Mixed-cropping between field pea varieties alters root bacterial and fungal communities

Modern agricultural practices have vastly increased crop production but negatively affected soil health. As such, there is a call to develop sustainable, ecologically-viable approaches to food production. Mixed-cropping of plant varieties can increase yields, although impacts on plant-associated microbial communities are unclear, despite their critical role in plant health and broader ecosystem function. We investigated how mixed-cropping between two field pea (Pisum sativum L.) varieties (Winfreda and Ambassador) influenced root-associated microbial communities and yield. The two varieties supported significantly different fungal and bacterial communities when grown as mono-crops. Mixed-cropping caused changes in microbial communities but with differences between varieties. Root bacterial communities of Winfreda remained stable in response to mixed-cropping, whereas those of Ambassador became more similar to Winfreda. Conversely, root fungal communities of Ambassador remained stable under mixed-cropping, and those of Winfreda shifted towards the composition of Ambassador. Microbial co-occurrence networks of both varieties were stronger and larger under mixed-cropping, which may improve stability and resilience in agricultural soils. Both varieties produced slightly higher yields under mixed-cropping, although overall Ambassador plants produced higher yields than Winfreda plants. Our results suggest that variety diversification may increase yield and promote microbial interactions

The cult of St Æthelwold and its context, c. 984-c. 1400

This thesis documents the cult of St Æthelwold, a tenth-century bishop of Winchester, from its inception (c. 984) until the late Middle Ages. During his life, Æthelwold was an authoritative figure who reformed monasteries in southern England. Those communities subsequently venerated him as a saint and this thesis examines his cult at those centres. In particular, it studies how his cult enabled monasteries to forge their identities and to protect their rights from avaricious bishops. It analyses the changing levels of veneration accorded to Æthelwold over a five hundred year period and compares this with other well-known saints’ cults. It uses diverse evidence from hagiographies, chronicles, chartularies, poems, church dedications, wall paintings, and architecture. Very few studies have attempted to chart the development of an early English saint's cult over such a long time period, and my multidisciplinary approach, using history, art, and literary studies, offers insight into the changing role of native saints in the English church and society over the course of the Middle Ages. The thesis has five chapters, excluding the introduction and conclusion. Chapter 1 compares Æthelwold's early cult and the concepts of sanctity displayed in his hagiography with contemporary English and continental cults and their written saints' lives. Chapter 2 analyses the cult in the turbulent post-Conquest period. Chapter 3 demonstrates that c.1111 there was a hitherto unstudied revival of the cult, which spread Æthelwold's relics across southern England. Chapter 4 analyses Æthelwold in twelfth-century monastic literature, examining the different depictions of Æthelwold, and how and why Æthelwold was employed by monastic communities to protect their rights and lands. Chapter 5 examines the cult in the later Middle Ages, analysing the continued liturgical veneration of Æthelwold at monastic houses throughout England, and how the community of Winchester used his cult to foster their internal monastic identity. The thesis places Æthelwold's cult in context and broadly examines how saints' cults, as a cultural phenomenon, developed and functioned in medieval society

Impact of rising seawater levels and subsequent flooding on microbial community function in terrestrial soils

Storm surges, flooding, and the encroaching of seawater onto agricultural land is predicted to increase with climate change fundamentally altering soil properties. It is therefore important to understand the knock-on effect seawater flooding may have on the microbial community and its functioning. This study uses a mesocosm approach to simulate the flooding of terrestrial soil and monitor 1) changes in soil environmental parameters (pH, metal concentration, conductivity), 2) microbial functioning (metabolic activity and degradative enzymes), and 3) microbial community composition (16S sequencing). The system chosen was a naturally occurring saltmarsh-terrestrial pasture gradient where three sites were sampled: Low and High elevation Saltmarsh and agricultural pastureland, incorporating a legacy of differing levels of seawater ingress and exposure. The hypotheses tested in this study were that (1) resistance of microbial community functioning and structure to not be altered during seawater flooding is a factor of pre-adaptation to the stress, and (2) this adaptation will result in communities resilient to flooding, returning to previous state prior to flooding. Soil mesocosms, established from soil taken at the sample sites, were exposed to seawater flooding for durations of 0, 1, 96- and 192-hours submersion. This equated to 72 mesocosms sampled both immediately after the flooding, and after a 14 day “recovery” period. The physicochemical properties significantly increased with seawater flooding in pasture, but not saltmarsh soils. Whilst metabolic activity decreased in all sites post flooding, the saltmarsh communities were more resilient to seawater inundation, and recovered at a faster rate to levels pre flooding. Communities from saltmarsh sites also had a higher resistance to flooding retaining enzymatic function following prolonged exposure. These results suggest that communities previously exposed to flooding have increased resistance / resilience to seawater inundation, and those that do not are significantly impacted even after short flooding durations

Know your enemy : a molecular approach to determine how the pygmy shrew (Sorex minutus) in Ireland succumbs to the invasion of the greater white-toothed shrew (Crocidura russula)

Ireland’s smallest resident mammal, the pygmy shrew (Sorex minutus) is rapidly being displaced by the invasive greater white-toothed shrew (Crocidura russula). The presence of this invasive shrew was first recorded in 2007 and they have been expanding their range at a rate of ~5km per year. Considering these two species co- inhabit other regions of Europe, this raises the question of why they seemingly cannot coexist in Ireland. This study applies DNA (and rRNA) metabarcoding to shrew gut contents to investigate the roles of resource competition and gut microbial community structure in this species replacement event. This was applied to over 300 shrews of both species sampled across radial transects in Ireland, two seasons, and a natural ‘control’ site in Belle Île (France) where both species occur together in high abundance. The results show that during the initial stage of colonisation there is little resource competition between the species allowing their ranges to overlap. Over time, interspecific competition increases as the long-term established populations of C. russula switch their diet to the core prey of S. minutus. This could be a result of C. russula exhausting local invertebrate resources, which could be damaging to Ireland’s invertebrate community structure. The Belle Île population of S. minutus can co-exist with C. russula by exploiting locally abundant key taxa, but the Irish S. minutus are not adapting their diet in response to the invader. In addition, Irish S. minutus have a different microbiome structure with a significantly reduced abundance of microbes associated with host immunity which may have left them susceptible to newly introduced stresses. No novel pathogens were detected in the invasive population of C. russula. This diet-microbiome analyses demonstrates that Irish S. minutus have not adapted to compete with another shrew species and could be completely replaced by C. russula in Ireland over time. This multi-faceted approach on this invasive system has demonstrated that subtle differences between populations of shrews can have significant effects on their ability to co-exist

Resource competition drives an invasion-replacement event among shrew species on an island

Invasive mammals are responsible for the majority of native species extinctions on islands. While most of these extinction events will be due to novel interactions between species (e.g. exotic predators and naive prey), it is more unusual to find incidences where a newly invasive species causes the decline/extinction of a native species on an island when they normally coexist elsewhere in their overlapping mainland ranges. We investigated if resource competition between two insectivorous small mammals was playing a significant role in the rapid replacement of the native pygmy shrew Sorex minutus in the presence of the recently invading greater white-toothed shrew Crocidura russula on the island of Ireland. We used DNA metabarcoding of gut contents from >300 individuals of both species to determine each species' diet and measured the body size (weight and length) during different stages of the invasion in Ireland (before, during and after the species come into contact with one another) and on a French island where both species have long coexisted (acting as a natural ‘control’ site). Dietary composition, niche width and overlap and body size were compared in these different stages. The body size of the invasive C. russula and composition of its diet changes between when it first invades an area and after it becomes established. During the initial stages of the invasion, individual shrews are larger and consume larger sized invertebrate prey species. During later stages of the invasion, C. russula switches to consuming smaller prey taxa that are more essential for the native species. As a result, the level of interspecific dietary overlap increases from between 11% and 14% when they first come into contact with each other to between 39% and 46% after the invasion. Here we show that an invasive species can quickly alter its dietary niche in a new environment, ultimately causing the replacement of a native species. In addition, the invasive shrew could also be potentially exhausting local resources of larger invertebrate species. These subsequent changes in terrestrial invertebrate communities could have severe impacts further downstream on ecosystem functioning and services

Genetic tools in the management of invasive mammals : recent trends and future perspectives

1. Invasive non-native species are now considered to be one of the greatest threats to biodiversity worldwide. Therefore, efficient and cost-effective management of species invasions requires robust knowledge of their demography, ecology and impacts, and genetic-based techniques are becoming more widely adopted in acquiring such knowledge. 2. We focus on the use of genetic tools in the applied management of mammalian invasions globally, as well as on their inherent advantages and disadvantages. We cover tools that are used in: (1) detecting and monitoring mammalian invaders; (2) identifying origins and invasive pathways; (3) assessing and quantifying the negative impacts of invaders; and 4) population management and potential eradication of invasive mammals. 3. We highlight changes in sequencing technologies, including how the use of techniques such as Sanger sequencing and microsatellite genotyping, for monitoring and tracing invasive pathways respectively, are now giving way to the use of high-throughput sequencing methods. These include the emergence of environmental DNA (eDNA) metabarcoding for the early detection of invasive mammals, and single nucleotide polymorphisms or whole genomes to trace the sources of invasive populations. We are now moving towards trials of genome-editing techniques and gene drives to control or eradicate invasive rodents. 4. Genetic tools can provide vital information that may not be accessible with non-genetic methods, for the implementation of conservation policies (e.g. early detection using systematic eDNA surveillance, the identification of novel pathogens). However, the lack of clear communication of novel genetic methods and results (including transparency and reproducibility) to relevant stakeholders can be prohibitive in translating these findings to appropriate management actions. Geneticists should engage early with stakeholders to co-design experiments in relation to management goals for invasive mammals

Environmental DNA metabarcoding as an effective and rapid tool for fish monitoring in canals

We focus on a case study along an English canal comparing environmental DNA (eDNA) metabarcoding with two types of electrofishing techniques (wade‐and‐reach and boom‐boat). In addition to corroborating data obtained by electrofishing, eDNA provided a wider snapshot of fish assemblages. Given the semi‐lotic nature of canals, we encourage the use of eDNA as a fast and cost‐effective tool to detect and monitor whole fish communities

Resource competition drives an invasion‐replacement event among shrew species on an island

Invasive mammals are responsible for the majority of native species extinctions on islands. While most of these extinction events will be due to novel interactions between species (e.g. exotic predators and naive prey), it is more unusual to find incidences where a newly invasive species causes the decline/extinction of a native species on an island when they normally coexist elsewhere in their overlapping mainland ranges. We investigated if resource competition between two insectivorous small mammals was playing a significant role in the rapid replacement of the native pygmy shrew Sorex minutus in the presence of the recently invading greater white‐toothed shrew Crocidura russula on the island of Ireland. We used DNA metabarcoding of gut contents from >300 individuals of both species to determine each species' diet and measured the body size (weight and length) during different stages of the invasion in Ireland (before, during and after the species come into contact with one another) and on a French island where both species have long coexisted (acting as a natural ‘control’ site). Dietary composition, niche width and overlap and body size were compared in these different stages. The body size of the invasive C. russula and composition of its diet changes between when it first invades an area and after it becomes established. During the initial stages of the invasion, individual shrews are larger and consume larger sized invertebrate prey species. During later stages of the invasion, C. russula switches to consuming smaller prey taxa that are more essential for the native species. As a result, the level of interspecific dietary overlap increases from between 11% and 14% when they first come into contact with each other to between 39% and 46% after the invasion. Here we show that an invasive species can quickly alter its dietary niche in a new environment, ultimately causing the replacement of a native species. In addition, the invasive shrew could also be potentially exhausting local resources of larger invertebrate species. These subsequent changes in terrestrial invertebrate communities could have severe impacts further downstream on ecosystem functioning and services

Resource competition drives an invasion-replacement event among shrew species on an island

Invasive mammals are responsible for the majority of native species extinctions on islands. While most of these extinction events will be due to novel interactions between species (e.g. exotic predators and naive prey), it is more unusual to find incidences where a newly invasive species causes the decline/extinction of a native species on an island when they normally coexist elsewhere in their overlapping mainland ranges. We investigated if resource competition between two insectivorous small mammals was playing a significant role in the rapid replacement of the native pygmy shrew Sorex minutus in the presence of the recently invading greater white-toothed shrew Crocidura russula on the island of Ireland. We used DNA metabarcoding of gut contents from >300 individuals of both species to determine each species' diet and measured the body size (weight and length) during different stages of the invasion in Ireland (before, during and after the species come into contact with one another) and on a French island where both species have long coexisted (acting as a natural ‘control’ site). Dietary composition, niche width and overlap and body size were compared in these different stages. The body size of the invasive C. russula and composition of its diet changes between when it first invades an area and after it becomes established. During the initial stages of the invasion, individual shrews are larger and consume larger sized invertebrate prey species. During later stages of the invasion, C. russula switches to consuming smaller prey taxa that are more essential for the native species. As a result, the level of interspecific dietary overlap increases from between 11% and 14% when they first come into contact with each other to between 39% and 46% after the invasion. Here we show that an invasive species can quickly alter its dietary niche in a new environment, ultimately causing the replacement of a native species. In addition, the invasive shrew could also be potentially exhausting local resources of larger invertebrate species. These subsequent changes in terrestrial invertebrate communities could have severe impacts further downstream on ecosystem functioning and services