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| 2. |
- Bengtson, Annika, et al.
(författare)
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Evolution and diversification related to rainfall regimes : diversification patterns in the South African genus Metalasia (Asteraceae-Gnaphalieae)
- 2015
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 42:1, s. 121-131
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Tidskriftsartikel (refereegranskat)abstract
- AimThe Cape region is known for its exceptional species richness, although much remains unknown regarding the appearance of the modern Cape flora. One explanation is that floral diversification was influenced by the establishment of winter rainfall/summer arid conditions hypothesized to have occurred towards the end of the Miocene. We studied the evolution and diversification of the plant genus Metalasia (Asteraceae-Gnaphalieae), with the aim of testing whether radiation patterns may have been influenced by the climatic changes. LocationSouth Africa, with emphasis on the south-west. MethodsThe radiation of Metalasia was investigated using two approaches: a species diffusion approach, which estimated the ancestral areas by means of a relaxed random walk while sampling from extant distributions; and a discrete approach, in which distributions were defined according to the phytogeographical centres of the Cape region. Secondarily derived clock rates from an earlier Gnaphalieae study were used for calibration purposes. ResultsOur analyses date Metalasia to approximately 6.9Ma, after the Miocene-Pliocene boundary and the establishment of the winter rainfall/summer arid conditions. Metalasia consists of two sister clades: Clade A and Clade B. Clade B, which is endemic to the winter rainfall area, is estimated to have diversified c. 6.4Ma, whereas Clade A, with a main distribution in the all-year rainfall area, is considerably younger, with a crown group age estimated to 3.3Ma. Diversification rates suggest an early rapid speciation, with rates decreasing through time both for Metalasia and for clades A and B separately. Ancestral area estimations show a possible scenario for the radiation of Metalasia to its current diversity and distribution, with no conflict between results inferred from diffusion or discrete methods. Main conclusionsThe diversification of Metalasia is estimated to have begun after the establishment of the winter rainfall/summer arid conditions, consistent with its radiation having been influenced by changes in the climatic regime.
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| 3. |
- Bengtson, Annika, et al.
(författare)
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New subtribal and generic limits in the tribe Athroismeae (Asteraceae) and further disintegration of the subtribe Madagasterinae of the tribe Astereae
- 2024
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Ingår i: Willdenowia. - 0511-9618 .- 1868-6397. ; 54:1, s. 103-116
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Tidskriftsartikel (refereegranskat)abstract
- The Astereae subtribe Madagasterinae (Asteraceae) sensu Nesom encompassing four Malagasy genera (Apodocephala, Madagaster, Rochonia and Vernoniopsis) is polyphyletic, as Apodocephala is a member of the Malagasy subtribe Lowryanthina of the tribe Athroismeae. While Madagaster was shown to belong to Astereae, the phylogenetic positions of Rochonia and Vernoniopsis (now Jalantzia) in this tribe remained to be tested with molecular data. Lowryanthinae presently contains Apodocephala with nine species and the monospecific Lowryanthus. The monophyly of Apodocephala remained to be assessed using a comprehensive sampling. The aims were to: (1) assess the phylogenetic placements of Rochonia and Jalantzia (Vernoniopsis) and test the monophyly of Jalantzia; (2) assess phylogenetic relationships within Lowryanthinae; and (3) re-assess the subtribal and generic limits within the tribe Athroismeae. New phylogenetic analyses based on plastid sequence data confirmed the position of Rochonia in Astereae. Jalantzia (Vernoniopsis) was resolved as sister to the subtribe Lowryanthinae and therefore transferred to Athroismeae. A new subtribe, Jalantziinae, is described to accommodate Jalantzia. Apodocephala is paraphyletic with respect to Lowryanthus, which is formally merged with Apodocephala. A description of the emended subtribe Madagasterinae containing Madagaster and Rochonia is presented.
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| 4. |
- Bengtson, Annika, et al.
(författare)
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Phylogeny and evolution of the South African genus Metalasia (Asteraceae-Gnaphalieae) inferred from molecular and morphological data
- 2014
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Ingår i: Botanical journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4074 .- 1095-8339. ; 174:2, s. 173-198
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Tidskriftsartikel (refereegranskat)abstract
- Metalasia is a genus in tribe Gnaphalieae (Asteraceae), endemic to South Africa and with its main distribution in the Cape Floristic Region. The genus comprises 57 species and, with a number of closely related genera, it constitutes the Metalasia clade'. A species-level phylogenetic analysis is presented, based on DNA sequences from two nuclear (internal and external transcribed spacer: ITS, ETS) and two plastid (psbA-trnH, trnL-trnF) regions together with morphological data. Analyses combining molecular and morphological data attempt not only to resolve species interrelationships, but also to detect patterns in character evolution. Phylogenetic analyses corroborate our earlier study and demonstrate that Metalasia is formed of two equally sized, well-supported sister groups, one of which is characterized by papillose cypselas. The results differ greatly from earlier hypotheses based on morphology alone, as few morphological characters support the phylogenetic patterns obtained. The two clades of Metalasia do, however, appear to differ in distribution, corresponding to the different rainfall regimes of South Africa. Analyses show a few taxa to be problematic; one example is the widely distributed M.densa which appears to be an intricate species complex.
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| 5. |
- Bengtson, Annika, et al.
(författare)
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PHYLOGENY AND GENERIC DELIMITATION OF THE METALASIA CLADE (ASTERACEAE-GNAPHALIEAE)
- 2011
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Ingår i: International journal of plant sciences. - : University of Chicago Press. - 1058-5893 .- 1537-5315. ; 172:8, s. 1067-1075
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Tidskriftsartikel (refereegranskat)abstract
- The Metalasia clade, which consists of the genus Metalasia and a number of much smaller satellite genera, is a South African group in the tribe Gnaphalieae (Asteraceae). This study scrutinizes the phylogenetic relationships of the Metalasia clade by means of chloroplast (trnL-trnF, psbA-trnH) and nuclear (external transcribed spacer, internal transcribed spacer) sequence data. The Metalasia clade is confirmed to be a monophyletic group, and the phylogenetic positions of the included genera are determined. The genus Metalasia may be monophyletic if the monotypic Planea is included, but the node has very poor support and further studies are needed. The Metalasia species fall into two well-supported groups, distinguishing the members of Karis's Metalasia densa group from the others. Lachnospermum is shown to be monophyletic and is placed as a possible sister group to Metalasia. Phaenocoma is placed as sister to the branch consisting of Metalasia and Lachnospermum. Calotesta, Hydroidea, and Atrichantha form a clade, with the monotypic Dolichothrix as their sister group.
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| 6. |
- Bengtson, Annika, et al.
(författare)
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Phylogeny of Anisopappus with species circumscriptions revisited (Asteraceae: Athroismeae)
- 2021
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Ingår i: Taxon. - : Wiley. - 0040-0262 .- 1996-8175. ; 70:2, s. 351-364
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Tidskriftsartikel (refereegranskat)abstract
- Anisopappus (Asteraceae: Athroismeae) is a genus with its main distribution in Africa (one species also in Asia), currently considered to include around 21 species. A molecular phylogenetic study of Anisopappus is presented for the first time, based on plastid (ndhF, trnL-trnF, trnQ-rps16) and nuclear (ETS, ITS) data. Anisopappus is confirmed to be monophyletic, and species interrelationships are resolved. The results differ from earlier treatments based on morphology, and the phylogenetic analyses reveal a need for changes in species circumscriptions as compared to those of the most recent treatment. Consequently, many taxa currently treated as synonyms are here shown to represent separate species indicating that the genus includes well over 40 species. Distribution patterns now emerge where several clades are found to consist of species restricted to a particular geographical region. The Anisopappus of Madagascar, many of which were earlier placed in synonymy with species found on the African continent, are here shown to be endemic, and the results reveal a need for further studies of that group.
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| 7. |
- Bengtson, Annika, 1982-, et al.
(författare)
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Phylogeny of the Athroismeae (Asteraceae), with a new circumscription of the tribe
- 2017
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Ingår i: Taxon. - : Wiley. - 0040-0262 .- 1996-8175. ; 66:2, s. 408-420
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Tidskriftsartikel (refereegranskat)abstract
- Athroismeae is a small tribe of the Asteraceae-Asteroideae, the members of which show considerable variation in morphology. A molecular phylogenetic study of the tribe is presented for the first time, based on plastid (ndhF, trnH-psbA, trnL-trnF) and nuclear data (ETS, ITS). The phylogenetic relationships between the different genera within Athroismeae are discussed, and in addition, three unispecific genera: Anisochaeta, Artemisiopsis and Symphyllocarpus as well as Duhaldea (Inula) stuhlmannii, all earlier placed in other tribes, are here shown to belong within Athroismeae. Symphyllocarpus is sister to Centipeda and the earlier Symphyllocarpinae includes Centipedinae in synonymy. Furthermore, Cardosoa and Philyrophyllum are found to be integrated within Anisopappus and their generic status cannot be maintained. An outline of an amended circumscription of the Athroismeae is presented, with three new combinations and a description of the new subtribe Lowryanthinae.
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| 8. |
- Bengtson, Annika, et al.
(författare)
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Species diversification in the Mediterranean genus Chiliadenus (Inuleae-Asteraceae)
- 2018
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Ingår i: Plant Systematics and Evolution. - : Springer Science and Business Media LLC. - 0378-2697 .- 1615-6110 .- 2199-6881. ; 304:7, s. 853-860
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Tidskriftsartikel (refereegranskat)abstract
- Chiliadenus is a small genus in the Inuleae (Asteraceae), consisting of ten species with allopatric distributions along the southern edge of the Mediterranean Sea. The different species have restricted areas of distribution, with only one being more widely distributed. The first molecular phylogenetic study of the genus with complete sampling, as well as a biogeographic analysis of the origin and biogeographic patterns leading to the current diversity of Chiliadenus is presented. Results confirm Chiliadenus as monophyletic and placed as sister to Dittrichia. The ancestor of Chiliadenus is dated to have diverged from that of Dittrichia around 5.45 Ma ago, coinciding with the Messinian salinity crisis, whereas the Chiliadenus crown group is dated to 2.29 Ma, around 3 million years later. Ancestral area reconstructions show the crown group to likely have originated in the area around Morocco and northwestern Algeria, which is also the area where the early divergences have occurred. Chiliadenus has then later diverged and dispersed over the Mediterranean to its current distribution. The evolution of the Chiliadenus crown group coincides with the onset of the Mediterranean climate, and its evolution may be connected to the subsequent climatic changes.
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| 9. |
- Bengtson, Annika, 1982-
(författare)
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Systematics and biogeography of the South African Metalasia clade (Asteraceae-Gnaphalieae)
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Metalasia clade (Asteraceae–Gnaphalieae) consisting of the genera Metalasia, Atrichantha, Calotesta, Dolichothrix, Hydroidea, Lachnospermum, Phaenocoma, and Planea is endemic to South Africa with a main distribution within the Cape Floristic Region (CFR), a region known for its remarkable botanical diversity.The monophyly of the Metalasia clade, the relationships of its genera, and the circumscription of these as well as their position within the tribe Gnaphalieae is investigated using molecular data. The study confirms the Metalasia clade to be a monophyletic group, untangling the relationships between the included genera.Five new Metalasia species have been described since the latest revision of the genus, three of which are described in the present work. An updated key to all 57 species of the genus is also provided.A phylogenetic study of the genus Metalasia, including all 57 species, based on a combination of morphological and molecular data shows that Metalasia consists of two sister clades, Clade A and Clade B, morphologically separated by the papillose cypselas of Clade A. Metalasia is, however, not supported as monophyletic, and Lachnospermum is placed together with the Metalasia species of Clade B. Further, the monotypic Planea, originally described as Metalasia schlechteri, is placed well within Clade B.A biogeographical study reveals Metalasia to have evolved in the CFR around 6.9 Ma. Ancestral area estimations present a possible scenario for the radiation of Metalasia and show a difference between Clade A and B, correlated to the different rainfall regimes of southern Africa. The results show that Clade B began to diversify around 6.4 Ma in the winter rainfall area, whereas the diversification of the Clade A crown group, which is estimated to only 3.3 Ma, was initiated in the all-year rainfall area.
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| 10. |
- Bengtson, Annika, et al.
(författare)
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The Malagasy enigmatic genus Apodocephala (Asteraceae), a new member of the tribe Athroismeae
- 2021
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Ingår i: Willdenowia. - : Botanic Garden and Botanical Museum Berlin, Freie Universitaet Berlin. - 0511-9618 .- 1868-6397. ; 51:2, s. 221-230
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Tidskriftsartikel (refereegranskat)abstract
- Apodocephala is a small genus of nine species of shrubs and trees endemic to Madagascar and currently classified in the tribe Astereae (Asteraceae). However, its present tribal position has been questioned, as it lacks some of the salient morphological features of that tribe. This study includes for the first time DNA sequences from Apodocephala (two species including the type of the generic name) to test its phylogenetic position. Phylogenetic analyses based on sequence data from nuclear ribosomal (ETS and ITS) and plastid (ndhF and trnL–trnF) DNA regions, using Bayesian inference and maximum parsimony methods, strongly reject the placement of Apodocephala in the Astereae. Our results, instead, support its position as sister to the Malagasy monospecific genus Lowryanthus within the tribe Athroismeae. Morphological comparison of these sister genera reveal similarities in cypsela morphology, and the inclusion of Apodocephala in the subtribe Lowryanthinae is proposed here. The tribe Athroismeae is now represented by ten genera (Anisochaeta, Anisopappus, Apodocephala, Artemisiopsis, Athroisma, Blepharispermum, Centipeda, Leucoblepharis, Lowryanthus and Symphyllocarpus), six of which occur in Madagascar. The Malagasy Athroismeae occur in all Malagasy terrestrial ecosystems (rainforests, deciduous dry forests, thicket spiny forests and savannas) and are likely the result of multiple independent colonization events mostly from mainland Africa.
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| 11. |
- Bengtson, Annika, et al.
(författare)
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Three new species of metalasia (asteraceae gnaphalieae) from the western cape and an updated key to the genus
- 2013
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Ingår i: South African Journal of Botany. - : Elsevier BV. - 0254-6299 .- 1727-9321. ; 84, s. 72-82
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Tidskriftsartikel (refereegranskat)abstract
- Three new species of Metalasia from the Western Cape of South Africa are described; Metalasia tristis A.Bengtson & P.O.Karis, a small shrublet from the Groot Winterhoek Mountains, and Metalasia formosa A.Bengtson & P.O.Karis and Metalasia eburnea A.Bengtson & P.O.Karis both found in the Langeberg Mountains. The morphology and relationships of the three new species are discussed, and an updated key to the genus is provided.
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| 14. |
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| 15. |
- Kool, Anneleen, et al.
(författare)
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Polyphyly of Polycarpon (Caryophyllaceae) inferred from DNA sequence data
- 2007
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Ingår i: Taxon. - 0040-0262 .- 1996-8175. ; 56:3, s. 775-782
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Tidskriftsartikel (refereegranskat)abstract
- A phylogenetic study of the genus Polycarpon was made using DNA sequence data from the chloroplast rpsl6 intron and nuclear RPB2 regions. Polycarpon as currently recognised is shown to be polyphyletic. The South American species P. coquimbense and P. suffruticosum are more closely related to Haya obovata (Socotra) and Polycarpaea spicata (paleotropical) than to the remaining species of Polycarpon, and the widespread tropical species P. prostratum is nested with Macaronesian species of Polycarpaea. All three should therefore be excluded from Polycarpon. The remaining species, the P. tetraphyllum group, has its main diversity in the Mediterranean region. It is a polyploid complex with morphologically very similar taxa mostly separated only by partially overlapping characters. The members of this group form a strongly supported, but largely unresolved clade. It is proposed that they are all included in a widely circumscribed P. tetraphyllum. The dehiscence of the capsules in P. tetraphyllum, by valves that elastically roll inwards and finally throw out the seeds, is unique in Caryophyllaceae and provides a strong synapomorphy for Polycarpon in this new restricted sense.
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| 16. |
- Moëll, Daniel, et al.
(författare)
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Large Eddy Simulation and Experimental Analysis of Combustion Dynamics in a Gas Turbine Burner
- 2019
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Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 0742-4795 .- 1528-8919. ; 141:7
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Tidskriftsartikel (refereegranskat)abstract
- Large eddy simulations (LES) and experiments (planar laser-induced fluorescence of the hydroxyl radical (OH-PLIF) and pressure transducer) have been carried out on a gas turbine burner fitted to an atmospheric combustion rig. This burner, from the Siemens SGT-800 gas turbine, is a low NOx, partially premixed burner, where preheat air temperature, flame temperature, and pressure drop across the burner are kept similar to engine full load conditions. The large eddy simulations are based on a flamelet-generated manifold (FGM) approach for representing the chemistry and the Smagorinsky model for subgrid turbulence. The experimental data and simulation data are in good agreement, both in terms of time averaged and time-resolved quantities. From the experiments and LES, three bands of frequencies of pressure fluctuations with high power spectral density are found in the combustion chamber. The first two bands are found to be axial pressure modes, triggered by coherent flow motions from the burner, such as the flame stabilization location and the precessing vortex core (PVC). The third band is found to be a cross flow directional mode interacting with two of the four combustion chamber walls in the square section of the combustion chamber, triggered from general flow motions. This study shows that LES of real gas turbine components is feasible and that the results give important insight into the flow, flame, and acoustic interactions in a specific combustion system.
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