Wojciech Solarz

Disentangling the role of environmental and human pressures on biological invasions across Europe

The accelerating rates of international trade, travel, and transport in the latter half of the twentieth century have led to the progressive mixing of biota from across the world and the number of species introduced to new regions continues to increase. The importance of biogeographic, climatic, economic, and demographic factors as drivers of this trend is increasingly being realized but as yet there is no consensus regarding their relative importance. Whereas little may be done to mitigate the effects of geography and climate on invasions, a wider range of options may exist to moderate the impacts of economic and demographic drivers. Here we use the most recent data available from Europe to partition between macroecological, economic, and demographic variables the variation in alien species richness of bryophytes, fungi, vascular plants, terrestrial insects, aquatic invertebrates, fish, amphibians, reptiles, birds, and mammals. Only national wealth and human population density were statistically significant predictors in the majority of models when analyzed jointly with climate, geography, and land cover. The economic and demographic variables reflect the intensity of human activities and integrate the effect of factors that directly determine the outcome of invasion such as propagule pressure, pathways of introduction, eutrophication, and the intensity of anthropogenic disturbance. The strong influence of economic and demographic variables on the levels of invasion by alien species demonstrates that future solutions to the problem of biological invasions at a national scale lie in mitigating the negative environmental consequences of human activities that generate wealth and by promoting more sustainable population growth.

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.

Alien cyanobacteria: an unsolved part of the “expansion and evolution” jigsaw puzzle?

Abstract Some algal species have extended their native range. Problems in settling on a proper definition of ‘alien’ for microorganisms have made it difficult to unequivocally assess whether their spread was natural or resulted from human intervention. As direct evidence seems to be virtually non-existent, the only option is to rely on circumstantial evidence. In this paper, we discuss the expansion routes of three cyanobacteria species: Cylindrospermopsis raciborskii, Raphidiopsis mediterranea and Cuspidothrix issatschenkoi. We analyse the information available for these species, which are commonly regarded as alien, in order to establish the context in which the migration and evolution of these microorganisms should be understood, so that a proper assessment of their geographic expansion can be made. A more complete picture of the expansion and evolution of microorganisms must combine many types of information, including the history of local expansions, ecological ranges, and data from studies in morphology, ecology, genetics and paleolimnology.

Hybridization between native and introduced species of deer in Eastern Europe

Abstract A consequence of introduction of alien species can be hybridization with a closely related native species. Hybridization can have a large effect on the genetic structure and conservation status of native populations. Here, we present a study of hybridization and introgression between native red deer (Cervus elaphus) and introduced sika deer (C. nippon) from 5 regions in Poland, the Kaliningrad District (Russia), and Lithuania. With a set of microsatellite loci and a mitochondrial marker, we uncovered extensive hybridization in all regions despite different population dynamics and no reports of hybrid individuals. We propose that sika populations in Eastern Europe were established with individuals coming from at least 2 different localities in southern Japan and eastern China. Legislation designed to reduce threats posed by sika deer could help to prevent further hybridization.

Territory choice during the breeding tenure of male sedge warblers

A territorial male can shift the location of its territory from year to year in order to increase its quality. The male can base its decision on environmental cues or else on its breeding experiences (when territory shift is caused by breeding failure in previous seasons). We tested these possible mechanisms of territory choice in the sedge warbler (Acrocephalus schoenobaenus), a territorial migrating passerine that occupies wetlands. This species bases its territory choices on an environmental cue: tall wetland vegetation cover. We found that the magnitude of territory quality improvement between seasons (measured as the area of tall wetland vegetation) increased throughout the early stages of a males breeding career as a result of territory shifts dependent on the earliness of arrival. The distance the territory was shifted between seasons depended negatively on the previous years territory quality and, less clearly, on the previous years mating success. On the other hand, previous mating or nesting success had no influence on territory quality improvement between seasons as measured in terms of vegetation. The results imply that tall wetland vegetation is a long-term, effective environmental cue and that a preference for territories in which this type of landcover prevails has evolved into a rigid behavioral mechanism, supplemented by short-term individual experiences of breeding failure.

Low incidence of polygyny revealed in a long term study of the sedge warbler Acrocephalus schoenobaenus in natural wetlands of the S Poland

Abstract. In 1996–2002, 227 breeding attempts were studied in a colour-ringed Sedge Warbler population. Although 11% of males in this population resumed singing in order to mate with another female after their first females had laid eggs, only two polygynous males (i.e. 0.6%) were recorded. This is a very low value in comparison to other studies (ca. 7% on average). The low level of polygyny is attributable to the low food abundance in a natural floodplain, as the nestlings in this population were fed on predominantly small food items. Both polygynous males were recorded in 2002; this year was unusual, because flooding in early June (around the hatching date) destroyed most of the broods. This could have led to an influx of new females into the study area, a change in the operational sex ratio, and new mating opportunities for males.

Developing a framework of minimum standards for the risk assessment of alien species

1. Biological invasions are a threat to biodiversity, society and the economy. There is an urgent need to provide evidence-based assessments of the risks posed by inva-sive alien species (IAS) to prioritize action. Risk assessments underpin IAS policies in many ways: informing legislation; providing justification of restrictions in trade or consumer activities; prioritizing surveillance and rapid response. There are benefits to ensuring consistency in content of IAS risk assessments globally, and this can be achieved by providing a framework of minimum standards as a checklist for quality assurance. 2. From a review of existing risk assessment protocols, and with reference to the r equirements of the EU Regulation on IAS (1143/2014) and international agreements including the World Trade Organisation, Convention on Biological Diversity and International Plant Protection Convention, coupled with consensus methods, we identified and agreed upon 14 minimum standards (attributes) a risk-assessment scheme should include. 3. The agreed minimum standards were as follows: (1) basic species description; (2) likelihood of invasion; (3) distribution, spread and impacts; (4) assessment of intro-duction pathways; (5) assessment of impacts on biodiversity and ecosystems; (6) Assessment of impact on ecosystem services; (7) assessment of socio-economic impacts; (8) consideration of status (threatened or protected) of species or habitat under threat; (9) assessment of effects of future climate change; (10) completion possible even when there is a lack of information; (11) documents information sources; (12) provides a summary in a consistent and interpretable form; (13) includes uncertainty; (14) includes quality assurance. In deriving these minimum standards, gaps in knowledge required for completing risk assessments and the scope of exist-ing risk assessment protocols were revealed, most notably in relation to assessing benefits, socio-economic impacts and impacts on ecosystem services but also inclu-sion of consideration of climate change. 4. Policy implications. We provide a checklist of components that should be within in-vasive alien species risk assessments and recommendations to develop risk assess-ments to meet these proposed minimum standards. Although inspired by implementation of the European Union Regulation on invasive alien species, and as such developed specifically within a European context, the derived framework and minimum standards could be applied globally.

Long-term changes in the species composition and distribution of Bombini (Apidae) in Cracow since the mid 1850s

Abstract Current distribution of bumblebee species in Cracow was studied in 2000–2003 in 23 atlas squares. The results were compared with historical data available for last 150 years, including published materials and museum collections. A total 28 bumblebee species were recorded throughout that period. Among them, 11 species are currently threatened in the study area. There were stated three tendencies among the studied bumblebee species. After 1850, 10 species were strongly regressing (withdrew from the Cracow area altogether or range contraction); further 11 species were more or less stable in their area; the next 6 species were strongly expanding in Cracow. 6 species were stated as a new for Cracow, including 2 species recorded between 1901–1972 and 4 between 1973–2003. Negative population tendencies by the Bombini in the Cracow area were the result of both natural and anthropogenic factors. Species protection and conservation of the most valuable areas as nature reserves are expected to prevent further decrease of bumblebees in the Cracow area.

On the song resumption, polyterritorial behaviour and their population context in the Sedge Warbler Acrocephalus schoenobaenus

Mating tactics in species with facultative polygyny seem to be very flexible and to depend on local environmental conditions. We analysed the habitat and population contexts of territorial behaviour, associated with polygyny, in a population of Sedge Warblers Acrocephalus schoenobaenus inhabiting natural wetlands. Nearly one-third of all breeding males (46 individuals) resumed song after completing their mating with the first female, in order to attract another one. Resuming males were usually the earliest arrivals. There was a continuity in the territorial behaviour between resuming song on first territory and polyterritorial behaviour. Fifty-nine percent of resuming males set up second territories, clearly separated from the first. The second territory was usually located close to the primary female activity area. The quality of the first and second territories were correlated, with second territories being significantly inferior. However, their quality was not significantly different from the territories of non-breeding males. The quality of the second territories was also negatively related to the distance from the first territories. Polyterritorialism was influenced by population numbers: the higher the number of territorial males, the lower the number of second territories settled and the lower their average quality. Although the polygyny frequency in the studied population was very low, polyterritorial males were significantly more likely to be polygynous. We concluded that polygyny frequency can be significantly influenced by population numbers, which might be one of the main factors responsible for the variability in the mating system in this species.

Alien Parasites May Survive Even if Their Original Hosts Do Not.

In their assessment of the role of parasites as drivers and passengers of biological invasions, Blackburn and Ewen (2016) argue that the average success of alien parasites is likely to be lower than for their hosts because they will not become aliens if their hosts fail to establish following arrival to new areas. This is certainly true if the hosts die already during their transport to new areas. However, if they manage to reach them but fail to establish, they still give the parasites they carry a chance to survive. The basic prerequisite of this scenario is spillover of parasites to new local hosts. In order to survive, it would seem that the parasites must find a new host before the original ones die out, but the complex life cycles of some parasites include free-living larvae, eggs, or resting stages that may survive long enough after their alien hosts’ extinction to allow them to find and acclimate to new ones. Some parasites may also be less susceptible to factors that are fatal to their hosts. For instance, internal parasites of warm-blooded tropical taxa may find equally suitable conditions inside new hosts living in cooler climates. The chances for alien parasites may also be higher because the establishment success of some of them is less affected by propagule pressure than it is for their hosts: asexual reproduction is more common among parasites than among their hosts, or male and female parasites may occur in the same host individual. The paucity of supportive examples for these scenarios is due in part to the fact that the chances of finding them are inversely related to the period of time in which the alien hosts managed to survive after introduction, and this time may be too short for their presence to be detected. This holds true particularly if such unsuccessful aliens are introduced unintentionally. The temporary occurrence of such species belonging to understudied taxonomic groups, or introduced in undersampled areas or habitats, is likely to remain unnoticed. When it comes the introductions dating back centuries, our knowledge will remain incomplete even if those introductions were intentional and successful. A spectacular example of an alien parasite’s survival long after its original host had died out is the discovery of the North American liver fluke (Fascioloides magna), recorded in southwestern Poland around 1930 and then in 1953 (Demiaszkiewicz et al. 2015). The parasite was found in the red deer (Cervus elaphus) in an area where the North American wapiti (Cervus canadensis) had been introduced in 1850. As there is no further information on the local wapiti population, they must certainly have died out quickly, so the first record of the parasite they brought in was about 80 years after that failure to establish. It took another 60 years to rediscover F. magna in that same area in 2015 (Demiaszkiewicz et al. 2015). The risk of new parasite invasions may be underestimated even if the transient occurrence of their hosts is well documented, such as in the case of escapes (or releases) of alien companion animals. While records of some of them have become so common that they stopped drawing anyPublished online: May 19, 2016