Los espacios de actividad económica y la movilidad generada en la comunidad de Madrid.

Las transformaciones sociales, económicas y territoriales que han tenido lugar en las últimas décadas en Madrid, convergen hacia un modelo de ciudad difuso, más disperso, fragmentado y polinuclear, cuya corona metropolitana está cada vez más poblada. Los cambios territoriales también llevan asociados unos cambios en las pautas de la movilidad más centradas en el vehículo privado, realizándose cada vez viajes más largos y dando lugar a redes de flujos con una complejidad creciente. La movilidad asociada a este nuevo desarrollo es de difícil sostenibilidad, provocando un mayor consumo energético y de recursos. Se estudiarán dentro de los espacios de actividad económica de Madrid, los centros comerciales, centros de ocio, etc. ya que son ámbitos funcionales con gran impacto sobre la movilidad de la región madrileña, pues se comportan como focos muy activos de atracción no sólo de viajeros, sino también de mercancías. El análisis de la movilidad en el espacio metropolitano de Madrid se ha realizado tradicional mente a partir de encuestas domiciliarias de movilidad, que tratan de recoger las características de la movilidad diaria de la población. En este caso se utilizarán los datos que recoge la última Encuesta Domiciliaria, la EDM'04. En ella se ver cómo algunos motivos cobran cada vez más importancia e influyen en las nuevas estructuras y nuevas formas de organización territorial y social de las áreas metropolitanas, como son los viajes a compras o los viajes cuyo motivo es el ocio

Impacts of existing and planned hydropower dams on river fragmentation in the Balkan Region

The Balkan region has some of the best conserved rivers in Europe, but is also the location of ~3000 planned hydropower dams that are expected to help decarbonise energy production. A conflict between policies that promote renewable hydropower and those that prioritise river conservation has ensued, which can only be resolved with the help of reliable information. Using ground-truthed barrier data, we analysed the extent of current longitudinal river fragmentation in the Balkan region and simulated nine dam construction scenarios that varied depending on the number, location and size of the planned dams. Balkan rivers are currently fragmented by 83,017 barriers and have an average barrier density of 0.33 barriers/km after correcting for barrier underreporting; this is 2.2 times lower than the mean barrier density found across Europe and serves to highlight the relatively unfragmented nature of these rivers. However, our analysis shows that all simulated dam construction scenarios would result in a significant loss of connectivity compared to existing conditions. The largest loss of connectivity (−47 %), measured as reduction in barrier-free length, would occur if all planned dams were built, 20 % of which would impact on protected areas. The smallest loss of connectivity (−8 %) would result if only large dams (>10 MW) were built. In contrast, building only small dams (<10 MW) would cause a 45 % loss of connectivity while only contributing 32 % to future hydropower capacity. Hence, the construction of many small hydropower plants will cause a disproportionately large increase in fragmentation that will not be accompanied by a corresponding increase in hydropower. At present, hydropower development in the Balkan rivers does not require Strategic Environmental Assessment, and does not consider cumulative impacts. We encourage planners and policy makers to explicitly consider trade-offs between gains in hydropower and losses in river connectivity at the river basin scale.Impacts of existing and planned hydropower dams on river fragmentation in the Balkan RegionpublishedVersio

Rare and fleeting: an example of interspecific recombination in animal mitochondrial DNA

Recombination is thought to occur only rarely in animal mitochondrial DNA ( mtDNA). However, detection of mtDNA recombination requires that cells become heteroplasmic through mutation, intramolecular recombination or ' leakage' of paternal mtDNA. Interspecific hybridization increases the probability of detecting mtDNA recombinants due to higher levels of sequence divergence and potentially higher levels of paternal leakage. During a study of historical variation in Atlantic salmon ( Salmo salar) mtDNA, an individual with a recombinant haplotype containing sequence from both Atlantic salmon and brown trout ( Salmo trutta) was detected. The individual was not an F1 hybrid but it did have an unusual nuclear genotype which suggested that it was a later-generation backcross. No other similar recombinant haplotype was found from the same population or three neighbouring Atlantic salmon populations in 717 individuals collected during 1948 - 2002. Interspecific recombination may increase mtDNA variability within species and can have implications for phylogenetic studies

Asymmetric gene flow and the evolutionary maintenance of genetic diversity in small, peripheral Atlantic salmon populations

Small populations may be expected to harbour less genetic variation than large populations, but the relation between census size (N), effective population size (Ne), and genetic diversity is not well understood. We compared microsatellite variation in four small peripheral Atlantic salmon populations from the Iberian peninsula and three larger populations from Scotland to test whether genetic diversity was related to population size. We also examined the historical decline of one Iberian population over a 50-year period using archival scales in order to test whether a marked reduction in abundance was accompanied by a decrease in genetic diversity. Estimates of effective population size (Ne) calculated by three temporal methods were consistently low in Iberian populations, ranging from 12 to 31 individuals per generation considering migration, and from 38 to 175 individuals per generation if they were regarded as closed populations. Corresponding Ne/N ratios varied from 0.02 to 0.04 assuming migration (mean=0.03) and from 0.04 to 0.18 (mean=0.10) assuming closed populations. Population bottlenecks, inferred from the excess of heterozygosity in relation to allelic diversity, were detected in all four Iberian populations, particularly in those year classes derived from a smaller number of returning adults. However, despite their small size and declining status, Iberian populations continue to displa