| 11. |
- Anderson, Cajsa Lisa, et al.
(author)
-
Divergence times of phylogenetically basal eudicots
- 2005
-
In: XVII International Botanical Congress. ; , s. 728-
-
Conference paper (peer-reviewed)abstract
- A molecular dating of the phylogenetically basal eudicots (Ranunculales, Proteales, Sabiales, Buxales and Trochodendrales sensu APGII) has been performed using several fossils as minimum age constraints. We have sampled all rbcL sequences available in GenBank for the taxa in focus. Dating was done using Penalized Likelihood, and compared with NonParametric Rate Smoothing. We show that choice of method and fossil constraints has a great impact on the age estimates, and that it is important to use several fossil constraints to yield good age estimates. We discuss the 14 fossils we have chosen to include in this study and present a critical review of other fossils potentially useful in dating studies within the basal eudicots. Our results suggest a rapid diversification during the Early-mid Cretaceous, with all the lineages of basal eudicots emerging during the latest part of the Early Cretaceous. The age of Ranunculales was estimated to 120 myr, Proteales to 119 myr, Sabiales to 118 myr, Buxales to 117 myr and Trochodendrales to 116 myr.
|
|
| 12. |
|
|
| 13. |
- Barreda, V. D., et al.
(author)
-
Eocene Patagonia Fossils of the Daisy Family
- 2010
-
In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 329:5999, s. 1621-1621
-
Journal article (peer-reviewed)abstract
- Fossil evidence suggests that daisies and sunflowers may have originated in South America more than 47 million years ago.
|
|
| 14. |
- Bremer, Kåre, et al.
(author)
-
An extinct Eocene taxon of the daisy family (Asteraceae) : evolutionary, ecological and biogeographical implications
- 2012
-
In: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 109:1, s. 127-134
-
Journal article (peer-reviewed)abstract
- Background and Aims: Morphological, molecular and biogeographical information bearing on early evolution of the sunflower alliance of families suggests that the clade containing the extant daisy family (Asteraceae) differentiated in South America during the Eocene, although palaeontological studies on this continent failed to reveal conclusive support for this hypothesis. Here we describe in detail Raiguenrayun cura gen. & sp. nov., an exceptionally well preserved capitulescence of Asteraceae recovered from Eocene deposits of northwestern Patagonia, Argentina.Methods: The fossil was collected from the 47.5 million-year-old Huitrera Formation at the Estancia Don Hipolito locality, Rio Negro Province, Argentina.Key Results: The arrangement of the capitula in a cymose capitulescence, the many-flowered capitula with multiseriate-imbricate involucral bracts and the pappus-like structures indicate a close morphological relationship with Asteraceae. Raiguenrayun cura and the associated pollen Mutisiapollis telleriae do not match exactly any living member of the family, and clearly represent extinct taxa. They share a mosaic of morphological features today recognized in taxa phylogenetically close to the root of Asteraceae, such as Stifftieae, Wunderlichioideae and Gochnatieae (Mutisioideae sensu lato) and Dicomeae and Oldenburgieae (Carduoideae), today endemic to or mainly distributed in South America and Africa, respectively.Conclusions: This is the first fossil genus of Asteraceae based on an outstandingly preserved capitulescence that might represent the ancestor of Mutisioideae-Carduoideae. It might have evolved in southern South America some time during the early Palaeogene and subsequently entered Africa, before the biogeographical isolation of these continents became much more pronounced. The new fossil represents the first reliable point for calibration, favouring an earlier date to the split between Barnadesioideae and the rest of Asteraceae than previously thought, which can be traced back at least 47.5 million years. This is the oldest well dated member of Asteraceae and perhaps the earliest indirect evidence for bird pollination in the family.
|
|
| 15. |
- Bremer, Kåre, 1948-
(author)
-
Rektorsbloggen
- 2015
-
Book (pop. science, debate, etc.)abstract
- Kåre Bremer startade sin blogg när han hade varit rektor vid Stockholms universitet i knappt ett och ett halvt år. Det blev ett par inlägg per vecka fram till hans avgång som rektor i januari 2013. Sammanlagt blev det 930 blogginlägg. Intentionen var att använda den för intern kommunikation. Snart visade det sig att bloggen lästes regelbundet av företrädare för andra lärosäten, myndigheter och media.Kåre Bremers blogg blev en effektiv informationskanal för Stockholms universitet både internt och externt – med många följare och stort genomslag. Rektorsbloggen är ett tidsdokument med ögonblicksbilder från Stockholms universitets och hela högskolesveriges historia under Kåre Bremers rektorstid.
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
- Britton, Tom, et al.
(author)
-
Estimating divergence times in large phylogenetic trees
- 2007
-
In: Systematic Biology. - : Oxford University Press (OUP). - 1063-5157 .- 1076-836X. ; 56:5, s. 741-752
-
Journal article (peer-reviewed)abstract
- A new method, PATHd8, for estimating ultrametric trees from trees with edge (branch) lengths proportional to the number of substitutions is proposed. The method allows for an arbitrary number of reference nodes for time calibration, each defined either as absolute age, minimum age, or maximum age, and the tree need not be fully resolved. The method is based on estimating node ages by mean path lengths from the node to the leaves but correcting for deviations from a molecular clock suggested by reference nodes. As opposed to most existing methods allowing substitution rate variation, the new method smoothes substitution rates locally, rather than simultaneously over the whole tree, thus allowing for analysis of very large trees. The performance of PATHd8 is compared with other frequently used methods for estimating divergence times. In analyses of three separate data sets, PATHd8 gives similar divergence times to other methods, the largest difference being between crown group ages, where unconstrained nodes get younger ages when analyzed with PATHd8. Overall, chronograms obtained from other methods appear smoother, whereas PATHd8 preserves more of the heterogeneity seen in the original edge lengths. Divergence times are most evenly spread over the chronograms obtained from the Bayesian implementation and the clock-based Langley-Fitch method, and these two methods produce very similar ages for most nodes. Evaluations of PATHd8 using simulated data suggest that PATHd8 is slightly less precise compared with penalized likelihood, but it gives more sensible answers for extreme data sets. A clear advantage with PATHd8 is that it is more or less instantaneous even with trees having several thousand leaves, whereas other programs often run into problems when analyzing trees with hundreds of leaves. PATHd8 is implemented in freely available software.
|
|
| 19. |
|
|
| 20. |
|
|
