| 1. |
- Alatalo, Juha, 1966-
(författare)
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Gender lability in trioecious Silene acaulis (Caryophyllaceae)
- 1997
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 17:2, s. 181-183
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Tidskriftsartikel (refereegranskat)abstract
- Gender expression of individual cushions of Silene acaulis was shown to vary between years. Fifteen of thirty-nine (= 38%) cushions monitored changed gender expression between 1993 and 1995. Cushions dominated by female flowers were shown to be more stable in gender expression than cushions dominated by male or hermaphrodite flowers.
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| 2. |
- Altola, Juha, 1966-, et al.
(författare)
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EFFECT OF ALTITUDE ON THE SEX-RATIO IN POPULATIONS OF SILENE ACAULIS (CARYOPHYLLACEAE)
- 1995
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 15:3, s. 251-256
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Tidskriftsartikel (refereegranskat)abstract
- Predicted increase of female frequencies in gynodioecious Silene acaulis was tested along an altitude gradient in northern Sweden. Average female frequencies for the four sites increased with altitude from 42% to 59% within a short geographical distance. This follows the outcrossing hypothesis, that female frequencies should be positively correlated with selfing rates of hermaphrodites in populations. More adverse environmental conditions should favour gynodioecy in areas where reproduction to a greater part relies on vegetative reproduction or selfing. Further, a significant difference in corolla width was found between females and the larger hermaphrodites, but not between sites. Cushion size and the number of flowers per cushion decreased with altitude.
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| 3. |
- Köchy, Martin, et al.
(författare)
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Biogeography of vascular plants on habitat islands, peninsulas and mainlands in an east-central Swedish agricultural landscape
- 1997
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 17:2, s. 215-223
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Tidskriftsartikel (refereegranskat)abstract
- The increase of island species richness with area can be explained by an increase in habitat diversity or by an equilibrium of species immigration and extinction. We examined vascular plant species richness in 39 sites (24 habitat islands, 7 ‘habitat peninsulas’ and 8 comparable ‘mainland’ sites). We sampled at three scales: whole sites, meadows within sites and quadrats (4 m × 4 m) within meadows. All sites (10–104 m2) contained natural vegetation within arable fields in eascentral Sweden. There was a strong correlation between species richness and area for whole sites and for meadows There was no correlation, however, between species richness in quadrats and site area. The difference between site and meadow results on one side and quadrat results on the other suggests that species richness increases with whole site area primarily because large sites are more diverse than smaller ones. Speciearea relationships did not differ between islands, peninsula and mainland sites. Thus, patterns of species richness on our sites were more consistent with habitat diversity than an immigratioextinction equilibrium.
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| 4. |
- Tekle, Kebrom, et al.
(författare)
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Vegetation on hill slopes in southern Wello, Ethiopia : Degradation and regeneration
- 1997
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 17:5, s. 483-493
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Tidskriftsartikel (refereegranskat)abstract
- A study was made of the vegetation in southern Wello (Ethiopia) in relation to human impact and the environment. 65 sample plots were laid out and analysed with respect to the cover value of vascular plant species. Altitude, slope, aspect and estimates of grazing pressure for each plot were also recorded along with physical and chemical soil properties analysed for samples taken from each plot. The following environmental factors, isolated by forward selection, show correlation with the axes of Canonical Correspondence Analysis (CCA): altitude, grazing, pH, K, Ca, Mg, slope and aspect.Through hierarchical and non-hierarchical clustering methods the vegetation was divided into eight types, from which one was secondary forest characterised by patch dominance of Juniperus procera and Olea europaea ssp. cuspidata. These forest patches are found at high altitude sites and because of their inaccessibility are usually characterised by low livestock density and consequently low grazing pressure. The presence of large boulders and stones in Podocarpus falcatus forest decreases accessibility and creates natural protection for the trees. The other vegetation types, most of which are found at lower altitude and associated with varying intensities of grazing, include grasslands (grazed and protected), regenerating sites dominated by Euclea racemosa and Dodonaea angustifolia, dense and open shrublands and Olea europaea ssp. cuspidata woodlands. Human interference has a major impact on the vegetation of the study area and its recovery will depend on the degree of participation of the local people.
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| 5. |
- Alatalo, Juha, 1966-, et al.
(författare)
-
Effect of Altitude on the Sex-Ratio in Populations of Silene Acaulis (Caryophyllaceae) : Effect of Altitude on the Sex-Ratio in Populations of Silene Acaulis (Caryophyllaceae)
- 1995
-
Ingår i: Nordic Journal of Botany. - 0107-055X .- 1756-1051. ; 15:3, s. 251-256
-
Tidskriftsartikel (refereegranskat)abstract
- Predicted increase of female frequencies in gynodioecious Silene acaulis was tested along an altitude gradient in northern Sweden. Average female frequencies for the four sites increased with altitude from 42% to 59% within a short geographical distance. This follows the outcrossing hypothesis, that female frequencies should be positively correlated with selfing rates of hermaphrodites in populations. More adverse environmental conditions should favour gynodioecy in areas where reproduction to a greater part relies on vegetative reproduction or selfing. Further, a significant difference in corolla width was found between females and the larger hermaphrodites, but not between sites. Cushion size and the number of flowers per cushion decreased with altitude.
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| 6. |
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| 7. |
- Hedberg, O
(författare)
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Studies in the genus Polycarpaea (Caryophyllaceae) in Ethiopia
- 1995
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Ingår i: NORDIC JOURNAL OF BOTANY. - : NORDIC JOURNAL OF BOTANY. - 0107-055X. ; 15:5, s. 513-517
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A case study is presented of a small critical group of Polycarpaea species in Ethiopia, comprising P. eriantha, P. corymbosa and P. linearifolia. Absence of clear discontinuities in individual features between the three species concerned invited the lumpi
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| 8. |
- Hedren, M
(författare)
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Electrophoretic evidence for allotetraploid origin of Dactylorhiza purpurella (Orchidaceae)
- 1996
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Ingår i: NORDIC JOURNAL OF BOTANY. - : NORDIC JOURNAL OF BOTANY. - 0107-055X. ; 16:2, s. 127-134
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Evidence from allozyme markers suggests that the NW European Dactylorhiza purpurella (Orchidaceae) is an allotetraploid which originated from taxa closely related to the present-day D, incarnata s. 1. and D, fuchsii/D. maculata. However, Dactylorhiza purp
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| 9. |
- Hedren, M, et al.
(författare)
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Ichthyostoma - A new genus in the Acanthaceae from NE tropical Africa
- 1996
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Ingår i: NORDIC JOURNAL OF BOTANY. - : NORDIC JOURNAL OF BOTANY. - 0107-055X. ; 16:4, s. 441-444
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Ichthyostoma thulinii, a new genus and species from Central Somalia and SE Ethiopia is described. Ichthyostoma is best placed in Acanthoideae - Odontoneminae, but is not closely related to any extant genus in that group.
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| 10. |
- Hedren, M
(författare)
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Notes on the esterase variation in Swedish Dactylorhiza incarnata s l (Orchidaceae)
- 1996
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Ingår i: NORDIC JOURNAL OF BOTANY. - : NORDIC JOURNAL OF BOTANY. - 0107-055X. ; 16:3, s. 253-256
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Swedish material of Dactylorhiza incarnata s. 1. shows little variation at commonly investigated allozyme loci. However, interpretable variation was found at one esterase locus. All plants investigated of D. incarnata var. cruenta from southern Sweden (wi
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