Microbiota of an Invasive Wasp Vespula vulgaris and Hymenopteran relatives: Interpreting the microbiome

<p>Invasive species represent a critical threat to ecosystems and ecological communities, causing changes through overwhelming predation as well as competing with native species for resources. Understanding the mechanisms behind invasive success is essential for understanding why they invade and the consequences of their invasions. Furthermore, invasive species, like all macroscopic organisms, harbour symbiotic and pathogenic microbes that constitute their microbiomes, which could explain invasive success. The complex ecological interaction networks within the microbiome can have a positive or negative impact on host abundance and dominance. These interactions may be significant for invasive species, where microbial influences acting on an exotic host can potentially drive the ecological success of an invasive population to the detriment of recipient communities. This thesis explores the microbiota of one of the most globally invasive species, the common wasp Vespula vulgaris, with the overall aim to investigate and characterise the microbiome of V. vulgaris, using metagenomics, bioinformatics and molecular techniques. The initial comparative microbiota study focused on three distinct life stages (larvae, worker and queen), from two ranges. This analysis revealed a core bacteriome community present in V. vulgaris. There was evidence of higher microbial diversity in wasp larvae compared with workers and queens. The Queen (gyne) microbiome revealed a more specific microbiome with absences of certain microbiota found in larvae and workers from the same nest, indicating a more distinctive microbiome. Interestingly, analysis of life stages between ranges showed significant dissimilarity in microbiomes, with microbiota loses, and acquisitions in the introduced New Zealand range. Using the same techniques, the microbiota of V. vulgaris and four hymenopteran hosts (Apis mellifera, Bombus terrestris, Vespula germanica and Linepithema humile), were comparatively analysed. The analysis investigated both shared microbiota and host specific microbiota. This analysis indicated the polyphagous V. vulgaris as having a diverse microbiome varying between nests and sites, indicating less specific microbiota in comparison to other hymenopteran hosts in this study. Vespid wasp colonies are known to occasionally crash in the presence of diseases; however, there is a lack of reliable evidence indicating pathogenic micro-organisms play an essential role in wasp colony dynamics. Incorporating knowledge gained in previous analyses, the next aim was to investigate V. vulgaris nests symptomatic of an infectious agent to discover the cause of pathology. Through molecular techniques, such as Illumina RNA-Seq, PCR and Sanger sequencing, the potential cause of infection and decline of diseased nests was examined. The metatranscriptomic comparison of diseased and healthy larvae highlighted five putative infectious agents. The bacteria Moellerella wisconsensis, Moku virus, Kashmir Bee Virus, Aspergillus and the microsporidian Vavraia culicis floridensis found in infected larvae, potentially causing pathology in the host. The first known instance of Moku virus, and potentially V. culicis floridensis and M. wisconsensis was documented as potential pathogens of V. vulgaris present in New Zealand. To test for potential virulence of these putative infectious agents, an infection study was carried out. Vespula vulgaris nests and larvae were orally infected in the lab using homogenised infected larvae. Subsequently, test and control larvae were sampled to conduct and quantify a time series analysis of infection using RT-qPCR using designed primers. This dissertation provided the first insight into the microbiome of V. vulgaris in the native and introduced range providing a baseline for further research. This analysis and the subsequent microbiota identified may play a role in wasp population dynamics, giving a better understanding of the observed thriving V. vulgaris population dynamics in New Zealand.</p>

Microbiota of an Invasive Wasp Vespula vulgaris and Hymenopteran relatives: Interpreting the microbiome

<p>Invasive species represent a critical threat to ecosystems and ecological communities, causing changes through overwhelming predation as well as competing with native species for resources. Understanding the mechanisms behind invasive success is essential for understanding why they invade and the consequences of their invasions. Furthermore, invasive species, like all macroscopic organisms, harbour symbiotic and pathogenic microbes that constitute their microbiomes, which could explain invasive success. The complex ecological interaction networks within the microbiome can have a positive or negative impact on host abundance and dominance. These interactions may be significant for invasive species, where microbial influences acting on an exotic host can potentially drive the ecological success of an invasive population to the detriment of recipient communities. This thesis explores the microbiota of one of the most globally invasive species, the common wasp Vespula vulgaris, with the overall aim to investigate and characterise the microbiome of V. vulgaris, using metagenomics, bioinformatics and molecular techniques. The initial comparative microbiota study focused on three distinct life stages (larvae, worker and queen), from two ranges. This analysis revealed a core bacteriome community present in V. vulgaris. There was evidence of higher microbial diversity in wasp larvae compared with workers and queens. The Queen (gyne) microbiome revealed a more specific microbiome with absences of certain microbiota found in larvae and workers from the same nest, indicating a more distinctive microbiome. Interestingly, analysis of life stages between ranges showed significant dissimilarity in microbiomes, with microbiota loses, and acquisitions in the introduced New Zealand range. Using the same techniques, the microbiota of V. vulgaris and four hymenopteran hosts (Apis mellifera, Bombus terrestris, Vespula germanica and Linepithema humile), were comparatively analysed. The analysis investigated both shared microbiota and host specific microbiota. This analysis indicated the polyphagous V. vulgaris as having a diverse microbiome varying between nests and sites, indicating less specific microbiota in comparison to other hymenopteran hosts in this study. Vespid wasp colonies are known to occasionally crash in the presence of diseases; however, there is a lack of reliable evidence indicating pathogenic micro-organisms play an essential role in wasp colony dynamics. Incorporating knowledge gained in previous analyses, the next aim was to investigate V. vulgaris nests symptomatic of an infectious agent to discover the cause of pathology. Through molecular techniques, such as Illumina RNA-Seq, PCR and Sanger sequencing, the potential cause of infection and decline of diseased nests was examined. The metatranscriptomic comparison of diseased and healthy larvae highlighted five putative infectious agents. The bacteria Moellerella wisconsensis, Moku virus, Kashmir Bee Virus, Aspergillus and the microsporidian Vavraia culicis floridensis found in infected larvae, potentially causing pathology in the host. The first known instance of Moku virus, and potentially V. culicis floridensis and M. wisconsensis was documented as potential pathogens of V. vulgaris present in New Zealand. To test for potential virulence of these putative infectious agents, an infection study was carried out. Vespula vulgaris nests and larvae were orally infected in the lab using homogenised infected larvae. Subsequently, test and control larvae were sampled to conduct and quantify a time series analysis of infection using RT-qPCR using designed primers. This dissertation provided the first insight into the microbiome of V. vulgaris in the native and introduced range providing a baseline for further research. This analysis and the subsequent microbiota identified may play a role in wasp population dynamics, giving a better understanding of the observed thriving V. vulgaris population dynamics in New Zealand.</p>

Foraging Behaviour and Individuality in the Common Wasp (Vespula vulgaris)

<p>The extreme ecological success of insect societies is frequently attributed to the division of labour within their colonies (Chittka & Muller, 2009; Holldobler & Wilson, 2009; E. Wilson & Hölldobler, 2005). Yet, we are far from understanding the causes and consequences of division of labour, implying workers’ specialization (Chittka & Muller, 2009; Dornhaus, 2008). Moreover, little studied is the behaviour of individual workers (Jeanson & Weidenmüller, 2013). Social wasps (Hymenoptera: Vespidae) have received less attention than social bees and ants, and our knowledge of basic aspect of their ecology is still poor (Jeanne, 1991; Greene, 1991). With my thesis, I aimed to contribute to a better understanding of the common wasp (Vespula vulgaris) foraging ecology and organization of labour. With a particular attention to their foraging behaviour, I investigated the inter-individual variability among wasp workers and their cooperation. My thesis shows evidence of information sharing and co-ordination in V. vulgaris foragers’ activity. In fact, the discovery and choice of resources by wasp foragers was assisted by information provided by experienced nestmates (Chapter 2). When resources known to portion of the workforce became newly available, the foraging effort of the whole colony increased. My observations of common wasps are hence consistent with foraging activation mechanisms and suggest piloting (in which one individual leads one or more nestmates to a resource) as a possible foraging recruitment mechanism in social wasps. I found huge variation in lifetime activity, task performance, and survival among common wasp workers (Chapter 3). Some individuals specialized on alternative foraging tasks over their lifetime, and a minority individuals performed a disproportionately high number of foraging trips (elitism). Foragers appeared to become more successful with age, accomplishing more trips and carrying heavier fluid loads. Compared to smaller nestmates, larger wasps contributed more to the colony foraging economies. High mortality was associated with the beginning of the foraging activity, relative to lower mortality in more experienced workers. I evaluated the performance of common wasp workers within the same insect colony, and found empirical support for the hypothesis that specialist foragers are more efficient than generalists (Chapter 4). In fact, V. vulgaris behavioural specialists performed more trips per foraging day and their trips tended to be shorter. Despite their more intense foraging effort, specialists lived longer than generalists. I investigated the intra-colonial variation in the sting extension response (SER) of common wasps, measured as a proxy for individual aggressiveness (Chapter 5). I found that wasps vary greatly in their SER and that individuals change during their life. Aggressive individuals tended to become more docile, while docile individuals more aggressive. Older wasps tended to be more aggressive. Wasp size was not significantly related to the SER. Wasp foragers had a less pronounced sting extension than individuals previously involved in nest defence. For the same individual, the aggressive response was proportional to the intensity of the negative stimulus.</p>

Foraging Behaviour and Individuality in the Common Wasp (Vespula vulgaris)

<p>The extreme ecological success of insect societies is frequently attributed to the division of labour within their colonies (Chittka & Muller, 2009; Holldobler & Wilson, 2009; E. Wilson & Hölldobler, 2005). Yet, we are far from understanding the causes and consequences of division of labour, implying workers’ specialization (Chittka & Muller, 2009; Dornhaus, 2008). Moreover, little studied is the behaviour of individual workers (Jeanson & Weidenmüller, 2013). Social wasps (Hymenoptera: Vespidae) have received less attention than social bees and ants, and our knowledge of basic aspect of their ecology is still poor (Jeanne, 1991; Greene, 1991). With my thesis, I aimed to contribute to a better understanding of the common wasp (Vespula vulgaris) foraging ecology and organization of labour. With a particular attention to their foraging behaviour, I investigated the inter-individual variability among wasp workers and their cooperation. My thesis shows evidence of information sharing and co-ordination in V. vulgaris foragers’ activity. In fact, the discovery and choice of resources by wasp foragers was assisted by information provided by experienced nestmates (Chapter 2). When resources known to portion of the workforce became newly available, the foraging effort of the whole colony increased. My observations of common wasps are hence consistent with foraging activation mechanisms and suggest piloting (in which one individual leads one or more nestmates to a resource) as a possible foraging recruitment mechanism in social wasps. I found huge variation in lifetime activity, task performance, and survival among common wasp workers (Chapter 3). Some individuals specialized on alternative foraging tasks over their lifetime, and a minority individuals performed a disproportionately high number of foraging trips (elitism). Foragers appeared to become more successful with age, accomplishing more trips and carrying heavier fluid loads. Compared to smaller nestmates, larger wasps contributed more to the colony foraging economies. High mortality was associated with the beginning of the foraging activity, relative to lower mortality in more experienced workers. I evaluated the performance of common wasp workers within the same insect colony, and found empirical support for the hypothesis that specialist foragers are more efficient than generalists (Chapter 4). In fact, V. vulgaris behavioural specialists performed more trips per foraging day and their trips tended to be shorter. Despite their more intense foraging effort, specialists lived longer than generalists. I investigated the intra-colonial variation in the sting extension response (SER) of common wasps, measured as a proxy for individual aggressiveness (Chapter 5). I found that wasps vary greatly in their SER and that individuals change during their life. Aggressive individuals tended to become more docile, while docile individuals more aggressive. Older wasps tended to be more aggressive. Wasp size was not significantly related to the SER. Wasp foragers had a less pronounced sting extension than individuals previously involved in nest defence. For the same individual, the aggressive response was proportional to the intensity of the negative stimulus.</p>

Ecological Features of the Exotic Wasp Vespula Vulgaris L. 1758 (Hymenoptera: Vespidae) Invading the Southernmost Unesco Biosphere Reserve

Invasive alien species may cause substantial changes and damaging impacts in the ecosystems they invade. Here, we document the current distribution and ecological interactions with native biota of the relatively recently introduced wasp, Vespula vulgaris, in the southern part of the Cape Horn Biosphere Reserve. We conducted surveys and field studies in four different habitats on Navarino Island: evergreen, deciduous and mixed forests, and shrublands. The spread of V. vulgaris through the island since its first detection has led to it occupying suitable habitats for nesting and foraging, both in urban and rural settings. The presence of V. vulgaris on islands and remote areas of the CHBR is likely the result of marine human movement through the channels withing the reserve. Wasp foraging composition was different on each of the four studied habitats, yet strongly linked to each habitat’s resources, indicating the inherent ability of V. vulgaris of exploiting surrounding resources efficiently. The lack of natural competitors and availability of multiple resources as allowed V. vulgaris to rapidly become a common pest in urban and rural settings in the southern extreme of South America. In this context, we believe that eradication would be impossible, although it would be possible to control populations at localized scales with proper planning and long-term management. Our results can act as a base for management planning, and we strongly recommend social engagement and dialog with pertinent governmental institutions to achieve this challenging task.

Phenotypic Plasticity of Common Wasps in an Industrially Polluted Environment in Southwestern Finland

Insects vary in the degree of their adaptability to environmental contamination. Determining the responses with phenotypic plasticity in ecologically important species in polluted environments will ease further conservation and control actions. Here, we investigated morphological characteristics such as body size, body mass, and color of the common wasp Vespula vulgaris in an industrially polluted environment, considering different levels of metal pollution, and we studied the localization of contaminants in the guts of wasps. We revealed some differences in morphological characteristics and melanization of wasps collected in habitats with high, moderate, and low levels of pollution. The results indicated that V. vulgaris from highly polluted environments had reduced melanin pigmentation on the face but increased melanin pigmentation on the 2nd tergite of the abdomen. In addition, with transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX), we found metal particles from the midgut of wasps originating from the polluted environment. Most of the particles were encapsulated with melanin pigment. This finding confirmed that in wasps, ingested metal particles are accumulated in guts and covered by melanin layers. Our data suggest that wasps can tolerate metal contamination but respond phenotypically with modification of their size, coloration, and probably with the directions of the melanin investments (immunity or coloration). Thus, in industrially polluted areas, wasps might probably survive by engaging phenotypic plasticity with no significant or visible impact on the population.

The genome sequence of the common wasp, Vespula vulgaris (Linnaeus, 1758)

We present a genome assembly from an individual female Vespula vulgaris (the common wasp; Arthropoda; Insecta; Hymenoptera; Vespidae). The genome sequence is 188 megabases in span. The majority of the assembly is scaffolded into 25 chromosomal pseudomolecules.

A Diverse Viral Community from Predatory Wasps in Their Native and Invaded Range, with a New Virus Infectious to Honey Bees

Wasps of the genus Vespula are social insects that have become major pests and predators in their introduced range. Viruses present in these wasps have been studied in the context of spillover from honey bees, yet we lack an understanding of the endogenous virome of wasps as potential reservoirs of novel emerging infectious diseases. We describe the characterization of 68 novel and nine previously identified virus sequences found in transcriptomes of Vespula vulgaris in colonies sampled from their native range (Belgium) and an invasive range (New Zealand). Many viruses present in the samples were from the Picorna-like virus family (38%). We identified one Luteo-like virus, Vespula vulgaris Luteo-like virus 1, present in the three life stages examined in all colonies from both locations, suggesting this virus is a highly prevalent and persistent infection in wasp colonies. Additionally, we identified a novel Iflavirus with similarity to a recently identified Moku virus, a known wasp and honey bee pathogen. Experimental infection of honey bees with this novel Vespula vulgaris Moku-like virus resulted in an active infection. The high viral diversity present in these invasive wasps is a likely indication that their polyphagous diet is a rich source of viral infections.

Effects of juvenile hormone in fertility and fertility-signaling in workers of the common wasp Vespula vulgaris

In the highly eusocial wasp, Vespula vulgaris, queens produce honest signals to alert their subordinate workers of their fertility status, and therefore they are reproductively suppressed and help in the colony. The honesty of the queen signals is likely maintained due to hormonal regulation, which affects fertility and fertility cue expression. Here, we tested if hormonal pleiotropy could support the hypothesis that juvenile hormone controls fertility and fertility signaling in workers. In addition, we aimed to check oocyte size as a proxy of fertility. To do that, we treated V. vulgaris workers with synthetic versions of juvenile hormone (JH) analogue and a JH inhibitor, methoprene and precocene, respectively. We dissected the treated females to check ovary activation and analyzed their chemical profile. Our results showed that juvenile hormone has an influence on the abundance of fertility linked compounds produced by workers, and it also showed to increase oocyte size in workers. Our results corroborate the hypothesis that juvenile hormone controls fertility and fertility signaling in workers, whereby workers are unable to reproduce without alerting other colony members of their fertility. This provides supports the hypothesis that hormonal pleiotropy contributes to keeping the queen fertility signals honest.