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- Bengtson, Sven-Axel, et al.
(författare)
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Man-dependence of House Sparrows (Passer domesticus) in the Faroe Islands: habitat patch characteristics as determinants of presence and numbers
- 2010
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Ingår i: Dorete - her book, Annales Societatis Scientiarum Færoensis, Suppl. 52. ; , s. 227-243
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The House Sparrow (Passer domesticus) began to colonize the Faroe Islands in the mid-1940s and occurs in most built-up areas. Breeding is confined to the discrete human habitations (settlements) that form a pattern of patches (”habitat-islands”). In 2002 all settlements were surveyed and the number of pairs of sparrows (total number ca. 2,700 pairs) and amount of vegetation (”green space”) were estimated. The settlements ranged in size from 0.01 km2 (a single farmstead) to 8.72 km2 (the capital) and 68% of them (n=118) were occupied by sparrows. Patch occupancy was positively correlated with both area and amount of vegetation (p < 0.001) but not quite with the degree of isolation (p = 0.15). The latter was crudely scored as a function of distance to nearest settlement with > 10 pairs (a possible source area) and topography (mainly mountains and open sea). The patch variables area, human population, number of houses and houses were strongly intercorrelated. Abundance (number of pairs) of sparrows was positively correlated with the number of houses (r = 0.84, p < 0.001). In all but one of the settlements with < 10 houses sparrows were absent, and also in many of those with 10-60 houses where the scatter swas wide (no significant correlation p = 0.25). All but one of the settlements with > 60 houses supported sparrows and the correlation with abundance was highly significant (p < 0.001). The absence of sparrows in small settlements is discussed in terms of risks of associated with small populations such as stochastic extinctions, Allee effects, competition, and predation (incl. persecution by Man). Various anthropogenic effects on abundance of sparrows are discussed; e.g. age, type and conditions of buildings and the presence of gardens, cultivations, and plantations all contributing to shelter and food resources. The Faroese House Sparrow as a metapopulation is briefly discussed.
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- Enckell, P H, et al.
(författare)
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The dispersal pattern of an anthropochorous species: Genetic variation in populations of Lumbricus terrestris L. (Lumbricidae) in the Faroe Islands
- 1986
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Ingår i: Hereditas. - : Springer Science and Business Media LLC. - 0018-0661 .- 1601-5223. ; 104:2, s. 253-261
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Tidskriftsartikel (refereegranskat)abstract
- Ten populations of the anthropochorous Lumbricus terrestris L. (Lumbricidae) from six islands in the Faroes were scored for enzyme variation by electrophoresis. The allele frequencies were analyzed by cluster analysis and information entropy relationships. There was a significant heterogeneity in allele frequencies among the samples. Four groups could be distinguished in the cluster analysis of which one was larger (at least five sites); two sites were defined as outliers. Information entropy showed that the allele frequency data were structured differently over the sites and that the most non-random site was also one of the outliers in the cluster space. The main group in the cluster analysis also forms a geographically central group in the islands. These results are discussed against the known colonization history of the Faroes. It is concluded that the genetic variation pattern does not indicate any single point of invasion of L. terrestris into the islands. Rather, it shows that former and present-day communications between the islands are responsible for similarities and dissimilarities in genetic variation in the L. terrestris populations.
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- Enckell, P H, et al.
(författare)
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Serf and waif colonization: different patterns in distribution and dispersal of invertebrate species in settlements in the Faroe Islands
- 1987
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Ingår i: Journal of Biogeography. - 0305-0270 .- 1365-2699. ; 14, s. 89-104
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Tidskriftsartikel (refereegranskat)abstract
- We measured the faunal similarityb etween samples of Coleoptera, Araneae and Gastropoda + Lumbricidae + Opiliones from infields ites in the Faroes by ordination,a nd compared the sites on a between-islandb asis. The aeriallyd ispersingA raneae did not show any island-specific pat-tern; the faunal similarityw as high between the islands. Coleoptera showed a patternw heres imilarityw ithini slandsw as highert hanb etween them.T he anthropochorous parto ft he Coleopteraf ormeda clear pattern reminiscentof t heg eographicala ppearanceo ft heF aroes; similarity within large islandsw as clearlyh ighert han betweeni slands. This indicatest hat one of the axes in thep rincipalc omponenta nalysisi s an approximationo f some measure of geographical distance. The small islands, however, showed the randomp atterno f a waifc olonizationa nd occurreds cattered in the factors pace. The anthropochorous groupsG astropoda + Lumbricidae+ Opiliones differedm arkedlyf roms uch a pattern,a nd were more similart o the aerially dispersingA raneae. We interprett his as being the result of a dispersalb etweena nd withinis landsd ependento n Man, and a persistence (of manys pecies) in man-madeh abitatso nly. We termt hiss erfc oloniza-tion to indicate those species' total dependence upon Man.
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