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The environmental impact of climate change is meanwhile not only discussed in the scientific community but also in the general public. However, little is known about the interaction between climate change and pollutants like pesticides. A combination of multiple stressors (e.g. temperature, pollutants, predators) may lead to severe alterations for organisms such as changes in time of reproduction, reproductive success and growth performance, mortality and geographic distribution. The questions if aquatic organisms tend to react more sensitive towards incidents under climate change conditions remains. Therefore, within the present thesis the aquatic ecotoxicological profile of the fungicide pyrimethanil, as an exemplarily anthropogenic used contaminant, was examined.
A large test battery of ecotoxicological standard tests and supplement bioassays with non-model species was conducted to investigate if species-specific or life stage-specific differences occur or if temperature alteration may change the impact of the fungicide. Two of the most sensitive species (Chironomus riparius and Daphnia magna) were used to investigate the acute and chronic thermal dependence of pyrimethanil effects. The results clearly depict that the ecotoxicity of pyrimethanil at optimal thermal conditions did not depend on the trophic level, but was species-specific. With regard to EC10 values the acute pyrimethanil toxicity on C. riparius increased with higher temperature (6.78 mg L-1 at 14°C and 3.06 mg L-1 at 26°C). The chronic response of D. magna to the NOEC (no observed effect concentration) of the fungicide (0.5 mg L-1) was examined in an experiment which lasted for several generations under three simulated near-natural temperature regimes (‘cold year, today’ (11 to 22.7°C), ‘warm year, today’ (14 to 25.2°C) and ‘warm year, 2080’ (16.5 to 28.1°C)). A pyrimethanil-induced mortality increase was buffered by the strongly related increase of the general reproductive capacity, while population growth was stronger influenced by temperature than by the fungicide. At a further pyrimethanil concentration (LOEC – lowest observed effect concentration: 1 mg L-1), a second generation could not be established by D. magna under all thermal regimes.
Besides daphnids, the midge C. riparius was used for a second multigeneration study. In a bifactorial test design it was tested if climate change conditions alter or affect the impact of a low fungicide concentration on life history and genetic diversity. The NOAEC/2 (half of the no observed adverse effect concentration derived from a standard toxicity test) was used as a low pyrimethanil concentration to which laboratory populations of the midges were chronically exposed under the mentioned temperature scenarios. During the 140-day-multigeneration study, survival, emergence, reproduction, population growth, and genetic diversity of C. riparius were analyzed. The results reveal that high temperatures and pyrimethanil act synergistically on life history parameters of C. riparius. In simulated present-day scenarios, a NOAEC/2 of pyrimethanil provoked only slight to moderate beneficial or adverse effects. In contrast, an exposure to a NOAEC/2 concentration of pyrimethanil at a thermal situation likely for a summer under the future expactations uncovered adverse effects on mortality and population growth rate. In addition, genetic diversity was considerably reduced by pyrimethanil in the ‘warm year, 2080’ scenario, but only slightly under current climatic conditions. The multigeneration studies under near-natural thermal conditions indicate that not only the impact of climate change, but also low concentrations of pesticides may pose a reasonable risk for aquatic invertebrates in the future. This clearly shows that thermal and multigenerational effects should be considered when appraising the ecotoxicity of pesticides and assessing their future risk for the environment.
In addition to temperature further multiple abiotic and biotic stressors alterate pollutant effects. Moreover, to better discriminate and understand the intrinsic and environmental correlates of changing aquatic ecosystems, it was experimentally unraveled how the effects of a low-dose of pyrimethanil on daphnids becomes modified by different temperatures (15°C, 20°C, 25°C) and in the presence/ absence of predator kairomones of Chaoborus flavicans larvae. The usage of a fractional multifactorial test design provided the possibility to investigate the individual growth, reproduction and population growth rate of Daphnia pulex via different exposure routes to the fungicide pyrimethanil at an environmentally relevant concentration (0.05 mg L-1) - either directly (via the water phase), indirectly (via algae food), dually (via water and food) or for multiple generations (fungicide treated source population).
The number of neonates increased with increasing temperatures. At a temperature of 25°C no significant differences between the individual treatment groups were observed although the growth was overall inhibited due to pyrimethanil. Besides, at 15 and 20°C it is obvious that daphnids which were fed with contaminated algae had the lowest reproduction and growth rate. The obtained results clearly demonstrate that multiple stress factors can modify the response of daphnids to pollutants. The exposure routes of the contaminant are of minor importance, while temperature and the presence of a predator are the dominant factors impacting the reproduction of D. pulex. It can be concluded that low concentrations of pyrimethanil may disturb the zooplankton community at suboptimal temperature conditions, but the effects will become masked if chaoborid larvae are present. Therefore it seems necessary to observe prospectively if the combination of several stress factors like pesticide exposure and suboptimal temperature may influence the life history and sensitivity of several aquatic invertebrates differently.
Besides standard test organisms it is inevitable to conduct test with aquatic invertebrate which are not yet considered regularly in ecotoxicological experiments. For example molluscs represent one of the largest phyla of macroinvertebrates with more than 100.000 species, being ecologically and economically important. Therefore, within the present study embryo, juvenile, half- and full-life cycle toxicity tests with the snail Physella acuta were performed to investigate the impact of pollutants on various life stages. Different concentrations of pyrimethanil (0.06-0.5 or 1.0 mg L-1) assessed at three temperatures (15°C, 20°C, 25°C) revealed that pyrimethanil caused concentration-dependent effects independent of temperature. Interestingly, the ecotoxicity of pyrimethanil was higher at lower temperature for the embryo hatching and F1 reproduction, but its ecotoxicity for the growth of juveniles and the F0 reproduction increased with increasing temperature. More specifically, it could have been observed that especially during the reproduction test high mortality rates occurred at the highest concentration of 1 mg L-1 at all temperatures. Due to high mortality rates no snails were available for the F1 at the highest concentrations (0.5 and 1.0 mg L-1). Compared to the F0, overall more egg masses were produced in the F1, being all fertile and no mortality occurred. For the F1-generation the strongest pyrimethanil effects were detected at 15°C. A comparison of effect concentrations between both generations showed that the F1 is more sensitive than the F0.
These results indicate that an exposure over more than one generation may give a better overview of the impact of xenobiotics. With the establishment of an embryo and reproduction test under different temperatures and various concentrations of pyrimethanil with P. acuta we could successfully show that molluscs can respond more sensitive than model organisms and that both, chemical and thermal stressor strongly influence the behaviour of the pulmonates. It can be concluded that the high susceptibility for the fungicide observed in gastropods clearly demonstrates the complexity of pesticide-temperature interactions and the challenge to draw conclusions for the ecotoxicological risk assessment of pesticides under the impact of global climate change.
Highlights
• Genomes for all five Natrix species, two represented by two distinct subspecies each, were sequenced.
• Two genomes were de-novo assembled to their 1.7 Gb length with a contig N50 of 4.6 Mbp and 1.5 Mbp.
• Evidence for interspecific hybridization, both between allopatric and widely sympatric species.
• Fossil-calibrated molecular clock using genomes indicates that species are ancient several million-year-old lineages.
• Our findings imply that speciation took place despite continued gene flow.
Abstract
Understanding speciation is one of the cornerstones of biological diversity research. Currently, speciation is often understood as a continuous process of divergence that continues until genetic or other incompatibilities minimize or prevent interbreeding. The Palearctic snake genus Natrix is an ideal group to study speciation, as it comprises taxa representing distinct stages of the speciation process, ranging from widely interbreeding parapatric taxa through parapatric species with very limited gene flow in narrow hybrid zones to widely sympatric species. To understand the evolution of reproductive isolation through time, we have sequenced the genomes of all five species within this genus and two additional subspecies. We used both long-read and short-read methods to sequence and de-novo-assemble two high-quality genomes (Natrix h. helvetica, Natrix n. natrix) to their 1.7 Gb length with a contig N50 of 4.6 Mbp and 1.5 Mbp, respectively, and used these as references to assemble the remaining short-read-based genomes. Our phylogenomic analyses yielded a well-supported dated phylogeny and evidence for a surprisingly complex history of interspecific gene flow, including between widely sympatric species. Furthermore, evidence for gene flow was also found for currently allopatric species pairs. Genetic exchange among these well-defined, distinct, and several million-year-old reptile species emphasizes that speciation and maintenance of species distinctness can occur despite continued genetic exchange.
Previous studies detected an influence of urban characteristics on song traits in passerine birds, that is, song adjustments to ambient noise in urban areas. Several studies already described the effect of weather conditions on the behavior of birds, but not the effect on song traits. We investigate, if song trait variability changes along a continuous urbanity gradient in Frankfurt am Main, Germany. We examined, for the first time on a larger scale, the influence of weather on song parameters. We made song recordings of three common passerine species: the blue and great tit (Cyanistes caeruleus (Linnaeus, 1758) and Parus major Linnaeus, 1758) and the European blackbird (Turdus merula Linnaeus, 1758). We measured different song traits and performed statistical analyses and modeling on a variety of variables—among them urbanity and weather parameters. Remarkably, we found only few cases of a significant influence of urbanity parameters on song traits. The influence of weather parameters (air pressure, atmospheric humidity, air and soil temperatures) on song traits was highly significant. Birds in Frankfurt face high noise pollution and might show different adaptations to high noise levels. The song trait variability of the investigated species is affected more by weather conditions than by urban characteristics in Frankfurt. However, the three species react differently to specific weather parameters. Smaller species seem to be more affected by weather than larger species.
Savannas are the most important timber and non-timber forest products (NTFPs) providing ecosystems in West Africa. They have been shaped by traditional human land-use (i.e. agriculture, grazing, and harvesting) for thousands of years. In the last decades, land-use has drastically changed due to the rapid population growth and the growing production of cash-crop in West Africa and this process is still continuing. The percentage of land intensively used for agriculture has increased, while the length of fallow periods has decreased. Such changes have enormous ecological, economic, and social consequences. In the context of land-use changes, there is an urgent need to better understand and evaluate the impact of land-use on savannas. Such an understanding provides insights on appropriate management activities that ensure the maintenance of savannas and guarantee the availability of savanna products for subsistence and commercial use of rural West African people.
The major objective of the present thesis was to study the impact of land-use on savanna vegetation and diversity as well as on populations of two important NTFP-providing tree species in a semi-arid area in West Africa. The study area was located in the south-eastern part of Burkina Faso and comprised the protected W National Park and its adjacent communal area.
In the first study (chapter 2), I investigated in cooperation with a colleague from Burkina Faso (Blandine Nacoulma) the impact of land-use on the savanna vegetation. We analyzed which environmental factors determine the occurrence of the vegetation types and investigated the effect of land-use on vegetation structure and the occurrence of life forms and highly valued tree species. Furthermore, we tested whether land-use has an impact on plant diversity pattern and if this impact differed between the vegetation types and layers (woody and herb layer). Vegetation relevés were performed and the vegetation and plant diversity of the protected W National Park were compared with those of its surrounding communal area. Our results reveal five vegetation types occurring in both areas. Elevation and physical soil characteristics and thus soil water availability for plants played the most important role for the occurrence of the vegetation types. The influence of land-use on plant diversity differed between the five vegetation types and the two layers. The impact was highest on the vegetation types with the most favorable soil conditions for cultivation and lowest on rocky habitats with poor soils. While the diversity of the woody layer was increased under human land-use, the diversity of the herb layer was diminished. Overall, as land-use effects were not only negative, our findings suggest that land-use does not automatically lead to a loss of plant species and to a degradation of savanna habitats. We conclude that both protected and communal areas are of great importance for the conservation of savanna vegetation and diversity. Our study highlights furthermore the importance of different management strategies for each vegetation type.
In the following two studies (chapter 3 and 4), the impact of land-use - and in particular of harvesting - on populations of Adansonia digitata L., the baobab tree, and Anogeissus leiocarpa (DC.) Guill. & Perr. was examined. These two tree species were chosen as they provide several NTFPs for the local population and as they show different levels of human protection and opposed life histories. Thus, they may react differently to land-use. Stands of the protected W National Park were compared with those of its surrounding communal area (in fallows, croplands, and villages). I applied dendrometric methods to study the population structures and combined it with rates and patterns of NTFP-harvesting (debarking and chopping/pruning). Furthermore, the impact of land-use and harvesting on the fruit production of A. digitata and on the sprouting ability of A. leiocarpa were studied. The inverse J-shaped size class distribution curve indicates that the stands of A. digitata were in a healthy state in the park, while the low number of smaller size classes in fallows, croplands, and villages may give evidence of an ageing population. However, a high number of seedlings were recorded in villages. The stands of A. leiocarpa were also in healthy states in the park and likewise in fallows. In contrast, the absence of saplings gives evidence of a declining population in croplands. Both species were strongly harvested by local people and harvesting was tree size-specific. Pruning in interaction with tree-size had a significant impact on fruit production of A. digitata. While smaller trees were more vulnerable to pruning, bigger trees benefited from slight-pruning. A. leiocarpa had a great ability to respond to chopping by sprouting. The sprouting ability increased even with higher chopping intensity. Results suggest that despite the intense harvesting and the land-use impact, populations of both species are still well preserved. While A. digitata can withstand the harvesting and land-use pressure by its longevity, extremely low adult mortality rates, and particularly due to positive human influences, A. leiocarpa is able to withstand the use pressure by its fast growing, high recruitment, and high sprouting ability. I conclude that a none protected tree species (A. leiocarpa) might not necessarily be at higher risk to the harvesting and land-use impact than a protected tree species (A. digitata) as the adverse impact of harvesting and land-use can be compensated by its specific life history.
Important additional information to such ecological findings can be provided by local people. Learning from traditional knowledge and management systems of local people will help to produce culturally and ecologically reasonable conservation and management strategies. Thus, I investigated local uses and management strategies of A. digitata and A. leiocarpa in the last two studies (chapter 5 and 6). Quantitative ethnobotanical surveys among the Gulimanceba people were conducted in the communal area in order to document uses of the different plant parts, harvesting modes, perceptions about the population status, and conservation status of both species. Hereby, differences in knowledge between gender, generations, and people from different villages were tested. Interviews reveal that both species are harvested for multipurpose and emphasize the high importance of both species for local people. Especially the leaves and fruits of A. digitata add valuable minerals and vitamins to the otherwise micronutrient-“poor” staple crops of the Gulimanceba people. In comparison with other studies in West Africa, it has turned out that people in this area could benefit even more from A. leiocarpa, e.g. for dyeing of clothes, for treatment of malaria and skin problems. Local knowledge did not differ between genders and generations, while it slightly differed between people from different villages. The lack of age differences suggests that the traditional knowledge about these two species is passed on from one generation to another. Differences between people from different villages might be explained by influences from the neighboring countries Niger and Benin. Current local harvesting modes and management strategies of both species resulted in sustainable use. However, ongoing land-use intensifications require adapted harvesting and management techniques to guarantee the persistence of these economically important species. These results provide, in combination with the ecological findings (chapter 3 and 4), appropriate management recommendations for A. digitata and A. leiocarpa that are reliable under currently practiced management strategies.
Background: Leaf venation traits are important for many research fields such as systematics and evolutionary biology, plant physiology, climate change, and paleoecology. In spite of an increasing demand for vein trait data, studies are often still data-limited because the development of methods that allow rapid generation of large sets of vein data has lagged behind. Recently, non-destructive X-ray technology has proven useful as an alternative to traditional slow and destructive chemical-based methods. Non-destructive techniques more readily allow the use of herbarium specimens, which provide an invaluable but underexploited resource of vein data and related environmental information. The utility of 2D X-ray technology and microfocus X-ray computed tomography, however, has been compromised by insufficient image resolution. Here, we advanced X-ray technology by increasing image resolution and throughput without the application of contrast agents.
Results: For 2D contact microradiography, we developed a method which allowed us to achieve image resolutions of up to 7 µm, i.e. a 3.6-fold increase compared to the industrial standard (25 µm resolution). Vein tracing was further optimized with our image processing standards that were specifically adjusted for different types of leaf structure and the needs of higher imaging throughput. Based on a test dataset, in 91% of the samples the 7 µm approach led to a significant improvement in estimations of minor vein density compared to the industrial standard. Using microfocus X-ray computed tomography, very high-resolution images were obtained from a virtual 3D–2D transformation process, which was superior to that of 3D images.
Conclusions: Our 2D X-ray method with a significantly improved resolution advances rapid non-destructive bulk scanning at a quality that in many cases is sufficient to determine key venation traits. Together with our high-resolution microfocus X-ray computed tomography method, both non-destructive approaches will help in vein trait data mining from museum collections, which provide an underexploited resource of historical and recent data on environmental and evolutionary change. In spite of the significant increase in effective image resolution, a combination of high-throughput and full visibility of the vein network (including the smallest veins and their connectivity) remains challenging, however.
Plastid DNA sequence data have been traditionally widely used in plant phylogenetics because of the high copy number of plastids, their uniparental inheritance, and the blend of coding and non-coding regions with divergent substitution rates that allow the reconstruction of phylogenetic relationships at different taxonomic ranks. In the present study, we evaluate the utility of the plastome for the reconstruction of phylogenetic relationships in the pantropical plant family Ochnaceae (Malpighiales). We used the off-target sequence read fraction of a targeted sequencing study (targeting nuclear loci only) to recover more than 100 kb of the plastid genome from the majority of the more than 200 species of Ochnaceae and all but two genera using de novo and reference-based assembly strategies. Most of the recalcitrant nodes in the family’s backbone were resolved by our plastome-based phylogenetic inference, corroborating the most recent classification system of Ochnaceae and findings from a phylogenomic study based on nuclear loci. Nonetheless, the phylogenetic relationships within the major clades of tribe Ochnineae, which comprise about two thirds of the family’s species diversity, received mostly low support. Generally, the phylogenetic resolution was lowest at the infrageneric level. Overall there was little phylogenetic conflict compared to a recent analysis of nuclear loci. Effects of taxon sampling were invoked as the most likely reason for some of the few well-supported discords. Our study demonstrates the utility of the off-target fraction of a target enrichment study for assembling near-complete plastid genomes for a large proportion of samples.
Ochnaceae is a pantropical family with multiple transoceanic disjunctions at deep and shallow levels. Earlier attempts to unravel the processes that led to such biogeographic patterns suffered from insufficient phylogenetic resolution and unclear delimitation of some of the genera. In the present study, we estimated divergence time and ancestral ranges based on a phylogenomic framework with a well-resolved phylogenetic backbone to tackle issues of the timing and direction of dispersal that may explain the modern global distribution of Ochnaceae. The nuclear data provided the more robust framework for divergence time estimation compared to the plastome-scale data, although differences in the inferred clade ages were mostly small. While Ochnaceae most likely originated in West Gondwana during the Late Cretaceous, all crown-group disjunctions are inferred as dispersal-based, most of them as transoceanic long-distance dispersal (LDD) during the Cenozoic. All LDDs occurred in an eastward direction except for the SE Asian clade of Sauvagesieae, which was founded by trans-Pacific dispersal from South America. The most species-rich clade by far, Ochninae, originated from either a widespread neotropical-African ancestor or a solely neotropical ancestor which then dispersed to Africa. The ancestors of this clade then diversified in Africa, followed by subsequent dispersal to the Malagasy region and tropical Asia on multiple instances in three genera during the Miocene-Pliocene. In particular, Ochna might have used the South Arabian land corridor to reach South Asia. Thus, the pantropical distribution of Ochnaceae is the result of LDD either transoceanic or via land bridges/corridors, whereas vicariance might have played a role only along the stem of the family.
The UN 2030 Agenda for Sustainable Development stresses the fundamental role science should play in implementing the 17 Sustainable Development Goals endorsed by the global community. But how can and should researchers respond to this societal demand on science? We argue that answering this question requires systematic engagement with the fundamental normative dimensions of the 2030 Agenda and those of the scientific community—and with the implications these dimensions have for research and practice. We suggest that the production of knowledge relevant to sustainable development entails analytic engagement with norms and values through four tasks. First, to unravel and critically reflect on the ethical values involved in sustainability, values should increasingly become an empirical and theoretical object of sustainability research. Second, to ensure that research on social–ecological systems is related to sustainability values, researchers should reflect on and spell out what sustainability values guide their research, taking into account possible interdependencies, synergies, and trade-offs. Third, to find common ground on what sustainability means for specific situations, scientists should engage in deliberative learning processes with societal actors, with a view to jointly reflecting on existing development visions and creating new, contextualized ones. Fourth, this implies that researchers and scientific disciplines must clarify their own ethical and epistemic values, as this defines accountability and shapes identification of problems, research questions, and results. We believe that ignoring these tasks, whether one is in favor or critical of the 2030 Agenda, will undermine the credibility and relevance of scientific contributions for sustainable development.