Michał Kozakiewicz

Influence of a shrub corridor on movements of passerine birds to a lake littoral zone

A pine forest was separated from a lake littoral zone by a meadow on one area (discontinuous) while these habitats were separated by a shrub strip in another area (continuous). This shrub strip acted as an ecological corridor enhancing the movements of birds between the forest and the littoral reed zone. The number of individuals of non-littoral species that visited the reed zone was higher (p < .001) on the area with the connecting shrub strip in autumn but the number of species visiting the littoral zone was not significantly higher. Significantly more (p < .001) autumn movements by birds in the continuous area were oriented along paths between the forest and the littoral zone whereas movements in the discontinuous area paralleled the littoral and forest zones (p < .001). Movements of birds were concentrated along the edge of the shrub strip. The spatial configuration of the landscape facilitated access by some forest birds to the littoral habitat.

Long-distance movements of individuals in a free-living bank vole population: an important element of male breeding strategy

The experiment involved two stages: the first one consisted of studying the dynamics of long-distance movements and the characteristics of moving individuals in a free-living population of bank voles and the second one — of an analysis of paternity of young individuals born to females representing specific breeding colonies (basing on an analysis of six microsatellite fragments). The study has shown that both male and female bank voles are capable of covering long distances of up to almost 1 km. Males moved significantly more frequently than females. The proportion of travelling males was the highest in spring and the lowest in autumn. Almost all moving males were adult and they were sexually active. Almost all moving females were adult, however, the majority of them were sexually inactive. This indicates that the character and causes of long-distance movements of females and males differ. Female movements are supposed to be related to the search for living and breeding grounds by young, already adult individuals, driven out from their mothers’ territory. Multiple paternity occurred in 25% of all litters analysed. Young whose fathers were males from outside of their mother’s breeding colonies occurred in litters throughout the whole breeding season. They made up 59% of all young analysed and in the spring (June) all the young animals were born to fathers originating outside of the female’s breeding colony. The results obtained may confirm the hypothesis that long-distance movements of male bank voles constitute a part of their breeding strategy, involving them in searching for breeding partners over an extensive area.

Anthropopressure gradients and the population genetic structure of Apodemus agrarius

We have attempted to describe the genetic structure and variability of the striped field mouse population inhabiting 17 locations in and around Warsaw, Poland, within a gradient of anthropopressure and discuss the possible factors that could potentially form the observed pattern. Ecological characteristics of the striped field mouse prevent decreases in genetic variability within local urban populations. High population density, ability to cross environmental barriers and to use “green corridors” allows this species to maintain gene flow in fragmented urban landscape. However, genetic variability and gene flow were efficiently reduced in the central part of the city. The results indicated that the degree of human pressure, defined based on the level of vegetation cover, is a good indicator of isolation. In the studied striped field mouse population, genetic interactions among particular locations (local populations) are modified in comparison with populations inhabiting natural areas, by replacement of the isolation-by-distance pattern of differentiation with the “isolation-by-infrastructure” pattern. As indicated by Bayesian analysis, the urban population from the right side of the Vistula river form common genetic cluster with ex-urban population located northward from the city, while the population from the left side of the river probably exchanges genes with neighbouring northern and southern ex-urban populations. However local populations at locations within the highest zone of anthropopressure are clearly isolated, and presently constitute separate genetic units.

The Effects of Urbanization — Small Mammal Communities in a Gradient of Human Pressure in Warsaw City, Poland

ABSTRACT: The aim of this study was to determine the influence of human pressure and spatial structure of landscape on the occurrence of populations of small mammals in the environment of a large urban agglomeration. The investigations were carried out in Warsaw, Poland in 17 locations. The study sites were located on both sides of the Vistula River, of different landscape spatial structure, in various distances from the city center, and were subject to different degrees of human pressure. Part of the city located on the left bank of the Vistula River is more strongly transformed by man than the part located on the right bank of the river. A total of 933 specimens of 8 species of small mammals were caught using the live-trapping method (Catch-Mark-Release). The richest species composition was found at the city borders and in rural areas. On the left side of Vistula, the species diversity was lower than on the right side, showing significant negative correlation with the human pressure degree. Such pattern was not confirmed on the right side of the river. The only species to occur in all sites on the left side of Vistula was the striped field mouse (Apodemus agrarius). On the right side of Vistula, the striped field mouse was accompanied by the yellow-necked mouse (Apodemus flavicollis) in all research sites. The results indicate that the degree of human pressure and spatial isolation are crucial for composition of small mammal community. Less advanced urbanization processes in areas on the right bank of Vistula, as compared to districts on the left side, provide better contact between local populations of small mammals, and offer better living conditions to a large number of species, even in areas located in the center of the city

Long-term dynamics and biodiversity changes in small mammal communities in a mosaic of agricultural and forest habitats

The long-term dynamics of small mammal communities inhabiting a mosaic of agricultural and forest habitats, that is, mixed forest, lakeside alderwood forest and arable land, set aside in the second period of the study, was analysed. No cyclicity was recorded in the numbers of the dominating species, that is, the bank vole (Myodes glareolus) and the yellow-necked mouse (Apodemus flavicollis). Fallowing of the arable land resulted in a decline in diversity and species richness of small mammals in the habitat mosaic under study. The greatest changes were recorded in the community inhabiting a narrow belt of spatially heterogeneous alderwood along the lakeshore. In this community, a considerable increase in the number of yellow-necked mice and a general increase in the dominance of forest species took place. We suggest that the fallowing of extensive arable lands, taking place in Poland for the last two decades, constitute an attractive source of food for small mammals and may lead to a considerable decline in small mammal species diversity within the landscape or even cause local extinctions in some species.

Landscape pattern and genetic structure of a yellow-necked mouse Apodemus flavicollis population in north-eastern Poland

Reduced connectivity among local populations inhabiting a spatially heterogeneous landscape may restrict gene flow and thus contribute to diminished genetic variation within a population. The aim of this study was to determine the role of geographic distance and habitat barriers in developing genetic structure of a yellow-necked mouse Apodemus flavicollis (Melchior, 1834) population, taking into consideration the spatial organization of the landscape. A field study was carried out in two plots located in NE Poland that differed considerably in terms of the scale of habitat fragmentation: (1) a continuous forest complex, and (2) a mosaic of smaller forest habitats. The plots were separated by a water barrier comprised of a chain of lakes. DNA samples from a total of 654 individuals were examined by microsatellite analysis (5 loci). The results showed that the yellow-necked mouse population was characterized by a poorly pronounced genetic structure throughout the study area, although the statistical significance of FST for most location pairs indicated that gene flow in the area was not free. The division of the mouse population into three genetically distinct groups clearly demonstrated the significant role of water bodies as a natural barrier effectively hindering free movement of animals and thus gene flow. Analysis of the genetic structure of the mouse population throughout the study area and also within the distinguished groups indicated that the entire study population may be considered as a single metapopulation. Our results suggest that geographic distance alone is not the predominant factor affecting the genetic structure of population, but in the mosaic landscape the relative isolation of individual forest fragments, and barriers hindering movements of individuals and limiting gene flow among local populations played a much more important role.

Multiple paternity in a wild population of the yellow-necked mouseApodemus flavicollis

Multiple paternity has been described in a wide range of taxonomic groups (eg invertebrates, fish, reptiles, birds, mammals). In rodents, multiple paternity seems to be common and can lead to both genetic (eg increase in offspring diversity, avoiding inbreeding) and direct (eg higher survival rate of the litter) benefits. The primary aim of this study was to confirm multiple paternity and evaluate its frequency in a wild population of yellow-necked mouseApodemus flavicollis (Melchior, 1834). Animals were trapped in north-eastern Poland in 2004–2006. Five microsatellite loci previously described for members of the genusApodemus were used to examine the occurrence of multiple paternity among the offspring of 10 pregnant females. The analyses were performed using multiplex PCR, estimating the length of amplified fragments with an automated sequencer. The presence of additional alleles indicating multiple paternity was found in 30% (3 out of 10) of the investigated litters. Offspring fathered by a single male were predominant in each litter, with the proportion of individuals originating from other males varying from 16.7 to 20% in the three multiple paternity cases. Our findings indicate that the promiscuous mating system may be considered as an alternative breeding strategy in the yellow-necked mouse.

The role of chemical information in shaping the spatial activity of bank voles in a free-living population

A field experiment was carried out in two types of forest environment — a relatively homogenous mixed coniferous forest with low plant species diversity and a reach and spatially differentiated alder wood. Spatial variation in activity of voles was sampled by placing ink pads and paper inside PVC waterpipes laid in a line on the forest floor. In the first stage of the experiment, use of space by bank volesClethrionomys glareolus (Schreber, 1780) was analysed without any bait in track collection tubes. In the second stage, we used an attractant in the form of scent collected from alien bank vole individuals of different sex (males, females), age (juveniles, adults) and physiological state (sexually active and not active). In the coniferous forest the distribution of number of visits in tracking tubes was of aggregated character both before and after providing odour of alien individuals. In the alder wood the aggregation level that had been initially lower than in the coniferous forest increased after providing scent. As a consequence, placing scent of alien individuals resulted in decreasing differences in animal distribution in both habitats. The results allow also to the supposition that the reaction to scent depends on sex, age, and the physiological state of the donor.