The fight against malaria vector mosquitoes is an essential strategy for eradicating this disease. Selective capture of anthropophilic Anopheles species is crucial for targeted vector control. In this study, the ability of synthetic attractants, 4-hydroxycoumarin and 7-decyloxychromone, and their combination with CO2 to selectively capture anthropophilic Anopheles species was evaluated in the field. To do this, nocturnal trappings were conducted using CDC light traps in rural area, in the highlands of Madagascar. Each night test, baited and unbaited traps were set up. The results confirm that 4-hydroxycoumarin efficiently and selectively attracts anthropophilic Anopheles (KI = 80%; SI = 5.1). 7-decyloxychromone has a similar attractive effect but with much lower selectivity (KI = 69%; SI = 1.6). The tested mixtures of products did not show any synergistic effect on selectivity for anthropophilic Anopheles species. A decrease or even elimination, in the number of anthropophilic Anopheles was observed during consecutive trapping nights. These results may indicate that using selective synthetic attractants in mass trapping could contribute to reducing malaria vector populations, offering a promising complementary approach for vector control programs.

In the past decade, dengue fever has emerged as a major public health on Réunion Island in the Southwest Indian Ocean. During the 2018-2022 outbreak, an unusual increase in ocular complications was reported in some patients. To investigate a potential viral cause, we analysed 447 blood samples from hospitalized patients with and without ophthalmic symptoms. Genetic sequencing revealed the co-circulation of two strains of dengue virus serotype 1, both genetically linked to strains previously identified in Asia. Notably, all patients with ophthalmic symptoms were infected with viruses from a single cluster within genotype I, which harbored several unique mutations. These findings suggest that the rare ocular complications observed during this outbreak may be associated with specific viral cluster. Further laboratory studies are required to confirm this potential link.

Gastrointestinal (GI) manifestations have been increasingly reported in COVID-19 patients. Here, we use the Drosophila melanogaster midgut model to investigate SARS-CoV-2-induced GI pathogenesis. The fly midgut exhibits susceptibility to orally administered virus, resulting in disrupted epithelial architecture, reduced organ size, and altered visceral muscle dynamics. These effects are accompanied by sustained proliferation of intestinal stem cells alongside decreased replenishment and viability of differentiated cells. Transcriptomic profiling reveals biphasic perturbations in midgut gene expression, particularly in pathways related to lipid metabolism. Intriguingly, SARS-CoV-2 elicits a dichotomous effect on lipid homeostasis, with lipid droplet accumulation in the posterior midgut and depletion in anterior segments. Treatment with Plitidepsin, a COVID-19 drug candidate, mitigates most SARS-CoV-2 pathogenic features in both the Drosophila midgut and human pulmonary cells, while modulating basal lipid droplet homeostasis in uninfected conditions. These findings establish the Drosophila midgut as a potent model for studying SARS-CoV-2 GI pathogenesis and evaluating antiviral compounds.

Understanding viral community ecology in bats is essential for elucidating shedding patterns and the drivers of co-infections. In this study, we explore the genetic diversity and within-host dynamics of herpesviruses (HSV) in Mormopterus francoismoutoui, a tropical insectivorous bat endemic to Reunion Island. Over three consecutive years, we collected saliva samples from seven roosts, including repeated samples from recaptured individuals. Illumina sequencing of HSV PCR-positive samples revealed a high diversity of strains (n = 20), belonging to alpha, beta and gamma-HSV subfamilies. Co-infection was frequent, with 44% of bats shedding strains from all three subfamilies. While most shedding patterns with different subfamilies appeared random, our results suggested a negative influence of gamma-HSV occurrence of the probability of co-shedding alpha-HSV. We also demonstrated a lower HSV diversity in juveniles as compared to adult bats, while pregnancy appeared to increase viral diversity-although this requires further confirmation. Longitudinal recaptures of bats revealed an accumulation of multiple HSV latent-infections over life, as the probability to be infected with a new subfamily increased with time interval between recaptures. Within-host strain dynamics were highly variable, with 79% of bats showing fluctuations in strain diversity over time-either gaining or losing strains-consistent with latency and reactivation mechanisms. These findings provide new insights into the ecological and evolutionary dynamics of herpesviruses in wild bat populations. ### Competing Interest Statement The authors have declared no competing interest.

Climate and land-use changes are accelerating the spread of the mosquito Aedes albopictus, a major arbovirus vector, leading to the emergence and autochthonous transmission of dengue or chikungunya viruses in temperate regions such as Italy and France. This has prompted the development of alternative control strategies to counteract growing insecticide resistance. The Incompatible Insect Technique (IIT) uses mass releases of Wolbachia-infected males that sterilize wild females through Cytoplasmic Incompatibility (CI). We conducted a six-month IIT suppression trial on a remote island in the Western Indian Ocean using a novel Aedes albopictus line with a single Wolbachia infection inducing bi-directional CI. This ensures both released males and accidentally released females are incompatible, avoiding population replacement, a common limitation of standard IIT. The trial was conducted under operational conditions, with release numbers adjusted to wild population densities. Eggs were produced in a central insectary over 1000 km away, shipped by plane and boat to the release site. Our results show: (i) over 95

BACKGROUND:Aedes albopictus and Aedes aegypti are key vectors involved in the transmission of human pathogens worldwide. Epidemiological studies have demonstrated varying levels of arbovirus transmission by these mosquito vectors, leading to an increasing number of investigations that assess vector competence (the ability of an insect to become infected and subsequently transmit a pathogen) of Ae. albopictus and Ae. aegypti lines, to decipher the risks associated with each species. In this study, we evaluated the vector competence of Ae. albopictus and Ae. aegypti lines from the Southwestern Indian Ocean (SWIO) for three arboviruses: Zika virus (ZIKV), dengue virus serotype-1 (DENV-1), and chikungunya virus (CHIKV). METHODS:Ten mosquito lines (eight Ae. albopictus and two Ae. aegypti lines), collected from five islands within SWIO (the Seychelles, the Comoros, and the Mascarene archipelagoes), were exposed to epidemic strains of ZIKV, DENV-1, and CHIKV. Three vector competence parameters (infection rate [IR], dissemination efficiency [DE], and transmission efficiency [TE]) were assessed at different days post exposure (dpe) to infectious blood meals, using plaque forming unit (PFU) assays. In addition, viral loads were quantified in positive saliva. These parameters were then compared between mosquito lines, geographic origins, and dpe for each virus. RESULTS:None of the mosquito lines were competent for the ZIKV strain tested. In contrast, both Ae. albopictus and Ae. aegypti lines were competent vectors for the strains of DENV-1 and CHIKV tested, with transmission efficiencies reaching 35.4% for DENV-1 and 62.5% for CHIKV. For both mosquito species, statistical analyses revealed that dpe significantly influenced vector competence parameters, whereas the geographic origin of mosquito lines did not. CONCLUSIONS:The observed vector competence patterns for the three tested viruses might partly explain their current epidemiology in the SWIO. This approach should involve a larger number of Ae. aegypti lines and should be extended to other ZIKV, DENV, and CHIKV strains, as well as to viruses not currently reported in the region, to better assess the risk of (re-)emergence of mosquito-borne viruses in the SWIO.

Co-infections are a common feature of wildlife systems, yet the factors influencing within-host viral dynamics remain largely unclear. In bats, understanding viral community ecology is essential for elucidating shedding patterns and potential drivers of zoonotic spillover risk. In this study, we explore the genetic diversity and within-host dynamics of herpesviruses (HSV) in Mormopterus francoismoutoui, a tropical insectivorous bat endemic to Reunion Island. Over 3 consecutive years, we collected saliva samples from seven roosts, including samples from recaptured individuals. Illumina sequencing of HSV PCR-positive samples revealed a high diversity of strains (n = 20), belonging to alpha, beta, and gamma-HSV subfamilies. Co-infection was frequent, with 44% of bats shedding strains from all three subfamilies. While most shedding patterns appeared random across subfamilies, our results suggest that gamma-HSV negatively affects the probability of alpha-HSV co-shedding. We also demonstrated a lower HSV diversity in juveniles as compared to adults, while pregnancy appeared to increase viral diversity-although this requires further confirmation. Longitudinal recaptures revealed an accumulation of multiple HSV latent infections over life, as the probability to be infected with a new subfamily increased with time interval between recaptures. Within-host strain dynamics were highly variable, with 79% of bats either gaining or losing strains, consistent with latency and reactivation mechanisms. This study provides rare empirical insight into the within-host viral ecology of a natural reservoir host and can help uncover complex pathways by which viruses interact.IMPORTANCEUnderstanding viral dynamics in bats is critical for anticipating and mitigating zoonotic emergence. This study provides rare, longitudinal insight into herpesvirus co-shedding patterns in Mormopterus francoismoutoui, an endemic bat species on Reunion Island. Here, we revealed high strain diversity and frequent multi-subfamily shedding, highlighting complex within-host viral ecology, shaped by host age, reproductive status, and infection history. Interactions between viral subfamilies suggest competitive dynamics that may influence shedding. These findings deepen our understanding of viral persistence and reactivation in bats and underscore the need to investigate how environmental and anthropogenic stressors may modulate co-shedding and increase the likelihood of spillover events.

Understanding processes driving pathogen transmission in bats is critical to prevent spillovers and emergence events. Although substantial research has addressed this topic, few studies have directly examined shedding dynamics (as opposed to serological studies) and co-infection patterns using fine-scale spatio-temporal datasets. Here, based on the monitoring of 5,714 Reunion free-tailed bats (Mormopterus francoismoutoui) in 17 roosts over 24 months, we studied the co-shedding dynamics of paramyxoviruses (PMV) and Leptospira bacteria (LEPTO) in urine, and herpesviruses (HSV) in saliva. We evidenced all year long shedding with high prevalence of all three infectious agents (37% - 87%), as well as an exceptionally high level of co-shedding (59%), with both positive and negative interactions between infectious agents. Shedding patterns displayed temporal synchrony among roosts, with a peak during summer months, but were not influenced by roost size. Repeated shedding in recaptured bats supports within-host persistence, though underlying mechanisms remain to be identified. Our results also showed rapid HSV infection of juveniles (< 6 months), and suggest longer protection of juveniles by maternal antibodies for PMV and LEPTO. Reproductively-active individuals (both during the pregnancy and mating) were associated with increased PMV and LEPTO shedding, which could result from tradeoffs between reproduction and infection in both sexes, and/or an age-related bias with the progressive infection of older juveniles during reproductive periods. This study highlights the significance of persistent shedding of multiple pathogens, including bacteria, and their intricate interactions within bat populations. Understanding how human-driven ecological changes may disrupt within-host processes and influence pathogen shedding in bats will help assessing the risk of pathogen spillover from bats to other species, including humans.

Located in the Southwest Indian Ocean area (SIOA), the two French overseas territories (FOTs) of Reunion and Mayotte islands are heavily impacted by antimicrobial resistance. The aim of this study was to investigate all cases of NDM-5 and OXA-181 carbapenemase-producing Escherichia coli (CPEc) in these two FOTs between 2015 and 2020, to better understand the regional spread of these last-line treatment resistant bacteria. All E. coli isolates not susceptible to ertapenem from various public and private hospitals on Reunion and Mayotte islands were screened for carbapenemase production. Clinical and microbiological data were collected for each case. Genotypic analysis of the isolates was carried out using WGS to determine the clonality relationship between the isolates and the genetic support of the carbapenemase-encoding genes. A total of 92 isolates of NDM-5 (n = 67) and OXA-181 (n = 25) CPEc was collected from Reunion (n = 55) and Mayotte (n = 37) islands. Whole-genome sequencing identified 4 majors STs (ST58, ST167, ST405 and ST410). Genotypic analysis demonstrated numerous intra-ST possible cross transmission events, including strains isolated in both islands. Finally, all isolates (100

Given the risk of zoonotic disease emergence, including new SARS-CoV-2 variants of COVID-19, rapid diagnostic tools are urgently needed to improve the control of the spread of infectious diseases. A one-pot triplex real-time RT-LAMP (reverse-transcription-loop-mediated isothermal amplification) assay, based on two regions of the genome SARS-CoV-2-specifically the Orf1ab and N genes-along with one internal control, the human RNase P gene, was developed. The multiplexing relies on the distinct melting peaks produced during an annealing step. This tool, named RUNCOV, was compared to the gold-standard reverse-transcription real-time quantitative PCR (RT-qPCR) assay. A simple sample preparation step was designed alongside the assay, making it ready for use on site, as a point-of-care diagnostic tool. RUNCOV is rapid (typically less than 40 minutes), highly sensitive and specific. When tested on clinical samples with known SARS-CoV-2 status, its limit of detection (LOD) ranges between 5 and 20 copies per reaction and its diagnostic sensitivity (97.44%) and specificity (100%) values are high compared to the RT-qPCR gold standard. These results were supported with an extensive in silico analysis of over 14 million genomes, demonstrating this tool was capable of detecting all known SARS-CoV-2 variants, including the most recent ones KP.3.1.1 and BA2.86.1. This molecular assay is portable, as demonstrated when it was used successfully in La R & eacute;union in different contexts outside the laboratory.

ABSTRACT The bacterium Wolbachia pipientis is increasingly studied for its potential use in controlling insect vectors or pests due to its ability to induce Cytoplasmic Incompatibility (CI). CI can be exploited by establishing an opportunistic Wolbachia infection in a targeted insect species through trans-infection and then releasing the infected males into the environment as sterilizing agents. Several host life history traits (LHT) have been reported to be negatively affected by artificial Wolbachia infection. Wolbachia is often considered the causative agent of these detrimental effects, and the importance of the host’s genetic origins in the outcome of trans-infection is generally overlooked. In this study, we investigated the impact of host genetic background using an Aedes albopictus line recently trans-infected with w Pip from the Culex pipiens mosquito, which exhibited some fitness costs. We measured several LHTs including fecundity, egg hatch rate, and male mating competitiveness in the incompatible line after four rounds of introgression aiming at restoring genetic diversity in the nuclear genome. Our results show that introgression with a wild genetic background restored most fitness traits and conferred mating competitiveness comparable to that of wild males. Finally, we show that introgression leads to faster and stronger population suppression under laboratory conditions. Overall, our data support that the host genome plays a decisive role in determining the fitness of Wolbachia -infected incompatible males. IMPORTANCE The bacterium Wolbachia pipientis is increasingly used to control insect vectors and pests through the Incompatible Insect Technique (IIT) inducing a form of conditional sterility when a Wolbachia -infected male mates with an uninfected or differently infected female. Wolbachia artificial trans-infection has been repeatedly reported to affect mosquitoes LHTs, which may in turn compromise the efficiency of IIT. Using a tiger mosquito ( Aedes albopictus ) line recently trans-infected with a Wolbachia strain from Culex pipiens and displaying reduced fitness, we show that restoring genetic diversity through introgression significantly mitigated the fitness costs associated with Wolbachia trans-infection. This was further demonstrated through experimental population suppression, showing that introgression is required to achieve mosquito population suppression under laboratory conditions. These findings are significant for the implementation of IIT programs, as an increase in female fecundity and male performance improves mass rearing productivity as well as the sterilizing capacity of released males.

Nearly 4 billion people live in a dengue risk area worldwide. The prevalence of dengue-related mucocutaneous manifestations and their association with severe dengue differ across studies. The aim of the study was to describe the characteristics of patients with dengue-related mucocutaneous manifestations and to investigate those were associated with severe dengue. A retrospective study was conducted in 2019 among patients with a positive RT-PCR for dengue at the University Hospital of Reunion, which has been experiencing a re-emergence of dengue since 2018. Of 847 patients with confirmed dengue, 283 (33.4%) developed mucocutaneous manifestations. Only manifestations of dehydration such as glossitis, dysgeusia, or conjunctivitis were associated with severe dengue, unlike pruritus and rash, in bivariate analysis but not in multivariate analysis. The rash and pruritus of dengue appear to be accompanied by a pronounced flu-like syndrome in younger people without comorbidity or severity, although careful examination of mucous membranes would better identify signs of dehydration and thus cases likely to worsen.

Dengue virus (DENV) is the most prevalent mosquito-borne Flavivirus that affects humans worldwide. Aedes albopictus, which is naturally infected with the bacteria Wolbachia, is considered to be a secondary vector of DENV. However, it was responsible for a recent DENV outbreak of unprecedented magnitude in Reunion Island, a French island in the South West Indian Ocean. Moreover, the distribution of the cases during this epidemic showed a spatially heterogeneous pattern across the island, leading to questions about the differential vector competence of mosquito populations from different geographic areas. The aim of this study was to gain a better understanding of the vector competence of the Ae. albopictus populations from Reunion Island for local DENV epidemic strains, while considering their infection by Wolbachia. Experimental infections were conducted using ten populations of Ae. albopictus sampled across Reunion Island and exposed to three DENV strains: one strain of DENV serotype 1 (DENV-1) and two strains of DENV serotype 2 (DENV-2). We analyzed three vector competence parameters including infection rate, dissemination efficiency and transmission efficiency, at different days post-exposition (dpe). We also assessed whether there was a correlation between the density of Wolbachia and viral load/vector competence parameters. Our results show that the Ae. albopictus populations tested were not able to transmit the two DENV-2 strains, while transmission efficiencies up to 40.79% were observed for the DENV-1 strain, probably due to difference in viral titres. Statistical analyses showed that the parameters mosquito population, generation, dpe and area of sampling significantly affect the transmission efficiencies of DENV-1. Although the density of Wolbachia varied according to mosquito population, no significant correlation was found between Wolbachia density and either viral load or vector competence parameters for DENV-1. Our results highlight the importance of using natural mosquito populations for a better understanding of transmission patterns of dengue.

Aedes albopictus mosquitoes face numerous anthropic stressors in urban areas. These xenobiotics not only impact mosquito physiology but also shape the composition of their microbiota, which play important roles in host physiological traits. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants known to alter mosquito metabolism, but no studies have yet investigated their impact on microbiota. Using a bespoke indoor mesocosm tailored for Ae. albopictus mosquitoes, we investigated the dynamics of bacterial communities in both mosquitoes and their larval breeding sites following chronic exposure to a cocktail of PAHs consisting of benzo[a]pyrene, benz[a]anthracene, chrysene and benzo[b]fluoranthene. Our findings showed that PAHs have a stage-specific effect on mosquito microbiota, with a higher impact in larvae than in adults, contributing to 12.5 % and 4.5 % of the PAHs-induced variations, respectively. The presence of PAHs in the treated mesocosm led to the enrichment of bacterial families and genera known for their ability to catabolize PAHs, such as Comamonadaceae and Raoultella (increasing from 19 % to 30 % and from 1.2 % to 5.6 %, respectively). Conversely, prevalent taxa found in mosquito microbiota like Wolbachia and Cedecea exhibited a reduction (decreasing from 4 % to 0.8 % and from 12.8 % to 6.4 %, respectively). This reduction could be attributed to the competitive advantage gained by PAH-degrading taxa, or it could reflect a direct sensitivity to PAH exposure. Overall, this indicates a shift in microbiota composition favoring bacteria that can thrive in a PAH-contaminated environment. PAHs persisted in the water of breeding sites only the first 45 days of the experiment. Benzo[a]pyrene and benzo[b]fluoranthene were more susceptible to bioaccumulation in larval tissues over time. Overall, this study enhances our understanding of the impact of pollution on mosquitoes and could facilitate future research on the importance of symbiosis in urban-dwelling insect disease vectors. Given the recent advancements in the generation of axenic (microbe-free) and gnotobiotic (mosquitoes with a defined or specific microbiota) mosquitoes, further studies are needed to explore how changes in microbiota composition could influence mosquito responses to pollution, particularly in relation to host fitness, immunity, and vector competence.

The global expansion of Aedes albopictus has stimulated the development of environmentally friendly methods aiming to control disease transmission through the suppression of natural vector populations. Sterile male release programmes are currently being deployed worldwide, and are challenged by the availability of an efficient sex separation which can be achieved mechanically at the pupal stage and/or by artificial intelligence at the adult stage, or through genetic sexing, which allows separating males and females at an early development stage. In this study, we combined the genetic sexing strain previously established based on the linkage of dieldrin resistance to the male locus with a Wolbachia transinfected line. For this, we introduced either the w Pip-I or the w Pip-IV strain from Culex pipiens in an asymbiotic Wolbachia -free Ae . albopictus line. We then measured the penetrance of cytoplasmic incompatibility and life-history traits of both transinfected lines, selected the w Pip-IV line and combined it with the genetic sexing strain. Population suppression experiments demonstrated a 90% reduction in population size and a 50% decrease in hatching rate. Presented results showed that such a combination has a high potential in terms of vector control but also highlighted associated fitness costs, which should be reduced before large-scale field assay.

The spread of antimicrobial resistance (AMR) is a major global concern, and the islands of the Southwest Indian Ocean (SWIO) are not exempt from this phenomenon. As strategic crossroads between Southern Africa and the Indian subcontinent, these islands are constantly threatened by the importation of multidrug-resistant bacteria from these regions. In this systematic review, our aim was to assess the epidemiological situation of AMR in humans in the SWIO islands, focusing on bacterial species listed as priority by the World Health Organization. Specifically, we examined Enterobacterales, Acinetobacter spp., Pseudomonas spp. resistant to carbapenems, and Enterococcus spp. resistant to vancomycin. Our main objectives were to map the distribution of these resistant bacteria in the SWIO islands and identify the genes involved in their resistance mechanisms. We conducted literature review focusing on Comoros, Madagascar, Maldives, Mauritius, Mayotte, Reunion Island, Seychelles, Sri Lanka, and Zanzibar. Our findings revealed a growing interest in the investigation of these pathogens and provided evidence of their active circulation in many of the territories investigated. However, we also identified disparities in terms of data availability between the targeted bacteria and among the different territories, emphasizing the need to strengthen collaborative efforts to establish an efficient regional surveillance network.

Introduction Reunion Island is a French overseas department in the South West Indian Ocean with a unique multi-ethnic population. Cardiovascular diseases are the most common chronic conditions with higher prevalences of hypertension and diabetes compared to mainland France. Moreover, Reunion Island is particularly exposed to vector-borne diseases such as chikungunya and dengue. Our objective is to describe the prevalence of cardiometabolic and infectious diseases in Reunion Island and explore causal mechanisms linking these diseases.Methods The REUNION study is an ongoing French prospective study. From January 2022, 2,000 consenting participants (18-68 years old) are being recruited from the general population according to polling lists and random generation of cellphone number. Baseline examination consists of (i) general health examination, assessment of cardiovascular risk factors, markers of subclinical atherosclerosis, bronchial obstruction, neuropathic and autonomic dysfunction, (ii) questionnaires to determine sociodemographic characteristics, diet, exposure to vector-borne diseases, mental health and cognitive functions, social inequalities in health and ethnic origins, (iii) biological sampling for determination of cardiovascular risk factors, seroprevalence of infectious diseases, innovative lipid biomarkers, advanced omics, composition of intestinal, periodontal and skin microbiota, and biobanking.Conclusions The REUNION study should provide new insights into the prevalence of cardiometabolic and infectious diseases, as well as their potential associations through the examination of various environmental pathways and a wide range of health aspects.

During biological invasion process, species encounter new environments and partially escape some ecological constraints they faced in their native range, while they face new ones. The Asian tiger mosquito Aedes albopictus is one of the most iconic invasive species introduced in every inhabited continent due to international trade. It has also been shown to be infected by a prevalent yet disregarded microbial entomoparasite Ascogregarina taiwanensis. In this study, we aimed at deciphering the factors that shape the global dynamics of A. taiwanensis infection in natural A. albopictus populations. We showed that A. albopictus populations are highly colonized by several parasite genotypes but recently introduced ones are escaping it. We further performed experiments based on the invasion process to explain such pattern. To that end, we hypothesized that (i) mosquito passive dispersal (i.e. human-aided egg transportation) may affect the parasite infectiveness, (ii) founder effects (i.e. population establishment by a small number of mosquitoes) may influence the parasite dynamics, and (iii) unparasitized mosquitoes are more prompt to found new populations through active flight dispersal. The two first hypotheses were supported as we showed that parasite infection decreases over time when dry eggs are stored and that experimental increase in mosquitoes' density improves the parasite horizontal transmission to larvae. Surprisingly, parasitized mosquitoes tend to be more active than their unparasitized relatives. Finally, this study highlights the importance of global trade as a driver of biological invasion of the most invasive arthropod vector species.

Island endemic bats are a considerable cause of conservation concerns, as islands are vulnerable ecosystems facing natural and anthropogenic threats such as growing urbanization. Here, we studied the Reunion free-tailed bat (Mormopterus francoismoutoui), an endemic species to Reunion Island that has adapted to urban settings. We investigated the evolutionary history of Mormopterus at a regional scale, as well as on Reunion Island sex-specific and seasonal patterns of genetic structure. We used an extensive spatio-temporal sampling including 1,136 individuals from 18 roosts and three biological seasons (non-reproductive/winter, pregnancy/summer, and mating), with additional samples of Mormopterus species from neighbouring islands (M. jugularis from Madagascar and M. acetabulosus from Mauritius). Complementary information gathered from both microsatellite and mitochondrial markers revealed high genetic diversity but no signal of spatial genetic structure and weak evidence of female philopatry. Regional analysis suggests a single colonization event for M. francoismoutoui, dated around 175,000 years ago, and followed by in-situ diversification and the evolution of divergent ancestral lineages, which today form a large metapopulation. Population expansion was relatively ancient (55,000 years ago) and thus not linked to human colonization and the availability of human-constructed day-roost sites. Discordant structure between mitochondrial and microsatellite markers suggests the presence of yet-unknown mating sites, or the recent evolution of putative ecological adaptations. Our study illustrates the challenge of detailed genetic studies to provide critical insights to insular ecology and evolutionary history, and the importance of both mitochondrial and nuclear DNA in exploring in-situ diversification of an urban-dwelling bat, endemic to a small island.

IntroductionThe influence of Wolbachia on mosquito reproduction and vector competence has led to renewed interest in studying the genetic diversity of these bacteria and the phenotypes they induced in mosquito vectors. In this study, we focused on two species of Eretmapodites, namely Eretmapodites quinquevittatus and Eretmapodites subsimplicipes, from three islands in the Comoros archipelago (in the Southwestern Indian Ocean).MethodsUsing the COI gene, we examined the mitochondrial genetic diversity of 879 Eretmapodites individuals from 54 sites. Additionally, we investigated the presence and genetic diversity of Wolbachia using the wsp marker and the diversity of five housekeeping genes commonly used for genotyping through Multiple Locus Sequence Typing (MLST).Results and discussionOverall, Er. quinquevittatus was the most abundant species in the three surveyed islands and both mosquito species occurred in sympatry in most of the investigated sites. We detected a higher mitochondrial genetic diversity in Er. quinquevittatus with 35 reported haplotypes (N = 615 specimens, Hd = 0.481 and π = 0.002) while 13 haplotypes were found in Er. subsimplicipes (N = 205 specimens, Hd = 0.338 and π = 0.001), this difference is likely due to the bias in sampling size between the two species. We report for the first time the presence of Wolbachia in these two Eretmapodites species. The prevalence of Wolbachia infection varied significantly between species, with a low prevalence recorded in Er. quinquevittatus (0.8%, N = 5/627) while infection was close to fixation in Er. subsimplicipes (87.7%, N = 221/252). Both male and female individuals of the two mosquito species appeared to be infected. The analysis of MLST genes revealed the presence of two Wolbachia strains corresponding to two new strain types (STs) within the supergroups A and B, which have been named wEretA and wEretB. These strains were found as mono-infections and are closely related, phylogenetically, to Wolbachia strains previously reported in Drosophila species. Finally, we demonstrate that maternal transmission of Wolbachia is imperfect in Er. subsimplicipes, which could explain the presence of a minority of uninfected individuals in the field.