A genetic and ecological dissection of the recent range expansion of the European wasp spider Argiope bruennichi - Consequence of climate change?
Author(s): Krehenwinkel, H, Tautz, D
Rapid, poleward range expansions are observed for an increasing number of species and commonly attributed to global warming. The role of contemporary adaptation in facilitating such range shifts is often neglected and remains to be discussed. A typical example for a recent range shift is provided by the European wasp spider Argiope bruennichi. Originally limited to the Mediterranean region, the species has greatly expanded its range in the past century and can now be found as far north as Finland. Here we present a detailed phylogeographic analysis of the spider’s range expansion, using mitochondrial DNA sequences, nuclear microsatellites and SNPs. We base our study on a dense, range wide sampling of more than 2000 contemporary samples and about 500 historical museum specimens from the time before the range expansion. The study is complemented by morphological data, thermal tolerance and -preference tests and a reciprocal transplant experiment of native and invasive European wasp spider populations. Using historical DNA, we can show that the spider’s range expansion is accompanied by an increasing admixture of formerly isolated, genetic lineages. At the same time, morphological changes are evident in invasive spiders. The reciprocal transplant experiment indicates local adaptation of recently established populations to their colder overwintering conditions. Moreover, our experiments show that invasive spiders have lowered their temperature tolerance and -preference, indicating a shift of their temperature niche. Based on these results, we speculate that genetic admixture at the species range edge has recently enabled an adaptation of wasp spiders to cold Northern European climates. Currently, we are investigating the genomic signatures of this adaptation, using a whole genome sequencing approach along environmental gradients.
Dipartimento di Scienze Ecologiche e Biologiche
A hotspot on fire: predicted impact of climate change on genetic diversity and disease tolerance in the endangered Apennine yellow-bellied toad Bombina pachypus
Author(s): Zampiglia, M, Canestrelli, D, Bisconti, R, Chiocchio, A, Nascetti, G
Climate change, emerging infectious diseases and levels of population genetic diversity can ‘conspire’ in yielding the decline and extinction of populations and species. We modeled species distribution and carried out a climate change vulnerability assessment for the endangered Bombina pachypus, an Italian endemic toad recently hypothesized to be faced with such ‘conspiracy’. For this species, southern Italy is the hotspot of genetic diversity and of disease tolerance to the chytrid pathogen Batrachochytrium dendrobatidis. This area showed the highest bioclimatic suitability for B. pachypus based on data for the years 1951-2000. Forecasted species distribution to 2080, under various models and emission scenarios, suggests that this area will become progressively less suitable, or even unsuitable for B. pachypus. Thus, loosing most of its evolutionary potential and historical resources to cope with chytrid outbreaks, B. pachypus will face a high extinction risk in the near future. On the other hand, in the northern regions, where populations are almost genetically invariable and demographically inconsistent, habitat suitability is predicted to increase in the near future. We suggest that captive breeding programs aimed at supporting translocation of genetic diversity from southern into northern populations (i.e. genetic rescue), are the only conservation actions with non-null probability to counteract this negative trend, and to attempt avoiding the human-driven extinction of this threatened amphibian species.
Department of Aquatic Ecology
Adaptive potential in a snail population
Author(s): Leicht, K, Seppälä, O
Adaptation to climate conditions is crucial for the existence and distribution of species and knowledge of adaptive potential will help us to predict how populations will be affected by climate change. Within-population genetic variation is the prior requirement for adaptation to changing environmental conditions, e.g. global warming. Here we examined if genetic variation in the responses to environmental change exists in a freshwater snail Lymnaea stagnalis. We exposed maternal family-lines originating from a Swiss snail population to thermal conditions similar to those during heat waves and assessed its effect on snail reproduction and immunocompetence. We found that high temperature increased snail reproduction and reduced immunocompetence. In addition we found family-level variation in snail reproduction and in all measured immune traits. However, we did not find family-level variation in response to a rise in temperature in any trait we measured indicated by non-significant family by temperature interactions. This suggests limited genetic potential to adapt to the predicted increase in the frequency of heat waves owing to climate change.
Department of Biology
Characterization of expression quantitative trait loci (eQTL) associated with response to thermal stress in the threespine stickleback, Gasterosteus aculeatus
Author(s): Pritchard, VL, Merilä, J, Nikinmaa, M, Primmer, C, Sävilammi, T, Viitaniemi, H, Leder, E
Ongoing climate change will expose populations to altered thermal regimens, which are likely to include more frequent and higher temperature maxima. Whether and how a resident population can withstand or adapt to these new conditions will depend on the genetic architecture underlying responses to temperature changes. This includes both coding genes and the regulatory regions that govern expression of these genes. Recent advances enabling the quantification of transcription levels for a large number of genes and the genotyping of many thousands of genetic markers throughout the genome, together with novel statistical methods, are facilitating the identification of such regulatory regions via expression quantitative trait locus (eQTL) analysis.
The threespine stickleback (Gasterosteus aculeatus) is an important model organism in evolutionary biology. The species occurs as resident populations in a wide range of habitats with different thermal profiles. We used sticklebacks derived from the Baltic coast of Finland to identify and localize eQTLs underlying changes in gene expression in response to thermal stress. Experimental subjects comprised 600 individuals in 30 sib–halfsib families, half of which were subject to a thermal challenge immediately prior to tissue collection. Liver mRNA expression was subsequently quantified using Agilent custom microarrays. Over 2000 genes were found to be differentially expressed between control and treatment groups. Genotyping of the families by sequencing on the Illumina platform, in combination with the existing G. aculeatus genome, was used to generate a linkage map that included over 10,000 SNPs. This enabled us to characterize and explore the regulatory networks underlying these changes in gene expression.
Department of Biological and Environmental Sciences
Climate and trematode-mollusk relationship
Author(s): Taskinen, J, Choo, JM
In trematode-mollusk relationships, climate warming may affect cercaria larvae production, virulence and competition between parasite species. In the present study we investigated the host-parasite relationship of the bucephalid trematodes Rhipidocotyle fennica and R. campanula which are transmitted from the unionid bivalve A. anatina to the second host, cyprinid fish Rutilus rutilus, via cercariae produced in the bivalve host. Results suggest that the annual period of cercarial production has become markedly longer in both parasite species from 1980’s to 2012—during the period of a climatic increase in temperature and length of summer. As compared to R. fennica, the parasite R. campanula started to produce cercariae much earlier in summer, resulting in a longer ceracariae production period annually. Early start of larval production was made possible in R. campanula by having cercaria production machinery ‘on standby’ throughout the year while R. fennica become inactive during winter. In line with this, R. campanula occurred in higher prevalences than R. fennica in northern areas, opposite to the south. The shorter summers towards north eventually limit the cercariae production period of the parasites, but due to the earlier onset of cercarial emission R. campanula is probably able to inhabit higher latitudes than R. fennica. However, R. campanula appeared to be more virulent than R. fennica (in terms of host survival and reproduction) which may be a cost of R. campanula’s ability to start cercariae production early seasonally. Impact of experimental temperature increase on annual cercarial production was positive in R. fennica but zero or negative in R. campanula. Thus, climate warming should benefit more R. fennica, and expand its range to the north. To conclude, climate change will presumably affect geographic distribution and abundance of Rhipidocotyle parasites, as well as modify the evolution of their virulence.
Climate change adaptation: genetic and genomic approaches in Drosophila
Author(s): Hoffmann, AA
It is being increasingly appreciated that rapid evolutionary changes can help species counter the negative effects of global warming, and also that they can allow species to exploit favourable conditions provided in a warming world. There are now several well documented cases of rapid genetic change in response to natural and experimental warming in animals and plants. The genetic and genomic basis of these changes can be understood through comparisons of populations. Moreover, the genes and genomic regions identified in these comparisons can be further investigated through functional analyses on model organisms and along environmental gradients. Because related species often differ in their evolutionary potential, there is also an opportunity to investigate the genomic basis of limits to climate change adaptation, particularly as more sequenced genomes become available. I illustrate the opportunities provided through this framework by considering recent research on Drosophila. However I also highlight limitations of these approaches for predicting the dynamics of adaptive shifts in populations. Ideally genetic and genomic approaches need to be combined with quantitative studies of selection in populations.
Climate change, host-parasite interactions and species invasions: an experiment initiated by Nature
Author(s): Wendling, CC, Wegner, MK
Biological invasions can be considered as an experiment performed by nature. They offer a unique way to study adaptation to new environments with all facets of new biotic and abiotic challenges like climate change and disease. On top of that, rising temperatures and risk of disease can interact and intensify selection pressure on invasive species to immunologically adapt to local parasites. The invasion of the Pacific oyster, Crassostrea gigas into the North Sea, is an ideal system to study the interactive effects of climate change and disease. Two independent invasions lead to the establishment of two genetically distinct populations, that differ in their selective history of disease outbreaks. While the Southern population is frequently subjected to natural selection induced by oyster summer mortality, with mortality rates exceeding 60%, Northern populations and hybrids in a secondary contact zone have been spared so far. Here, the interaction of high temperatures and bacteria of the genus Vibrio are believed to be the main causative agents of such mortalities. To test for differential selection gradients within the two invasion waves, we infected wild and artificially bred oysters with allopatric and sympatric Vibrio splendidus strains at prevailing and proposed future water temperatures. Based on mortality rates, immune response, and bacterial infection loads we observed that at high water temperatures oysters were severely impacted by Vibrio infection. However, while we consistently observed specific host immunological adaptation to sympatric parasites also at lower temperatures, direct advantages in terms of host fitness could only be detected at high temperatures indicating that the selective environment can unveil otherwise cryptic patterns of local adaptation.
Institute of Hydrobiology
Climate warming: Who suffers more in a host-parasite
Author(s): Dusi, E, Krenek, S, Sachse, R, Kaltz, O, Berendonk, TU
Climate change can alter species distributions, interactions and community compositions. Further, it can accelerate evolutionary processes. In host-parasite interactions it is difficult to predict whether the parasite or the host benefits most from global warming, because milder winter periods or higher nighttime temperatures can cause changes in development or transmission rates and may support the host/parasite. This study focuses on parasite virulence and prevalence in the context of stressful temperature conditions. We examined different strains of the host species Paramecium tetraurelia, a common freshwater ciliate, infected with the obligate intracellular bacterium Caedibacter taeniospiralis. This parasite is located in the cytoplasm of its host and vertically transmitted. An experimental approach was used to investigate if parasite virulence, defined as host’s fitness reduction caused by the parasite, is increasing under acute stress temperature conditions. Fitness of infected and uninfected P. tetraurelia was measured and the fitness-reduction/virulence was calculated at five different temperatures including a host stress temperature. The virulence caused by C. taeniospiralis was rising with higher temperature, but parasite prevalence was reduced at the host stress temperature. In an evolutionary context, the parasite could go extinct under acute stress conditions and the host would become cured of infection. Therefore, it was also tested how the parasite evolves under stress and optimum temperatures in long-term. The parasites that evolved under stress conditions seem to reduce costs to the host while having a higher prevalence compared to parasites that evolved under optimal conditions. Acute and intense stress might harm the parasite and seem to cause its extinction, but the parasite appears to be able to evolve and adapt to high-temperature stress conditions as caused by climate change.
Department of Biology & Environment
Co-evolution overrides climate change in cuckoo and reed warbler arms-race
Author(s): Markman, S, Berkowic, D, Stokke, BG, Meiri, S
The evolution of host organisms is influenced by their parasites and vice versa, and a co-evolutionary arms race often develops between the two. Evolution is also influenced by climate, but the interaction between co-evolution and climate has largely been overlooked. Here, we show that the co-evolutionary arms race between the parasitic common cuckoo (Cuculus canorus) and its host, the reed warbler (Acrocephalus scirpaceus), overrides climatic factors in affecting the egg sizes of both species. Cuckoo egg volume decreased during the 20th century while reed warbler egg volume in parasitized nests increased, resulting in cuckoo eggs that were closer in size to those of the reed warbler. Egg volumes of sympatric reed warblers in non-parasitized nests, however, remained stable during that period. Cuckoo body size indices remained constant or increased over the same period, whereas reed warbler body size remained stable. Temperature and precipitation were uncorrelated with egg volume of either species. We suggest that cuckoos evolved to lay smaller eggs, to reduce rejection probability. Furthermore, our results point to the possibility that cuckoos may actively selected host nests with the largest host eggs. We suggest that cuckoos recently gained the upper hand in their co-evolutionary arms race with reed warblers, overriding the effects of recent climatic changes.
Institute of Environmental Sciences
Complex response in life history traits of the bulb mites in elevated thermal conditions – an experimental evolution approach
Author(s): Plesnar-Bielak, A, Jawor, A, Kramarz, P
Temperature is a key environmental factor affecting almost all the aspects of life histories in ectotherms. The theory predicts that organisms grow faster, reach smaller sizes and produce smaller offspring when temperature increases. In addition, temperature changes, through their effects on metabolism, may also influence the expression of alternative reproductive phenotypes (ARP). Although many studies investigated reaction norms of life history traits in relation to temperature change, little is known about how these reaction norms evolve. In our study we subjected the bulb mites to experimental evolution in two temperature treatments: control and elevated. After 18 generations we measured adult body size, eggs size and development time of both treatments at control as well as at elevated temperature. Thus, we were able to distinguish genetic changes (the effect of selection temperature) from environmental effects. The ARP expression was recorded in each generation. We found that mites developed faster and reached smaller sizes at increased temperature, but genetic effects of thermal adaptation were not always parallel to the observed reaction norms revealing quite complex patterns of life history traits response to temperature. Despite smaller body sizes females laid larger eggs at higher temperature. This effect was more pronounced in animals evolving at elevated temperature. Evolution at increased temperature affected also ARP expression with the proportion of armored fighters decreasing from generation to generation. We propose that this could be the consequence of temperature sensitiveness of cost to benefits ratio of expressing ARPs.