Michał Żmihorski

Wild bees along an urban gradient: winners and losers

The variability of bee communities along an urban gradient has a potentially strong impact on pollinator-plant interactions. We investigated changes in bee species richness and community composition in the city centre and suburbs of Poznań, Poland. During 2006–2008 we recorded 2,495 individuals from 104 species. The most abundant species was Andrena haemmorhoa. Other abundant species were Bombus pascuorum, Andrena vaga, Andrena nitida, Bombus terrestris. Several species appeared to be more abundant in the city centre whereas others showed an opposite tendency. We have found that the urbanized landscape can act as a filter for the bee community since some specific ecological traits facilitate colonization of the city centre. Small-bodied species that start their activity later in the season and are not solitary preferred the city centre. However, bee species diversity and richness remained stable across the urban gradient indicating some advantages of being a city dwelling bee. We suggest that a city can be a very important habitat for a diverse bee fauna and that conservation of a wide range of habitats of different urbanization levels seems to be the most suitable strategy for conservation of bee diversity in cities.

Reliability assessment of null allele detection: inconsistencies between and within different methods

Microsatellite loci are widely used in population genetic studies, but the presence of null alleles may lead to biased results. Here, we assessed five methods that indirectly detect null alleles and found large inconsistencies among them. Our analysis was based on 20 microsatellite loci genotyped in a natural population of Microtus oeconomus sampled during 8 years, together with 1200 simulated populations without null alleles, but experiencing bottlenecks of varying duration and intensity, and 120 simulated populations with known null alleles. In the natural population, 29% of positive results were consistent between the methods in pairwise comparisons, and in the simulated data set, this proportion was 14%. The positive results were also inconsistent between different years in the natural population. In the null‐allele‐free simulated data set, the number of false positives increased with increased bottleneck intensity and duration. We also found a low concordance in null allele detection between the original simulated populations and their 20% random subsets. In the populations simulated to include null alleles, between 22% and 42% of true null alleles remained undetected, which highlighted that detection errors are not restricted to false positives. None of the evaluated methods clearly outperformed the others when both false‐positive and false‐negative rates were considered. Accepting only the positive results consistent between at least two methods should considerably reduce the false‐positive rate, but this approach may increase the false‐negative rate. Our study demonstrates the need for novel null allele detection methods that could be reliably applied to natural populations.

Muskrat (Ondatra zibethicus) decline after the expansion of American mink (Neovison vison) in Poland

Field survey data in Central Poland revealed that the proportion of sites inhabited by muskrats decreased from 44% to 7% over one decade. This corresponded to the decline in hunting bags of muskrat over the whole of Poland. The largest hunting harvest of muskrat was recorded in 1987/1988 (66,416 individuals), the smallest in 2007/2008 (4,567 individuals). The decline in hunting bags occurred in all regions analysed; however, it was most rapid in the north and north-east. Before the expansion of mink, which started in northern Poland at the beginning of the 1980s, muskrat densities in particular regions depended on the availability of aquatic habitats. A comparison of hunting bags of muskrat and American mink in years 2002–2008 indicated a significant negative correlation between the numbers of these two species harvested in seven regions of Poland. The negative correlation between numbers of muskrat and mink suggests that mink predation is one of the most important factors in the decline of the muskrat population in Poland.

The effect of contrasting management types on two distinct taxonomic groups in a large-scaled windthrow

Improving ways of managing disturbed areas is in urgent need of further research. We assessed the effect of two contrasting management types—salvage logging and set aside for natural regeneration—applied to a large-scale windthrow in NE Poland on two distinct taxonomic groups of animals: scuttle flies and birds. In total, 5,368 individual scuttle flies were trapped and 1,649 individual birds were recorded. In both taxonomic groups, we recorded the “winners and losers” of the effects of salvage logging. The responses of particular species in both groups were independent of their body size. Species diversity, assessed by rarefaction, increased as a result of the logging in birds and declined in scuttle flies. The species richness, corrected for unseen species of scuttle flies and birds, was higher on the managed windthrow when compared to the natural one. Comparison of the results obtained with published data from the intact stands of Białowieża Primeval Forest suggests that salvage logging reduced the similarity of the fly and bird community to those reported from undisturbed, natural forest areas. Our results concern mostly the common species. We conclude that salvage logging has considerable influence on assemblages of common species in the post-disturbance forests. Birds and flies did not respond similarly to salvage logging in term of species diversity, although both groups included species that were attracted to either managed or unmanaged windthrow sites.

The effects of forest patch size and ownership structure on tree stand characteristics in a highly deforested landscape of central Poland.

Forest structure is influenced by the origin, history and manner of forest management. All these aspects may affect the occurrence of many forest dwelling organisms. We investigated the simultaneous impact of forest patch size and ownership structure on selected forest characteristics in central Poland. We sampled stand composition, the DBH of particular tree species, basal area, species number and species diversity in all 32 forest patches found in a farmland-dominated area of 150xa0km2. Forest ownership status was linked to patch size: large patches were state-owned and small ones were private. Ownership status also affected the average DBH and basal area of all tree species pooled, with lower DBH and basal area found in private forests. The share of deciduous trees was negatively affected by forest size, while pine was positively affected, which could suggest that forest management and economic interests may be related to this factor. The share of non-native species was higher in state forests. Our results showed that forest patch size could be associated with its ownership status, which is commonly ignored in research on the relationship between forest size and species occurrence. Historical as well as sociological aspects related to private forests in Poland are also presented.

Nonlinear Distribution Pattern of Hibernating Bats in Caves along an Elevational Gradient in Mountain (Carpathians, Southern Poland)

Background Thermal gradients along changes in elevation in mountainous environments are reflected by different biotas. Although there have been studies of elevation variation in bat assemblages in summer, winter changes in the same gradients remain unknown. Methodology/Principal Findings The objective of this study was to document changes in the species composition of bats hibernating in caves along a temperate elevational gradient. We studied 70 caves between from 300 m to 1,930 m altitude along a slope of the Carpathian Mountains in southern Poland. We recorded changes in bats, including species richness, abundance, altitudinal distribution and dominance during consecutive winters between 2003 and 2009. Similarity of dominance of faunal structure was assessed by using the Bray-Curtis similarity index. We used the generalised additive model and rarefaction to study the variation in species richness, and generalized additive mixed models to examine the effect of abiotic factors on the qualitative and quantitative structure of bat assemblages. During 351 surveys we recorded 13,856 hibernating bats from 15 species. Species richness peaked around mid-elevation (1,100–1,400 m a.s.l.) with richness declining at both higher and lower elevations. Based on the results of a cluster analysis, we could distinguish among four altitudinal zones that differed in species richness and dominance structure. Conclusions/Significance This is the first study documenting changes in species richness and variation of structure of bats hibernating in caves along an elevational gradient. The most surprising and key finding is the fact that changes in the structure of assemblages of hibernating bats along the altitudinal gradient occurred in jumps, forming zones similar to those observed in the vegetation zones. Moreover, species richness and dominance structure of assemblages of hibernating bats in the mountains depended not only on location above sea level, but also on local geomorphologic conditions which strongly affected the microclimate of the caves.