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trnK Intron (trnk + intron)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Patterns of recurrent evolution and geographic parthenogenesis within apomictic polyploid Easter daises (Townsendia hookeri)

MOLECULAR ECOLOGY, Issue 11 2006
STACEY LEE THOMPSON
Abstract Geographic patterns of parthenogenesis and the number of transitions from sexual diploidy to asexual (apomictic) autopolyploidy were examined for 40 populations of the Easter daisy, Townsendia hookeri. Analyses of pollen diameter and stainability characterized 15 sexual diploid and 25 apomictic polyploid populations from throughout the plant's western North American range. Sexual diploids were restricted to two Wisconsin refugia: Colorado/Wyoming, south of the ice sheets, and northern Yukon/Beringia. Chloroplast DNA sequencing uncovered 17 polymorphisms within the ndhF gene and trnK intron, yielding 10 haplotypes. Phylogenetic analyses indicated that five exclusively polyploid haplotypes were derived from four haplotypes that are shared among ploidies, conservatively inferring a minimum of four origins of apomictic polyploidy. Three of these apomictic polyploid origins were derived from southern sexual diploids, while the fourth origin was derived from northern sexual diploids. Analyses of regional diversity were suggestive of a formerly broad distribution for sexual diploids that has become subsequently fragmented, possibly due to the last round of glaciation. As sexual diploids were exclusively found north and south of the glacial maximum, while formerly glaciated areas were exclusively inhabited by asexual polyploids derived from both northern and southern sexual lineages, it is more likely that patterns of glaciation, as opposed to a particular latitudinal trend, played a causal role in the establishment of the observed pattern of geographic parthenogenesis in Easter daisies. [source]

Introduction of a Nuclear Marker for Phylogenetic Analysis of Nepenthaceae

PLANT BIOLOGY, Issue 6 2006
H. Meimberg
Abstract: Nepenthaceae, the pitcher plants of the Old World tropics show a remarkable diversity in SE Asia, especially on the islands of Borneo and Sumatra. This region is considered as a secondary center of diversity. Sequence analysis of the cpDNA trnK intron supports this hypothesis showing the species of the Malay Archipelago as neighbour group to the isolated species from Sri Lanka, the Seychelles, and Madagascar. Based on phylogenetic reconstructions an origin of recent Nepenthaceae in the Indian subcontinent is assumed. A recent investigation focused on a non-plastid, translocated copy of the trnK intron has revealed an incongruence to tree topology based on the cpDNA trnK intron. Although the translocated copy emerged as insufficient for phylogenetic reconstruction of Nepenthaceae some taxa showed, contrary to the cpDNA dataset, relatively high distances to the rest of the taxa. These results indicated that the phylogeny of the trnK intron could not reflect true phylogenetic relationships. We investigated the peptide transferase 1 (PTR1), to develop a phylogenetic marker that is based on a nuclear low copy gene in Nepenthes. All sequences obtained were probably functional, indicated by the ratio of point mutations of the single codon positions in exon and intron regions. Comparative analysis showed that this locus is of similar variability as the cpDNA trnK intron and, contrary to the translocated copy of trnK, potential useful for phylogenetic reconstruction. While in parts congruent to the plastid trnK intron phylogeny, a higher divergence of some sequences in PRT1 and in the previously reported, non cpDNA dataset indicates that remnants of an older species stock persisted east of Wallace's line and on the Sunda Shelf. This suggests that plastid haplotypes existing today in the main distribution center of the Nepenthaceae could be descendants of more recently dispersed lineages that had been transmitted to an old species stock. [source]

Phylogenetic relationships of Clematis (Ranunculaceae) based on chloroplast and nuclear DNA sequences

BOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2006
OSAMU MIIKEDA
Phylogenetic relationships within Clematis, including Naravelia, Archiclematis and Clematopsis, were analysed using nucleotide sequences of chloroplast DNA [(1) matK and trnK introns; (2) atpB,rbcL spacer; (3) rpoB,trnC spacer; (4) psbA,trnH,trnQ spacer; (5) rbcL,accD spacer] and the nuclear ITS regions. The phylogenetic trees resulting from these analyses suggested nine major clades. The genera Archiclematis, Naravelia and Clematopsis were found to be nested within the genus Clematis, and should be included within it. Within the genus Clematis, the traditional subgenus Viorna was found to be monophyletic. The remaining subgenera (Flammula, Clematis and Campanella) and sections Flammula, Clematis and Cheiropsis, however, were found to be paraphyletic or polyphyletic. Recircumscription of several groups in Clematis was suggested. Enormous morphological diversification and very few nucleotide substitutions within Clematis indicate the recent radiation of the genus. Clematidinae shares a gene order with Anemoninae between the starting point of large single copy region and trnQ of chloroplast DNA, although Hepatica, a genus in Anemoninae, shows a different order in the region near trnH. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 152, 153,168. [source]