Roads and highways represent one of the most important anthropogenic impacts on natural areas and contribute to habitat fragmentation, because they are linear features that can inhibit animal movement, thereby causing barrier effects by subdividing the populations adjacent to the roads. The study presented here aims to determine, to which extent roads act as a barrier, subdividing populations of three species of small forest mammals: bank vole, yellow-necked mouse and common shrew, and what is the relative importance of road width and traffic intensity on the barrier effect. The study was carried out at four 25 m long segments of roads, close to the city of České Budějovice. All segments crossed a forest. The capture-recapture method was applied to determine the crossing rates of animals. The traps were checked three times each day during four consecutive nights, in summer and in autumn. We found that: (1) roads strongly prevent crossing movements in all three studied species, (2) there are interspecific differences in road crossing rates, (3) species cross more often narrow than wide roads, (4) traffic intensity does not affect the crossing rates.
I review the effects of habitat fragmentation on carabid beetles (Coleoptera, Carabidae) and examine whether the taxon could be used as an indicator of fragmentation. Related to this, I study the conservation needs of carabids. The reviewed studies showed that habitat fragmentation affects carabid assemblages. Many species that require habitat types found in interiors of fragments are threatened by fragmentation. On the other hand, the species composition of small fragments of habitat (up to a few hectares) is often altered by species invading from the surroundings. Recommendations for mitigating these adverse effects include maintenance of large habitat patches and connections between them. Furthermore, landscape homogenisation should be avoided by maintaining heterogeneity of habitat types. It appears that at least in the Northern Hemisphere there is enough data about carabids for them to be fruitfully used to signal changes in land use practices. Many carabid species have been classified as threatened. Maintenance of the red-listed carabids in the landscape requires species-specific or assemblage-specific measures.
Which factors influence the occurrence, population size and density of species in fragmented habitat patches are key questions in population and conservation ecology. Metapopulation theory predicts that larger and less isolated habitat patches should positively influence species occurrence and population size. However, recent studies have shown that habitat quality, human activity and permeability of the landscape surrounding habitat patches may be also important. In this paper we test the relative effects of habitat patch characteristics, human settlement and landscape permeability on the occurrence, local population size and density of the Chalk-hill Blue Polyommatus coridon a charismatic butterfly inhabiting calcareous grasslands in a fragmented landscape in southern Poland. Patch occupancy rate (corrected for the butterfly detection probability) was 0.45. Habitat patch area, proximity of human settlement and cover of larval food plants positively affected occurrence of the Chalk-hill Blue. Local population size of the Chalk-hill Blue was positively affected by patch area and proximity of human settlement, and negatively by patch isolation. Local density was higher in patches located close to human settlement. Our study is one of the few showing a positive effect of human settlement on a grassland specialist butterfly although the mechanism hidden behind this phenomenon is unknown and requires further examination. In order to maintain local populations of the Chalk-hill Blue in southern Poland, conservation action should be focused on large, closely connected calcareous grasslands. Moreover, extensive management of this habitat should be maintained by local inhabitants who are better placed to undertake such work. and Zuzanna M. ROSIN, Piotr SKÓRKA, Magdalena LENDA, Dawid MORON, Tim H. SPARKS, Piotr TRYJANOWSKI.
Infrastructure is one of the main causes of landscape fragmentation, which results in isolation and loss of populations. Although the negative effect of roads on insects is well documented, only a minority of studies has focused on roads in the context of barriers to dispersal. Flying species in particular have been neglected. We investigated the effect of a four-lane motorway as a barrier to the movement of an isolated population of the threatened dragonfly Sympetrum depressiusculum in an agricultural landscape in Central Europe. Generalized additive models were used to assess the motorway's effect on (i) the distribution of adult dragonflies in patches of terrestrial habitat surrounding their natal site, and (ii) individual flight behaviour (i.e. willingness or unwillingness to cross the motorway). Movement patterns of marked adults throughout the landscape were also investigated. During one season, significantly fewer adults were found at patches located on the far side of the motorway, indicating it has a barrier effect. Observations on flight behaviour revealed no apparent effect of the motorway. The possible barrier effect for the species studied was therefore presumed to be a consequence of road mortality. Our results indicate that the motorway may influence the dispersal of this threatened species of dragonfly, which is a habitat specialist with particular requirements for its terrestrial environment. Negative effects on other species with similar behaviour and strategy can be presumed. When establishing new habitats, carrying out reintroductions or translocations, it is necessary to consider that roadways may reduce population size and affect population dynamics by limiting dispersal., Hana Šigutová, Filip Harabiš, Michal Hykel, Aleš Dolný., and Obsahuje bibliografii
We studied movement and abundance of barbel, Barbus barbus , over three years (October 1995 to September 1998) in two stretches (Woolmer’s Park, Holwell Bridge) of a section of the River Lee (Hertfordshire, England) delimitated by water retention structures. Of 349 tagged individuals (168 at Woolmer’s Park; 181 at Holwell Bridge), 51.8 % and 13.3 % respectively were recaptured at least once, with a much higher rate of multiple recaptures at Woolmer’s Park, where monitoring of movements was over a longer period, than at Holwell Bridge, where too few recaptures were made for further movement analysis. At Woolmer’s Park, 77.1 % of the barbel showed limited (i.e. resident component) and the rest greater between- capture movements (i.e. mobile component). There was no preferential directional movement across size classes. Based on the available recapture data, population size (estimated through a Bayesian method) first increased moderately (1995–96) and then sharply (1996–97) at Woolmer’s Park, and even further later at Holwell Bridge (1998–99). This may reflect a recovery phase in the local population, or possibly a rising part of a cyclic recruitment pattern, such as reported for barbel elsewhere and for other cyprinids in the UK. Habitat enhancement is recommended over stocking, given the adequate abundance of barbel in areas with suitable habitat. However, it remains unclear whether fencing-off of the banks from livestock will enhance 0+ barbel numbers, which appear to be low relative to some European rivers of similar width and depth.
Higher nest predation at habitat edges is a major problem for conservation biology. We studied nest predation using artificial nests resembling great reed warblers’ nests at edges and interiors of reedbeds in four large wetlands in Europe: Lake Hornborga (Sweden), Lake Neusiedl (Austria), Lake Velence (Central-Hungary) and Kis-Balaton marshland (West-Hungary). Nest losses showed great local and temporal variation, and in general there was larger nest predation at the edges than in the interior reedbeds. Predation rates of artificial nests along different reedbed edges showed great variation. In contrast, predation rates of interiors were more similar across all experiments, with less variation. This may indicate the existence of a habitat-specific predation rate with less variation in interiors of large habitats, while edges are more exposed to the influences of other factors, which resulted in higher variation of predation rates among study sites. Therefore, reedbed conservation should prefer large stands if considering only passerine nest predation, because (1) nest survival seems to be higher in interior than at edges, and (2) because interiors are less variable, i.e. more stable than edges. The designation of reedbeds cannot rely on reedbed edges, where predation can change due to factors not related to the reed habitat at all.
Landscapes are constantly changing and, for plant species, this means that some suitable patches disappear while others emerge. Distribution of species in the landscape depends, therefore, not only on actual distribution of suitable habitat patches but also on a species’ ability to persist in habitats that are already unsuitable and disperse to habitats that have become suitable. Distribution of species in such landscapes thus strongly depends on the spatio-temporal structure of the landscape and species traits. The present study aims to determine to what degree past land use affects the present distribution of dry grassland plant species at a regional scale. We studied the distribution of 52 dry grassland species in 215 grassland patches. Data on bedrock, slope, potential irradiation, area and past land use for two periods (1950s and 1980s) were collected from maps. Multivariate analysis was performed to assess the relative contribution of environmental and historical factors on present species distribution. In addition, analyses were carried out to reveal the relationship between past land use and occurrence of single species. This study shows that dry grasslands are habitats with rapid land-use changes. Distribution of species in these habitats is largely determined by environmental conditions, but past land-use also has a significant effect. In many species, the effect of past land use is even more important than the effect of environmental conditions. For the species investigated, those restricted both to former pastures and fields could be identified. Only a minority of species are restricted to continuous grasslands. This indicates that many species colonized places cultivated in 1950 within 50 years, suggesting that the dynamics of these species is relatively fast. The results suggest that many dry grassland communities in the region are of recent origin and the distribution of species in these habitats is partly determined by past land use. In addition to information on environmental conditions, detailed knowledge of land use history, landscape structure and species attributes is needed in order to understand the distribution of species in dry grassland communities.