The Origin and Invasion Pathway of Brown Rats Rattus norvegicus on Dok-Do Island Revealed by Genome-Wide Markers from 3-RADseq Approach.

Biological invasions are known to cause local extinctions on islands. Dok-do, a small, remote volcanic island in the East Sea of Korea in the western Pacific, has recently been invaded by rats, posing ecological problems. To infer their origin and invasion pathway, we collected rats from Dok-do and from the potential introduction source locations, Ulleung-do in the Pacific Ocean, and four east coastal ports. First, we identified that the brown rat (Rattus norvegicus) was the only rat species occurring at collecting sites based on the key morphological characteristics. To determine the population-level genetic diversity pattern, we applied the 3-RADseq approach. After a series of filtrations (minor allele frequency < 0.05, Hardy-Weinberg equilibrium p < 1 × 10-7), 4042 SNPs were retained for the final dataset from the 25,439 SNPs initially isolated. The spatial structure and genetic diversity pattern of brown rats suggested that the rat population on Dok-do was likely introduced from Ulleung-do. Our work provides practical information that will assist in the management of invasive brown rats in vulnerable island ecosystems.

Angiostrongylus cantonensis Nematode Invasion Pathway, Mallorca, Spain.

Neural angiostrongyliasis is an emerging zoonosis caused by the rat lungworm, Angiostrongylus cantonensis. In humans, infection with this nematode often results in eosinophilic meningitis and other severe disorders of the central nervous system. Europe was deemed a nonendemic region until 2018, when A. cantonensis worms were detected on the Mediterranean island of Mallorca, Spain, a tourism hotspot. Since that time, a sentinel surveillance system and a molecular approach have been used to follow the invasion path of the rat lungworm on the island. A. cantonensis worms have been found in animals from 8 locations on the island over 3 consecutive years. Our preliminary results show a recognizable pattern of clinical signs in infected hedgehogs and a single mitochondrial haplotype circulating in Mallorca. We present strong evidence confirming that the rat lungworm has successfully established and colonized an island in Europe and discuss observations and possible strategies for its early detection across continental Europe.

Prevention is better than cure: Integrating habitat suitability and invasion threat to assess global biological invasion risk by insect pests under climate change.

BACKGROUND: Invasive alien species cause substantial impacts on ecosystem, economy, and public health. Therefore, identifying areas at risk of invasion and establishment is essential for the development and implementation of preventive measures. In this study, we integrated information on species habitat suitability, location of airports and ports, and invasion threat maps to assess global invasion risk under climate change using the cucurbit beetle, Diabrotica speciosa (Germar, 1824), as a model organism. RESULTS: Suitable and optimal habitats for D. speciosa were estimated in several regions beyond its native range and comprised all continents. A decrease in the extent of suitable and optimal habitats for D. speciosa was predicted in different climate change scenarios, resulting in a reduction in invasion risk in most regions. However, regions such as western Europe and isolated areas in southern Asia and Oceania were predicted to face an increase in invasion risk under climate change. Invasion pathways via airports and ports were identified in all continents. CONCLUSION: Our findings can be used in the development of phytosanitary measures against D. speciosa in high-risk areas. Furthermore, the approach used in this study provides a framework for estimating the global risk of invasion by insect pests and other terrestrial organisms in different climate change scenarios. This information can be used by policy makers to develop preventive measures against species with potential to invade and spread in regions beyond their native range. © 2021 Society of Chemical Industry.

A modified two-color flow cytometry assay to quantify in-vitro reinvasion and determine invasion phenotypes at low Plasmodium falciparum parasitemia.

Invasion of human red blood cells (RBCs) by Plasmodium parasites is a crucial yet poorly characterised phenotype. Two-color flow cytometry (2cFCM) promises to be a very sensitive and high throughput method for phenotyping parasite invasion. However, current protocols require high (~1.0%) parasitemia for assay set-up and need to be adapted for low parasitemia samples, which are becoming increasingly common in low transmission settings. Background fluorescence from nuclei-containing uninfected RBCs and high autologous reinvasion rates (merozoite invasion of donor uninfected RBCs present at 50% assay volume) are some of the limitations to the method's sensitivity to enumerate low parasitemia (<0.5%) with nucleic acid-based stains. Here, we describe modifications for plating unlabeled donor to labeled target RBCs per assay well and for gating parasitemia, that produces accurate quantifications of low reinvasion parasitemia. Plasmodium falciparum 3D7, Dd2 and field isolates at various low and high parasitemia (0.05%-2.0%) were used to set-up SyBr Green 1-based 2cFCM invasion assays. Target RBCs were labeled with CTFR proliferation dye. We show that this dye combination allowed for efficient parasite invasion into target RBCs and that a 1:3 ratio of unlabeled to labeled RBCs per assay greatly skewed autologous reinvasion (p < 0.001). Accuracy of quantifying reinvasion was limited to an assay parasitemia of 0.02% with minimal background interference. Invasion inhibition by enzymatic treatments increased averagely by 10% (p<0.05) across the entire parasitemia range. The effect was greater for samples with <0.5% parasitemia. Overall, a more sensitive method for phenotyping invasion of low P. falciparum parasitemia is described.

Bioorthogonal Metabolic Labeling Utilizing Protein Biosynthesis for Dynamic Visualization of Nonenveloped Enterovirus 71 Infection.

Bioorthogonal metabolic labeling through the endogenous cellular metabolic pathways (e.g., phospholipid and sugar) is a promising approach for effectively labeling live viruses. However, it remains a big challenge to label nonenveloped viruses due to lack of host-derived envelopes. Herein, a novel bioorthogonal labeling strategy is developed utilizing protein synthesis pathway to label and trace nonenveloped viruses. The results show that l-azidohomoalanine (Aha), an azido derivative of methionine, is more effective than azido sugars to introduce azido motifs into viral capsid proteins by substituting methionine residues during viral protein biosynthesis and assembly. The azide-modified EV71 (N3-EV71) particles are then effectively labeled with dibenzocyclooctyl (DBCO)-functionalized fluorescence probes through an in situ bioorthogonal reaction with well-preserved viral infectivity. Dual-labeled imaging clearly clarifies that EV71 virions primarily bind to scavenger receptors and are internalized through clathrin-mediated endocytosis. The viral particles are then transported into early and late endosomes where viral RNA is released in a low-pH dependent manner at about 70 min postinfection. These results first reveal viral trafficking and uncoating mechanisms, which may shed light on the pathogenesis of EV71 infection and contribute to antiviral drug discovery.

Total incombustible (mineral) content of Cherax quadricarinatus differs between feral populations in Central-Eastern Australia.

Cherax quadricarinatus has been widely translocated within Australia, and a number of self-sustaining feral populations have established, and persisted, in central-eastern Australia for over 20 years: however, the biology and ecology of feral populations remain poorly understood. Using the loss-by-ignition method, this study investigated differences in the total content of incombustible material (as a proxy for total mineral content), between feral C. quadricarinatus populations in southeast Queensland and northeastern New South Wales. A total of 102 C. quadricarinatus were ignited, and percent total incombustible material was not proportional to the body size, or gender of the crayfish. Incombustible content was however, significantly different between some locations of capture (i.e., waterbodies). The site where incombustible content in crayfish was atypical, Lake Ainsworth, is a naturally acidic coastal lake, and we suggest that acidity and low concentration of calcium in that waterbody are likely responsible for the difference in mineral content detected in that population. Mechanism(s) driving the difference detected in the Lake Ainsworth population are unknown, but we suggest the acidic environment could directly impact maintenance of internal calcium reserves in the crayfish (intermoult), during recalcification of the cuticle (postmoult), or both. Limited calcium availability in the lake may also be a direct, or indirect, contributing factor. The ability of C. quadricarinatus to occupy acidic habitats while managing biomineralization challenges possibly could enable additional range-expansion of the species, and potential impacts on both endangered ecological communities and other biota occupying the acidic coastal habitats of Eastern Australia.

Exploiting Genetic Information to Trace Plant Virus Dispersal in Landscapes.

During the past decade, knowledge of pathogen life history has greatly benefited from the advent and development of molecular epidemiology. This branch of epidemiology uses information on pathogen variation at the molecular level to gain insights into a pathogen's niche and evolution and to characterize pathogen dispersal within and between host populations. Here, we review molecular epidemiology approaches that have been developed to trace plant virus dispersal in landscapes. In particular, we highlight how virus molecular epidemiology, nourished with powerful sequencing technologies, can provide novel insights at the crossroads between the blooming fields of landscape genetics, phylogeography, and evolutionary epidemiology. We present existing approaches and their limitations and contributions to the understanding of plant virus epidemiology.

Unraveling the biogeographic origins of the Eurasian watermilfoil (Myriophyllum spicatum) invasion in North America.

PREMISE OF THE STUDY: Using phylogeographic analyses to determine the geographic origins of biological invaders is important for identifying environmental adaptations and genetic composition in their native range as well as biocontrol agents among indigenous herbivores. Eurasian watermilfoil (Myriophyllum spicatum) and its hybrid with northern watermilfoil (M. sibiricum) are found throughout the contiguous United States and southern Canada, forming one of the most economically costly aquatic plant invasions in North America, yet the geographic origin of the invasion remains unknown. The objectives of our study included determining the geographic origin of Eurasian watermilfoil in North America as well as the maternal lineage of the hybrids. METHODS: DNA sequence data from a cpDNA intron and the nrDNA ITS region were compiled for accessions from 110 populations of Eurasian watermilfoil and hybrids from North America and the native range (including Europe, Asia, and Africa). Datasets were analyzed using statistical parsimony and Bayesian phylogenetics to assess the geographic origin of the invasion. KEY RESULTS: The two Eurasian watermilfoil cpDNA haplotypes in North America are also found from China and Korea, but not elsewhere in the native range. These haplotypes did not overlap and were limited in native geographic range. The ovule parent for hybrids can come from either parental lineage, and multiple haplotypes from both parental species were found. CONCLUSIONS: The geographic origin of this prolific aquatic plant invasion of North America is in Asia. This provides critical information to better understand the invasion pathway and inform management into the future.

The role of life history traits in mammalian invasion success.

Why some organisms become invasive when introduced into novel regions while others fail to even establish is a fundamental question in ecology. Barriers to success are expected to filter species at each stage along the invasion pathway. No study to date, however, has investigated how species traits associate with success from introduction to spread at a large spatial scale in any group. Using the largest data set of mammalian introductions at the global scale and recently developed phylogenetic comparative methods, we show that human-mediated introductions considerably bias which species have the opportunity to become invasive, as highly productive mammals with longer reproductive lifespans are far more likely to be introduced. Subsequently, greater reproductive output and higher introduction effort are associated with success at both the establishment and spread stages. High productivity thus supports population growth and invasion success, with barriers at each invasion stage filtering species with progressively greater fecundity.

Understanding the biological invasion risk posed by the global wildlife trade: propagule pressure drives the introduction and establishment of Nearctic turtles.

Biological invasions are a key component of human-induced global change. The continuing increase in global wildlife trade has raised concerns about the parallel increase in the number of new invasive species. However, the factors that link the wildlife trade to the biological invasion process are still poorly understood. Moreover, there are analytical challenges in researching the role of global wildlife trade in biological invasions, particularly issues related to the under-reporting of introduced and established populations in areas with reduced sampling effort. In this work, we use high-quality data on the international trade in Nearctic turtles (1999-2009) coupled with a statistical modelling framework, which explicitly accounts for detection, to investigate the factors that influence the introduction (release, or escape into the wild) of globally traded Nearctic turtles and the establishment success (self-sustaining exotic populations) of slider turtles (Trachemys scripta), the most frequently traded turtle species. We found that the introduction of a species was influenced by the total number of turtles exported to a jurisdiction and the age at maturity of the species, while the establishment success of slider turtles was best associated with the propagule number (number of release events), and the number of native turtles in the jurisdiction of introduction. These results indicate both a direct and indirect association between the wildlife trade and the introduction of turtles and establishment success of slider turtles, respectively. Our results highlight the existence of gaps in the number of globally recorded introduction events and established populations of slider turtles, although the expected bias is low. We emphasize the importance of researching independently the factors that affect the different stages of the invasion pathway. Critically, we observe that the number of traded individuals might not always be an adequate proxy for propagule pressure and establishment success.

Population genetics suggest that multiple invasion processes need to be addressed in the management plan of a plant disease vector.

The use of a multidisciplinary approach is becoming increasingly important when developing management strategies that mitigate the economic and biological costs associated with invasive pests. A framework of simulated dispersal is combined with life-history information and analyses of population genetic structure to investigate the invasion dynamics of a plant disease vector, the island sugarcane planthopper (Eumetopina flavipes), through an archipelago of significant Australian quarantine concern. Analysis of eight microsatellite loci from 648 individuals suggests that frequent, wind-assisted immigration from multiple sources in Papua New Guinea contributes significantly to repeated colonization of far northern islands. However, intermittent wind-assisted immigration better explains patterns of genetic diversity and structure in the southern islands and on the tip of mainland Australia. Significant population structuring associated with the presence of clusters of highly related individuals results from breeding in-situ following colonization, with little postestablishment movement. Results also suggest that less important secondary movements occur between islands; these appear to be human mediated and restricted by quarantine zones. Control of the planthopper may be very difficult on islands close to Papua New Guinea given the apparent propensity for multiple invasion, but may be achievable further south where local populations appear highly independent and isolated.