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- Articus, Kristina, et al.
(författare)
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Phylogenetic studies in Usnea.
- 2000
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Ingår i: The Fourth IAL Symposium Progress and Problems in Lichenology at the Turn of the Millenium, Abstracts: 100. Barcelona..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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- Articus, Kristina, 1971-
(författare)
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Phylogenetic Studies in Usnea (Parmeliaceae) and Allied Genera
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the phylogeny of the lichen genus Usnea (Parmeliaceae, Ascomycetes). The relationships and the morphological variation among Usnea species has been studied, as well as the relationship of Usnea to allied genera. Two species, U. florida and U. subfloridana, which earlier were regarded to form two separate species have been synonymized. In an analysis based on sequence data these two taxa formed a monophyletic group of intermixed specimens. Usnea florida and U. subfloridana have earlier been regarded to form a species pair, but the species pairs concept cannot be applied in this case. The morphological characters traditionally used for species recognition of a number of European Usnea species have been analyzed regarding their reliability. The evolution and distribution of the morphological characters was studied in relation to a phylogeny based on sequence data. Most characters proved to be homoplastic in relation to the phylogeny. Few characters were consistent in a clade, and the same character could be inconsistent in another clade. Therefore a combination of several characters is recommended for species recognition. The relationship of Neuropogon to Usnea was investigated based on sequence data. Neuropogon showed to be closely related to Usnea subg. Usnea. The subgenera Eumitria and Dolichousnea formed the sister group to the clade comprising subg. Usnea and Neuropogon. Usnea is paraphyletic in this investigation. Eumitria is treated as a genus and the subgenus Dolichousnea is elevated to generic rank. The position of Usnea, Neuropogon, Eumitria, and Dolichousnea in the family Parmeliaceae was investigated based on a phylogeny obtained by sequence data. Protousnea probably forms the sister group to the clade of Usnea, Neuropogon, Eumitria, and Dolichousnea. Several monophyletic groups in the family Parmeliaceae were identified.
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- Articus, Kristina, et al.
(författare)
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Ribosomal DNA and beta-tubulin data do not support the separation of the lichens Usnea florida and U-subfloridana as distinct species
- 2002
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Ingår i: Mycological Research. - 0953-7562 .- 1469-8102. ; 106, s. 412-418
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Tidskriftsartikel (refereegranskat)abstract
- The lichens Usnea florida and U. subfloridana have since long been recognised as distinct species. They show many similarities in morphology, but have different reproductive strategies. Usnea florida is always provided with many apothecia and produces no specialised asexual propagules. Usnea subfloridana has soralia, isidiomorphs and occasionally apothecia. Phylogenetic analyses based on continuous sequences of the ITS and LSU regions of the nuclear ribosomal DNA and the gene coding for beta-tubulin, show that specimens of the two species form one monophyletic group of intermixed specimens, and not two groups corresponding to morphology, which Would have been expected if two species were at hand. The 'species pair' concept in lichenology is discussed. Other Usnea species included in the study are: U. articulata, U. barbata, U. ceratina, U. filipendula. U. hirta, U. rigida and U. wasmuthii.
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- Bärring, Lars, et al.
(författare)
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Wind erosion on arable land in Scania, Sweden and the relation to the wind climate - a review
- 2003
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Ingår i: Catena. - 0341-8162. ; 52:3-4, s. 173-190
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses variations in the wind climate in relation to changes in the impact of wind erosion on agricultural lands with Scania, the southernmost province of Sweden, as an example. The literature concerning wind erosion in the region is reviewed and the conclusions are linked to recent analyses of the regional wind climate. Presently, wind erosion occasionally induces problems in light soil areas of the intensively cultivated Scania. It is not a new phenomenon that results from modem farming practice; it was documented already in the 18th century. This was an era of major land use changes because the increasing population required new and more vulnerable areas to be cultivated, which resulted in an ecological crisis due to increased wind erosion. Partly overlapping in time, a series of land amalgamation reforms transformed the land-use resulting in larger fields. Analyses of the frequency of wind directions indicate that variations in the large-scale wind climate occurred at that time. Wind erosion again became a topic of concern in the 20th century. Extensive analyses of several aspects of the wind climate (e.g., storminess and cyclone intensity) of Scandinavia and northwestern Europe show that there have been interdecadal variations but no sign of an overall long-term trend. The recurring periods of intensified wind erosion problems can best be explained as the combined result of a varying wind climate and the lack of appropriate long-term maintenance strategies for protective measures through the intervening periods of benign wind climate. (C) 2003 Elsevier Science B.V. All rights reserved.
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