate clades, one clade from the Kimberley and Northern Territory, and one clade from eastern and southern Australia. For extra-Australian Dianella, the widespread D. ensifolia was also polyphyletic occurring in multiple clades with distinct taxonomic units able to be recognised. Chromosome counts available from the literature were plotted on the phylogeny for Dianella and indicated that polyploidy has arisen multiple times, particularly in taxa of some of the Australian species complexes and in D. ensifolia sensu lato. These results indicate the need to recognise new species and to resurrect other taxa for Australian and extra-Australian Dianella. Chapter six is a morphometric, multivariate analysis (using phenetic clustering and ordination methods) of Hawaiian Dianella to determine the number of species on the islands. Field collections were made on Oahu, Maui, Hawaii and Kauai to examine populations in situ, develop species concepts and collect plant material for the dataset. The results indicate that five operational taxonomic units should be recognised including the current taxon D. sandwicensis. Fruit morphology is unique, with distinctive fruit dye colour and fruit surface colour in some taxa. D. lavarum, a narrow endemic that inhabits recent dry lava flows, observed in the Hawaii Volcanoes National Park, is to be resurrected. A review of herbarium specimens confirmed its distributional range extends to Maui, which is in agreement with Otto Degener who originally described the species. The D. caerulea complex was also analysed further in Chapter 7, based on extensive fieldwork in Queensland, New South Wales, Victoria and Western Australia, using multivariate analysis of a morphological data set. Morphometric clusters were largely in agreement with Henderson's varieties, but it is recommended that some be raised to species level. D. caerulea var. assera and D. caerulea var. producta, which appear to be sister taxa based on the shared character extravaginal branching, were each found to include morphological variation. It is recommended that these taxa be recognised as species with three subgroups recognised in D. caerulea var. assera, and five subgroups in D. caerulea var. producta; however, further field sampling is required for taxonomic revision.
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