| 1. |
- Rydin, Catarina, et al.
(författare)
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Phylogeny of Isoetes (Lycopsida) : resolving basal relationships using rbcL sequences
- 2002
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Ingår i: Taxon. - : Wiley. - 0040-0262 .- 1996-8175. ; 51:1, s. 83-89
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Tidskriftsartikel (refereegranskat)abstract
- The phylogenetic relationships of Isoëtes (Isoëtaceae) were investigated by means of a cladistic analysis using plastid rbcL sequences and a representative sample of 18 species. The analysis supports a basal split in Isoëtes separating two main groups, one including aquatic species from South America (I. bradei and I. amazonica) and West Africa (I. kersiiand I. schweinfurthii), and the other including aquatic, amphibious and terrestrial species representing all major continents. Higher level relationships remain unresolved, but supported groups do conflict with previous morphologybased hypotheses. Comparatively low levels of sequence divergence indicate that the use of more rapidly evolving regions will be required to resolve higher level relationships. The phylogenetically isolated nature of Isoëtes will in such analyses make standard outgroup comparisons problematic, and results presented here will in this respect prove important by providing support for choosing among alternative rooting options.
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| 2. |
- Sanderson, Michael J., et al.
(författare)
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Molecular evidence on plant divergence times
- 2004
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Ingår i: American Journal of Botany: The plant tree of life. ; 91:10, s. 1656-1665
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Tidskriftsartikel (refereegranskat)abstract
- Estimation of divergence times from sequence data has become increasingly feasible in recent years. Conflicts between fossil evidence and molecular dates have sparked the development of new methods for inferring divergence times, further encouraging these efforts. In this paper, available methods for estimating divergence times are reviewed, especially those geared toward handling the widespread variation in rates of molecular evolution observed among lineages. The assumptions, strengths, and weaknesses of local clock, Bayesian, and rate smoothing methods are described. The rapidly growing literature applying these methods to key divergence times in plant evolutionary history is also reviewed. These include the crown group ages of green plants, land plants, seed plants, angiosperms, and major subclades of angiosperms. Finally, attempts to infer divergence times are described in the context of two very different temporal settings: recent adaptive radiations and much more ancient biogeographic patterns.
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| 3. |
- Wikström, Niklas, et al.
(författare)
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Angiosperm divergence times: congruence and incongruence between fossils and sequence divergence estimates
- 2003
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Ingår i: Telling the Evolutionary Time. - : Taylor & Francis. - 0415275245 ; , s. 142-165
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Bokkapitel (refereegranskat)abstract
- The documentation of derived angiosperm lineages from increasingly older geological deposits, and growing evidence of considerable diversity in ower, seed, and pollen morphology in the mid-Cretaceous both imply that the timing of early angiosperm cladogenesis may be older then our current fossil-based estimates indicate. An alternative to fossils for calibrating the phylogenetic tree comes from divergence in DNA sequence data. Here, we report on an analysis using non-parametric rate smoothing and a three gene dataset covering c. 75 per cent of all angiosperm families recognized in recent classi cations. The results provide an initial hypothesis of angiosperm diversi cation times; by using an internal calibration point, an independent evaluation of angiosperm and eudicot origins is accomplished. Results are compared with fossil-based estimates of both magnolids and eudicot divergence times, and possible directions of future analyses are discussed.
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