Effect of social structure and introduction history on genetic diversity and differentiation

Invasive species are a global threat to biodiversity, and understanding their history and biology is a major goal of invasion biology. Population-genetic approaches allow insights into these features, as population structure is shaped by factors such as invasion history (number, origin and age of introductions) and life-history traits (e.g., mating system, dispersal capability). We compared the relative importance of these factors by investigating two closely related ants, Tetramorium immigrans and Tetramorium tsushimae, that differ in their social structure and invasion history in North America. We used mitochondrial DNA sequences and microsatellite alleles to estimate the source and number of introduction events of the two species, and compared genetic structure among native and introduced populations. Genetic diversity of both species was strongly reduced in introduced populations, which also differed genetically from native populations. Genetic differentiation between ranges and the reduction in microsatellite diversity were more severe in the more recently introduced and supercolonial T. tsushimae. However, the loss of mitochondrial haplotype diversity was more pronounced in T. immigrans, which has single-queen colonies and was introduced earlier. Tetramorium immigrans was introduced at least twice from Western Europe to North America and once independently to South America. Its monogyny might have limited genetic diversity per introduction, but new mutations and successive introductions over a long time may have added to the gene pool in the introduced range. Polygyny in T. tsushimae probably facilitated the simultaneous introduction of several queens from a Japanese population to St. Louis, USA. In addition to identifying introduction pathways, our results reveal how social structure can influence the population-genetic consequences of founder events

A liquid-crystalline hexagonal columnar phase in highly-dilute suspensions of imogolite nanotubes

International audienceLiquid crystals have found wide applications in many fields ranging from detergents to information displays and they are also increasingly being used in the 'bottom-up' self-assembly approach of material nano-structuration. Moreover, liquid-crystalline organizations are frequently observed by biologists. Here we show that one of the four major lyotropic liquid-crystal phases, the columnar one, is much more stable on dilution than reported so far in literature. Indeed, aqueous suspensions of imogolite nanotubes, at low ionic strength, display the columnar liquid-crystal phase at volume fractions as low as B0.2%. Consequently, due to its low visco-elasticity, this columnar phase is easily aligned in an alternating current electric field, in contrast with usual columnar liquid-crystal phases. These findings should have important implications for the statistical physics of the suspensions of charged rods and could also be exploited in materials science to prepare ordered nanocomposites and in biophysics to better understand solutions of rod-like biopolymers

Electrochemistry at nanoscale electrodes : individual single-walled carbon nanotubes (SWNTs) and SWNT-templated metal nanowires

Individual nanowires (NWs) and native single-walled carbon nanotubes (SWNTs) can be readily used as well-defined nanoscale electrodes (NSEs) for voltammetric analysis. Here, the simple photolithography-free fabrication of submillimeter long Au, Pt, and Pd NWs, with sub-100 nm heights, by templated electrodeposition onto ultralong flow-aligned SWNTs is demonstrated. Both individual Au NWs and SWNTs are employed as NSEs for electron-transfer (ET) kinetic quantification, using cyclic voltammetry (CV), in conjunction with a microcapillary-based electrochemical method. A small capillary with internal diameter in the range 30–70 μm, filled with solution containing a redox-active mediator (FcTMA+ ((trimethylammonium)methylferrocene), Fe(CN)64–, or hydrazine) is positioned above the NSE, so that the solution meniscus completes an electrochemical cell. A 3D finite-element model, faithfully reproducing the experimental geometry, is used to both analyze the experimental CVs and derive the rate of heterogeneous ET, using Butler–Volmer kinetics. For a 70 nm height Au NW, intrinsic rate constants, k0, up to ca. 1 cm s–1 can be resolved. Using the same experimental configuration the electrochemistry of individual SWNTs can also be accessed. For FcTMA+/2+ electrolysis the simulated ET kinetic parameters yield very fast ET kinetics (k0 > 2 ± 1 cm s–1). Some deviation between the experimental voltammetry and the idealized model is noted, suggesting that double-layer effects may influence ET at the nanoscale

Genomic Signature of Shifts in Selection in a Subalpine Ant and Its Physiological Adaptations

Understanding how organisms adapt to extreme environments is fundamental and can provide insightful case studies for both evolutionary biology and climate-change biology. Here, we take advantage of the vast diversity of lifestyles in ants to identify genomic signatures of adaptation to extreme habitats such as high altitude. We hypothesized two parallel patterns would occur in a genome adapting to an extreme habitat: 1) strong positive selection on genes related to adaptation and 2) a relaxation of previous purifying selection. We tested this hypothesis by sequencing the high-elevation specialist Tetramorium alpestre and four other phylogenetically related species. In support of our hypothesis, we recorded a strong shift of selective forces in T. alpestre, in particular a stronger magnitude of diversifying and relaxed selection when compared with all other ants. We further disentangled candidate molecular adaptations in both gene expression and protein-coding sequence that were identified by our genome-wide analyses. In particular, we demonstrate that T. alpestre has 1) a higher level of expression for stv and other heat-shock proteins in chill-shock tests and 2) enzymatic enhancement of Hex-T1, a rate-limiting regulatory enzyme that controls the entry of glucose into the glycolytic pathway. Together, our analyses highlight the adaptive molecular changes that support colonization of high-altitude environments.Research was supported by the Austrian Science Fund (FWF, P23409 and P30861)

Toll-like receptor 3 signalling mediates angiogenic response upon shock wave treatment of ischaemic muscle

Aims Shock wave therapy (SWT) represents a clinically widely used angiogenic and thus regenerative approach for the treatment of ischaemic heart or limb disease. Despite promising results in preclinical and clinical trials, the exact mechanism of action remains unknown. Toll-like receptor 3, which is part of the innate immunity, is activated by binding doublestranded (ds) RNA. It plays a key role in inflammation, a process that is needed also for angiogenesis. We hypothesize that SWT causes cellular cavitation without damaging the target cells, thus liberating cytoplasmic RNA that in turn activates TLR3. Methods and results SWT induces TLR3 and IFN-b1 gene expression as well as RNA liberation from endothelial cells in a time-dependant manner. Conditioned medium from SWT-treated HUVECs induced TLR3 signalling in reporter cells. The response was lost when the medium was treated with RNase III to abolish dsRNAs or when TLR3 was silenced using siRNAs. In a mouse hind limb ischaemia model using wt and TLR3 2/2 mice (n ¼ 6), SWT induced angiogenesis and arteriogenesis only in wt animals. These effects were accompanied by improved blood perfusion of treated limbs. Analysis of main molecules of the TLR3 pathways confirmed TLR3 signalling in vivo following SWT. Conclusion Our data reveal a central role of the innate immune system, namely Toll-like receptor 3, to mediate angiogenesis upon release of cytoplasmic RNAs by mechanotransduction of SWT. -

Genomic Signature of Shifts in Selection in a Subalpine Ant and Its Physiological Adaptations

Understanding how organisms adapt to extreme environments is fundamental and can provide insightful case studies for both evolutionary biology and climate-change biology. Here, we take advantage of the vast diversity of lifestyles in ants to identify genomic signatures of adaptation to extreme habitats such as high altitude. We hypothesized two parallel patterns would occur in a genome adapting to an extreme habitat: 1) strong positive selection on genes related to adaptation and 2) a relaxation of previous purifying selection. We tested this hypothesis by sequencing the high-elevation specialist Tetramorium alpestre and four other phylogenetically related species. In support of our hypothesis, we recorded a strong shift of selective forces in T. alpestre, in particular a stronger magnitude of diversifying and relaxed selection when compared with all other ants. We further disentangled candidate molecular adaptations in both gene expression and protein-coding sequence that were identified by our genome-wide analyses. In particular, we demonstrate that T. alpestre has 1) a higher level of expression for stv and other heat-shock proteins in chill-shock tests and 2) enzymatic enhancement of Hex-T1, a rate-limiting regulatory enzyme that controls the entry of glucose into the glycolytic pathway. Together, our analyses highlight the adaptive molecular changes that support colonization of high-altitude environments

ECMO for COVID-19 patients in Europe and Israel

Since March 15th, 2020, 177 centres from Europe and Israel have joined the study, routinely reporting on the ECMO support they provide to COVID-19 patients. The mean annual number of cases treated with ECMO in the participating centres before the pandemic (2019) was 55. The number of COVID-19 patients has increased rapidly each week reaching 1531 treated patients as of September 14th. The greatest number of cases has been reported from France (n = 385), UK (n = 193), Germany (n = 176), Spain (n = 166), and Italy (n = 136) .The mean age of treated patients was 52.6 years (range 16–80), 79% were male. The ECMO configuration used was VV in 91% of cases, VA in 5% and other in 4%. The mean PaO2 before ECMO implantation was 65 mmHg. The mean duration of ECMO support thus far has been 18 days and the mean ICU length of stay of these patients was 33 days. As of the 14th September, overall 841 patients have been weaned from ECMO support, 601 died during ECMO support, 71 died after withdrawal of ECMO, 79 are still receiving ECMO support and for 10 patients status n.a. . Our preliminary data suggest that patients placed on ECMO with severe refractory respiratory or cardiac failure secondary to COVID-19 have a reasonable (55%) chance of survival. Further extensive data analysis is expected to provide invaluable information on the demographics, severity of illness, indications and different ECMO management strategies in these patients

Contribution of the public to the modelling of the distributions of species: Occurrence and current and potential distribution of the ant Manica rubida (Hymenoptera: Formicidae)

Maps and models of the distributions of animals and plants are important for assessing their current and future status. Such models rely on information on the environment and occurrence of species. While data on the environment are often easily gathered that on the occurrence of species is often tedious and expensive to collect. An easy way to gather data on species occurrences is to use online platforms such as GBIF or iNaturalist, which rely on the public. This data can be used to produce maps and develop models of the distributions of various animals, such as ants. Even though there are a few in depth studies on the distributions of ant species, knowledge of the distribution and status of many species is lacking. One such species is the widespread ant Manica rubida, which is currently not included in the international Red List. Here, data on the occurrence of M. rubida recorded in online platforms, literature and collected during a field survey were used to develop a map of its distribution and a species model, in order to evaluate its current status. A total of 611 occurrences were found and indicate that this species mainly occurs in the European Alps and other Eurasian mountain ranges. Records of most occurrences were obtained from online platforms and the number increased significantly over the last two decades and indicate this species occurs over an altitudinal range of 3000 m. The species model revealed that there are potential areas of suitable habitat for M. rubida in the Pyrenees, European Uplands, Pindus Mountains, Balkan Mountains and Pontic mountains. Currently, M. rubida does not seem to be threatened by climate change, but it is recommended that the monitoring of its distribution should be continued. This study reveals that data from online platforms can provide the information necessary for developing species models, which can be used to assess the current status and estimate the potential effect of climate change on a species and plan conservation strategies

Social organisation and aggressive behaviour in the ant Tetramorium alpestre (Hymenoptera: Formicidae)

Ameisen sind mitunter die häufigsten Tiere auf der Welt und bisher wurden mehr als 13.000 Ameisenarten beschrieben. Obwohl es weltweit so viele Ameisenarten gibt, weiß man nur von wenigen Arten über deren Lebenszyklus genau Bescheid. Innerhalb und zwischen den Ameisenarten variieren verschiedene Merkmale wie Ökologie, Morphologie, soziale Struktur und das Verhalten. Ein interessantes Beispiel für so eine polymorphe Art ist Tetramorium alpestre, die Gebirgsameise im Tetramorium caespitum-Komplex. Tetramorium alpestre unterscheidet sich ökologisch von den anderen Arten im Komplex und die Art zeigt Tendenzen eines sozialen und Verhaltenspolymorphismus: Kolonien haben eine oder mehrere Königinnen (mit Superkolonien) und Arbeiterinnen verhalten sich aggressiv oder friedlich. Tetramorium alpestre ist ein idealer Organismus um die soziale Struktur, das Verhalten und die potentielle Entwicklung von Superkolonien zu untersuchen. In dieser Dissertation, habe ich im ersten Teil die soziale Struktur und das Verhalten von 11 Nestern in Tirol (Österreich) untersucht. Ich konnte feststellen, dass alle Nester monogyn waren (eine Königin besitzen). Dies ist gegensätzlich zu früheren Daten die auf eine polygyne Population in Kärnten (Österreich) verweisen. Das Vorkommen von Monogynie und Polygynie bestätigte allerdings den vermuteten sozialen Polymorphismus. Ich stellte zudem fest, dass nestfremde Ameisen unterschiedlicher Kolonien in dyadischen Aufeinandertreffen friedlich zueinander waren. Aggressives Verhalten wurde nur selten beobachtet und war nicht beeinflusst von dem Verwandtschaftsgrad innerhalb und zwischen den Kolonien oder von der geographischen Distanz zwischen Kolonien. Ich vermute, dass chemische oder ökologische Faktoren das aggressive Verhalten beeinflussen. Durch die Verwendung von mehreren Verhaltensindices konnte ich feststellen, dass diese unterschiedlichen Ergebnisse liefern. Aufgrund dieser Unterschiede, habe ich zweiten Teil der Dissertation drei neue Verhaltensindices erschaffen und diese mit bereits existierenden verglichen um mögliche Unterschiede und Einflüsse der Indices auf Verhaltensdaten festzustellen. Dabei habe ich drei existierende Datensätze verwendet, sowie acht Datensätze durch Simulationen erzeugt. Ich stellte fest, dass die Ergebnisse sehr von dem gewählten Index abhängen und die Interpretation beeinflussen. Zudem konnte ich zeigen, dass eine Kombination von mehreren Verhaltensindices das gesamte Verhaltensspektrum von Arbeiterinnen am besten darstellt. Im dritten Teil der Dissertation testete ich, ob der soziale und Verhaltenspolymorphismus in 47 T. alpestre Nestern gesammelt in acht Populationen über den Alpenraum besteht. Ich führte Verhaltensversuche durch und testete, ob chemische, geographische, morphometrische und populationsgenetische Parameter einen Einfluss auf das Verhalten haben. Ich stellte fest, dass aggressives Verhalten von den Arbeiterinnen abhängt, die im Aufeinandertreffen aggressiv reagierten, von der Präsenz von alaten Gynen im Nest während des Sammelns, und von der quantitativen Zusammensetzung von Alkanen mit Methylzweig und Alkanen, sowie deren Kombination. Das vielfach beobachtete friedliche Verhalten zwischen Kolonien könnte als Nebenprodukt von ökologischen Faktoren entstanden sein: Tetramorium alpestre lebt vorwiegend unter der Erde und nutzt Läuse zur Honigtaugewinnung. Dieses Leben unter der Erde, sowie eine konstante Nahrungsquelle können eine Reduktion von aggressivem Verhalten mit sich gebracht haben. Geringere Aggression bedeutet mehr Energie, Zeit und Arbeiter, die für das Koloniewachstum und die Reproduktion eingesetzt werden können.Ants are among the most abundant animals in the world, and more than 13,000 species have been described until today. Despite this high number, in-depth knowledge of life histories is available for only a relatively small number of species. In those, various traits such as behaviour, ecology, morphology, and social structure often differ among and within species. An interesting example of such a polymorphic species is Tetramorium alpestre, a mountain species in the Tetramorium caespitum complex. It differs ecologically from the other species in the complex, and a social and behavioural polymorphisms have been assumed: Colonies are monogynous or polygynous (with a functional supercolony), and workers might behave both aggressively and peacefully. Tetramorium alpestre thus seems an ideal study species to explore its social structure, behaviour, and the potential development of supercolonies. Within this PhD thesis, firstly, I analysed the social structure and behaviour of T. alpestre workers from 11 nests collected in Tyrol Austria). I determined that all nests were monogynous, which contrasted previous findings of a polygynous population from Carinthia (Austria), but confirmed the assumed social polymorphism. I further revealed that non-nestmates used in one-on-one encounters were mainly peaceful towards each other. Aggressive behaviour between non-nestmates was rare and not influenced by intranest or internest relatedness or spatial distance between colonies. I speculated that other chemical or ecological parameters influenced aggressive behaviour. By applying two behaviour indices, I detected that they yielded contrasting results. Based on this incongruence in indices, secondly, I established three new behaviour indices and compared them with two existing ones to determine the influence of different behaviour indices on behaviour data. I applied the indices to three observed and eight simulated data sets. I detected that results differed with the choice of the index likely affecting their interpretation. Further, I revealed that only the combination of multiple behaviour indices enabled to determine the complete behaviour range of a worker towards another one. Thirdly, I explored the presence or absence of the social and behaviour polymorphism in 47 T. alpestre nests collected in eight populations across the European Alps. I conducted behaviour assays and explored the potential influence of chemical, population-genetic, morphometric, and spatial parameters on the behaviour. I revealed that aggressive behaviour was influenced by the worker that started aggressive behaviour, the presence of alate gynes during collection, and the quantitative composition of methylbranched alkanes and the combination of n-alkanes and methylbranched alkanes. The multiply observed peaceful behaviour among colonies likely has arisen as a by-product of ecological factors: As T. alpestre lives belowground and tends aphids, it might has reduced its aggressive behaviour saving energy, time, and workers, which can be invested in colony growth and reproduction.by Patrick Krapf, MSc BScKumulative Dissertation aus drei ArtikelnAbweichender Titel laut Übersetzung des VerfassersUniversity of Innsbruck, Dissertation, 2019(VLID)366280

Plasma Membrane is Compartmentalized by a Self-Similar Cortical Actin Meshwork

A broad range of membrane proteins display anomalous diffusion on the cell surface. Different methods provide evidence for obstructed subdiffusion and diffusion on a fractal space, but the underlying structure inducing anomalous diffusion has never been visualized because of experimental challenges. We addressed this problem by imaging the cortical actin at high resolution while simultaneously tracking individual membrane proteins in live mammalian cells. Our data confirm that actin introduces barriers leading to compartmentalization of the plasma membrane and that membrane proteins are transiently confined within actin fences. Furthermore, superresolution imaging shows that the cortical actin is organized into a self-similar meshwork. These results present a hierarchical nanoscale picture of the plasma membrane