The Role of Behavioural Changes in Biological Invasions

All ecosystems on Earth are undergoing rapid human-induced changes. One important component of these changes is the transport of species to new ecosystems, where they often establish and spread, and cause ecological disruption as invasive species. Behaviour plays a major role in this process, not only by enabling species to spread or establish, but also in the native species’ response to invasion. These behavioural changes drive population dynamics, and the speed at which they happen are crucial. The shared evolutionary history between two species influences how fast or effective these changes happen. To study these complicated interactions, this thesis combines a comparative study of the existing literature with novel concepts and metadata, as well as analyses of laboratory experiments and field data. For Chapter 1, a large cross-taxonomical dataset on behavioural changes in biological invasions was gathered and analysed. It is the first to include native and non-native species, to identify types of behaviour and mechanisms of change and to quantify the speed of the behavioural change. This gave us the opportunity to test hypotheses in invasion ecology, but also to explore the distribution of learning across types of behaviour and its implications for the speed of behavioural change. All analyses were conducted considering the biases in the data and differences in the ecology of native and invasive species. In Chapter 2, the behavioural differences between an established non-native crayfish species, the spiny-cheek crayfish Faxonius limosus, and the novel non-native marbled crayfish (Procambarus virginalis) were experimentally quantified, and findings were used to predict the invasion success of the latter species. Experiments were designed to show the outcome of inter-specific agonistic interactions, activity and exploration. Finally, not only inter-specific differences were tested but also between both sexes of the spiny-cheek crayfish, and between lab-reared and wild-caught individuals of the marbled crayfish. Apart from predicting invasion success, these analyses help to better understand behavioural plasticity in this special clonal species. Chapter 3 contains the application of two classification schemes - of animal innovation and eco-evolutionary experience - to the dataset of Chapter 1. I encourage the use of this general quantification scheme of animal innovation to mine a broader range of behavioural changes. The scheme was applied in this study to specifically investigate if big changes in behaviour help native species to cope with invasion. It was also tested if high eco-evolutionary experience with that species buffers negative population consequences for native species. We reject the first hypothesis and accept the latter and found as well a negative relationship between both parameters, as lower experience necessitates bigger change. Therefore, these classifications can help a priori predictions of invasion impact on specific native species. In Chapter 4, the population dynamics and nesting behaviour of the common eider (Somateria mollissima) in West Iceland was analysed from field data. The dataset encompasses yearly nest count data on 134 islands over up to 123 years. Therefore, we were able to investigate how long-term climate dynamics affect the eider colonies and how that changed with the invasion of the American mink (Neovison vison) into the region in 1948. Similarly, the arctic fox (Vulpes lagopus), the only native terrestrial nest predator, was absent from the study area for decades and we compared the behavioural response to both predators. The differences between the effects of specific predators help to direct targeted conservation efforts to protect the common eider. Finally, Chapter 5 presents population dynamics of the American mink in Iceland, Denmark, Germany and its native range in the USA estimated from hunting bag data using a novel method. Effects of anthropogenic factors on the hunting bag were quantified, namely the global price of American mink fur, the production of fur in the respective country, and hunting effort and legislation connected to hunting and fur production. While we were able to test several hypotheses on American mink population dynamics in Europe - for example, if it follows a boom-bust dynamic - the utility of this method stretches beyond this system and can be applied whenever population numbers are estimated from hunting bag data. My thesis explores a novel dataset on behavioural changes in biological invasions (Chapter 1). It includes experimental results on the role of behaviour in an over-invasion scenario of crayfish in Europe (Chapter 2) and expands the horizon of behavioural studies in invasions by introducing classification schemes for eco-evolutionary experience and animal innovation (Chapter 3). Finally, the introduction of the American mink in Europe is studied, by its consequences for the Icelandic avifauna (Chapter 4) and the estimation of its population dynamics through hunting bag data in several countries (Chapter 5)

Drivers of spatio-temporal variation in mosquito submissions to the citizen science project ‘Mückenatlas’

Intensified travel activities of humans and the ever growing global trade create opportunities of arthropod-borne disease agents and their vectors, such as mosquitoes, to establish in new regions. To update the knowledge of mosquito occurrence and distribution, a national mosquito monitoring programme was initiated in Germany in 2011, which has been complemented by a citizen science project, the ‘Mückenatlas’ since 2012. We analysed the ‘Mückenatlas’ dataset to (1) investigate causes of variation in submission numbers from the start of the project until 2017 and to (2) reveal biases induced by opportunistic data collection. Our results show that the temporal variation of submissions over the years is driven by fluctuating topicality of mosquito-borne diseases in the media and large-scale climate conditions. Hurdle models suggest a positive association of submission numbers with human population, catch location in the former political East Germany and the presence of water bodies, whereas precipitation and wind speed are negative predictors. We conclude that most anthropogenic and environmental effects on submission patterns are associated with the participants’ (recording) behaviour. Understanding how the citizen scientists’ behaviour shape opportunistic datasets help to take full advantage of the available information

Long-term data reveal contrasting impacts of native versus invasive nest predators in Iceland

Bird species on islands are strongly impacted by biological invasions, with the Icelandic common eider (Somateria mollissima borealis) being particularly threatened. Down collection by local families in Breiðafjörður, West Iceland, provided long-term datasets of nests from two archipelagos, covering 95 islands over 123 years and 39 islands over 27 years, respectively. Using these exceptional datasets, we found that the arrival of the invasive semi-aquatic American mink (Neogale vison) was a more impactful driver of population dynamics than climate. This invasive predator heavily reduced eider nest numbers by ca. 60% in the Brokey archipelago. In contrast, we detected an apparently adaptive response to the return of the native fox in the Purkey archipelago, with dense nests on islands inaccessible to the fox and no apparent impact on eider populations. This difference might be due to the eiders lacking a joint evolutionary history with the mink and therefore lacking appropriate antipredator responses

Batrachochytrium salamandrivorans’ Amphibian Host Species and Invasion Range

Batrachochytrium salamandrivorans (Bsal), a species related to the destructive pathogen Batrachochytrium dendrobatidis (Bd), was found and identified in Europe in 2013. Now, a decade later, a large amount of information is available. This includes data from studies in the field, reports of infection in captive amphibians, laboratory studies testing host susceptibility, and data from prospective studies that test for Bsal’s presence in a location. We conducted a systematic review of the published literature and compiled a dataset of Bsal tests. We identified 67 species that have been reported positive for Bsal, 20 of which have a threatened conservation status. The distribution of species that have been found with infection encompasses 69 countries, highlighting the potential threat that Bsal poses. We point out where surveillance to detect Bsal have taken place and highlight areas that have not been well monitored. The large number of host species belonging to the families Plethodontidae and Salamandridae suggests a taxonomic pattern of susceptibility. Our results provide insight into the risk posed by Bsal and identifies vulnerable species and areas where surveillance is needed to fill existing knowledge gaps

A conceptual map of invasion biology: Integrating hypotheses into a consensus network

Background and aims Since its emergence in the mid‐20th century, invasion biology has matured into a productive research field addressing questions of fundamental and applied importance. Not only has the number of empirical studies increased through time, but also has the number of competing, overlapping and, in some cases, contradictory hypotheses about biological invasions. To make these contradictions and redundancies explicit, and to gain insight into the field’s current theoretical structure, we developed and applied a Delphi approach to create a consensus network of 39 existing invasion hypotheses. Results The resulting network was analysed with a link‐clustering algorithm that revealed five concept clusters (resource availability, biotic interaction, propagule, trait and Darwin’s clusters) representing complementary areas in the theory of invasion biology. The network also displays hypotheses that link two or more clusters, called connecting hypotheses, which are important in determining network structure. The network indicates hypotheses that are logically linked either positively (77 connections of support) or negatively (that is, they contradict each other; 6 connections). Significance The network visually synthesizes how invasion biology’s predominant hypotheses are conceptually related to each other, and thus, reveals an emergent structure – a conceptual map – that can serve as a navigation tool for scholars, practitioners and students, both inside and outside of the field of invasion biology, and guide the development of a more coherent foundation of theory. Additionally, the outlined approach can be more widely applied to create a conceptual map for the larger fields of ecology and biogeography

How biological invasions affect animal behaviour: A global, cross-taxonomic analysis

In the Anthropocene, species are faced with drastic challenges due to rapid, human-induced changes, such as habitat destruction, pollution and biological invasions. In the case of invasions, native species may change their behaviour to minimize the impacts they sustain from invasive species, and invaders may also adapt to the conditions in their new environment in order to survive and establish self-sustaining populations. We aimed at giving an overview of which changes in behaviour are studied in invasions, and what is known about the types of behaviour that change, the underlying mechanisms and the speed of behavioural changes. Based on a review of the literature, we identified 191 studies and 360 records (some studies reported multiple records) documenting behavioural changes caused by biological invasions in native (236 records from 148 species) or invasive (124 records from 50 species) animal species. This global dataset, which we make openly available, is not restricted to particular taxonomic groups. We found a mild taxonomic bias in the literature towards mammals, birds and insects. In line with the enemy release hypothesis, native species changed their anti-predator behaviour more frequently than invasive species. Rates of behavioural change were evenly distributed across taxa, but not across the types of behaviour. Our findings may help to better understand the role of behaviour in biological invasions as well as temporal changes in both population densities and traits of invasive species, and of native species affected by them

Alternative splicing of MALT1 controls signalling and activation of CD4+ T cells

MALT1 channels proximal T-cell receptor (TCR) signalling to downstream signalling pathways. With MALT1A and MALT1B two conserved splice variants exist and we demonstrate here that MALT1 alternative splicing supports optimal T-cell activation. Inclusion of exon7 in MALT1A facilitates the recruitment of TRAF6, which augments MALT1 scaffolding function, but not protease activity. Naive CD4+ T cells express almost exclusively MALT1B and MALT1A expression is induced by TCR stimulation. We identify hnRNP U as a suppressor of exon7 inclusion. Whereas selective depletion of MALT1A impairs T-cell signalling and activation, downregulation of hnRNP U enhances MALT1A expression and T-cell activation. Thus, TCR-induced alternative splicing augments MALT1 scaffolding to enhance downstream signalling and to promote optimal T-cell activation

The microbial metabolite desaminotyrosine enhances T-cell priming and cancer immunotherapy with immune checkpoint inhibitors

Background Inter-individual differences in response to immune checkpoint inhibitors (ICI) remain a major challenge in cancer treatment. The composition of the gut microbiome has been associated with differential ICI outcome, but the underlying molecular mechanisms remain unclear, and therapeutic modulation challenging. Methods We established an in vivo model to treat C57Bl/6j mice with the type-I interferon (IFN-I)-modulating, bacterial-derived metabolite desaminotyrosine (DAT) to improve ICI therapy. Broad spectrum antibiotics were used to mimic gut microbial dysbiosis and associated ICI resistance. We utilized genetic mouse models to address the role of host IFN-I in DAT-modulated antitumour immunity. Changes in gut microbiota were assessed using 16S-rRNA sequencing analyses. Findings We found that oral supplementation of mice with the microbial metabolite DAT delays tumour growth and promotes ICI immunotherapy with anti-CTLA-4 or anti-PD-1. DAT-enhanced antitumour immunity was associated with more activated T cells and natural killer cells in the tumour microenvironment and was dependent on host IFN-I signalling. Consistent with this, DAT potently enhanced expansion of antigen-specific T cells following vaccination with an IFN-I-inducing adjuvant. DAT supplementation in mice compensated for the negative effects of broad-spectrum antibiotic-induced dysbiosis on anti-CTLA-4-mediated antitumour immunity. Oral administration of DAT altered the gut microbial composition in mice with increased abundance of bacterial taxa that are associated with beneficial response to ICI immunotherapy. Interpretation We introduce the therapeutic use of an IFN-I-modulating bacterial-derived metabolite to overcome resistance to ICI. This approach is a promising strategy particularly for patients with a history of broad-spectrum antibiotic use and associated loss of gut microbial diversity

Blockchain for Education: Lifelong Learning Passport

Certificates play an important role in education and in professional development in companies. Individual learning records become essential for people’s professional careers. It is therefore important that these records are stored in long-term available and tamper-proof ledgers. A blockchain records transactions in a verifiable and permanent way, therefore it is very suitable to store fingerprints of certificates or other educational items. Blockchain reveals forgery of certificates and it supports learning histories. In this paper, we present the Blockchain for Education platform as a practical solution for issuing, validating and sharing of certificates. At first, we describe the conceptual system overview and then we present in detail the platform implementation including management of certification authorities and certificates, smart contracts as well as services for certifiers, learners and third parties such as employers. Finally, we describe use cases and first evaluation results that we gathered from end user tests with certifiers and conclude with a discussion

ABO subgroup incompatibility with severe hemolysis after consecutive allogeneic stem cell transplantations

Abstract Allogeneic hematopoietic stem cell transplantations (HSCTs) represent a curative strategy for treating hematologic malignancies yet bear dangerous and frequently life‐threatening complications including the development of graft‐versus‐host disease. Here, we present a case of a patient that suffered from relapsed/refractory multiple myeloma, a hematologic neoplasm characterized by clonal proliferation of malignant plasma cells in the bone marrow. During the course of his disease, the patient underwent consecutive allogeneic HSCTs, during which he developed a clinical meaningful and hitherto unreported ABO subgroup incompatibility, leading to persistent hemolysis. Testing for ABO subgroups during donor selection, especially after consecutive allogeneic HSCTs, may therefore aid to prevent these complications