Molecular systematics of the Lomandra Labill. Complex (Asparagales: Laxmanniaceae).
Date
2010
Authors
Donnon, Matthew J.
Editors
Advisors
Conran, John Godfrey
Hill, Bob
Hill, Bob
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Thesis
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Abstract
The “Lomandra complex” (or Lomandra grouping) is an informally
recognised grade resulting from the subdivision of the Laxmanniaceae into two
groups (Conran, 1998); the ‘Lomandra complex” (Acanthocarpus, Chamaexeros,
Lomandra, Romnalda and Xerolirion), and the remainder as the Arthropodoids
(Arthropodium, Chamaescilla, Cordyline, Eustrephus, Laxmannia, Murchisonia,
Sowerbaea, Thysanotus and Trichopetalum). Laxmanniaceae are an Australiacentred,
tropical to temperate family of 14 genera with around 180 species from
Australasia, SE Asia, the Mascarenes, New Caledonia, New Guinea, New Zealand,
North and South America and the Pacific Islands. There have been no detailed
phylogenetic studies in Laxmanniaceae and the relationships within and between the
genera is poorly understood.
This study utilised molecular data from chloroplast trnL-F and nuclear
ribosomal ITS2 regions analysed with maximum parsimony and bayesian inference
methods to reconstruct the phylogeny of the genera of the ‘Lomandra complex’,
using species of Arthropodium, Eustrephus, Laxmannia and Thysanotus as
outgroups. The molecular phylogeny shows that Lomandra forms four primary
clades; with members from the classical anatomy, inflorescence-defined section and
series distributed amongst these, typically in large islands. The monotypic genus
Xerolirion resides deeply within Lomandra, raising questions about the
appropriateness of this genus. Additionally, the other genera of the Lomandra
complex (Acanthocarpus, Chamaexeros and Romnalda) form a clade positioned
sister to one of four primary Lomandra clades, but nested inside Lomandra sens. lat., indicating a closer relationship between these genera than previously thought. The
affiliation of these bisexual, hermaphroditic genera within the otherwise unisexual,
dioecious Lomandra clade supports the recognition of the ‘Lomandra complex’ as an
expanded genus, Lomandra; and represents either an example of the evolution of
unisexuality followed by reversion, or else multiple losses of hermaphrodite flowers.
Morphological and anatomical data were obtained for leaf and floral
macroscopic characters, mid-leaf section anatomy and cuticle microscopic features
and analysed with maximum parsimony and bayesian inference methods to
reconstruct the anatomical phylogeny. These data were also utilised to generate a
DELTA key for identifying species of Lomandra from a combination of macroscopic
morphological and microscopic leaf anatomical features.
School/Discipline
School of Earth and Environmental Sciences
Dissertation Note
Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Sciences, 2010
Provenance
Copyright material removed from digital thesis. See print copy in University of Adelaide Library for full text.