Soil and changes in vegetation may affect ant assemblages, but the relative importance of each in different habitats is not well characterized. In particular, information on the effects of ecological restoration on arthropods is scarce. It was decided, therefore, to study how reforestation may affect an ant assemblage. Ants were sampled in area that had been reforested and adjacent grassland using pitfall traps. Soil surface and vegetation were characterized. The disturbance of the vegetation caused by reforestation resulted in a decrease in the cover of Stipa tenacissima and Cistaceae and an increase in the cover of pine. The mechanical preparation of the site also resulted in changes in the soil surface, with an increase in the cover of stones and rocks. Ant species richness and abundance were greater at the reforested site than in the grassland and more species showed a positive than a negative response to reforestation. The underlying causes of this pattern are mainly related to changes in vegetation and structure of the soil surface and are associated with the increase in the cover of pine, which most probably provided additional food resources, and the greater cover of stones and rocks that provided more shelter for the ant assemblage., Chema Catarineu, Joaquín Reyes-López, Joan A. Herraiz, Gonzalo G. Barberá., and Obsahuje bibliografii
The Old World ladybird Coccinella septempunctata has rapidly established itself as an abundant, widespread species throughout North America. Overwintering individuals of this species, and of native ladybirds, were collected from early season alfalfa in northern Utah during the period of initial establishment of the invader (1989 to 1999), and were measured for body size. Adult body size can vary widely within insect species, often reflecting differential success of individuals as immatures in obtaining food. Here I examine patterns of ladybird body size to address two questions associated with the establishment of C. septempunctata: (1) is there evidence for adverse impact on native species?, and (2) why has the invader has been so successful in establishment? As an indirect test of adverse competitive effect of the invader on native species, I determined whether mean body size of adults of the five most common native species (Coccinella tranversoguttata, Hippodamia convergens, H. quinquesignata, H. sinuata, and H. tredecimpunctata) declined over the period 1991-1997 as the invader increased rapidly in abundance. No such decline was observed for any of these species, thus providing no evidence that the invader's establishment has significantly increased scramble competition for food among immature ladybirds. I also compared body size distribution of the invading species with that of native species. The invader was distinctive in having particularly large variation in body size among individuals (i.e., in having relatively high proportions of both unusually large and small individuals). Such results are consistent with the hypothesis that the invader's success derives from being a generalist with much "ecological flexibility" in regard to the conditions under which it engages and succeeds in reproduction.
Invasive American mink and native polecats were live-trapped over a period of six years and radio-tracked during one winter-spring season in the lakeside habitats in NE Poland. The number of mink declined whereas number of polecats was stable during 1995–2000, however, except during one winter, mink were always more abundant in the study area than polecats. Significant differences in habitat utilization between radio-collared mink and polecats were observed. Mink moved only along the lake shoreline and showed no seasonal shift in habitat selection. In winter, polecats were most frequently located close to the lake banks, but they also stayed in barns and stables. In spring, they moved further from the lakes. There was considerable interspecies overlap of mink and polecat home ranges in February, and common use of the banks of the 500 m long unfrozen canal was recorded for 4 mink and 5 polecats. The pattern of daily activity of polecat and mink differed: mink were most active at dawn and in early morning whereas polecats at dusk and in beginning of the night. Individuals of both species coexisted in this small area at relatively high densities and to some degree exploited the same habitats, particularly in the vicinity of sites with access to open water.