In my project I aim at a better understanding of the evolution of malacostracan crustaceans, which includes very different groups such as mantis shrimps, krill and lobsters. Previous studies on Malacostraca, on extant as well as on fossil representatives, focussed on adult morphology.In contrast to such approaches, I will apply a Palaeo-Evo-Devo approach to shed new light on the evolution of Malacostraca. Palaeo-Evo-Devo uses data of different developmental stages of fossil malacostracan crustaceans, such as larval and juvenile stages. With this approach I aim at bridging morphological gaps between the different diverse lineages of modern malacostracans by providing new insights into the character evolution in these lineages.An extensive number of larval and juvenile malacostracans is present in the fossil record, but which have only scarcely been studied. The backbone of this project will be on malacostracans from the Solnhofen Lithographic Limestones (ca. 150 million years old), which are especially well preserved and exhibit minute details. During previous studies, I developed new documentation methods for tiny fossils from these deposits, e.g., fluorescence composite microscopy, and also discovered the first fossil mantis shrimp larvae. For malcostracan groups that do not occur in Solnhofen, I will investigate fossils from other lagerstätten, e.g., Mazon Creek and Bear Gulch (USA), or Montceaules- Mines and La-Voulte-sur-Rhône (France). The main groups in focus are mantis shrimps and certain other shrimps (e.g., mysids, caridoids), as well as the bottom-living ten-footed crustaceans (reptantians). Examples for studied structures are leg details, including the feeding apparatus, but also eyes. The results will contribute to the reconstruction of 3D computer models.The data collected in this project will be used for evaluating the relationships within Malacostraca, but mainly for providing plausible evolutionary scenarios, how the modern malacostracan diversity evolved. With the Palaeo-Evo-Devo approach, I am also able to detect shifts in developmental timing, called heterochrony, which is interpreted as one of the major driving forces of evolution. Finally, the reconstructed evolutionary patterns can be compared between the different lineages for convergencies. These comparisons might help to explain the convergent adaptation to similar ecological niches in different malacostracan groups, e.g., life in the deep sea, life on the sea bottom, evolution of metamorphosis or of predatory larvae.As the project requires the investigation of a large number of specimens in different groups, I will assign distinct sub-projects to three doctoral researchers. The results of this project will not only be published in peer-reviewed journals, but will also be presented to the non-scientific public, e.g., during fossil fairs or museum exhibitions with 3D models engraved in glass blocks.
In many plant species, FLOWERING LOCUS T and related proteins are the mobile signal that communicates information on photoperiod from the leaves to the shoots, where the transition to flowering is realized. FT expression is tightly controlled at the transcriptional level so that it is restricted to leaves, occurs only in appropriate photoperiods, and integrates ambient temperature and developmental cues, as well as information on biotic and abiotic stress. We previously established that FT transcription in the model plant Arabidopsis thaliana requires proximal promoter cis-elements and a distal enhancer, both evolutionary conserved among Brassicacea species. In addition, FT transcription is blocked prior vernalization in biannual accessions and vernalization-dependency of FT is controlled through a CArG-box located in the first intron that binds the transcriptional repressor FLOWERING LOCUS C (FLC). Chromatin-mediated repression by the Polycomb Group (PcG) pathway is required for photoperiod-dependent FT regulation and participates in FT expression level modulation in response to other cues.In this project, I propose to explore the available sequence data from the 1001 genome project in Arabidopsis to evaluate how often changes in regulatory cis-elements at FT have occurred and how these translate into an adaptive value. Allele-specific FT expression pattern will be measured in F1 hybrids of different accessions in response to varying environmental conditions. FT alleles that show cis-regulatory variation will be further analyzed to pinpoint the causal regulatory changes and study their effect in more detail. The allotetrapolyploid species Brassica napus is a hybrid of two Brassiceae species belonging to the A- and C-type genome, which are in turn mesopolyploid due to a genome triplication that occurred ca. 10x106 years ago. We will determine allele-specific expression of FT paralogs from both genomes of a collection of B. napus accessions. The plants will be grown in the field in changing environmental conditions to maximize the chance to detect expression variation of the paralogs. We will compare the contribution of the founder genomes to the regulation of flowering time and asses variation in this contribution. A particular focus will be to study the impact of chromatin-mediated repression on allele selection in B. napus.
Predictions of effects of climate change on species distributions assume constant climatic niches. Our current understanding of how climate niches developed through evolution is very limited. This project shall analyse how climate niche of the 5488 mammal species worldwide is related to their phylogenetic position. The hypothesis is that closely related species will also have similar climate niches, indicating climate niche conservation. Based on current distributions and environmental data, we shall quantify the climate niche of each species and compare it to that of its closest relative (sister species). We shall investigate whether climate niche position is similarly phylogenetically constrained as other species traits such as body weight, gestation length or litter size. The huge breadth of mammal ecologies, their highly resolved phylogenetic tree, their high conservation relevance and their relatively well-known geographical distribution make them an ideal study system. In the process of this study, new methodological standards for the analysis of niche evolution will be developed, including randomisation tests, virtual species analysis and character tracing of climate niche position. In the end, we shall be able to specify the adaptation potential to climate change for a large number of species studied.
Most plants rely on insects for their pollination, protection (e.g., from herbivores) and/or seed dispersal, and have formed a mutually beneficial interaction, or mutualism. The current research investigates the evolution of plant traits involved in plant-insect mutualisms. In particular, it focuses on the evolution of extrafloral nectaries (EFNs): secretory structures on plant parts outside the flower, which offer carbohydrate-rich, water-based secretions (=nectar) to ants in return for their protection from herbivores (i.e. protective mutualisms). EFNs occur in some ferns and over hundred families of flowering plants, especially the legume family. However, their phylogenetic distribution within families, morphological diversity and evolution, and evolutionary role are poorly understood. Also EFN plant-ant interactions are known to shape entire tropical and savannah-like ecosystems, but their unexpected occurrence in deserts - where plants need to manage water carefully - has been studied only in a few cacti. This study investigated the diversity and evolution of EFNs at three different levels: (1) in the Leguminosae, the third largest and second economically most important angiosperm family, which also dominates many kinds of vegetation worldwide; (2) in the legume genus Senna, a case study where EFNs represent a key innovation (see past SNF project by B. Marazzi); and (3) in Sonoran Desert plants. Current results show that EFNs occur in species of over 130 legume genera (over twice as many as in the last published account of EFNs in this family). They are particularly abundant in the subfamily Mimosoideae, and may have evolved independently at least 30 times in the family. This incredible number of origins suggests the action of some evolutionary (perhaps genetic) precursor that allowed some clades to evolve EFNs more 'easily' given ceartin selective regimes. Most legume EFNs occur on the (typically pinnate) leaves, less often on stipules and different parts of inflorescences. In Senna, ancestral leaf EFNs appear to have evolved first between the proximal pair of leaflets only (some 40 Million years ago), and later also between the other pairs of leaflets (several times) or only at the base of the leaf stalk (once). In the Sonoran Desert area (including also mountain habitats), EFNs may occur in species from up to 32 families, in several cacti and in particular Leguminosae, dominant in this vegetation. EFNs have apparently been reduced but have been retained in a functional state (i.e., secreting nectar) in most desert legumes, and are thus capable of participating in protective mutualisms with desert ants. This research shows that EFNs are more widespread in plants than previously thought, suggesting that we may have underestimated the role of protective ant-plant interactions in shaping ecosystem ecology and evolution
Natural populations are increasingly exposed to extreme environmental changes as a result of human activities. These changes threaten the existence of populations and cause strong natural selection at short time-scales. In the long term, the persistence of populations is determined by their capacity to respond to this selection via genetic adaptation. It is therefore crucial to understand how evolutionary processes influence the ability of populations to cope with the ongoing environmental changes. This project focuses on studying two major factors that influence the ability of populations to adapt to rapid environmental change: gene flow (movement of genes resulting from dispersal of individuals) and maternal effects (the effects of a mother's traits that, in addition to offspring's own genes, affect offspring performance), both of which have the potential to either impede or speed up adaptation. On this vein, the proposed research focuses in particular on understanding how gene flow and maternal effects affect the ability of populations to adapt to environmental changes. The main part of the research will be conducted on Swedish populations of the moor frog (Rana arvalis) that inhabit areas affected to different extents by human-induced acidification. The main questions to be targeted are i) to what extent is the level of local adaptation to acidification explained by variation in the extent of gene flow or variation in the strength of selection among populations, ii) how wide-spread are maternal effects as adaptations and iii) how is maternally determined local adaptation maintained in the face of gene flow? Because experimental manipulations are not possible in these natural populations, related questions will in parallel be addressed in a pilot study on laboratory populations of Daphnia. Here the main questions to be targeted are i) under which conditions does gene flow have positive vs. negative effects on adaptation to novel environments and ii) how do maternal effects influence the ability to respond genetically to rapid environmental changes? Different complementary approaches will be used in the different subprojects to allow rigorous inferences and predictions. The main methods to be used include large-scale geographic sampling (for environmental, molecular genetic, and phenotypic variation) and mark-recapture studies in nature, molecular and quantitative genetic analyses in the laboratory, and fitness assays in semi-natural and laboratory conditions. The results from this research will illustrate to what extent gene flow and maternal effects influence variation in the phenotypes that we see in nature, and how they can affect the ability of organisms to adapt to novel environments. Ultimately this research aims at understanding the short-term ecological and evolutionary processes that create, maintain and change biological diversity, and will be of broad significance for evolutionary biology as well as conservation biology.
Processes and mechanisms of antagonistic coevolution The research I am proposing addresses basic aspects of the coevolution between hosts and their parasites. Many biological and medical phenomena have been explained to be a consequence of reciprocal host-parasite coevolution. Some of these explanations require specific and rapid antagonistic coevolution to take place. Experimental coevolution of viruses in bacteria or cell cultures gave evidence for coevolution by selective sweeps, but we have little, and mostly indirect evidence for coevolution with plant and animal hosts. However, population genetic consideration suggests that rapid antagonistic coevolution in plant and animal host systems should be dominated by negative frequency dependent selection. In this proposal I ask for funds to carry out experiments with populations of the waterfleas Daphnia magna and its microparasites to deepen our understanding of the genetic processes and mechanisms of coevolution. D. magna reproduce sexually and clonally, the later with a generation time of only 10 days. Two parasites, the microsporidium, Octosporea bayeri, and the bacterium, Pasteuria ramosa, will be used in the experiments. I propose a project with 3 sub-projects to elucidate the mechanisms and patterns of host-parasite coevolution. Sub-Project A aims to find direct experimental evidence for rapid and specific coevolution with Daphnia and a microsporidian parasite under natural conditions. This will include time-shift cross-infection experiments using hosts and parasites stored at different times of the coevolution. Sub-Project B is about finding the infectivity genes in the bacterial parasite, Pasteuria. Sub-Project C proposes experiments to elucidate the mechanisms at work shaping the genetic epidemiology and coevolution of Pasteuria with its waterflea host. With my research I hope to establish a case study, which would provide urgently needed data to test assumptions and to estimate parameters for epidemiological and (co-)evolutionary models of infectious diseases. It would allow streamlining treatments against pests and parasites and to make more accurate predictions about infectious diseases evolution. It will further provide insight into natural phenomena, which are suggested to be a consequence of rapid antagonistic coevolution.
How new species arise is a central question in biology, and how climate change affects speciation is currently a key question. Our understanding of the molecular mechanisms underlying the origin of reproductive barriers among infraspecific populations is a highly debated topic. However, in contrast to the situation in animals, some evidence suggests that new plant species commonly evolve in response to chromosomal rearrangements. Since plant genomes are remarkably dynamic, probably in relation to their high content in transposable elements, it is a timely task to investigate the way genome responds to climate change and whether this translates into the origin of new species. To expand the knowledge about the origin of species, the present project aims at addressing whether microchromosomal rearrangements, and particularly those related to transposable elements, stimulate intrinsic postzygotic isolation in plants. This is best done in an explicit spatiotemporal framework including changing climate as a potential environmental cue. Accordingly, the origin of cryptic biological species within the circumpolar plant Draba nivalis will be dissected by scoring quantitative trait loci (QTL) for sterility in populations grown from reciprocal incompatible crosses, using both Amplified Fragment Length Polymorphism (AFLP) and Sequence-Specific Amplified Polymorphism (SSAP, marking insertions of transposable elements). In order to further analyse the genetic factors involved in the quick rise of reproductive barriers, these sterility QTLs will be characterised by massively sequencing the AFLP/SSAP markers in parallel. Finally, a comparative phylogeograhic analysis of the sterility QTLs and neutral non-QTL markers will allow to reconstruct the history of reproductive barriers, assessing the corresponding evolutionary processes underlying the recent speciation in D. nivalis during the ice age.
The main goal of the study presented here was to test whether extrafloral nectaries (EFNs) are a key innovation in plant defense strategies. EFNs occur in greater than 90 flowering plant families, typically in Leguminosae (=Fabaceae). Located commonly on vegetative parts, EFNs secrete nectar, attracting ants and forming ecologically important ant-plant mutualisms. These mutualisms may confer a higher fitness to EFN-plants and, thus, an increased potential for survival, dispersal, and adaptation, and ultimately to undergo speciation. Key innovations are one of the most important triggers of radiations and large-scale diversifications in nature. But, unraveling the diversification history of old, species-rich and widespread clades is difficult, because of extinction, undersampling and taxonomic problems. In the context of these challenges, we investigated the timing and mode of lineage diversification in the widespread legume genus Senna to gain insights into the evolutionary role of its EFNs. In Senna, EFNs characterize one large clade (EFN clade), including 80Prozent of its 350 species. Fossil evidence indicates that Senna dates from the Eocene, predating many legume genera. We outlined a novel powerful framework for key innovation hypothesis testing in old, widespread and species-rich clades, like Senna. This consists of the combination of a list of four criteria for morphological novelties to qualify as key innovation, together with an accurate inference of the diversification history of the entire study group (i.e. accurate estimation of divergence times, diversification rates, and clade sizes), and an adequate method for testing shifts in diversification rates. Our molecular dating analyses suggest that Senna originated in the early Eocene (ca. 50 Million years (My) ago), and its major lineages appeared during early/mid Eocene to early Oligocene. EFNs evolved in the late Eocene (ca. 35-40 My ago), after the main radiation of ants. The EFN clade diversified faster, becoming significantly more species-rich than non-EFN clades. The shift in diversification rates associated with EFN evolution supports the hypothesis that EFNs represent a (relatively old) key innovation in Senna. EFNs may have promoted the colonization of new habitats appearing with the early uplift of the Andes. This would explain the distinctive geographic concentration of the EFN clade in South America (144 species). Evolution of the EFNs may have helped the EFN clade to undergo a rapid radiation leading to the outstanding floral diversity observed in extant taxa. The study is the first to provide evidence for the role of a plant-ant protective mutualism in triggering plant diversification.
For effective crop improvement, breeders must be able to select on relevant phenotypic traits without compromising yield. This project proposes to investigate the evolutionary consequences of flowering time modifications on a second trait of major importance for plant breeding: immunity. This will have implications both for understanding cross-talks between flowering time and defense network and for developing efficient breeding strategies. There is clear evidence that plant maturity influences levels and effectiveness of defense. Theoretical models actually predict that changes in life-history can modulate the balance between costs and benefits of immunity. Simultaneously, actors of the immune system have often been observed to alter flowering time. Two alternative and possibly complementary hypotheses can explain this link: genetic constraints due to the pleiotropic action of players in either systems, or co-evolution, if flowering-time changes modulate the cost-benefit balance of immunity. We will conduct field assays in Arabidopsis thaliana, using constructed lines as well as recombinant inbred lines and natural accessions, to differentiate the action of the two explanatory hypotheses. Using transcriptome analyses, we will identify defense genes associating with flowering time modification (f-t-a defense genes). We will quantify their expression along the assay and test whether it varies with both flowering time and fitness. We will further test whether flowering time and immunity interact to determine yield in tomato and potato.
The project will use analysis of long-term data, resurrection ecology and modeling to investigate the ecological and evolutionary response of an aquatic key herbivore, Daphnia, to environmental change. In addition, the results obtained will enable to estimate the consequences of the evolutionary response of Daphnia for its population dynamics, persistence and consequently, overall ecosystem dynamics. The project will analyze in detail the response of Daphnia, its food, competitors and predators to oligo-trophication in a model ecosystem, i.e., Lake Constance and additionally variability in Daphnia population dynamics in several of the best studied lakes of the world. Historical field samples from Lake Constance will be re-analyzed to study the phenotypic life history and morphological responses of Daphnia to oligo-trophication. Using resurrection ecology we will analyze the evolutionary response of Daphnia galeata life history parameters to oligo-trophication - with special emphasis on its investment into sexual reproduction/production of resting eggs as well as life history plasticity in response to invertebrate predators and declining food levels. These analyses (in combination with model simulations) will provide key data for understanding the role of Daphnia life cycle strategy (overwintering in the plankton or in resting eggs) for Daphnia persistence in permanent lakes, for the interpretation of Daphnia resting egg banks, and the evolution of the genetic variances and co-variances of life history parameters.
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