No abstract

Animal dispersal and subsequent settlement is a key process in the life history of many organisms, when individuals use demographic and environmental cues to target post-dispersal habitats where fitness will be highest. To investigate the hypothesis that environmental disturbance (habitat fragmentation) may alter these cues, we compared dispersal patterns of 60 red squirrels (Sciurus vulgaris) in three study sites that differ in habitat composition and fragmentation. We determined dispersal distances, pre-and post-dispersal habitat types and survival using a combination of capture-mark-recapture, radiotracking and genetic parentage assignment. Most (75%) squirrels emigrated from the natal home range with mean dispersal distance of 1,014 ± 925 m (range 51-4,118 m). There were no sex-related differences in dispersal patterns and no differences in average dispersal distance, and the proportion of dispersers did not differ between sites. In one of the sites, dispersers settled in patches where density was lower than in the natal patch. In the least fragmented site, 90% of animals settled in the natal habitat type (habitat cuing) against 44-54% in the more strongly fragmented sites. Overall, more squirrels settled in the natal habitat type than expected based on habitat availability, but this was mainly due to individuals remaining within the natal wood. In the highly fragmented landscape, habitat cuing among emigrants did not occur more frequently than expected. We concluded that increased habitat fragmentation seemed to reduce reliable cues for habitat choice, but that dispersing squirrels settled in patches with lower densities of same-sex animals than at the natal home range or patch, independent of degree of fragmentation.

We studied population dynamics of red squirrels in a group of small forest fragments, that cover only 6.5% of the total study area (4664 ha) and where distances to the nearest source population were up to 2.2 km. We tested effects of patch size, quality and isolation and supplementary feeding on patch occupation during 1995–99. Larger patches and patches with supplementary feeding had a higher probability of being occupied. No patch <3.5 ha was ever occupied. No effects of isolation were found, suggesting that the forest habitat in the study area is not sufficiently fragmented to influence red squirrel distribution across patches. For medium sized patches (3.7–21 ha), that were occupied some years, there was an increase in patch occupation over the years, even though overall population size tended to decrease. These patches had a high turnover, especially of males. Patches in which the squirrel population went extinct were recolonized within a year. For patches that were at least some years occupied, squirrel density depended on patch quality only. No effects of patch size, isolation and winter temperature on population density were found. These data suggest that in our study area habitat fragmentation has no effect on local squirrel density and that the random sample hypothesis explains the distribution pattern across patches.

No abstract

Robust identification of species and significant evolutionary units (ESUs) is essential to implement appropriate conservation strategies for endangered species. However, definitions of species or ESUs are numerous and sometimes controversial, which might lead to biased conclusions, with serious consequences for the management of endangered species. The hazel dormouse, an arboreal rodent of conservation concern throughout Europe is an ideal model species to investigate the relevance of species identification for conservation purposes. This species is a member of the Gliridae family, which is protected in Europe and seriously threatened in the northern part of its range. We assessed the extent of genetic subdivision in the hazel dormouse by sequencing one mitochondrial gene (cytb) and two nuclear genes (BFIBR, APOB) and genotyping 10 autosomal microsatellites. These data were analysed using a combination of phylogenetic analyses and species delimitation methods. Multilocus analyses revealed the presence of two genetically distinct lineages (approximately 11 % cytb genetic divergence, no nuclear alleles shared) for the hazel dormouse in Europe, which presumably diverged during the Late Miocene. The phylogenetic patterns suggests that Muscardinus avellanarius populations could be split into two cryptic species respectively distributed in western and central-eastern Europe and Accession numbers are available at the ''European Nucleotide Archive'' browser at the address http://www.ebi.ac.uk/ena/data/view/ LT614830-LT614893 and in Supplementary Anatolia. However, the comparison of several species definitions and methods estimated the number of species between 1 and 10. Our results revealed the difficulty in choosing and applying an appropriate criterion and markers to identify species and highlight the fact that consensus guidelines are essential for species delimitation in the future. In addition, this study contributes to a better knowledge about the evolutionary history of the species.