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Scattered Distribution (scattered + distribution)

Distribution by Scientific Domains
Life Sciences75%

Selected Abstracts

Can low densities of carnivores result in genetic depletion?

JOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 3 2006
An investigation within French polecat populations
Summary Carnivores as top predators are commonly found in relatively low densities even in optimal habitats. Despite a lack of empirical studies, it could be suspected that long-term low density could result in genetic depletion. The genetic structure of European polecat Mustela putorius natural populations was investigated by allozyme electrophoresis in five distinct areas. Density estimates significantly differed among sites from 0.17 to 0.83 individuals/km2 with an average of 0.56 individuals per km2, resulting in a scattered distribution. Genetic structure varied among distinct populations both in number of polymorphic loci and heterozygosity. Polecats from Brittany revealed a very low observed heterozygosity (HO = 0.028) whereas mean heterozygosity reached HO = 0.072 in Brière. That the lowest heterozygosity levels and highest inbreeding coefficient FIS were significantly associated with the lowest densities suggests that low densities may affect populations of carnivores. Both the loss of polymorphic loci and the reduction in heterozygosity rates suggest a density-dependent effect and population density can be arguably regarded as a factor affecting genetic diversity in top carnivores. [source]

Embryonic undifferentiated cells show scattering activity on a surface coated with immobilized E-cadherin

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2008
Masato Nagaoka
Abstract Rearrangement of cell,cell adhesion is a critical event in embryonic development and tissue formation. We investigated the regulatory function of E-cadherin, a key adhesion protein, in the developmental process by using E-cadherin/IgG Fc fusion protein as an adhesion matrix in cell culture. F9 embryonal carcinoma cells usually form colonies when cultured on gelatin or fibronectin matrices. However, F9 cells cultured on the E-cadherin/IgG Fc fusion protein matrix formed a scattered distribution, with a different cytoskeletal organization and E-cadherin-rich protrusions that were regulated by Rac1 activity. The same scattering activity was observed in P19 embryonal carcinoma cells. In contrast, three types of differentiated cells, NMuMG mammary gland cells, MDCK kidney epithelial cells, and mouse primary isolated hepatocytes, did not show the scattering activity observed in F9 and P19 cells. These results suggest that migratory behavior on an E-cadherin-immobilized surface is only observed in embryonic cells, and that the regulatory mechanisms underlying E-cadherin-mediated cell adhesion vary with the state of differentiation. J. Cell. Biochem. 103: 296,310, 2008. © 2007 Wiley-Liss, Inc. [source]

Mitochondrial DNA diversity and origins of South and Central American goats

ANIMAL GENETICS, Issue 3 2009
M. Amills
Summary We have analysed the genetic diversity of South and Central American (SCA) goats by partially sequencing the mitochondrial control region of 93 individuals with a wide geographical distribution. Nucleotide and haplotype diversities reached values of 0.020 ± 0.00081 and 0.963 ± 0.0012 respectively. We have also observed a rather weak phylogeographic structure, with almost 69% of genetic variation included in the within-breed variance component. The topology of a median-joining network analysis including 286 European, Iberian, Atlantic and SCA mitochondrial sequences was very complex, with most of the haplotypes forming part of independent small clusters. SCA sequences showed a scattered distribution throughout the network, and clustering with Spanish and Portuguese sequences occurred only occasionally, not allowing the distinguishing of a clear Iberian signature. Conversely, we found a prominent cluster including Canarian, Chilean, Argentinian and Bolivian mitochondrial haplotypes. This result was independently confirmed by constructing a Bayesian phylogenetic tree (posterior probability of 0.97). Sharing of mitochondrial haplotypes by SCA and Canarian goats suggests that goat populations from the Atlantic archipelagos, where Spanish and Portuguese ships en route to the New World used to stow food and supplies, participated in the foundation of SCA caprine breeds. [source]

Constraints on home range behaviour affect nutritional condition in urban house sparrows (Passer domesticus)

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010
CARL VANGESTEL
In human-dominated landscapes (semi)natural habitats are typically embedded in tracts of unsuitable habitat. Under such conditions, habitat characteristics and grain size of the surrounding landscape may affect how much food, and at what cost, is available for sedentary species with low home-range plasticity. Here we combine behavioural radio-tracking, feather ptilochronology, and landscape analysis to test how nutritional condition varies with home range size in 13 house sparrow [Passer domesticus (Linnaeus, 1758)] populations along an urban gradient. Urban individuals occupied smaller home ranges than conspecifics from rural areas, most distinctly if key cover was highly scattered. In urban plots, patch connectivity, home range sizes, and activity areas were positively correlated, indicating that individual ranging behaviour was related to the spatial distribution of suitable habitat. Urban House sparrows also showed the smallest feather growth bars, which were positively related to home range size at plot level. In contrast, growth bar widths and home range sizes were negatively related in rural populations, whereas in suburban populations, both variables varied independently. We conclude that individuals from progressively more built-up areas show a restricted ability to adjust their daily ranging behaviour to the scattered distribution of critical resources. This may complement other putative causes of the widespread population decline of urban house sparrows. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 41,50. [source]