Paweł Olejniczak

The decline of the bumble bees and cuckoo bees (Hymenoptera: Apidae: Bombini) of Western and Central Europe

The bumble and cuckooo bees (Hymenoptera: Apidae: Bombini; Bombus spp. and Psithyrus spp., respectively) are important plant pollinators and any decline in numbers or species constitutes a significant threat both to biological diversity and to whole economies. The distribution, status and factors threatening all 60 known taxa (species and subspecies) of Bombini of 11 countries of Western and Central Europe (Belgium, the Netherlands, Luxembourg, Denmark, Germany, Switzerland, Austria, Czech Republic, Slovakia, Hungary, Poland) were assessed from the beginning of the 20th century. The analysis was based on a literature review, unpublished data, personal communications, our own observations, and an expert review. The IUCN Red List categories were used for assessing the threat of extinction. Eighty per cent of taxa were threatened in at least one country of the region, and 30% of taxa were threatened throughout their range in the countries considered. More species went extinct per country in the second than in the first half of the 20th century, and four taxa went extinct in all 11 countries during 1951–2000. Amongst the factors adversely affecting the Bombini anthropogenic factors (particularly those associated with large-scale farming schemes) appear to be of greater importance than natural factors. To halt population declines and species extinctions it will be necessary to preserve aspects of traditional farming practices and for all Bombini to be afforded legal protection in all countries of the region. The implementation of the European Unions Common Agricultural Policy is likely to have the greatest single impact upon pollinators in the near future.

Costs of reproduction in life history of a perennial plant Carex secalina

We tested a hypothesis based on life history theory that examines reproductive costs incurred by individuals in consecutive years of their life. A multi-year dataset of resource allocation to vegetative and reproductive structures was analysed in Carex secalina — a perennial, monoecious sedge, reproducing only sexually. In a four-year garden experiment, we assessed above-ground biomass at the end of each season and reproductive allocation expressed as the total length of male and female spikes. The study was aimed at determining how size and age of a plant relates to its reproduction, and how the rate of reproduction affects the year-toyear biomass change in Carex secalina. We observed that after each reproductive episode, individuals had significantly smaller sizes and produced a lower number of generative tillers. The total production of reproductive structures decreased significantly with age in all populations. Moreover, the decrease in plant biomass was greater when more reproductive structures were produced in a previous year, which indicates that the plants incur costs of reproduction in terms of above-ground biomass production.

Man-made habitats - hotspots of evolutionary game between grass, fungus and fly.

Man-made habitats - hotspots of evolutionary game between grass, fungus and fly The origin and effects of an evolutionary game between species from three different kingdoms (plants, fungi and animals) are presented. We provide scientific evidence that the interaction discovered in man-made habitats leads to an early stage of coevolution. The grass Puccinellia distans was observed to rapidly spread in new man-made habitats, while at the same time, it was colonised by the fungus Epichloë typhina. The invasion of infected grasses is accompanied by alterations in life histories of both species: P. distans developed features promoting long-distance spreading, whereas E. typhina changed its life cycle by forming sexual structures for the second time, later in the vegetative season. This enables the fungus to make use of the late shoots of the grass for sexual reproduction, even though it cannot be completed because the vector of spermatia necessary for fertilisation, female Botanophila flies, is not present at that time. This indicates that such uncoordinated evolutionary processes had taken place before interactions between organisms became so specialised that it is difficult to presume they were the result of natural selection. Moreover, these processes could have been initiated in man-made habitats that, in particular circumstances, can become coevolutionary hotspots.

The seeds of success: release from fungal attack on seeds may influence the invasiveness of alien Impatiens

Although closely related, Impatiens glandulifera and Impatiens balfourii differ in their invasiveness in Europe; only the former is highly invasive there. Following the assumptions of the enemy release hypothesis (ERH), we tested whether these differences may be explained by the levels of seed infestation by pathogenic fungi. Using seeds collected along the Swiss-Italian border, we recorded four true pathogens of seeds: Fusarium culmorum, F. oxysporum, F. sporotrichoides, and Giberella avenacea. In Italy the seeds of I. balfourii were infected by fungal pathogens more often than those of I. glandulifera, while in Switzerland both species were under the same level of pressure. However, the overall differences in pathogen abundance were consistent with the ERH: seeds of the more invasive species were attacked less. This could be a result of differences between the communities of fungal pathogens attacking the seeds of both species in each country. The number of colonies of secondary pathogens (Cladosporium cladosporioides, Alternaria alternata) correlated negatively with the number of colonies of true pathogens; we suggest that the secondary pathogens may have prevented the occurrence of the true pathogens. The reason for the between-country differences in the fungal pathogen communities is unclear. A possible explanation is that Italy and Switzerland differ in their road and green-area maintenance work schemes, which may have influenced pathogen pressure on seeds. This study is one of the few that offers results indicating that release from enemies may be crucial to the invasion success of plants as early as the seed stage.

Seed size in mountain herbaceous plants changes with elevation in a species-specific manner

Research devoted to investigating the relationship between elevation and seed size in alpine plants gives contradictory results. Some studies document a positive correlation between seed size and elevation, whereas in others a negative correlation is reported. We propose a novel approach to the problem by looking at the whole strategy of seed production, including seed number, and by focusing on a range of environmental variables. In the Tatra Mountains (southern Poland), we selected 73 sites at which seeds of six widely occurring mountain herbaceous species were collected. Each site was characterized by 13 parameters that included climatic and physicochemical soil variables. For each parameter, residuals from a linear regression against elevation were calculated and the residuals were used in a factor analysis. The obtained factors, together with elevation, were used as independent variables in a multiple regression analysis. Elevation affected seed size in four species: in two species the correlation was positive, and in two others it was negative. In three species seed number was related to elevation, and the correlation was negative in all cases. Our results indicate that elevation-dependence of seed production is specific to the species and reflects different resource allocation strategies. Diverse correlations of plant characteristics with elevation may also result from area-specific patterns, because different mountain ranges may exhibit different correlations between elevation and environmental factors. Only by attaining a reproductive allocation perspective and thorough assessment of environmental factors, a full understanding of elevational variation in seed size is possible.

In vitro culture of glochidia of the threatened freshwater mussel Unio crassus Philipsson 1788 – the dilution problem

Abstract We applied in vitro techniques in culturing glochidia of the thick-shelled river mussel Unio crassus, seriously threatened European species. Glochidia were freshly isolated from a gravid female. The sterile phase of the cultures was terminated at different time points to assess the optimal length of this phase. We imitated the process of juvenile excision from a fish host by diluting the culture with water at regular time intervals. The metamorphosed juveniles that survived until the end of the experiment and started growing their shells were observed for 24–27 days from the start of the culture in samples diluted for the first time between days 13 and 17. Long-lasting cultures usually became infected and died, whereas in those that were terminated too early, glochidia were unable to develop further in clean water. The transfer of juveniles from an artificial medium to pure water should be done gradually, through a series of dilutions, so that the larvae have the opportunity to feed on the diluted medium after metamorphosis. Only individuals with an active foot capable of operating outside the shell were ready to inhabit water and forage on solid food from the external environment.