| 1. |
- Leebens-Mack, James H., et al.
(författare)
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One thousand plant transcriptomes and the phylogenomics of green plants
- 2019
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 574:7780, s. 679-
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Tidskriftsartikel (refereegranskat)abstract
- Green plants (Viridiplantae) include around 450,000-500,000 species(1,2) of great diversity and have important roles in terrestrial and aquatic ecosystems. Here, as part of the One Thousand Plant Transcriptomes Initiative, we sequenced the vegetative transcriptomes of 1,124 species that span the diversity of plants in a broad sense (Archaeplastida), including green plants (Viridiplantae), glaucophytes (Glaucophyta) and red algae (Rhodophyta). Our analysis provides a robust phylogenomic framework for examining the evolution of green plants. Most inferred species relationships are well supported across multiple species tree and supermatrix analyses, but discordance among plastid and nuclear gene trees at a few important nodes highlights the complexity of plant genome evolution, including polyploidy, periods of rapid speciation, and extinction. Incomplete sorting of ancestral variation, polyploidization and massive expansions of gene families punctuate the evolutionary history of green plants. Notably, we find that large expansions of gene families preceded the origins of green plants, land plants and vascular plants, whereas whole-genome duplications are inferred to have occurred repeatedly throughout the evolution of flowering plants and ferns. The increasing availability of high-quality plant genome sequences and advances in functional genomics are enabling research on genome evolution across the green tree of life.
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| 2. |
- Weststrand, Stina, 1987-
(författare)
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Spikemoss patterns : Systematics and historical biogeography of Selaginellaceae
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Selaginellaceae, spikemosses, is a heterosporous plant family belonging to the lycophytes. With an estimated age of some 350 million years, the family is historically important as one of the oldest known groups of vascular plants. Selaginellaceae is herbaceous with a worldwide distribution. However, the majority of the ca. 750 species in the single genus Selaginella are found in the tropics and subtropics.This thesis aims at elucidating the systematics and historical biogeography of Selaginellaceae. The evolutionary relationships of the family were inferred from DNA sequence data (plastid and single-copy nuclear) of one-third of the species richness in the group. Attention was paid to cover the previously undersampled taxonomic, morphological, and geographical diversity. Morphological features were studied and mapped onto the phylogeny. The results show an overall well-supported phylogeny and even more complex morphological patterns than previously reported. Despite this, many clades can be distinguished by unique suites of morphological features.With the phylogeny as a basis, together with the thorough morphological studies, a new subgeneric classification with seven subgenera, representing strongly supported monophyletic groups, is presented for Selaginella. By mainly using gross morphological features, easily studied by the naked eye or with a hand lens, the intention is that the classification should be useful to a broader audience.During the work with species determinations, it was revealed that the correct name for an endemic Madagascan Selaginella species is S. pectinata Spring, not S. polymorpha Badré as previously proposed.The robust phylogeny of Selaginellaceae allowed for a historical biogeographical analysis of the group. A time-calibrated phylogeny, together with extant species distribution data, formed the basis. The results show pre-Pangean diversification patterns, Gondwanan vicariance, and more recent Cenozoic long-distance dispersals. The many inferred transoceanic dispersals during the last 50 million years are surprising considering Selaginella’s large megaspores that are thought to have a negative effect on dispersal.In conclusion, this thesis presents a well-founded hypothesis of the evolutionary history of Selaginellaceae including its phylogeny, morphology, and historical biogeography. The thesis forms a firm basis for further studies on Selaginellaceae in particular, and gives us a better understanding of early land plant evolution in general.
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| 3. |
- Weststrand, Stina, 1987-
(författare)
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The first large-scale historical biogeographical study of spikemosses reveals surprising patterns
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Selaginellaceae, spikemosses, is a lycophyte family with a history dating back some 350 million years. Selaginella selaginoides (dvärglummer) is the single Swedish species; the rest of the ca. 750 species are mainly found in the tropics. Recently, we presented a large-scale phylogeny of Selaginellaceae and with that as a framework, we have studied the historical biogeography of the group. Besides its old age, Selaginellaceae is an interesting study system due to its heterospory. Both small microspores and large megaspores are involved in reproduction and the "large" size of the megaspores (0.2–1.2 mm) is thought to have a negative effect on dispersal. The results of our historical biogeographical analyses are surprising and change our view on which plants that disperse over long distances.
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