Tomasz Gortat

Use of space by bank voles (Clethrionomys glareolus) in a polish farm landscape

Movements of bank voles (Clethrionomys glareolus) were studied in a farmland mosaic in Poland. Distances crossed by animals in short-time periods are significantly longer in heterogenous than in homogenous habitats. In long-time and large-spatial scales, a significant portion of the animals in a population travel among habitat elements of the mosaic, reducing the degree of isolation of patch populations and decreasing the probability of local extinction.

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

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.