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Evolution of the south-western Pacific genus Melicytus (Violaceae): evidence from DNA sequence data, cytology and sex expression

Evolution of the south-western Pacific genus Melicytus (Violaceae): evidence from DNA sequence... Phylogenetic analyses of nuclear DNA external transcribed spacer (ETS) and chloroplast DNA trn L– trn F markers were undertaken to reconstruct the evolutionary history of the South Pacific genus Melicytus . Bayesian analyses of the ETS sequence data produced a phylogenetic tree with several well supported groups, including clades comprising: (1) species from Australia, Tasmania and Lord Howe Island; (2) the Norfolk Island M. latifolius and New Zealand off-shore island M. novae - zelandiae subsp. novae - zelandiae ; (3) the large-leaved M. ramiflorus complex; (4) M. fasciger and M. micranthus ; and (5) M. obovatus and allies from the Cook Strait region. Phylogenetic analysis of trn L– trn F sequence data also retrieved some of these groups although, in general, was not as well resolved. The relationships of M. lanceolatus are equivocal, as in the ETS phylogeny it is sister to a clade comprising the large-leaved tree species M. fasciger and M. ramiflorus complex and the small-leaved M. micranthus , whereas in the trn L– trn F phylogeny it is sister to a clade of small-leaved shrub species such as M. alpinus and M. crassifolius . Several biogeographic patterns are evident, with dispersal to the west from New Zealand, to Australia, involving small-leaved shrub species. Dispersal to the north from New Zealand, to Norfolk Island and Fiji, involves large-leaved tree species. The sex expression is documented for all named species and undescribed entities, with these being either hermaphroditic or dioecious. When sex expression is mapped onto the phylogeny, the hermaphroditic system is inferred to have evolved from the dioecious system. New chromosome counts are presented for M. angustifolius (2 n = 64) and M. dentatus (2 n = 32), and earlier counts of 2 n = 64 are confirmed for M. crassifolius and M. alpinus . An additional 17 counts are provided for two natural hybrids and several undescribed entities from Australia and New Zealand. The polyploid chromosome number of 2 n = 64 occurs most frequently in small-leaved divariate plants with hermaphroditic flowers. When chromosome numbers are plotted onto the phylogeny it is inferred that high polyploids (e.g. 2 n = 64) and small-leaved shrubs have evolved from large-leaved trees with functional diploid (e.g. 2 n = 32) chromosome numbers. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Australian Systematic Botany CSIRO Publishing

Evolution of the south-western Pacific genus Melicytus (Violaceae): evidence from DNA sequence data, cytology and sex expression

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Publisher
CSIRO Publishing
Copyright
CSIRO
ISSN
1030-1887
eISSN
1446-4701
DOI
10.1071/SB08042
Publisher site
See Article on Publisher Site

Abstract

Phylogenetic analyses of nuclear DNA external transcribed spacer (ETS) and chloroplast DNA trn L– trn F markers were undertaken to reconstruct the evolutionary history of the South Pacific genus Melicytus . Bayesian analyses of the ETS sequence data produced a phylogenetic tree with several well supported groups, including clades comprising: (1) species from Australia, Tasmania and Lord Howe Island; (2) the Norfolk Island M. latifolius and New Zealand off-shore island M. novae - zelandiae subsp. novae - zelandiae ; (3) the large-leaved M. ramiflorus complex; (4) M. fasciger and M. micranthus ; and (5) M. obovatus and allies from the Cook Strait region. Phylogenetic analysis of trn L– trn F sequence data also retrieved some of these groups although, in general, was not as well resolved. The relationships of M. lanceolatus are equivocal, as in the ETS phylogeny it is sister to a clade comprising the large-leaved tree species M. fasciger and M. ramiflorus complex and the small-leaved M. micranthus , whereas in the trn L– trn F phylogeny it is sister to a clade of small-leaved shrub species such as M. alpinus and M. crassifolius . Several biogeographic patterns are evident, with dispersal to the west from New Zealand, to Australia, involving small-leaved shrub species. Dispersal to the north from New Zealand, to Norfolk Island and Fiji, involves large-leaved tree species. The sex expression is documented for all named species and undescribed entities, with these being either hermaphroditic or dioecious. When sex expression is mapped onto the phylogeny, the hermaphroditic system is inferred to have evolved from the dioecious system. New chromosome counts are presented for M. angustifolius (2 n = 64) and M. dentatus (2 n = 32), and earlier counts of 2 n = 64 are confirmed for M. crassifolius and M. alpinus . An additional 17 counts are provided for two natural hybrids and several undescribed entities from Australia and New Zealand. The polyploid chromosome number of 2 n = 64 occurs most frequently in small-leaved divariate plants with hermaphroditic flowers. When chromosome numbers are plotted onto the phylogeny it is inferred that high polyploids (e.g. 2 n = 64) and small-leaved shrubs have evolved from large-leaved trees with functional diploid (e.g. 2 n = 32) chromosome numbers.

Journal

Australian Systematic BotanyCSIRO Publishing

Published: Jun 10, 2009

References