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Phylogenetic origins of the Himalayan endemic Dolomiaea, Diplazoptilon and Xanthopappus (Asteraceae: Cardueae) based on three DNA regions.

ABSTRACT: BACKGROUND AND AIMS:It is an enduring question as to the mechanisms leading to the high diversity and the processes producing endemics with unusual morphologies in the Himalayan alpine region. In the present study, the phylogenetic relationships and origins of three such endemic genera were analysed, Dolomiaea, Diplazoptilon and Xanthopappus, all in the tribe Cardueae of Asteraceae. METHODS:The nuclear rDNA internal transcribed spacer (ITS) and plastid trnL-F and psbA-trnH regions of these three genera were sequenced. The same regions for other related genera in Cardueae were also sequenced or downloaded from GenBank. Phylogenetic trees were constructed from individual and combined data sets of the three types of sequences using maximum parsimony, maximum likelihood and Bayesian analyses. KEY RESULTS:The phylogenetic tree obtained allowed earlier hypotheses concerning the relationships of these three endemic genera based on gross morphology to be rejected. Frolovia and Saussurea costus were deeply nested within Dolomiaea, and the strong statistical support for the Dolomiaea-Frolovia clade suggested that circumscription of Dolomiaea should be more broadly redefined. Diplazoptilon was resolved as sister to Himalaiella, and these two together are sister to Lipschitziella. The clade comprising these three genera is sister to Jurinea, and together these four genera are sister to the Dolomiaea-Frolovia clade. Xanthopappus, previously hypothesized to be closely related to Carduus, was found to be nested within a well-supported but not fully resolved Onopordum group with Alfredia, Ancathia, Lamyropappus, Olgaea, Synurus and Syreitschikovia, rather than the Carduus group. The crude dating based on ITS sequence divergence revealed that the divergence time of Dolomiaea-Frolovia from its sister group probably occurred 13.6-12.2 million years ago (Ma), and the divergence times of the other two genera, Xanthopappus and Diplazoptilon, from their close relatives around 5.7-4.7 Ma and 2.0-1.6 Ma, respectively. CONCLUSIONS:The findings provide an improved understanding of the intergeneric relationships in Cardueae. The crude calibration of lineages indicates that the uplifts of the Qiinghai-Tibetan Plateau since the Miocene might have served as a continuous stimulus for the production of these morphologically aberrant endemic elements of the Himalayan flora.

SUBMITTER: Wang YJ

PROVIDER: S-EPMC2802998 | biostudies-literature | 2007 Feb

REPOSITORIES: biostudies-literature

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Phylogenetic origins of the Himalayan endemic Dolomiaea, Diplazoptilon and Xanthopappus (Asteraceae: Cardueae) based on three DNA regions.

Wang Yu-Jin YJ Liu Jian-Quan JQ Miehe Georg G

Annals of botany. 20070111 2

<h4>Background and aims</h4>It is an enduring question as to the mechanisms leading to the high diversity and the processes producing endemics with unusual morphologies in the Himalayan alpine region. In the present study, the phylogenetic relationships and origins of three such endemic genera were analysed, Dolomiaea, Diplazoptilon and Xanthopappus, all in the tribe Cardueae of Asteraceae.<h4>Methods</h4>The nuclear rDNA internal transcribed spacer (ITS) and plastid trnL-F and psbA-trnH regions ...[more]

PMID: 17218340

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Project description:BackgroundConsidered a biodiversity hotspot, the Canary Islands have been the key subjects of numerous evolutionary studies concerning a large variety of organisms. The genus Cheirolophus (Asteraceae) represents one of the largest plant radiations in the Canarian archipelago. In contrast, only a few species occur in the Mediterranean region, the putative ancestral area of the genus. Here, our main aim was to reconstruct the phylogenetic and biogeographic history of Cheirolophus with special focus on explaining the origin of the large Canarian radiation.ResultsWe found significant incongruence in phylogenetic relationships between nuclear and plastid markers. Each dataset provided resolution at different levels in Cheirolophus: the nuclear markers resolved the backbone of the phylogeny while the plastid data provided better resolution within the Canarian clade. The origin of Cheirolophus was dated in the Mid-Late Miocene, followed by rapid diversification into the three main Mediterranean lineages and the Macaronesian clade. A decrease in diversification rates was inferred at the end of the Miocene, with a new increase in the Late Pliocene concurrent with the onset of the Mediterranean climate. Diversification within the Macaronesian clade started in the Early-Mid Pleistocene, with unusually high speciation rates giving rise to the extant insular diversity.ConclusionsClimate-driven diversification likely explains the early evolutionary history of Cheirolophus in the Mediterranean region. It appears that the exceptionally high diversification rate in the Canarian clade was mainly driven by allopatric speciation (including intra- and interisland diversification). Several intrinsic (e.g. breeding system, polyploid origin, seed dispersal syndrome) and extrinsic (e.g. fragmented landscape, isolated habitats, climatic and geological changes) factors probably contributed to the progressive differentiation of populations resulting in numerous microendemisms. Finally, hybridization events and emerging ecological adaptation may have also reinforced the diversification process.

Dataset Information

Phylogenetic origins of the Himalayan endemic Dolomiaea, Diplazoptilon and Xanthopappus (Asteraceae: Cardueae) based on three DNA regions.

Publications

Phylogenetic origins of the Himalayan endemic Dolomiaea, Diplazoptilon and Xanthopappus (Asteraceae: Cardueae) based on three DNA regions.

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