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- Armstrong, Kate E., et al.
(författare)
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Patterns of diversification amongst tropical regions compared: a case study in Sapotaceae.
- 2014
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Ingår i: Frontiers in Genetics. - : Frontiers Media SA. - 1664-8021. ; 5:362
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Tidskriftsartikel (refereegranskat)abstract
- Species diversity is unequally distributed across the globe,with the greatest concentration occurring in the tropics. Even within the tropics, there are significant differences in the numbers of taxa found in each continental region. Manilkara is a pantropical genus of trees in the Sapotaceae comprising c.78 species. Its distribution allows for biogeographic investigation and testing of whether rates of diversification differ amongst tropical regions. The age and geographical origin of Manilkara are inferred to determine whether Gondwanan break-up, boreotropical migration or long distance dispersal have shaped its current disjunct distribution. Diversification rates through time are also analyzed to determine whether the timing and tempo of speciation on each continent coincides with geoclimatic events. Bayesian analyses of nuclear (ITS) and plastid (rpl32-trnL,rps16-trnK,and trnS-trnFM) sequences were used to reconstruct a species level phylogeny of Manilkara and related genera in the tribe Mimusopeae. Analyses of the nuclear data using a fossil-calibrated relaxed molecular clock indicate that Manilkara evolved 32–29 million years ago (Mya) in Africa. Lineages within the genus dispersed to the Neotropics 26–18 Mya and to Asia 28–15 Mya. Higher speciation rates are found in the Neotropical Manilkara clade than in either African or Asian clades. Dating of regional diversification correlates with known palaeoclimatic events. In South America, the divergence between Atlantic coastal forest and Amazonian clades coincides with the formation of drier Cerrado and Caatinga habitats between them. In Africa diversification coincides with Tertiary cycles of aridification an duplif tof the east African plateaux. In South east Asia dispersal may have been limited by the relatively recent emergence of land in New Guinea and islands further east c.10 Mya.
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| 2. |
- Freire, Susana E., et al.
(författare)
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The Lucilia group (Asteraceae, Gnaphalieae): phylogenetic and taxonomic considerations based on molecular and morphological evidence.
- 2015
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Ingår i: Plant Systematics and Evolution. - : Springer Science and Business Media LLC. - 0378-2697 .- 1615-6110 .- 2199-6881. ; 301, s. 1227-1248
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Tidskriftsartikel (refereegranskat)abstract
- The Lucilia group sensu Anderberg and Freire comprises nine South American genera: Belloa, Berroa, Chevreulia, Cuatrecasasiella, Facelis, Gamochaetopsis, Jalcophila, Lucilia and Luciliocline. The aims of this contribution were, using DNA sequences from plastid (rpl32-trnL, trnL-F) and nuclear (ITS and ETS) markers, together with morphological characters, to test the monophyly of the Lucilia group and provide new insight into generic circumscriptions. Our studies, including a broad taxon sampling of Gnaphalieae species, suggest that the Lucilia group is paraphyletic, since Antennaria, Chionolaena, Gamochaeta, Loricaria, Micropsis, Mniodes and Stuckertiella are all nested within the Lucilia group. Morphology and molecular analyses combined showed that the traditional generic circumscription of most of the genera (e.g., Berroa, Chevreulia, Chionolaena, Cuatrecasasiella, Facelis, Jalcophila and Micropsis) correlates with the inferred phylogenetic relationships. Conversely, Lucilia and Luciliocline are non-monophyletic. Lucilia is nested in a clade with Berroa, Facelis and Micropsis. Luciliocline is strongly embedded within the clade Belloa pp + Mniodes. Our results are consistent with Dillon’s study that considered Belloa as a montotypic genus (B. chilensis). Luciliocline and the remaining species of Belloa are accommodated in the genus Mniodes, and the necessary combinations are proposed for the expanded Mniodes. All the analyses showed that the monotypic genera Stuckertiella and Gamochaetopsis are in a well-supported clade nested within Gamochaeta, which implies that taxonomic changes are required also for these genera. Internal relationships in the group and the key morphological characters used in the taxonomy of the group, as well as incongruences found between morphological and molecular analyses, are discussed.
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| 4. |
- 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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| 6. |
- Shekar, S., et al.
(författare)
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The genus Duhaldea in India
- 2020
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Ingår i: Rheedea. - Calicut, India. ; 30:2, s. 257-269
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Tidskriftsartikel (refereegranskat)abstract
- Based on the field and herbarium data, six species of the genus Duhaldea (sensu stricto) are recognized in India. A key to the Indian species, brief descriptions and illustrations are provided along with data on phenology, distribution, ecology, chromosome numbers and ethnobotanical uses.
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| 7. |
- Torices, R., et al.
(författare)
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Architectural traits constrain the evolution of unisexual flowers and sexual segregation within inflorescences: an interspecific approach.
- 2019
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Ingår i: PCI Evolutionary Biology. - : Cold Spring Harbor Laboratory.
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Tidskriftsartikel (refereegranskat)abstract
- Male and female unisexual flowers have repeatedly evolved from the ancestral bisexual flowers in different lineages of flowering plants. This sex specialization in different flowers often occurs within inflorescences. We hypothesize that inflorescence architecture may impose a constraint on resource availability for late flowers, potentially leading to different optima in floral sex allocation and unisexuality. Under this hypothesis we expect that inflorescence traits increasing the difference in resource availability between early and late flowers would be phylogenetically correlated with a higher level of sexual specialization. To test this hypothesis, we performed a comparative analysis of inflorescence traits (inflorescence size, number of flowers and flower density) in the sunflower family, which displays an extraordinary variation in floral sexual specialization at the inflorescence level, i.e. hermaphroditic, gynomonoecious and monoecious species. We found that species with a complete sex separation in unisexual flowers (monoecy) had significantly denser inflorescences. Furthermore, those species arranging their flowers in denser inflorescences also showed greater differences in the size of early and late fruits, a proxy of resource variation between flowers. Our findings support the idea that floral sexual specialization and consequently sexual segregation may be the consequence of different floral sex allocation optima driven by the sequential development of flowers that results in a persistent resource decline from earlier to later flowers.
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| 8. |
- Urtubey, Estrella, et al.
(författare)
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New circumscription of the genus Gamochaeta (Asteraceae, Gnaphalieae) inferred from nuclear and plastid DNA sequences
- 2016
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Ingår i: Plant Systematics and Evolution. - : Springer Science and Business Media LLC. - 0378-2697 .- 1615-6110 .- 2199-6881. ; 302, s. 1047-1066
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Tidskriftsartikel (refereegranskat)abstract
- Gamochaeta (tribe Gnaphalieae, Asteraceae) is composed of ca. 60 species primarily distributed in tropical and subtropical America. Within the tribe Gnaphalieae, the genus is characterized by capitula arranged in spikes or head-like clusters, few hermaphroditic central florets, truncate style branches with apical sweeping trichomes, pappus bristles connate at the base into a ring falling as a unit, and achenes with globose twin trichomes. Previous molecular phylogenetic studies have suggested the paraphyly of the genus, but have not provided a basis for redefining generic limits due to incomplete taxon sampling. To address this problem, DNA sequences from the plastid (trnL-F) and nuclear (ETS and ITS) genomes were analyzed from a broad taxon sample representing the full range of morphological variation known in the genus. Our results affirm that Gamochaeta is paraphyletic as presently circumscribed. Two clades can be recognized: one clade that includes the majority of the species currently assigned to Gamochaeta and a second clade that includes Gamochaetopsis, Stuckertiella and seven species of Gamochaeta. We present here a new circumscription of Gamochaeta, including two new combinations, Gamochaeta alpina and Gamochaeta peregrina, and the resurrection of Gamochaeta capitata. Our results also show Omalotheca supina, O. norvegica and O. sylvatica, which were placed by some authors in Gamochaeta or in Gnaphalium, form a monophyletic group distantly related to both genera.
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