Studies in the genus Livistona (Coryphoideae: Arecaceae)

Dowe, John Leslie (2001) Studies in the genus Livistona (Coryphoideae: Arecaceae). PhD thesis, James Cook University.

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Abstract

This thesis provides new insights into the genus Livistona based on taxonomy, cladistic analyses, molecular investigation, historical biogeography, and gender function. The taxonomic treatment recognises 35 currently accepted taxa. Four new species, Livistona chocolatina, L. concinna, L. surru and L. tothur, are described as part of this treatment. They will be formally published elsewhere. Literature research revealed that 92 names have used Livistona as part of the binomial. Of these, 68 are typified by extant herbarium specimens. Five names are typified by illustrations. Of the remaining 19 names, types were never designated. It is proposed that eleven names require typification, including Livistona saribus, Chamaerops biroo, Corypha decora, Corypha minor, Livistona altissima, Livistona hoogendorpii, Livistona jenkinsiana, Livistona spectabilis, Livistona tonkinensis, Saribus olivaeformis and Saribus subglobosus. New names are proposed for L. decipiens, which becomes L. decora, and L. mariae var. occidentalis, which becomes L. nasmophila. Phylogenetic relationships were examined using cladistic analyses based on morphological characters. Forty-three characters and 35 taxa were investigated with two character weighting options: unweighted and successive weighting. In the most robust analysis, the following major lineages were evident:

• exigua lineage — small understorey palms with irregularly segmented leaves, inflorescence not basally branched • saribus lineage — large canopy palms with irregularly segmented leaves, inflorescence not basally branched • chinensis subclade — inflorescence not basally branched, fruit green, blue or purple, regularly segmented leaves • rotundifolia subclade — inflorescence basally branched, fruit passing through orange/red to mature either orange, red or black, regularly segmented leaves • humilis subclade - inflorescence not basally branched, fruit dark brown or black, regularly segmented leaves with deeply segmented lamina • mariae subclade - inflorescence not basally branched, fruit dark brown or black, regularly segmented leaves with moderately segmented lamina

Although topological resolution was satisfactory, statistical support was low for the analyses and the result cannot be accepted as a reliable estimate of phylogeny. The internal transcribed spacer (ITS) regions of nrDNA and the intervening 5.8S region of a group of Livistona species were investigated to determine if a useful phylogeny could be inferred from that region. DNA was amplified via polymerase chain reaction (PCR) using three primers. Multiple (polymorphic) bands were produced consistently for most species and some sequences had lost the entire ITS2 portion. The results indicate that a Livistona-specific primer will need to be designed and that more refined screening of products will be necessary if full length and non-polymorphic sequences are to be obtained. Hypotheses of historical biogeography were developed utilising three lines of investigation. Firstly, the fossil record suggests a Laurasian origin for the genus. Secondly, an analysis of area endemism, based on the Parsimony Analysis of Endemism (PAE) method, indicates a close relationship of some contiguous areas in which Livistona species occur. Thirdly, a cladistic analysis suggests a number of possible scenarios, including an exclusively Laurasian origin, or combinations of both Laurasian and Gondwanan origin. The distribution of species in otherwise floristically unrelated regions suggests that the genus is 'ancient', and that initial radiation may have occurred prior to tectonic events that isolated the landmasses on which ancestral species occurred. Extensive speciation has since occurred in Australia and Malesia, with putatively relictual species occurring in Africa and Australia. The occurrence of Livistona in Australia is most plausibly the result of migration from a Laurasian source, rather than being an autochthonous element. Morphological aspects of a group of representative species were investigated to determine if there were any trends in gender function from hermaphroditism to functional dioecy. Based on predictive morphological criteria, a trend from hermaphroditism to dioecy was indicated in the four species that were studied, and Livistona chinensis, L. muelleri, L. decora and L. lanuginosa can be ranked in increasing degrees of dioeciousness respectively. Functional dioecy in Livistona may be related to the evolution of species in drier, stressful environments.

Item ID: 24103
Item Type: Thesis (PhD)
Keywords: cladistics analysis; classification; Livistona; palynotaxonomy
Date Deposited: 13 Dec 2012 00:12
FoR Codes: 06 BIOLOGICAL SCIENCES > 0603 Evolutionary Biology > 060310 Plant Systematics and Taxonomy @ 100%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960805 Flora, Fauna and Biodiversity at Regional or Larger Scales @ 100%
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