The influence of semiochemicals on the co-occurrence patterns of a global invader and native species

Mapping Intimacies ◽

10.26686/wgtn.17012432.v1 ◽

2021 ◽

Author(s):

◽

Fabian Westermann

Keyword(s):

Chemical Communication ◽

Argentine Ant ◽

Food Sources ◽

Large Field ◽

Pest Species ◽

Foraging Success ◽

Resident Species ◽

Argentine Ants ◽

Invasive Ant ◽

Introduced Range

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.

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The influence of semiochemicals on the co-occurrence patterns of a global invader and native species

10.26686/wgtn.17012432 ◽

2021 ◽

Author(s):

◽

Fabian Westermann

Keyword(s):

Chemical Communication ◽

Argentine Ant ◽

Food Sources ◽

Large Field ◽

Pest Species ◽

Foraging Success ◽

Resident Species ◽

Argentine Ants ◽

Invasive Ant ◽

Introduced Range

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Influence of the Number of Queens on Nest Establishment: Native and Invasive Ant Species

Animals ◽

10.3390/ani11030591 ◽

2021 ◽

Vol 11 (3) ◽

pp. 591

Author(s):

Irene Castañeda ◽

Elsa Bonnaud ◽

Franck Courchamp ◽

Gloria Luque

Keyword(s):

Species Differences ◽

Argentine Ants ◽

Invasive Ant ◽

Internal Factors ◽

Ant Colonies ◽

Worker Behavior ◽

Key Factor ◽

Nest Maintenance ◽

Set Up ◽

Tapinoma Nigerrimum

As a critical stage in the life cycle of ant colonies, nest establishment depends on external and internal factors. This study investigates the effect of the number of queens on queen and worker behavior during nest establishment in invasive Argentine ants (Linepitema humile) and native Mediterranean Tapinoma nigerrimum. We set up experimental colonies with the same number of workers but with one or six queens. At different time points, we recorded the positions of queens and workers inside and outside the nest. Our results highlight the influence of the number of queens on the position of queens and workers with between-species differences. Queens of both species entered the nests more quickly when there were six queens. During nest establishment, more workers were inside nests with six queens for both species, with this effect being greater for T. nigerrimum. Once nests were established, fewer workers of both species were engaged in nest maintenance and feeding in nests with six queens; T. nigerrimum had fewer workers engaged in patrolling. These results suggest that the number of queens is a key factor driving queen and worker behavior during and after nest establishment with different species responses.

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The widespread collapse of an invasive species: Argentine ants ( Linepithema humile ) in New Zealand

Biology Letters ◽

10.1098/rsbl.2011.1014 ◽

2011 ◽

Vol 8 (3) ◽

pp. 430-433 ◽

Cited By ~ 34

Author(s):

Meghan Cooling ◽

Stephen Hartley ◽

Dalice A. Sim ◽

Philip J. Lester

Keyword(s):

Climate Change ◽

Invasive Species ◽

New Zealand ◽

Argentine Ant ◽

Environmental Costs ◽

Argentine Ants ◽

Ant Communities ◽

Mean Survival Time ◽

Colony Collapse ◽

Increasing Temperature

Synergies between invasive species and climate change are widely considered to be a major biodiversity threat. However, invasive species are also hypothesized to be susceptible to population collapse, as we demonstrate for a globally important invasive species in New Zealand. We observed Argentine ant populations to have collapsed in 40 per cent of surveyed sites. Populations had a mean survival time of 14.1 years (95% CI = 12.9–15.3 years). Resident ant communities had recovered or partly recovered after their collapse. Our models suggest that climate change will delay colony collapse, as increasing temperature and decreasing rainfall significantly increased their longevity, but only by a few years. Economic and environmental costs of invasive species may be small if populations collapse on their own accord.

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Multi-host viruses in Argentine ants and honey bees: Increased viral disease in honey bees is associated with Argentine ants

10.26686/wgtn.16912519 ◽

2021 ◽

Author(s):

◽

Jana Dobelmann

Keyword(s):

Honey Bees ◽

Rna Viruses ◽

Population Control ◽

Argentine Ant ◽

Viral Dynamics ◽

Invasive Ants ◽

Argentine Ants ◽

Deformed Wing Virus ◽

Tomato Ringspot Virus ◽

Bee Health

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. 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. 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. 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.

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Update on the invasion status of the Argentine ant, Linepithema humile (Mayr, 1868), in Madrid, a large city in the interior of the Iberian Peninsula

Journal of Hymenoptera Research ◽

10.3897/jhr.85.65725 ◽

2021 ◽

Vol 85 ◽

pp. 161-177

Author(s):

Diego López-Collar ◽

Francisco J. Cabrero-Sañudo

Keyword(s):

Urban Areas ◽

Necessary Conditions ◽

Large City ◽

Linepithema Humile ◽

Argentine Ant ◽

Invasive Ant ◽

Personal Communications ◽

Great Capacity ◽

Green Areas ◽

The City

New geolocated records of the invasive ant Linepithema humile (Mayr, 1868) are added to the previous references for the city of Madrid and its surroundings, and the possible causes of the occurrence and permanence of this species in urban areas are discussed. The data collection corresponds to a series of samplings carried out for the last three years in green areas of the city, bibliographic searches, citizen science platforms and personal communications. To date, eleven locations in the urban area of Madrid and four points outside the city have been registered. The city of Madrid is undergoing a colonisation by the Argentine ant, although it is not widespread yet, since observations over time and space are isolated and apparently unrelated. However, this species has a great capacity to disperse and establish new colonies, mainly human-mediated through the transport of goods, plants, gardening tools, etc. Considering the numerous colonizable urban green areas in the city that can provide the necessary conditions for its expansion, the Argentine ant should not be underestimated, and immediate action is strongly recommended.

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The interface between invasive species science and legal regulation, using Hymenopteran species and their pathogens as a model system

10.26686/wgtn.17131952.v1 ◽

2021 ◽

Author(s):

◽

Evan Brenton-Rule

Keyword(s):

Invasive Species ◽

New Zealand ◽

Biological Invasions ◽

Honey Bee ◽

Legal Regulation ◽

Argentine Ants ◽

Deformed Wing Virus ◽

Introduced Range ◽

The Impact ◽

Bee Virus

Biological invasions are one of the major causes of biodiversity decline on the planet. The key driver of the global movement of invasive species is international trade. As a response to trade driven invasive species risk, international and domestic regulations have been promulgated with the goal of managing the spread and impact of non-native species. My aims in this thesis were twofold. First, my goal was to review a subset of international and domestic regulations with a view to commenting on their fitness for purpose and suggesting potential improvements. Second, I used the example of non-native and invasive Hymenoptera, as well as their pathogens, to illustrate the risks posed by invasive species and gaps in their management. In order to assess international and domestic regulations, I reviewed the World Trade Organization’s (WTO) Agreement on Sanitary and Phytosanitary Measures, as well as associated disputes. I argue that the WTO’s regulatory system does, for the most part, allow domestic regulators to manage invasive species risk as they see fit. Subsequently, the focus of the thesis narrows to investigate New Zealand’s pre- and post-border regime managing invasive species. I argue that New Zealand’s pre-border approach represents international best practice, but the post-border management of species is fragmented. The power to manage invasive species has been delegated to sub-national and regional bodies, which typically approach invasive species management in different ways. This variation has led to regulatory inconsistencies in pests managed and funding allocated. There appears to be a substantial lack of planning in some spaces, such as the risk of aquatic invasions. I make recommendations to ameliorate these inconsistencies. My second aim involved the study of non-native and invasive Hymenoptera in New Zealand, as well as the pathogens they carry, in order to illustrate the risks posed by invasive species and gaps in their management. I show that the globally widespread invasive Argentine ant (Linepithema humile) may play a role in the pathogen dynamics and mortality of honey bee hives where the species occur sympatrically. Hives in the presence of Argentine ants suffered significantly higher mortality rates relative to hives without ants and always had higher levels of a honey bee pathogen Deformed wing virus. I demonstrate that honey bee pathogens are found in a range of invasive Hymenoptera in New Zealand. I amplify entire genomes of the honey bee virus Kashmir bee virus (KBV) from three species of non-native or invasive Hymenoptera (Argentine ants, common wasps and honey bees). I show that there is KBV strain variability within and between regions, but more between regions. Further, I demonstrate the result that as sampled KBV sequence length increases, so too does sampled diversity. These results highlight how ‘an’ invasive species is typically not alone: they carry a range of diseases that are almost always not considered in international and regional management plans. Patterns of non-native Hymenoptera carrying honey bee diseases were not restricted to New Zealand. I used mitochondrial DNA to find the likely origin of invasive populations of the globally distributed invasive German wasp. I demonstrate that German wasps show reduced genetic diversity in the invaded range compared to the native range. Populations in the introduced range are likely to have arrived from different source populations. In some regions there were likely multiple introductions. Other regions are genetically homogenous and represent potential areas for use of gene drive technologies. All four different honey bee pathogens assayed for were found in German wasp populations worldwide. These results highlight how the introduction of one exotic species likely brings a range of pathogens. This example of pathogens in Hymenoptera is likely to be true for nearly all non-native introductions. Many of the impacts of biological invasions, such as predation and competition, are relatively obvious and are frequently studied. However some, such as the impact of pathogens, are unseen and poorly understood. Legal regulation is often a post-hoc response implemented once a problem has already arisen. At a global level regulatory regimes operate relatively effectively. As the focus becomes more granular, such as the case of pathogens of Hymenoptera, fewer controls exists. This thesis helps to reduce uncertainty in this area as well as makes recommendations as to how these risks may be managed.

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Argentine Ant (Hymenoptera: Formicidae) Foraging Activity Response to Selected Containerized Baits

Journal of Entomological Science ◽

10.18474/0749-8004-29.2.209 ◽

1994 ◽

Vol 29 (2) ◽

pp. 209-214 ◽

Cited By ~ 10

Author(s):

Brian T. Forschler ◽

G. Michael Evans

Keyword(s):

Untreated Control ◽

Fish Meal ◽

Nest Site ◽

Peanut Butter ◽

Argentine Ant ◽

Foraging Activity ◽

Argentine Ants ◽

Ant Foraging ◽

Bait Station ◽

To Receive

Bait acceptance and effect of toxic bait consumption on the foraging activity of field colonies of Argentine ants, Linepithema humile (Mayr), were assessed. Nine individual colonies were randomly assigned to receive one of three treatments: a containerized bait containing 0.5% sulfluramid in a peanut butter matrix, a containerized bait containing 0.9% hydramethylnon in an insect pupae-fish meal matrix, and an untreated control. Ant foraging activity was measured using honey-water monitoring stations placed at 0, 1, and 3 m from the colony nest-site. Both containerized baits reduced ant foraging activity to zero ants per monitor within 6 wks, if the equivalent of one containerized bait station was consumed by the colony.

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Deterrency and Toxicity of Essential Oils to Argentine and Red Imported Fire Ants (Hymenoptera: Formicidae)

Journal of Entomological Science ◽

10.18474/0749-8004-42.2.239 ◽

2007 ◽

Vol 42 (2) ◽

pp. 239-249 ◽

Cited By ~ 10

Author(s):

Beverly A. Wiltz ◽

Daniel R. Suiter ◽

Wayne A. Gardner

Keyword(s):

Essential Oils ◽

Argentine Ant ◽

Fire Ants ◽

Continuous Exposure ◽

Tea Tree Oil ◽

Argentine Ants ◽

Tea Tree ◽

Citronella Oil ◽

Imported Fire Ants ◽

Red Imported Fire Ants

Laboratory assays were conducted to evaluate deterrency and contact toxicity of six essential oils to the Argentine ant, Linepithema humile (Mayr), and the red imported fire ant, Solenopsis invicta Buren. In choice tests, both Argentine ants and fire ants crossed barriers treated with multiple rates of basil, citronella, lemon, peppermint, or tea tree oil less frequently than paired control barriers. Eucalyptus oil did not prevent movement of either species at any of the rates tested. In continuous exposure assays, citronella oil killed 50% of Argentine ants in 34.3 min and was the only treatment to cause 100% Argentine ant mortality after 24 h. Argentine ant mortality after 24 h was 89.8% with peppermint oil and 85.7% with tea tree oil, with the remaining treatments having mortality not significantly different from the control. Only citronella oil caused significant mortality of red imported fire ants, with 50.6% of the ants being dead after 24 h of continuous exposure.

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Inter-species horizontal toxicity: Experimental control of Argentine ants and their citrophilus mealybug mutualists in a viticultural system

10.26686/wgtn.17072675 ◽

2021 ◽

Author(s):

◽

Catherine Hardiman

Keyword(s):

Natural Enemies ◽

Control Method ◽

Cropping Systems ◽

Pinot Noir ◽

Wine Quality ◽

Argentine Ants ◽

Invasive Ant ◽

Food Research ◽

Leafroll Disease ◽

Low Toxicity

The invasive Argentine ant, Linepithema humile, is known to form a trophobiotic association with honeydew excreting homopterans Pseudococcus sp. providing protection from natural enemies in exchange for the honeydew they excrete. The vine mealybug Pseudococcus calceolariae, can transmit Grapevine leafroll- associated virus 3 (GLRaV-3) between vines as it travels and feeds with the ensuing leafroll disease negatively impacting on vine health and wine quality. Therefore, if an effective chemical control method targeting incursions of Argentine ants in vineyards contributes to the dissociation of this invasive ant species with its citrophilus mealybug mutualist, then in theory the spread of GLRaV-3 in vineyards by its mealybug vector can be stemmed. Three insecticidal treatments targeting Argentine ants in the canopy of potted Pinot Noir grapevines inoculated with citrophilus mealybugs were trialled at a field site established in Nelson during the summer of 2016/2017. Bifenthrin (1200ppm) was sprayed on vine trunks and the low- toxicity baits, thiamethoxam (0.0006%) or boric acid (0.5%) carried in polyacrylamide gel with 25% sucrose and 0.15% citric acid solution, were placed at the base of vines. A significant decline in ant activity (p < 0.001) and citrophilus mealybugs was observed for the bifenthrin treatment. A follow-on bioassay was conducted at Mt. Albert Plant and Food Research, in the absence of P. calceolariae’s natural enemies to test the hypothesis that the decline in citrophilus mealybugs in response to vines treated with bifenthrin, could in fact be due to inter-species horizontal toxicity because of Argentine ants transferring the toxicant bifenthrin to citrophilus mealybugs while tending them or contaminating the substrate that they fed on. The significant decrease in average citrophilus mealybug activity rate (p < 0.001) for bifenthrin treatments compared with the controls provides evidence for inter-species horizontal toxicity. Bifenthrin sprayed on grapevine trunks may be suitable to control Argentine ants in the vine canopy and indirectly control P. calceolariae, a known vector of GLRaV-3 between grapevine hosts. The concept of inter-species horizontal toxicity could become a model for targeted pest management by exploiting different insect mutualisms in various horticultural cropping systems.

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Bacterial diversity and viral discovery in the invasive Argentine ant (Linepithema humile)

10.26686/wgtn.17014649.v1 ◽

2021 ◽

Author(s):

◽

Alexandra Sébastien

Keyword(s):

Biological Control ◽

Invasive Species ◽

Population Dynamics ◽

New Zealand ◽

Bacterial Diversity ◽

Linepithema Humile ◽

Argentine Ant ◽

Invasive Ants ◽

Argentine Ants ◽

Species Population

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.

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