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Revealing long-term effects of contaminants on the genetic structure of organisms inhabiting polluted environments should encompass analyses at the population, molecular, and cellular level. Following this concept, we studied the genetic constitution of zebra mussel populations from a polluted (Dp) and reference sites (Cl) at the river Drava, Croatia, and applied microsatellite and DNA damage analyses (Comet assay, micronucleus test (MNT)). Additionally, mussels from both populations were exposed to polluted wastewater in the laboratory for three days, and DNA damage was analyzed to evaluate acclimatization and genetic adaptation of the investigated populations to the polluted environment. The two populations differed in their genetic constitution. Microsatellite analysis suggested that Dp had undergone a genetic bottleneck. Comet assay did not indicate any difference in DNA damage between the two populations, but MNT revealed that Dp had an increased percentage of micronuclei in hemocytes in comparison to Cl. The laboratory experiment revealed that Dp had a lower percentage of tail DNA and a higher percentage of micronuclei than Cl. These differences between populations were possibly caused by an overall decreased fitness of Dp due to genetic drift and by an enhanced DNA repair mechanism due to acclimatization to pollution in the source habitat.

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BACKGROUND: Modern societies depend on environmental sustainability and on new generations of individuals well-trained by environmental research and teaching institutions. In the past, significant contributions to the identification, assessment, and management of chemical stressors with legal consequences have been made. MAIN FEATURES: Within this article, we intend to elucidate the merits and the emerging challenges of chemicals-related environmental sciences. The manuscript is supported by more than 70 professors and university academics of leading institutions in Germany, Switzerland, Austria, and other countries in Europe, but addresses topics of global concern. RESULTS AND DISCUSSION: Many environmental problems of pollutants remain to be addresses, since new chemical compounds or classes of new compounds are continuously developed and brought to the market and sooner or later "emerge" in the environment. Further issues are the inclusion of transformation products and chemical mixtures in environmental risk assessment, the long-term presence of xenobiotics bound to soils and sediments, as well as an understanding of the ecological relevance of ecotoxicological end points. CONCLUSION AND PERSPECTIVES: We point out the need for a strong academic research and education system in chemicals-related environmental sciences to ministries, politicians, and research funding institutions and we propose to create specific units in the national funding bodies that address basic and interdisciplinary research in this field.

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The addition of a novel host plant to a phytophagous insect's diet may result in subsequent host-plant specialisation, and is believed to be a key cause for speciation in this trophic group. In northern Britain, the tephritid fly Tephritis conura has experienced a unique host-plant expansion, from the melancholy thistle Cirsium heterophyllum to the marsh thistle C. palustre. Here, we examine whether the incorporation of C. palustre in the repertoire of British T. conura flies has caused genetic divergence between populations infesting the old host and the novel host, and how British populations differ from populations infesting C. heterophyllum in continental Europe where C. palustre is not infested. No evidence for restricted gene flow among British C. palustre and C. heterophyllum flies was found. Significant differentiation between British and continental T. conura was found at only one allozyme locus, hexokinase, and caused by a new allele, Hex_95. Hexokinase is related to host-race formation in continental European flies infesting C. heterophyllum and C. oleraceum, and might be linked to loci determining host choice. Based on morphological and phenological data from previous studies, we suggest that T. conura in Britain has adapted to the novel host but that host-race formation is impeded by similar plant phenologies.

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We describe the isolation of 11 polymorphic trinucleotide microsatellite loci from the stonefly Arcynopteryx compacta. Loci were highly variable with 3 to 14 alleles (mean = 6.45). Observed heterozygosity ranged from 0 to 0.867. Seven loci showed significant deviation from Hardy-Weinberg equilibrium across both populations. There was no evidence for null alleles, and thus, Hardy-Weinberg departures could have resulted from genetic structure between populations or subpopulations. No linkage between loci was found. The 11 loci should prove highly informative for population genetic studies.

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The thistle-infesting fruit fly Tephritis conura Loew (Diptera: Tephritidae) forms host races on the melancholy thistle, Cirsium hetewphyllum (L.) Hill (Asterales: Asteraceae) and the cabbage thistle, Cirsium olemceum (L.). Scop. Previous research indicates that the host shift occurred from C. hetewphyllum to C. oleraceum. In this paper we address whether the host shift involved physiological adaptations by studying oviposition acceptance and survival of the two host races on the derived host C. oleraceum. Performance differed significantly between host races. T. conura originating from C. oleraceum produced adults in 75% of all egg-laying trials in contrast to only 6.6% in T. conura originating from C. hetewphyllum. Population fitness components measured as a function of life-stage was linear decreasing for T. conura on C. oleraceum but stepwise for T. conura on C. heterophyllum. Low performance of T. conura on C. hetewphyllum was determined by low plant acceptance and high mortality during the larval stage, whereas hatching (at least one larva per batch) and pupae survival were not affected.

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We describe the isolation of ten polymorphic microsatellite loci from the mayfly Ameletus inopinatus. Loci had di- or trinucleotide repeat motifs and were highly variable with three to 17 alleles (mean = 7.15). Observed heterozygosity ranged from 0.143 to 0.905. One locus (Ami_202) showed significant deviation from Hardy-Weinberg equilibrium in one population, but no evidence for null alleles. One locus (Ami_73) was significantly linked with three other loci. The remaining nine loci should prove highly informative for population genetic studies.

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Zebra mussels (Dreissena polymorpha, Pallas, 1771) have had unprecedented success in colonizing European and North American waters under strongly differing temperature regimes. Thus, the mussel is an excellent model of a species which is able to cope with increasing water temperatures expected under global change. We study three principle scenarios for successful survival of the mussel under rising temperatures: (1) no adaptation to future thermal conditions is needed, existing performance is great enough; (2) a shift (adaptation) towards higher temperatures is required; or (3) a broadening of the range of tolerated temperatures (adaptation) is needed. We developed a stochastic individual-based model which describes the demographic growth of D. polymorpha to determine which of the alternative scenarios might enable future survival. It is a day-degree model which is determined by ambient water temperature. Daily temperatures are generated based on long-term data of the River Rhine. Predictions under temperature conditions as recently observed for this river that are made for the phenology of reproduction, the age distribution and the shell length distribution conform with field observations. Our simulations show that temporal patterns in the life cycle of the mussel will be altered under rising temperatures. In all scenarios spawning started earlier in the year and the total reproductive output of a population was dominated by the events later in the spawning period. For maximum temperatures between 20 and 26 degrees C no thermal adaptation of the mussel is required. No extinctions and stable age distributions over generations were observed in scenario 2 for all maximum temperatures studied. In contrast, no population with a fixed range of tolerated temperatures survived in scenario 3 with high maximum temperatures (28, 30, 32 degrees C). Age distributions showed an excess of 0+ individuals which resulted in an extinction of the population for several thermal ranges investigated.

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Host-race evolution is a prime candidate for sympatric speciation because host shifts must take place in the presence of both hosts. However, the geographic context in which the shift takes place may have strong allopatric or peripatric components if the primary host within a localized area is scarce or even goes extinct. Inference of the relative importance of the geographic mode of speciation may be gained from phylogeographic imprints. Here, we investigate the phylogeography of host races of the tephritid fly Tephritis conura from sympatric, parapatric and allopatric populations of Cirsium heterophyllum and Cirsium oleraceum (Asteraceae) in Europe, for addressing the age and direction, and the geographic context of host-race formation. Haplotype networks of the host races differed significantly in molecular diversity and topology. However, host-race haplotypes were nested within the same network, with a central haplotype H1 being the most common haplotype in both host races. C. heterophyllum flies were genetically more diverse and substructured than flies from C. oleraceum, suggesting that the latter is the derived race. The phylogeographic imprint indicates either that C. heterophyllum flies colonized C. oleraceum during range expansion or that heterophyllum flies went extinct in an area where oleraceum flies persisted (followed by re-immigration). These imprints are in concordance with peripatric diversification, probably in the European Alps and related to the last ice age, where the host-race diversification was largely completed before the postglacial range expansion on C. oleraceum to current areas of sympatry and parapatry with C. heterophyllum.

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The distribution of species is limited by their ability to adapt to local environments. For adaptation by selection, genetic variability is crucial. As founder effects reduce genetic variability, extension of species' range borders is usually slow due to the reduced probability of successful colonization. However, the range limit might be extended by incorporating locally adapted genes. In western Palaearctic waterfrogs, interspecies hybrids show hemiclonal gametogenesis, are fertile and reproductively mimic one parental species. Genetic analysis, using allozyme loci, shows that they mediate gene exchange between the two parental species. Selection analysis provides evidence for local adaptation of single locus genotypes. This suggests that hybridogenesis presents a process which increases the number of neoform parental genotypes, exposing these to selection, and thereby revealing locally adapted genotypes which are essential for species range expansion.

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In the present study we investigate a contact zone between two population groups of the tephritid fly Urophora cardui. We investigate scenarios that may have produced the genetic differentiation of the two groups, and we describe the 'rare allele phenomenon' from the contact zone. The rare allele phenomenon refers to alleles that are found at high frequency in contact zones but are rare or lacking outside the contact zone. The phenomenon is often observed in hybrid zones between subspecies of limited reproductive compatibility, but seldom in populations with random mating. Clinal genetic variation was observed at three loci in the contact zone. Three alleles at the locus Aat showed steep clines, between 20-70 km wide. A rare Aat-A allele occurred at high frequency in the centre of the contact zone. Two further loci, Hk and Pgd, showed less steep clinal genetic variation, the transition being in and slightly south of the centre of the Aat cline. Populations showed Hardy-Weinberg proportions and there was no evidence for linkage disequlibrium. These findings suggest random mating and gradual introgression between the population systems, which may originate from at least two range expansions. Aat's steep clines and rare allele may indicate selection on Aat alleles, although we presently can not quantify any agents. Because U. cardui experiences random mating in the contact zone with no apparent 'hybrid' incompatibility, mating experiments offer the possibility for future enquiries about the genetic basis of the rare allele phenomenon.

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Population genetic patterns of species at their range margin have important implications for species conservation. We performed allozyme electrophoresis of 19 loci to investigate patterns of the genetic structure of 17 populations (538 individuals) of the butterfly Polyommatus coridon, a monophagous habitat specialist with a patchy distribution. The butterfly and its larval food plant Hippocrepis comosa reach their northern distribution margin in the study region (southern Lower Saxony, Germany). Butterfly population size increased with host plant population size. The genetic differentiation between populations was low but significant (FST = 0.013). No isolation-by-distance was found. Hierarchical F-statistics revealed significant differentiation between a western and an eastern subregion, separated by a river valley. The combination of genetic and ecological data sets revealed that the expected heterozygosity (mean: 18.5%) decreased with increasing distance to the nearest P. coridon population. The population size of P. coridon and the size of larval food plant population had no effect on the genetic diversity. The genetic diversity of edge populations of P. coridon was reduced compared to populations from the centre of its distribution. This might be explained by (i). an increasing habitat fragmentation towards the edge of the distribution range and/or (ii). a general reduction of genetic variability towards the northern edge of its distribution.

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In order to explore the involvement of terrestrial birds in the ecology of Lyme disease spirochetes, we determined the presence of Borrelia burgdorferi s. I. DNA in tick larvae feeding on the hosts. Birds were caught at several study sites along the Rhine valley in SW Germany between August 1999 and March 2001. A total of 987 Ixodes ricinus larvae were collected from 225 birds belonging to 20 host species. The following four passerine species that have not yet been subject to detailed reservoir competence analyses were investigated: Nightingale (Luscinia megarhynchos), Dunnock (Prunella modularis), Chiffchaff (Phylloscopus collybita) and Reed warbler (Acrocephalus scirpaceus). Borrelia DNA was analysed in attached ticks and for one species, the Nightingale, blood samples were included. Borrelia DNA was amplified by means of the polymerase chain reaction (PCR) targeting the ospA gene of B. burgdorferi s. l. and 1-2 larvae per bird were analysed. On the basis of one larva per individual bird, Borrelia DNA could be detected in six out of nine larval ticks from the Nightingale, in one out of ten ticks from the Dunnock, in three of nine ticks from the Chiffchaff, and in two out of 21 larval ticks from Reed warblers. Five out of nine ticks removed from Robins Erithacus rubecula in winter were found to be Borrelia positive. Blood samples of Nightingales caught during the breeding period were ospA-gene-positive in 71 of 138 birds (51%).

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Since the mid-1980s the zebra mussel, Dreissena polymorpha, Pallas 1771, has become the protagonist of a spectacular freshwater invasion in North America due to its large economic and biological impact. Several genetic studies on American populations have failed to detect any large-scale geographical patterns. In western Europe, where D. polymorpha has been a classical invader from the Pontocaspian since the early 19th century, the situation is strikingly different. Here, we show with genetic markers that two major western European invasion lineages with lowered genetic variability within and among populations can be discriminated. These two invasion lineages correspond with two separate navigable waterways to western Europe. We found a rapid and asymmetrical genetic interchange of the two invasion lines after the construction of the Main-Danube canal in 1992, which interconnected the two waterways across the main watershed.

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Daphnia hyalina and Daphnia cucullata were kept in flow-through chambers in lake water (I), water from mass cultures of D. hyalina (II) and water from mass cultures of D. cucullata (III). A good correlation between body length and clutch size of the Daphnia was found in all cases. The regression lines of the different treatments were compared with respect to different slopes and different intercepts. D. hyalina showed the same reaction to medium II and III, but a lower regression coefficient and higher intercept in medium I. In contrast D. cucullata showed the same reaction to medium I and II, but a higher regression coefficient in medium III.

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Data are presented which make it most probable that selection according to relative visibility (represented by body size and egg ratio) and relative mortality stabilize the coexistence of Daphnia hyalina hyalina Leydig, D. galeata gracilis Hellich and D. cucullata Sars in the prealpine Klostersee. The results are based on multiple and partial correlation analyses which showed positive partial correlation between relative size and/or relative egg ratio and/or relative abundance, and the index of selectivity (W) according to Vanderploeg and Scavia (1979). Further it turned out that besides size, abundance, and egg ratio, the lake temperature but not other environmental parameters are related with the mortality of Daphnia. From these data a verbal descriptive model is derived which explains the seasonal segregation and stable coexistence of the three species.

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1. In the Klostersee in southern Bavaria three species of Daphnia have coexisted for at least several decades: Daphnia hyalina (H), D. galeata (G) and D. cucullata (C). These three species differ in size and compete for food. 2. All three species show marked seasonal fluctuation of abundance, with H and G dominating during spring and late autumn and C dominating during summer. The fluctuations of H and G are stronger correlated than H and C or G and C. 3. The three species are vertically segregated. C preferes the upper strata, H the lower and G the intermediate. This behaviour favours the smaller species C. On the average (from early spring to late autumn), C develops 1.2 times faster than G and 1.5 times faster than H. 4. H and G show higher clutch sizes than C throughout the year. This advantage however is compensated by the higher speed of development of C during thermally stratified seasons. 5. The egg ratio is influenced by both the age structure of the populations and the cluth size of the gravid females. 6. The clutch size depends mainly on the size of the females. The reaction of clutch size to environmental factors follows with a time lag of approximately D (duration of embryonic development). C and G depend more on meteorological influences than H. which is probably related to the vertical distribution. 7. The importance of the differential vertical distribution and the reaction to environmental stress as well as the impact on the size-efficiency hypothesis are discussed.

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A two-instar and a three-instar model for the calculation of birth and death rates is proposed which both use only a minimum of assumptions. It is shown that the proposed approach is a generalization of the methods of Edmondson (1960, 1968), Caswell (1972), and Paloheimo (1974). The validity of the two methods is compared with two-instar and three-instar models according to Edmondson, Caswell and Paloheimo. Since it is impossible to use field data for the comparison, a set of 27 computer simulations was run. From these simulations the "true" and estimated values were obtained. The comparisons showed that it is better to use the new "two-instar" model in an environment with no instarspecific mortality. But it is better to use "three-instar" models when strong instarspecific selection prevails. Among the "three-instar" models the best results are obtained by the method of Paloheimo when predicting birth rates of young and of adults. It proved that the bias produced by the several methods is mainly influenced by the amount of deviation from the situation of steady state.