argentine ant
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<p>A salient question in invasion biology is to elucidate what traits make some species invasive and not others. Recently, the introduction process has been hypothesised to function as a filter, selecting for traits that promote invasiveness in introduced populations. Behaviour has been increasingly recognised as a significant driver of animal invasions, but few studies focus on how the introduction process may affect behavioural variation across an invader’s range. This thesis aims at investigating the consequences of the introduction process on behavioural variation along an introduction pathway in the globally widespread Argentine ant. In Chapter I, I investigated transcriptome-wide variations associated with morphological caste as well as worker foraging propensity. I found a number of transcripts showed caste and behaviour-specific expression profiles, and that foraging workers exhibit higher expression of genes related to chemosensory receptors and neurological pathways known to be associated with foraging behaviour and aggression. In chapter II, I investigated octopamine-mediated modulation of foraging behaviour and aggression using pharmacological manipulations using synthetic octopamine (OA) and one of its antagonists. I found that OA was associated with colony-level foraging activity, but did not appear to similarly drive changes in individual behaviour. However, my results suggest that OA is associated with individual aggressiveness, and I also found an association between OA and foraging propensity. In chapter III, I tested the hypothesis that the introduction process selected for increased risk-taking behaviour along the Argentine ant introduction pathway. I used behavioural assays combined with OA diet supplementation in four regions along the introduction pathway, and showed that both behavioural variation and plasticity were consistent across the range, not in support of our hypothesis. Finally, in chapter IV I investigated transcriptome-wide expression profiles in workers along the introduction pathway and discovered distinct transcriptomic signatures associated with range. I found that specific immune and neural pathways were differentially regulated in the introduced range compared to the native range. Overall, my results contribute to a better understanding of caste differentiation and neuromodulation of key behaviours in invasive ants. While I did not find behavioural differentiation between native and invasive Argentine ant populations, I show that they are characterised by specific transcriptomic signatures perhaps underlying the ant’s invasion success. This is one of the first global and integrative studies to focus on changes associated with the introduction of invasive species, and may have important implications for the understanding of biological invasions.</p>
<p>A salient question in invasion biology is to elucidate what traits make some species invasive and not others. Recently, the introduction process has been hypothesised to function as a filter, selecting for traits that promote invasiveness in introduced populations. Behaviour has been increasingly recognised as a significant driver of animal invasions, but few studies focus on how the introduction process may affect behavioural variation across an invader’s range. This thesis aims at investigating the consequences of the introduction process on behavioural variation along an introduction pathway in the globally widespread Argentine ant. In Chapter I, I investigated transcriptome-wide variations associated with morphological caste as well as worker foraging propensity. I found a number of transcripts showed caste and behaviour-specific expression profiles, and that foraging workers exhibit higher expression of genes related to chemosensory receptors and neurological pathways known to be associated with foraging behaviour and aggression. In chapter II, I investigated octopamine-mediated modulation of foraging behaviour and aggression using pharmacological manipulations using synthetic octopamine (OA) and one of its antagonists. I found that OA was associated with colony-level foraging activity, but did not appear to similarly drive changes in individual behaviour. However, my results suggest that OA is associated with individual aggressiveness, and I also found an association between OA and foraging propensity. In chapter III, I tested the hypothesis that the introduction process selected for increased risk-taking behaviour along the Argentine ant introduction pathway. I used behavioural assays combined with OA diet supplementation in four regions along the introduction pathway, and showed that both behavioural variation and plasticity were consistent across the range, not in support of our hypothesis. Finally, in chapter IV I investigated transcriptome-wide expression profiles in workers along the introduction pathway and discovered distinct transcriptomic signatures associated with range. I found that specific immune and neural pathways were differentially regulated in the introduced range compared to the native range. Overall, my results contribute to a better understanding of caste differentiation and neuromodulation of key behaviours in invasive ants. While I did not find behavioural differentiation between native and invasive Argentine ant populations, I show that they are characterised by specific transcriptomic signatures perhaps underlying the ant’s invasion success. This is one of the first global and integrative studies to focus on changes associated with the introduction of invasive species, and may have important implications for the understanding of biological invasions.</p>
The influence of semiochemicals on the co-occurrence patterns of a global invader and native species
<p>The success of invasive species in their introduced range is often influenced by interactions with resident species communities. Chemical communication is one the factors which contributes to a variety of aspects of a species life cycle, ranging from mating, to food localization and interactions with members of the same and other species. In my thesis, I investigate the effects of venoms and semiochemicals on interactions between the invasive Argentine ant (Linepethima humile) with other resident ant species and demonstrate how pheromones can potentially be utilized as an area wide control mechanism of this species, by disrupting their foraging success. I studied the effects of venom composition, their toxicity and utilization on the outcome of aggressive interactions between the Argentine ant and the four Monomorium species in New Zealand occurring. The toxicity of the venom of the two species co-occurring with Argentine ants was significantly higher than the toxicity of the species which do not. However, no correlation between venom toxicity and Monomorium survival was found. For M. antipodum a significant relationship between venom utilization and its mortality was found, indicating that the way venom is used might be an important aspect of these interactions. Physical Aggression between Monomorium and Argentine ants also had strong effects on Monomorium worker mortality, which provided evidence that a variety of factors and strategies contribute to the ability of interacting organisms to withstand the pressure of a dominant invader at high abundance. I conducted bioassays with food sources and synthetic trail pheromones, providing a proof of concept on disrupting the foraging ability of Argentine ants. Other resident species benefited from the reduced success of Argentine ants, but to a varying degree. Behavioural variations between the resident species provided an explanation for observed differences in foraging success and how much each of these individual competitors was able to increase their foraging. The mechanism for the observed increase in resource acquisition of resident species appeared to be a decrease in aggressive behaviour displayed by Argentine ants. I expanded the usage of the synthetic pheromone to a commercial vineyard, were Argentine ants can have negative effects on crop development by dispersing and tending to homopteran pest species. Argentine ants’ access to the crop canopy could be significantly reduced by placing pheromone dispensers at the base of the vine plant, while dispensers in the plant canopy had little effect on Argentine ant numbers. Doubling the amount of pheromone did not result in an additional reduction of ant activity. Lastly incorporating the knowledge gained in the previous chapter, I extended the application of the pheromone to a large field trial over a three month period. Argentine ant activity and foraging success was significantly supressed compared to untreated control plots, providing evidence that this form of large scale application might be a possible way to control large invasive ant populations by disrupting their trail following and foraging behaviour for a prolonged period of time. While initial calculations have suggested that the treatment is currently not feasible (13.3 US$/mg/ha), I found a significant reduction in body fat in workers collected from treated plots compared with untreated plots, suggesting adverse effects on nest fitness. My findings provide new insights into chemical communication between invasive and resident species, support existing dominance hierarchy models in ant populations, and help to establish a target specific potential management technique of wide-spread invasive ant species.</p>
<p>Invasive species can lead to major economic and ecological issues. For this reason, biological controls are being developed in order to help with invasive species population management. Pathogenic bacteria and viruses offer good biological control opportunities as both micro-organisms have played a role in natural population declines. However, beneficial bacteria and viruses associated with the targeted invasive species may interfere with biological controls, by protecting their hosts from infections. Previous knowledge on both pathogenic and beneficial bacteria and viruses present in invasive species may then support the development of an active and efficient biological control. The Argentine ant, Linepithema humile, is a South American invasive ant species that has successfully spread over five continents. The ants were introduced to New Zealand after a complex invasion path, from Argentina their home range to Europe, then to Australia and finally to New Zealand. In their new environments, invasive Argentine ants affect species diversity and can cause agricultural losses. In the absence of any biological controls, the Argentine ant population is controlled by chemical sprays and poison baits. Management of these invasive ants in New Zealand is estimated to cost NZ$ 60 million a year. The Argentine ant population in New Zealand was reported to have unexpectedly declined. It was hypothesised that pathogens were the cause of this population collapse. In this study, bacteria and viruses present in the invasive ants were investigated using 454 sequencing and Illumina sequencing for future developments of possible biological controls for the Argentine ants, and a better understanding of the observed population decline in New Zealand. Bacterial diversity present in Argentine ants either declined or diminished along the invasion pathway. At the same time, the invasive ants maintained a core of nine bacteria genera, including Lactobacillus and Gluconobacter, two bacterial genera with members known for their beneficial associations with honey bees. The presence of these core bacteria may have participated in the success of Argentine ants in their new environments. In the laboratory, the use of ampicillin and gentamicin antibiotics on the ants increased bacterial diversity present in the ants. Furthermore, ampicillin, kanamycin and spectinomycin antibiotic treatments increased ant survival but did not affect the ant fitness or intra-species aggressiveness. Only spectinomycin treated ants presented a higher level of inter-species aggressiveness. Bacterial diversity may play an important role in the ant health and at length population dynamics. Finally, Argentine ants are the hosts of two viruses: the Deformed wing virus (DWV) involved in colony collapse disorder in honey bees, and Linepithema humile virus 1 (LHUV-1), a new virus related to DWV. Both viruses actively replicate within the ants, indicating a possible reservoir role of the ants. However, the effects of the viruses on the ants are not yet known. Further viral infection in the laboratory under different stress conditions and / or antibiotic treatment will give an insight in the role played by these viruses in the observed population collapse of Argentine ants in New Zealand. LHUV-1 may offer a possibility in the development of the first biological control for Argentine ants, depending on its specificity and its effects. This dissertation provides a first insight in the core bacteria as well as potential harmful viruses present in Argentine ants. These bacteria and viruses may play a role in the ant population dynamics. Invasive species may co-introduce harmful pathogens with them, and participate to the spread of local ones. The pathogens may affect both invasive ants and native species population dynamics.</p>
The influence of semiochemicals on the co-occurrence patterns of a global invader and native species
<p>The success of invasive species in their introduced range is often influenced by interactions with resident species communities. Chemical communication is one the factors which contributes to a variety of aspects of a species life cycle, ranging from mating, to food localization and interactions with members of the same and other species. In my thesis, I investigate the effects of venoms and semiochemicals on interactions between the invasive Argentine ant (Linepethima humile) with other resident ant species and demonstrate how pheromones can potentially be utilized as an area wide control mechanism of this species, by disrupting their foraging success. I studied the effects of venom composition, their toxicity and utilization on the outcome of aggressive interactions between the Argentine ant and the four Monomorium species in New Zealand occurring. The toxicity of the venom of the two species co-occurring with Argentine ants was significantly higher than the toxicity of the species which do not. However, no correlation between venom toxicity and Monomorium survival was found. For M. antipodum a significant relationship between venom utilization and its mortality was found, indicating that the way venom is used might be an important aspect of these interactions. Physical Aggression between Monomorium and Argentine ants also had strong effects on Monomorium worker mortality, which provided evidence that a variety of factors and strategies contribute to the ability of interacting organisms to withstand the pressure of a dominant invader at high abundance. I conducted bioassays with food sources and synthetic trail pheromones, providing a proof of concept on disrupting the foraging ability of Argentine ants. Other resident species benefited from the reduced success of Argentine ants, but to a varying degree. Behavioural variations between the resident species provided an explanation for observed differences in foraging success and how much each of these individual competitors was able to increase their foraging. The mechanism for the observed increase in resource acquisition of resident species appeared to be a decrease in aggressive behaviour displayed by Argentine ants. I expanded the usage of the synthetic pheromone to a commercial vineyard, were Argentine ants can have negative effects on crop development by dispersing and tending to homopteran pest species. Argentine ants’ access to the crop canopy could be significantly reduced by placing pheromone dispensers at the base of the vine plant, while dispensers in the plant canopy had little effect on Argentine ant numbers. Doubling the amount of pheromone did not result in an additional reduction of ant activity. Lastly incorporating the knowledge gained in the previous chapter, I extended the application of the pheromone to a large field trial over a three month period. Argentine ant activity and foraging success was significantly supressed compared to untreated control plots, providing evidence that this form of large scale application might be a possible way to control large invasive ant populations by disrupting their trail following and foraging behaviour for a prolonged period of time. While initial calculations have suggested that the treatment is currently not feasible (13.3 US$/mg/ha), I found a significant reduction in body fat in workers collected from treated plots compared with untreated plots, suggesting adverse effects on nest fitness. My findings provide new insights into chemical communication between invasive and resident species, support existing dominance hierarchy models in ant populations, and help to establish a target specific potential management technique of wide-spread invasive ant species.</p>
<p>Invasive species can lead to major economic and ecological issues. For this reason, biological controls are being developed in order to help with invasive species population management. Pathogenic bacteria and viruses offer good biological control opportunities as both micro-organisms have played a role in natural population declines. However, beneficial bacteria and viruses associated with the targeted invasive species may interfere with biological controls, by protecting their hosts from infections. Previous knowledge on both pathogenic and beneficial bacteria and viruses present in invasive species may then support the development of an active and efficient biological control. The Argentine ant, Linepithema humile, is a South American invasive ant species that has successfully spread over five continents. The ants were introduced to New Zealand after a complex invasion path, from Argentina their home range to Europe, then to Australia and finally to New Zealand. In their new environments, invasive Argentine ants affect species diversity and can cause agricultural losses. In the absence of any biological controls, the Argentine ant population is controlled by chemical sprays and poison baits. Management of these invasive ants in New Zealand is estimated to cost NZ$ 60 million a year. The Argentine ant population in New Zealand was reported to have unexpectedly declined. It was hypothesised that pathogens were the cause of this population collapse. In this study, bacteria and viruses present in the invasive ants were investigated using 454 sequencing and Illumina sequencing for future developments of possible biological controls for the Argentine ants, and a better understanding of the observed population decline in New Zealand. Bacterial diversity present in Argentine ants either declined or diminished along the invasion pathway. At the same time, the invasive ants maintained a core of nine bacteria genera, including Lactobacillus and Gluconobacter, two bacterial genera with members known for their beneficial associations with honey bees. The presence of these core bacteria may have participated in the success of Argentine ants in their new environments. In the laboratory, the use of ampicillin and gentamicin antibiotics on the ants increased bacterial diversity present in the ants. Furthermore, ampicillin, kanamycin and spectinomycin antibiotic treatments increased ant survival but did not affect the ant fitness or intra-species aggressiveness. Only spectinomycin treated ants presented a higher level of inter-species aggressiveness. Bacterial diversity may play an important role in the ant health and at length population dynamics. Finally, Argentine ants are the hosts of two viruses: the Deformed wing virus (DWV) involved in colony collapse disorder in honey bees, and Linepithema humile virus 1 (LHUV-1), a new virus related to DWV. Both viruses actively replicate within the ants, indicating a possible reservoir role of the ants. However, the effects of the viruses on the ants are not yet known. Further viral infection in the laboratory under different stress conditions and / or antibiotic treatment will give an insight in the role played by these viruses in the observed population collapse of Argentine ants in New Zealand. LHUV-1 may offer a possibility in the development of the first biological control for Argentine ants, depending on its specificity and its effects. This dissertation provides a first insight in the core bacteria as well as potential harmful viruses present in Argentine ants. These bacteria and viruses may play a role in the ant population dynamics. Invasive species may co-introduce harmful pathogens with them, and participate to the spread of local ones. The pathogens may affect both invasive ants and native species population dynamics.</p>
<p>Invasive ants are a serious ecological problem around the world. The Argentine ant has had devastating effects on resident ant communities and may negatively impact other invertebrates in its introduced range. First detected in Auckland in 1990, this invader has since spread widely around the country. The effect of Argentine ants on invertebrates in New Zealand was investigated by comparing ground-dwelling arthropod species richness and abundance between and among paired uninvaded and invaded sites in seven cities across this invader's New Zealand range. In order to study density-dependent effects, invaded sites were chosen so as to differ in Argentine ant population density. The effects of rainfall and mean maximum temperature on Argentine ant abundance and the species richness and abundance were also examined. Argentine ant population persistence in New Zealand was examined by re-surveying sites of past infestation across this species range. The influence of climate on population persistence was investigated, and how this effect may vary after climate change. Additionally, the potential of community recovery after invasion was also examined. Epigaeic (above ground foraging) ant species richness and abundance was negatively associated with Argentine ant abundance; however, no discernable impact was found on hypogaeic (below ground foraging) ant species. The effect of Argentine ant abundance on non-ant arthropod species richness and abundance was mixed, with most arthropod orders being unaffected. Diplopoda was negatively influenced by Argentine ant abundance while Hemiptera was positively influenced. Annual rainfall and mean maximum temperature were found to have no effect on Argentine ant abundance or resident ant species richness and abundance, though these variables did help explain the distribution of several non-ant arthropod orders. Argentine ant populations appear to be collapsing in New Zealand. Populations had a mean survival time of 14.1 years (95% CI= 12.9- 15.3 years). Climate change may prolong population survival, as survival time increased with increasing temperature and decreasing rainfall, but only by a few years. Formerly invaded Auckland ant communities were indistinguishable from those that had never been invaded, suggesting ant communities will recover after Argentine ant collapse.</p>
<p>Invasive ants are a serious ecological problem around the world. The Argentine ant has had devastating effects on resident ant communities and may negatively impact other invertebrates in its introduced range. First detected in Auckland in 1990, this invader has since spread widely around the country. The effect of Argentine ants on invertebrates in New Zealand was investigated by comparing ground-dwelling arthropod species richness and abundance between and among paired uninvaded and invaded sites in seven cities across this invader's New Zealand range. In order to study density-dependent effects, invaded sites were chosen so as to differ in Argentine ant population density. The effects of rainfall and mean maximum temperature on Argentine ant abundance and the species richness and abundance were also examined. Argentine ant population persistence in New Zealand was examined by re-surveying sites of past infestation across this species range. The influence of climate on population persistence was investigated, and how this effect may vary after climate change. Additionally, the potential of community recovery after invasion was also examined. Epigaeic (above ground foraging) ant species richness and abundance was negatively associated with Argentine ant abundance; however, no discernable impact was found on hypogaeic (below ground foraging) ant species. The effect of Argentine ant abundance on non-ant arthropod species richness and abundance was mixed, with most arthropod orders being unaffected. Diplopoda was negatively influenced by Argentine ant abundance while Hemiptera was positively influenced. Annual rainfall and mean maximum temperature were found to have no effect on Argentine ant abundance or resident ant species richness and abundance, though these variables did help explain the distribution of several non-ant arthropod orders. Argentine ant populations appear to be collapsing in New Zealand. Populations had a mean survival time of 14.1 years (95% CI= 12.9- 15.3 years). Climate change may prolong population survival, as survival time increased with increasing temperature and decreasing rainfall, but only by a few years. Formerly invaded Auckland ant communities were indistinguishable from those that had never been invaded, suggesting ant communities will recover after Argentine ant collapse.</p>
<p><b>Emerging infectious diseases threaten public health, livestock economies, and wildlife. Human-mediated species introductions can alter host and pathogen communities that shape the dynamics of infectious diseases. Several RNA viruses that have been linked to population declines in wild pollinators and losses of managed honey bees have been detected in multiple other species and are suspected to circulate within insect communities. Yet, we lack an understanding of how disease dynamics are affected by the introduction of novel species. These introduced species include invasive ants, which can disturb honey bees and become a pest in apiaries. The Argentine ant (Linepithema humile) is a globally successful invader that has been observed to attack bees and multiple bee-associated viruses have been detected in this ant species.</b></p> <p>Here, I studied interactions between Argentine ants and European honey bees (Apis mellifera) and how these interactions affect viral dynamics in beehives. I first tested a range of pollinators and associated insects for RNA viruses that are pathogenic to honey bees. Bee-associated viruses showed evidence for active viral replication in several pollinator species but also in species that cohabit in beehives such as ants, spiders, and cockroaches. Using phylogenetic analyses, I found that viral transmission within communities was shaped by geographic origin rather than being restricted by species barriers. Next, I used a longitudinal field study to test whether Argentine ant presence affected pathogen infections and survival in beehives. Argentine ants tested positive for three bee-associated viruses even before beehives were moved into ant-infested sites. Increased levels of deformed wing virus in beehives in autumn were associated with ant presence, although hive mortality was not affected by ants over the duration of this experiment. I used RNA sequencing on a subset of honey bee samples collected during autumn to study the RNA virome and identify transcriptomic responses associated with ant presence. Twelve RNA viruses were found in beehives, among those, three plant-associated viruses and an unclassified RNA virus that had not previously been observed in honey bees. Deformed wing virus showed the highest viral titres in most hives, but was only marginally affected by ant presence. Sacbrood virus and tomato ringspot virus levels were increased in hives with ants, however, both viruses are not known to infect Argentine ants and the plant-associated tomato ringspot virus seems unlikely to affect bee health.</p> <p>Lastly, I tested the feasibility of controlling Argentine ants in apiaries using a novel pest control strategy. RNA interference is a conserved cellular gene regulation mechanism that could be used to silence specific genes in ants. Using double-stranded RNA (dsRNA) to silence two immune-related genes in Argentine ants was expected to increase pathogen susceptibility, which could then lead to higher pathogen levels that reduce ant numbers. My results indicated that no consistent immune silencing could be achieved in the field. Immune gene expression changes were observed, but pathogen titres were not affected, and ant numbers stayed high. Argentine ant control using a conventional insecticide significantly increased bee survival, whereas many hives in the dsRNA and control group abandoned their hives due to ant attacks. Although population control was not successful using the two Argentine ant-specific dsRNAs, insights into ant immunity and ant-bee interactions could improve the development of novel control strategies.</p> <p>Bee-associated viruses have repeatedly been detected in ant species, yet, this is one of the first studies to investigate whether ants affect viral dynamics in honey bees. I showed that invasive Argentine ants are associated with increases in viral pathogens in honey bees. The mechanisms by which ants affect bee disease are unknown, although there is some evidence for ants transmitting viruses or causing stress responses in bees that affect immunity. The findings of this thesis highlight the risk of invasive ant species disrupting pollination services. New and environmentally-friendly methods to control invasive species are urgently needed to improve bee health and limit the spread of invasive ants, such as Argentine ants. The high prevalence of bee-associated viruses and viral diversity in ants suggests that pathogens that are suitable for population control might be present in ant populations, although risks of spillovers into other species need to be carefully considered.</p>
<p><b>Emerging infectious diseases threaten public health, livestock economies, and wildlife. Human-mediated species introductions can alter host and pathogen communities that shape the dynamics of infectious diseases. Several RNA viruses that have been linked to population declines in wild pollinators and losses of managed honey bees have been detected in multiple other species and are suspected to circulate within insect communities. Yet, we lack an understanding of how disease dynamics are affected by the introduction of novel species. These introduced species include invasive ants, which can disturb honey bees and become a pest in apiaries. The Argentine ant (Linepithema humile) is a globally successful invader that has been observed to attack bees and multiple bee-associated viruses have been detected in this ant species.</b></p> <p>Here, I studied interactions between Argentine ants and European honey bees (Apis mellifera) and how these interactions affect viral dynamics in beehives. I first tested a range of pollinators and associated insects for RNA viruses that are pathogenic to honey bees. Bee-associated viruses showed evidence for active viral replication in several pollinator species but also in species that cohabit in beehives such as ants, spiders, and cockroaches. Using phylogenetic analyses, I found that viral transmission within communities was shaped by geographic origin rather than being restricted by species barriers. Next, I used a longitudinal field study to test whether Argentine ant presence affected pathogen infections and survival in beehives. Argentine ants tested positive for three bee-associated viruses even before beehives were moved into ant-infested sites. Increased levels of deformed wing virus in beehives in autumn were associated with ant presence, although hive mortality was not affected by ants over the duration of this experiment. I used RNA sequencing on a subset of honey bee samples collected during autumn to study the RNA virome and identify transcriptomic responses associated with ant presence. Twelve RNA viruses were found in beehives, among those, three plant-associated viruses and an unclassified RNA virus that had not previously been observed in honey bees. Deformed wing virus showed the highest viral titres in most hives, but was only marginally affected by ant presence. Sacbrood virus and tomato ringspot virus levels were increased in hives with ants, however, both viruses are not known to infect Argentine ants and the plant-associated tomato ringspot virus seems unlikely to affect bee health.</p> <p>Lastly, I tested the feasibility of controlling Argentine ants in apiaries using a novel pest control strategy. RNA interference is a conserved cellular gene regulation mechanism that could be used to silence specific genes in ants. Using double-stranded RNA (dsRNA) to silence two immune-related genes in Argentine ants was expected to increase pathogen susceptibility, which could then lead to higher pathogen levels that reduce ant numbers. My results indicated that no consistent immune silencing could be achieved in the field. Immune gene expression changes were observed, but pathogen titres were not affected, and ant numbers stayed high. Argentine ant control using a conventional insecticide significantly increased bee survival, whereas many hives in the dsRNA and control group abandoned their hives due to ant attacks. Although population control was not successful using the two Argentine ant-specific dsRNAs, insights into ant immunity and ant-bee interactions could improve the development of novel control strategies.</p> <p>Bee-associated viruses have repeatedly been detected in ant species, yet, this is one of the first studies to investigate whether ants affect viral dynamics in honey bees. I showed that invasive Argentine ants are associated with increases in viral pathogens in honey bees. The mechanisms by which ants affect bee disease are unknown, although there is some evidence for ants transmitting viruses or causing stress responses in bees that affect immunity. The findings of this thesis highlight the risk of invasive ant species disrupting pollination services. New and environmentally-friendly methods to control invasive species are urgently needed to improve bee health and limit the spread of invasive ants, such as Argentine ants. The high prevalence of bee-associated viruses and viral diversity in ants suggests that pathogens that are suitable for population control might be present in ant populations, although risks of spillovers into other species need to be carefully considered.</p>
