Invasion Of Africa Research Articles

A systematic review of poeciliid fish invasions in Africa

BackgroundThis review compiles and synthesises the existing information concerning non-native poeciliid introductions to Africa. The recent upsurge in research on invasive poeciliids has revealed their widespread occurrence in Africa.ResultsWithin the 87 relevant articles, 74% reported on the presence of Gambusia spp., 33% on P. reticulata, 19% on X. hellerii, 11% on X. maculatus, and 5% on other ornamental poeciliids. Overall, poeciliids have been documented as introduced to 25 different countries in Africa. With Gambusia spp. being introduced to 16 countries and P. reticulata to 19 countries. Our results are representative of the current state of research on invasive poeciliids in Africa. There was a concentration of studies in South Africa, with limited research elsewhere. Current distribution data is relatively patchy, although widespread surveys of multiple river systems in Morocco and South Africa, confirmed widespread and abundant established poeciliid populations. The ecological impacts of invasive poeciliids in Africa remain understudied but evidence indicates deleterious effects on native fish, invertebrates, and amphibians, many of which are critically endangered or endemic.ConclusionCurrent research is limited in reporting from certain countries and ecological impacts. An increased effort to monitor species composition in vulnerable waterbodies, especially in the many African countries where invasive poeciliids are reported, should be completed to reveal further established populations. Future research should prioritise quantifying the ecological impacts of invasive poeciliids in the field and identifying both vulnerable and resistant native ecosystems to guide future management decisions.

Control Potential of Multiple Nucleopolyhedrovirus (SfMNPV) Isolated from Fall Armyworm in Nigeria (West Africa).

The fall armyworm (FAW) Spodoptera frugiperda (Lepidoptera, Noctuidae) has now become an invasive pest of global concern. The pest was first detected in Central and Western Africa in early 2016. Sustainable management options explored by stakeholders during early FAW invasion in Africa included the use of biopesticides and biological control. The current study aimed to compare the susceptibility of FAW larvae to SfMNPV with the assumption that the virus isolated from FAW populations in Africa has higher virulence compared with an isolate from Argentina (SfMNPV-ARG). We also hypothesized that host plant plays a role in SfMNPV efficacy and that cannibalism mediates horizontal and vertical transmission of the virus. This work provides pioneering data on the virulence of the new SfMNPV isolate from Nigeria (SfMNPV-KA1), which proved more effective than its exotic counterpart from Argentina (SfMNPV-ARG). The host plant effect made a significant difference between maize and onion with more FAW death in the larvae fed with contaminated onion 5 days post treatment. The study demonstrates and discusses the effect of cannibalism on virus transmission.

The Fall Armyworm and Larger Grain Borer Pest Invasions in Africa: Drivers, Impacts and Implications for Food Systems.

Invasive alien species (IAS) are a major biosecurity threat affecting globalisation and the international trade of agricultural products and natural ecosystems. In recent decades, for example, field crop and postharvest grain insect pests have independently accounted for a significant decline in food quantity and quality. Nevertheless, how their interaction and cumulative effects along the ever-evolving field production to postharvest continuum contribute towards food insecurity remain scant in the literature. To address this within the context of Africa, we focus on the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), and the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), two of the most important field and postharvest IAS, respectively, that have invaded Africa. Both insect pests have shown high invasion success, managing to establish themselves in >50% of the African continent within a decade post-introduction. The successive and summative nature of field and postharvest damage by invasive insect pests on the same crop along its value chain results in exacerbated food losses. This systematic review assesses the drivers, impacts and management of the fall armyworm and larger grain borer and their effects on food systems in Africa. Interrogating these issues is important in early warning systems, holistic management of IAS, maintenance of integral food systems in Africa and the development of effective management strategies.

Fertilizer-bioinsecticide synergy improves maize resilience to Spodoptera frugiperda infestation

Fall armyworm (FAW), Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), invasion in Africa has threatened food security. Optimization of plant tolerance and post-infestation recovery are among the management tactics that are being promoted for the integrated management of this pest, but these techniques are poorly studied in sub-Saharan Africa. Our study examined the efficacy of enriched compost, split-NPK fertilization, conventional fertilization, and bioinsecticides on FAW infestation rates, maize plant resilience, natural enemy presence, and grain yield. We found that split-NPK fertilization significantly improved maize plant robustness and reduced FAW incidence and leaf damage in a phenology-dependent manner, leading to higher grain yields. A synergistic effect was observed when split-NPK was coupled with bioinsecticides, resulting in increased populations of natural predators, and specifically the egg endoparasitoid, Telenomus remus (Nixon) (Hymenoptera: Scelionidae). Multivariate analyses confirmed that factors like split-NPK fertilization, bioinsecticide usage, stem circumference, and overall plant robustness are major determinants of maize grain yield. Our results endorse soil fertility management via split-NPK fertilization as an effective cultural control measure against FAW, providing an alternative to synthetic insecticides. These insights set the stage for future research focused on assessing the economic viability of this integrated approach, exploring the integration of split-NPK with alternative insecticides, evaluating environmental impacts, and examining the underlying resilience mechanisms to FAW, among other avenues.

Characterization of five pigmentation genes as transgenic markers in Spodoptera frugiperda (Lepidoptera: Noctuidae)

The fall armyworm, Spodoptera frugiperda (J. E. Smith), has become one of the most damaging pests worldwide since its invasion of Africa, Asia and Oceania from 2016, threatening plants in 76 families including important crops. Genetics-based methods have proved to be an efficient way to control pests, especially invasive species, but many difficulties must be overcome to develop a transgenic insect strain, especially for a non-model species. Here we thus sought to identify a visible marker that would facilitate the distinction between genetically modified (GM) and non-transgenic insects, thereby simplifying mutation identification and facilitating the broader application of genome editing tools in non-model insects. Five genes (sfyellow-y, sfebony, sflaccase2, sfscarlet, and sfok) that are orthologs of well-studied genes in pigment metabolism were knocked out using the CRISPR/Cas9 system to identify candidate gene markers. Two genes, Sfebony and Sfscarlet, were identified responsible for body and compound eye coloration, respectively, in S. frugiperda, and could be potential visual markers for genetics-based pest management strategies.

Reliability of Pheromone Trap Catches and Maize Plant Damage as Criteria for Timing Fall Armyworm Control Interventions in Humid Forest Agroecology of Central Africa.

Control of fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) since its invasion of Africa still depends on pesticides. Early detection of adults is considered the key to the success of larvae control in the crop field. However, FAW control thresholds based on current monitoring techniques are not well established in Africa. We investigated the efficacy of moth capture frequencies and FAW incidence levels as decision tools for FAW management. Experiments were conducted over two maize cropping seasons during which FAW incidence, severity, and larvae count were recorded during destructive sampling after the application of a homologated insecticide. During the first season, the FAW incidence ranged from 37.5 ± 5.6% in the 25% incidence threshold treatment to 48.1 ± 8.1% in the control. During the second season, the incidence was significantly lower in the 25% incidence threshold treatment (55.8 ± 5.7%) compared with the control (75.7 ± 3.0%). Over the two seasons, no significant difference in FAW damage severity was recorded between the treatments and control. The highest number of larvae per plant (4.0 ± 0.6) was observed in the 10% incidence threshold treatment. Insecticide application did not consistently contribute to reducing FAW incidence and observed plant damage did not translate into yield loss. FAW control needs further investigation to establish a threshold above which damage translates into yield loss, thus necessitating control intervention.

A systematic methodological approach to estimate the impacts of a classical biological control agent’s dispersal at landscape: Application to fruit fly Bactrocera dorsalis and its endoparasitoid Fopius arisanus

Following the invasion of Africa by the oriental fruit fly, Bactrocera dorsalis, Classical biological control (CBC) has been exploited as a safer alternative for its suppression by the introduction and release of the koinobiont endoparasitoid, Fopius arisanus. Although the parasitoids have been released in several African countries, the extent of their dispersal and the resulting extent in benefits to fruit growers have not yet been elucidated. This paper proposes an innovative, multi-level CBC impact analysis that combines cellular automata (CA) and ecological niche models to estimate parasitoid dispersal ranges and the range of farmers who benefit from it. Firstly, we provided a generic, systematic methodological approach using CA rules incorporated into species distribution. Secondly, the model was used to estimate the dispersal range of the parasitoid, based on the life history and bioecology of the host insect (fruit fly) and the parasitoid. Finally, the parasitoid dispersal coverage was mapped across fruit crops attacked by the target fruit fly, and the number of households that benefited from the parasitoids release programme was extracted from the area of the dispersal. The data was projected across all countries where the parasitoid has been released and validated. In Kenya, the model showed that F. arisanus had covered a total area of 50.34 km2 from the initial point of open field release; and at the continental scale, the model predicted that the parasitoid had covered a total area of 229.97 km2. The model estimated that 351,855 and 3,731,330 households had directly benefited from the release of F. arisanus between 2013 and 2018 in Kenya and at the continental level, respectively. The study's outcome is appropriate for providing feedback information on the impact of CBC to government and development partners to assist in making informed decisions on technological interventions.

Russia’s Invasion of Ukraine, the Driving Forces, and Implications for Africa

The study interrogates the issues surrounding Russia’s invasion of Ukraine and the ongoing war between the two Eastern European countries. It examines the remote and immediate causes of the invasion as well as the position of leading and other members of the UN Security Council and other world leaders on the aggression. The study also analysed Russia’s justification of the invasion based on the fact that Russia’s security is being threatened by the continued expansion of NATO to Eastern Europe, against which Moscow claims it is a red line that cannot be tolerated. A brief background of the crisis that led to the invasion/war was examined, as well as the internal and external factors that triggered the invasion. Finally, the paper examined the implications of Russia’s invasion of Africa. The study relied on documentary evidence sourced mainly from the internet and applied the realist theory in analysing the issues. The study found that though NATO’s expansion eastwards and Ukraine’s intention to join the security alliance were the immediate triggers for the invasion, several other remote factors contributed to the invasion. The study also found that though Africa is miles away from the theatre of conflict, it is being affected in several ways by the conflict. Amongst others, the paper recommends that Africa should maintain its non-aligned posture in the conflict, and should seek closer ties within the continent and with non-European partners to cushion the effects of the war.

Interaction effects of desiccation and temperature stress resistance across Spodoptera frugiperda (Lepidoptera, Noctuidae) developmental stages

Insects encounter multiple overlapping physiologically challenging environmental stressors in their habitats. As such, the ability of insects to withstand these stressors singly or interactively is fundamental in population persistence. Following its invasion in Africa, Spodoptera frugiperda (Lepidoptera: Noctuidae) has successfully established and spread in most parts of the continent. However, the mechanisms behind its successful survival across arid and semi-arid African environments are relatively unknown. Here, we investigated the water balance of S. frugiperda across its developmental stages. Given the relationships between desiccation stress, temperature stress and other life history traits in arid ecosystems, we also measured interaction effects across metrics of these traits. Specifically, we measured basal body water content (BWC), water loss rates (WLRs) and the effects of desiccation pre-treatment on critical thermal minimum (CTmin), critical thermal maximum (CTmax) and fecundity. Body water content and WLR increased with age across larval instars. However, the effects of desiccation environments on WLRs were more dramatic for 5th and 6th larval instars. The 5th and 6th instars exhibited highest BWC and magnitude of WLRs plastic responses following desiccation treatment. The effects of desiccation pre-treatment on temperature tolerance were less apparent, only significantly improving CTmin in 2nd and 3rd larval instars and reducing CTmax in 5th instars. In addition, desiccation pre-treatment showed no significant effects on fecundity. These results show that water balance traits differ with developmental stage, while the effects of desiccation pre-treatment were more dramatic and inconclusive. The differential desiccation resistance, high proportional BWC and no desiccation pre-treatment effects on fecundity may help the species survive in arid and semi-arid environments. This information provides insights into understanding S. frugiperda survival under desiccating arid and semi-arid tropical environments and is significant in predicting pest outbreaks.

The effect of climate variability in the efficacy of the entomopathogenic fungus Metarhizium acridum against the desert locust Schistocerca gregaria

Despite substantial efforts to control locusts they remain periodically a major burden in Africa, causing severe yield loss and hence loss of food and income. Distribution maps indicating the value of the basic reproduction number R0 was used to identify areas where an insect pest can be controlled by a natural enemy. A dynamic process-based mathematical model integrating essential features of a natural enemy and its interaction with the pest is used to generate R0 risk maps for insect pest outbreaks, using desert locust and the entomopathogenic fungus Metarhizium acridum (Synn. Metarhizium anisoliae var. acridum) as a case study. This approach provides a tool for evaluating the impact of climatic variables such as temperature and relative humidity and mapping spatial variability on the efficacy of M. acridum as a biocontrol agent against desert locust invasion in Africa. Applications of M. acridum against desert locust in a few selected African countries including Morocco, Kenya, Mali, and Mauritania through monthly spatial projection of R0 maps for the prevailing climatic condition are illustrated. By combining mathematical modeling with a geographic information system in a spatiotemporal projection as we do in this study, the field implementation of microbial control against locust in an integrated pest management system may be improved. Finally, the practical utility of this model provides insights that may improve the timing of pesticide application in a selected area where efficacy is highly expected.

Ratio dependence effects of the parasitoid Dolichogenidea gelechiidivoris on its associated host Tuta absoluta

ABSTRACT The invasion of Africa by the South American leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has caused a severe threat to the production of tomato, Solanum lycopersicum L. (Solanaceae) crops. The excessive use of pesticides for controlling this pest has increased, together with the associated environmental and human health risks. The parasitoid, Dolichogenedia gelechiidivoris Marsh. (Hymenoptera: Braconidae), has been imported into Africa for classical biological control of T. absoluta. To facilitate the mass production of the parasitoid and to predict the success under field conditions, its performance under laboratory conditions was investigated at five densities of T. absoluta larvae, viz. 20, 50, 100, 150, and 200 offered to either a single or group of mated parasitoid females. The findings revealed that D. gelechiidivoris exhibited a type II functional response. Host and parasitoid densities affected superparasitism, which was generally low, less than 5%. Parasitoid offspring emergence ranged from 8 to 39 wasps for a single foraging female, and 6-59 wasps, for a group of foraging females. The host larval densities did not affect the male: female ratio. This study showed that D. gelechiidivoris acts in a density-dependent manner. Therefore, for optimisation of the mass production of the parasitoid, the maximum number of hosts should be offered to a female. The results suggest that D. gelechiidivoris could be effective for classical biological control of T. absoluta, albeit field evaluation is required to validate this finding.

The economic costs of biological invasions in Africa: a growing but neglected threat?

Biological invasions can dramatically impact natural ecosystems and human societies. However, although knowledge of the economic impacts of biological invasions provides crucial insights for efficient management and policy, reliable syntheses are still lacking. This is particularly true for low income countries where economic resources are insufficient to control the effects of invasions. In this study, we relied on the recently developed "InvaCost" database – the most comprehensive repository on the monetised impacts of invasive alien species worldwide – to produce the first synthesis of economic costs of biological invasions on the African continent. We found that the reported costs of invasions ranged between US$ 18.2 billion and US$ 78.9 billion between 1970 and 2020. This represents a massive, yet highly underestimated economic burden for African countries. More alarmingly, these costs are exponentially increasing over time, without any signs of abatement in the near future. The reported costs were mostly driven by damage caused by invaders rather than expenses incurred for management. This trend was highly skewed towards a few regions (i.e. Southern and Eastern Africa) and activity sectors (i.e. agriculture) and incurred by a small number of invasive taxa (i.e. mainly three insect pests: Chilo partellus, Tuta absoluta, Spodoptera frugiperda). We also highlight crucial, large gaps in current knowledge on the economic costs of invasions that still need to be bridged with more widespread research effort and management actions across the continent. Finally, our study provides support for developing and implementing preventive measures as well as integrated post-invasion management actions at both national and regional levels. Considering the complex societal and economic realities in African countries, the currently neglected problem of biological invasions should become a priority for sustainable development.

Non-Chemical Post-Harvest Disinfestation of Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) in Tommy Atkins Mango Using Hot-Water Immersion Treatment

Mango production and trade is a major source of employment, food and income in Sub Saharan Africa (SSA). Most of its production in SSA is under smallholder farming with a few commercial farms undertaking production. Fruits are traded both locally and some exported, with improved exotic varieties being preferred by consumers. However, mango export which is more lucrative to most exporters in terms of foreign currency exchange earnings, is currently faced with serious quarantine restrictions because of the invasive fruit fly, Bactrocera dorsalis. Since its invasion in Africa, yield losses of up to 100 % have been recorded. In addition, loss of export due to restrictions has resulted in loss of potential revenue from lucrative markets such as the European Union. This study aimed at determining postharvest disinfestation parameters for B. dorsalis using hot-water treatments. To attain this, the development of B. dorsalis in the mango cultivar Tommy Atkins was determined. This information was used to treat different immature life stages at 46.1 °C for 12, 24, 36, 48, 60 and 72 min. Mortality of the different life stages over the different duration of treatments was determined. There was an increase in mortality with increasing duration of treatment for all life stages. The egg and first instar life stages were the most heat susceptible stages followed by the second instar larvae. The third instar was the most heat tolerant life stage evaluated and required treatment at 46.1 °C for 86.7 min (95 % CL (77.830–99.880)) to achieve 100 % mortality. Validation experiments at this temperature and treatment duration resulted in no survivors from the 41 542 third instar larvae treated in Tommy Atkins weighing 500–700 g. These results provide an effective treatment protocol which can be adopted by exporters in re-accessing currently inaccessible lucrative export markets in the U.S.A. and Europe.

Invasive crayfish outperform Potamonautid crabs at higher temperatures

Abstract Data on ecological impacts of freshwater crayfish invasions in Africa are scarce but invasion history suggests the likelihood of negative implications for biodiversity. To evaluate the potential for ecological impacts we describe the consumer‐resource dynamics of two established crayfish species (Cherax quadricarinatus and Procambarus clarkii) in comparison with the native trophic analogue, the freshwater crab Potamonautes perlatus preying upon Clarias gariepinus fry using comparative functional responses (FRs) and FR ratio (FRR). Experiments were conducted under dark and light conditions as well as low (19°C) and high (28°C) temperature treatments. All three species exhibited potentially population destabilising Type II (hyperbolic) FRs towards prey, which was significantly higher in the dark than in the light. At low temperatures, P. perlatus exhibited the highest maximum feeding estimate although the FR curve was not significantly different from C. quadricarinatus at the highest prey densities. Both crayfish species had higher attack rates at both temperatures and consumed significantly more prey at the high temperature than P. perlatus. The FRR of both crayfish species at the high temperature treatment was higher than that of P. perlatus due to high attack rate and low handling parameters. At 19°C, P. perlatus had a higher or negligible relative FR magnitude compared to P. clarkii and C. quadricarinatus respectively, which suggests some degree of biotic resistance at this temperature; however, this resistance is decreased at 28°C. Cherax quadricarinatus consistently had disruptive FR parameters across both temperatures. Findings from this study represent an important step towards understanding the impacts of crayfish in Africa for public authorities and environmental managers. The two invasive crayfish species have the potential to exert greater per capita impacts on benthic prey communities in invaded systems as shown by their high FRs and FRRs. Furthermore, C. quadricarinatus is an emerging invader globally and our results provide evidence of potential for negative ecological impact regardless of thermal conditions. African countries and their respective environmental managers should therefore maximise efforts to prevent the introduction and spread of these invaders to conserve native biodiversity.

Horizon Scanning for Plant Health: report on 2017‐2020 activities

To support the newEuropean Union (EU) Plant Health law, the European Commission (EC) DG SANTE requested EFSA in December 2016 to carry out a horizon scanning exercise in order to identify new plant health threats for the EU. To address this request, EFSA has extended in collaboration with the EC Joint Research Centre (JRC), Ispra, Italy, the monitoring system based on the automatic public health surveillance platform MEDISYS, scanning more than 12,000 sources in 72 languages from 196 countries, covering all world's regions. So far, 1,148 plant pests (pests regulated in the EU, pests listed by EPPO and new plant pests) have been daily monitored in media and scientific literature. The results are presented monthly to EC and Member States and published in monthly Media and Scientific Newsletters.In the period January 2017-March 2020, 60,480 news items on 494 pests were automatically selected by MEDISYS from 3841 sourcesin 52 languages from 173 countries. 85% of the media articles concerned regulated pests in the EU. Xylella fastidiosa is the most popular pest, with 26% of media items. Time series of articles on pests and pest's stories included in the newsletters illustrate the media relevance of various plant health issues (pest outbreaks or findings, pest impacts or control measures).In the same period, 11,365 scientific articles on 573 pests were automatically selected from 348 sources. Articles were in 14 languages, 90% of them in English. 6% of the papers focused onSpodoptera frugiperda, the most reported pest following its invasion of Africa in 2017 and its rapid spread in other world regions. Pests not listedin scientific literaturerepresent a larger group than in media, showing the interest of literature monitoring to identify new plant health risks.Future activities will focus on the further platform deployment for scientific literature monitoring.

Potential Distribution and Niche Differentiation of Spodoptera frugiperda in Africa.

The fall armyworm, Spodoptera frugiperda (J.E. Smith) is a serious agricultural pest. The species originates from the tropical and subtropical regions of the Americas and has now become established in many countries. Its strong migratory ability is the key factor in the rapidly expanding range of S. frugiperda in Africa, where food security faces unprecedented challenges. Exploring potential distributions and niche differentiation of S. frugiperda could provide new insights into the nature of climate niche shifts and our ability to anticipate further invasions. In this study, the occurrence population records (native, source, global, and African) and environmental variables of S. frugiperda were selected to fit ecological niche models (ENMs), with an evaluation of niche conservatism during its invasion of Africa. The results showed that the potential distributions of S. frugiperda are mainly in tropical and subtropical areas in Africa. The climate spaces occupied by its native population and introduced African population broadly overlap. Although, climate niches were conserved during invasion of Africa, many climate spaces were unoccupied, suggesting a high remaining invasion potential in Africa. The selection of the biogeographic realm is an important factor in model construction, and has a great influence on the transferability of the models. Indeed, the global model produced the best performance, following the source and native models.

Monitoring the silver carp invasion in Africa: a case study using environmental DNA (eDNA) in dangerous watersheds

Biodiverse habitats are increasingly subject to an intensification of anthropogenic stressors that may severely diminish species richness. Invasive species pose a dominant threat to biodiversity and biosecurity, particularly in biodiversity hotspots like Kruger National Park, South Africa. The invasive silver carp, Hypophthalmichthys molitrix, was introduced into the Olifants River and may experience range spread owing to favorable environmental conditions. Intensive monitoring protocols are necessary to effectively manage invasions of species like silver carp. Unfortunately, tropical and sub-tropical aquatic systems are difficult to monitor using conventional methods (e.g., netting, electrofishing and snorkeling) owing to a range of factors including the presence of dangerous megafauna. Conservation of such systems may be advanced by the adoption of novel methods, including environmental DNA (eDNA) detection. Here, we explore the utility of environmental DNA (eDNA) to conduct safe, reliable and repeatable surveys in dangerous watersheds using silver carp as a case study. We conducted eDNA surveys at 12 sites in two neighbouring watersheds, and determined that the species has expanded its range within the Olifants River and to the south in the Sabie River. Expansion in the former is consistent with the presence of suitable spawning conditions. We discuss the implications of this survey for biodiversity monitoring in similar aquatic systems in the tropics and advocate an integrative approach to biomonitoring in these ecosystems.

Quodvultdeus’ sermons on the creed: A reassessment of his polemics against the Jews, pagans, and Arians

The sermons of Quodvultdeus Bishop of Carthage during the time of the Van­dal invasion of Africa are characterised by their harsh polemics against the Jews, Pagans, and Arians (De symbolo 1-3; Contra Iudaeos, paganos, et Arrianos; De accedentibus ad gratiam 1-2). The polemics against the Arians derived from the fact that the new lords of Africa, the Vandals, were Arians who promoted their belief and persecuted the Romans for professing their Catholic faith. This paper aims to reassess the polemical character of Quodvultdeus’ sermons. They are exa­mined in their liturgical context and compared to other contemporary writings on the Creed, and finally discussed in their historical and religious context. In view of this analysis, it can be stated that the works of Quodvultdeus studied here are not primarily anti-heretical, but they rather focus on affirming the doctrine of the Church and on the adherence of the newly baptised to the Church as a means of salvation. Quodvultdeus’ harsh anti-heretical language is not exceptional in the Latin tradition of creedal catechesis during the 4th and 5th centuries and has there­fore chiefly a catechetical function.

DNA barcoding of the medically important freshwater snail Physa acuta reveals multiple invasion events into Africa

The medically important freshwater snail Physa acuta is highly invasive and has been reported in several freshwater environments across Africa. To identify species and provide initial insights into the origins of P. acuta into African freshwater environments standard molecular barcoding analyses, using the mitochondrial cytochrome c oxidase subunit I gene (COI), was performed on P. acuta isolates from Angola, Burundi and South Africa. Phylogenetic analyses of isolates from Africa could not be distinguished from P. acuta populations from other countries. Comparisons of COI sequences between isolates of P. acuta showed there to be no geographically specific clusters and the African isolates were distributed across four distinct unrelated clades suggesting several independent invasion events. Haplotype analyses indicated that there were a high number of haplotypes with low variation between them, which led to significant differences in AMOVA analyses between countries. This was further evidence of multiple invasion events suggesting multiple novel haplotypes being continually and independently introduced to each country. This approach not only provides initial insight into the invasion of Africa by P. acuta but a molecular method to monitor and manage the use of an agent of biological control.

Epigenetic and genetic variation among three separate introductions of the house sparrow (Passer domesticus) into Australia.

Invasive populations are often associated with low levels of genetic diversity owing to population bottlenecks at the initial stages of invasion. Despite this, the ability of invasive species to adapt rapidly in response to novel environments is well documented. Epigenetic mechanisms have recently been proposed to facilitate the success of invasive species by compensating for reduced levels of genetic variation. Here, we use methylation sensitive-amplification fragment length polymorphism and microsatellite analyses to compare levels of epigenetic and genetic diversity and differentiation across 15 sites in the introduced Australian house sparrow population. We find patterns of epigenetic and genetic differentiation that are consistent with historical descriptions of three distinct, introductions events. However unlike genetic differentiation, epigenetic differentiation was higher among sample sites than among invasion clusters, suggesting that patterns of epigenetic variation are more strongly influenced by local environmental stimuli or sequential founder events than the initial diversity in the introduction population. Interestingly, we fail to detect correlations between pairwise site comparisons of epigenetic and genetic differentiation, suggesting that some of the observed epigenetic variation has arisen independently of genetic variation. We also fail to detect the potentially compensatory relationship between epigenetic and genetic diversity that has been detected in a more recent house sparrow invasion in Africa. We discuss the potential for this relationship to be obscured by recovered genetic diversity in more established populations, and highlight the importance of incorporating introduction history into population-wide epigenetic analyses.