A field test for competitive effects of<Emphasis Type="Italic"> Aedes albopictus</Emphasis> on<Emphasis Type="Italic"> A. aegypti</Emphasis> in South Florida: differences between sites of coexistence and exclusion?

We tested whether interspecific competition from Aedes albopictus had measurable effects on A. aegypti at the typical numbers of larval mosquitoes found in cemetery vases in south Florida. We also tested whether the effect of interspecific competition from A. albopictus on A. aegypti differed between sites where A. aegypti either persists or went extinct following invasion by A. albopictus. Similar experiments manipulating numbers of A. albopictus in cemetery vases were conducted at three sites of A. aegypti persistence and three sites where A. aegypti was apparently extinct. The experiments were done using numbers of larvae that were determined by observed numbers of larvae for each site, and with resources (leaf detritus) that accumulated in experimental vases placed into each field site. In both the early rainy season (when number of mosquito larvae was low) and the late rainy season (when number of mosquito larvae was high), there was a significant effect of treatment on developmental progress of experimental A. aegypti. In the late rainy season, when numbers of larvae were high, there was also a significant effect of treatment on survivorship of A. aegypti. However, the competition treatment × site type (A. aegypti persists vs extinct) interaction was never significant, indicating that the competitive effect of A. albopictus on A. aegypti did not differ systematically between persistence versus extinction sites. Thus, although competition from A. albopictus is strong under field conditions at all sites, we find no evidence that variation in the impact of interspecific competition is associated with coexistence or exclusion. Interspecific competition among larvae is thus a viable explanation for exclusion or reduction of A. aegypti in south Florida, but variation in the persistence of A. aegypti following invasion does not seem to be primarily a product of variation in the conditions in the aquatic environments of cemetery vases.     

Interpopulation differences in competitive effect and response of the mosquito Aedes aegypti and resistance to invasion by a superior competitor

Geographic variation in species interactions can have major effects on species distributions and can be important for the resistance of resident communities to invasive species. We tested the hypothesis that coexistence or replacement of a resident North American mosquito Aedes aegypti with the invasive Aedes albopictus is affected by interpopulation variation in the inherent competitive ability of A. aegypti and variation in the fecundity–size relationship. We postulated that such variation creates differential population-level outcomes of competition with A. albopictus. We compared competitive abilities of eight North American populations of A. aegypti, four populations sympatric to A. albopictus, and four populations allopatric to A. albopictus. Competition among larvae from each A. aegypti population and a single A. albopictus population was tested in laboratory microcosms in a response-surface design. We found origin of A. aegypti influences its competitive response to competition from A. albopictus and competitive effect on A. albopictus. A. aegypti from allopatric sites preformed better in competition with A. albopictus than did A. aegypti from sympatric sites because they had a stronger average effect on A. albopictus. This average was strongly influenced by the allopatric population from Miami. Competitive effect and response were uncorrelated among populations, indicating inconsistent ranking of A. aegypti in competitive effect and response. Although A. albopictus is generally a superior competitor to A. aegypti, a stronger competitive effect of particular A. aegypti populations on invading A. albopictus may contribute to competition-mediated biotic resistance to the invader. These results suggest that interpopulation variation in competitive ability of A. aegypti may contribute to failure of A. albopictus to invade parts of the southeastern United States and offer evidence of a contribution to biotic resistance by an inferior competitor. Geographic variation in competitive ability may be common and one general cause of variation in invasion success and impact.     

Desiccation and thermal tolerance of eggs and the coexistence of competing mosquitoes

We tested the hypothesis that differences in temperature and desiccation tolerances of eggs of the container-dwelling mosquitoes Aedes albopictus and Aedes aegypti influence whether invading A. albopictus coexist with or exclude A. aegypti in Florida. In the laboratory, egg mortality through 30 days for A. albopictus was strongly temperature and humidity dependent, with low humidity and high temperature producing greatest mortality. In contrast, mortality through 30 days and through 60 days for A. aegypti was very low and independent of temperature and humidity. Mortality through 90 days for A. aegypti showed significant effects of both temperature and humidity. In the field, the proportion of vases occupied by A. albopictus was significantly lower at four of six sites at the start of the wet season (after a dry period) versus well into the wet season (after containers had held water for weeks). The proportion of vases occupied by A. aegypti was independent of when during the wet season vases were sampled. These results imply that dry periods cause disproportionately greater mortality of A. albopictus eggs compared to A. aegypti eggs. Container occupancy at tire and cemetery sites was significantly related to two principal components derived from long-term average climate data. Occupancy of containers by A. albopictus was greatest at cool sites with little or no dry season, and decreased significantly with increasing mean temperature and increasing number of dry months. In contrast, occupancy of containers by A. aegypti was lowest at cool sites with little or no dry season, and increased significantly with increasing mean temperature and increasing dry season length, and decreased significantly with total precipitation and number of wet months. We suggest that local coexistence of these species is possible because warm, dry climates favor A. aegypti and alleviate effects of competition from A. albopictus via differential mortality of A. albopictus eggs.     

Satyrization and satyrization‐resistance in competitive displacements of invasive mosquito species

Competitive displacements or reductions of resident populations of insects, often effected by a related species, may be caused by a variety of mechanisms. Satyrization is a form of mating interference in which males of one species mate with females of another species, significantly decreasing their fitness and not generating hybrids. Satyrization has been established to be the probable cause of competitive displacements of resident mosquitoes by invasive species, especially of Aedes aegypti by Aedes albopictus, two important vectors of dengue and chikungunya viruses. Mathematical models predict that even low levels of asymmetric mating interference are capable of producing competitive displacements or reductions. Couplings of virgin Ae. aegypti females with Ae. albopictus males effectively sterilize these females through the monogamizing actions of male accessory gland products, but the converse interspecific mating does not impact the future reproduction of Ae. albopictus females. Populations of Ae. aegypti exposed to satyrization quickly evolve resistance to interspecific mating, which is believed to ameliorate reproductive interference from, and promote co‐existence with, Ae. albopictus. The evolution of satyrization resistance among Ae. aegypti in laboratory cages is accompanied by fitness costs, such as reduced fecundity and slower receptivity to conspecific males. Cage experiments and field observations indicate that Ae. albopictus males are capable of satyrizing females of other species of the Stegomyia subgenus, potentially leading to competitive displacements, and possible extinctions, especially of endemic species on islands. Examination of other examples of reproductive interference in insects reveals few parallels to the mechanism and outcomes of satyrization by Ae. albopictus. We conclude by posing the hypothesis that satyrization may favor the ecological success of Ae. albopictus, and suggest many lines for future research on this phenomenon.     

Testing Predictions of Displacement of Native Aedes by the Invasive Asian Tiger Mosquito Aedes Albopictus in Florida, USA

The Asian Tiger Mosquito Aedes albopictus arrived in the USA in 1985 in used automobile tires from Japan and became established in Texas. This species has since spread to become the most abundant container-inhabiting mosquito in the southeastern USA, including Florida, where it has reduced the range of another non-indigenous mosquito, Aedes aegypti. To assess the accuracy of predictions that A. albopictus would competitively exclude the native Eastern Treehole Mosquito Aedes triseriatus from tires but not from treeholes (Livdahl and Willey (1991) Science 253: 189–191), we extensively monitored the abundances of mosquito immatures before and after the Asian Tiger invaded these habitats in south Florida. These field data failed to demonstrate exclusion of A. triseriatus from treeholes following the establishment of A. albopictus in this microhabitat in 1991. However, A. albopictus had significantly higher metamorphic success and showed a significant increase in mean crowding on A. triseriatus in treeholes monitored from 1991 to 1999. In urban and suburban sites, A. triseriatus was uncommon in abandoned tires even before the arrival of A. albopictus. In some wooded sites, there is evidence for a decline in numbers of A. triseriatus in used tires and cemetery vases, but the native species has not been excluded from these habitats. Overall, the negative effect of A. albopictus on A. triseriatus has been less severe than that on A. aegypti. Experiments outdoors in surrogate treeholes showed that A. albopictus was more successful than A. triseriatus in survival to emergence in the presence of predatory larvae of the native mosquito Toxorhynchites rutilus when first instar predators encountered both prey species shortly after their hatch. Eggs of A. albopictus also hatched more rapidly than those of A. triseriatus, giving larvae of the invasive species an initial developmental advantage to escape predation. Biological traits that may favor A. albopictus are offset partly by greater treehole occupancy by A. triseriatus and the infrequency of the invasive mosquito species in undisturbed woodlands, which mitigates against displacement of the native mosquito in these habitats.     

Field evaluation of the response of Aedes albopictus (Stegomyia albopicta) to three oviposition attractants and different ovitrap placements using black and clear autocidal ovitraps in a rural area of Same,Timor‐Leste

Known oviposition attractants or stimulants were compared, singly and in combination, using inexpensive autocidal ovitraps designed to trap emerging adults, in a rural area of Timor‐Leste during the dry season. In this area, the dengue vector Aedes albopictus (Stegomyia albopicta) Skuse (Diptera: Culicidae) was abundant, but Aedes aegypti (Stegomyia aegypti) L. was not detected. The attractants were: (a) a compound found in Aedes eggs (dodecanoic acid); (b) components of nitrogen, phosphorous and potassium‐based (NPK) fertilizer, and (c) infusions of discarded cigarette butts. A solution of ammonium phosphate and potassium nitrate was significantly more attractive to gravid Ae. albopictus than water only. Dodecanoic acid and cigarette butt infusions were not significantly more attractive than the control; however, they attracted various other Diptera and many non‐culicid larvae developed in ovitraps in which these substances were used; thus, the presence of eggs or larvae of other species may have deterred Aedes oviposition. Significantly more Aedes eggs were found in ovitraps under vegetation than in ovitraps placed inside houses or against external walls. Clear‐sided ovitraps in which black mesh was placed over a black ring floating on the water surface collected significantly fewer eggs than black ovitraps with identically placed mesh and rings.     

Rapid evolution and the genomic consequences of selection against interspecific mating

While few species introduced into a new environment become invasive, those that do provide critical information on ecological mechanisms that determine invasions success and the evolutionary responses that follow invasion. Aedes albopictus (the Asian tiger mosquito) was introduced into the naturalized range of Aedes aegypti (the yellow fever mosquito) in the United States in the mid‐1980s, resulting in the displacement of A. aegypti in much of the south‐eastern United States. The rapid displacement was likely due to the superior competitive ability of A. albopictus as larvae and asymmetric mating interference competition, in which male A. albopictus mate with and sterilize A. aegypti females, a process called “satyrization.” The goal of this study was to examine the genomic responses of a resident species to an invasive species in which the mechanism of character displacement is understood. We used double‐digest restriction enzyme DNA sequencing (ddRADseq) to analyse outlier loci between selected and control lines of laboratory‐reared A. aegypti females from two populations (Tucson, AZ and Key West, Florida, USA), and individual females classified as either “resisted” or “mated with” A. albopictus males via mating trials of wild‐derived females from four populations in Florida. We found significant outlier loci in comparing selected and control lines and between mated and nonmated A. aegypti females in the laboratory and wild‐derived populations, respectively. We found overlap in specific outlier loci between different source populations that support consistent genomic signatures of selection within A. aegypti. Our results point to regions of the A. aegypti genome and potential candidate genes that may be involved in mating behaviour, and specifically in avoiding interspecific mating choices.     

Environmental characteristics of the cemeteries of Buenos Aires City (Argentina) and infestation levels of Aedes aegypti (Diptera: Culicidae)

Cemeteries with many water-filled containers, flowers, sources of human blood, and shade are favorable urban habitats for the proliferation of Aedes aegypti, a vector of yellow fever and dengue. A total of 22,956 containers was examined in the five cemeteries of the city of Buenos Aires, Argentina. The vector was found in four cemeteries that showed an average infestation level of 5.5% (617 positive out of 11,196 water-filled containers). The four cemeteries positive for Ae. aegypti showed significantly different (p<0.01) infestation levels. Vegetation cover and percentage of infestation were significantly correlated (p<0.01), but neither cemetery area nor number of available containers were significantly related to the proportion of positive vases. Our results suggest that the cemeteries of Buenos Aires represent a gradient of habitat favorableness for this vector species, some of which may act as foci for its proliferation and dispersal.     

Roles of spatial partitioning,competition, and predation in the North American invasion of an exotic mosquito

Invasion success and species coexistence are often mediated by species interactions across patchily distributed habitats and resources. The invasive mosquito Aedes japonicus japonicus has established in the North American range of the competitively superior resident congener, Aedes albopictus, and the predatory native mosquito Toxorhynchites rutilus. We tested predictions for two hypotheses of invasion success and species coexistence: keystone predation and spatial partitioning. We tested competition between A. japonicus japonicus and A. albopictus with or without T. rutilus in laboratory microcosms, and measured abundances of A. japonicus japonicus, A. albopictus, other resident competing mosquito species, and the presence of T. rutilus among tree holes and tires in metropolitan Washington, DC. In laboratory microcosms, A. albopictus was competitively dominant over A. japonicus japonicus, which is consistent with the few prior studies of competition between these two Aedes species. T. rutilus predation severely lowered performances of both Aedes species but more severely lowered A. japonicus japonicus performance than A. albopictus performance when all three species co-occurred, thus yielding no evidence for keystone predation. Consistent with the spatial partitioning hypothesis, A. japonicus japonicus was negatively correlated and independently aggregated with A. albopictus and all combined resident mosquito competitors and was not associated with T. rutilus among field containers. These results suggest that predation from T. rutilus and competition from A. albopictus are barriers to the spread of A. japonicus japonicus, but that A. japonicus japonicus may escape these interspecific effects by utilizing spatially partitioned container habitats.     

Male origin determines satyrization potential of <Emphasis Type="Italic">Aedes aegypti</Emphasis> by invasive <Emphasis Type="Italic">Aedes albopictus</Emphasis>

Rapid displacements of resident Aedes aegypti by invasions of Aedes albopictus have been documented in the southeastern United States and Bermuda. Interspecific mating has been detected in nature between these species and proposed as a likely mechanism for these displacements by means of asymmetric reproductive interference, or satyrization. However, rapid displacements of A. aegypti have not been detected in most localities where these two invasive species are known to co-occur. Aedes albopictus invaded the United States and Brazil at approximately the same time, in the mid-1980s, but the origins of the invading strains are known to be different. Here we tested the hypothesis, in standardized cage environments, that A. albopictus males from Brazil are less capable of satyrizing A. aegypti females than A. albopictus males from the United States. Using strains of A. aegypti and A. albopictus from the United States of known susceptibility to and capacity for interspecific mating, we demonstrate that A. albopictus colonized from collections in the Brazilian cities of Rio de Janeiro and Manaus were relatively unsuccessful in inseminating virgin female A. aegypti from Key West Florida compared to A. albopictus from peninsular Florida. We suggest that the low satyrization potential of Brazilian A. albopictus males may contribute to the lack of documented competitive displacements of A. aegypti in that country.     

Do natural container habitats impede invader dominance? Predator-mediated coexistence of invasive and native container-dwelling mosquitoes

Predator-mediated coexistence of competitors occurs when a species that is superior in competition is also more vulnerable to a shared predator compared to a poorer competitor. The invasive mosquito Aedes albopictus is usually competitively superior to Ochlerotatus triseriatus. Among second instar larvae, A. albopictus show a lesser degree of behavioral modification in response to water-borne cues from predation by the larval midge Corethrella appendiculata than do O. triseriatus, rendering A. albopictus more vulnerable to predation by C. appendiculata than O. triseriatus. The hypothesis that C. appendiculata predation favors coexistence of these competitors predicts that C. appendiculata abundances will be negatively and positively correlated with A. albopictus and O. triseriatus abundances, respectively, and that coexistence will occur where C. appendiculata are common. Actual abundances of O. triseriatus, A. albopictus, and C. appendiculata in three habitats fit this prediction. In natural container habitats like tree holes, C. appendiculata were abundant and competitors co-existed at similar densities. In cemeteries and tires, which occur primarily in non-forested, human-dominated habitats, A. albopictus dominated, with abundances twice those found in tree holes, but C. appendiculata and O. triseriatus were rare or absent. We also tested for whether antipredatory behavioral responses of A. albopictus differed among habitats or populations, or were correlated with local C. appendiculata abundances. We could detect no differences in A. albopictus antipredatory behavioral responses to water-borne cues from predation. Tree hole habitats appear to promote co-existence of O. triseriatus and A. albopictus through interactions with predatory C. appendiculata, and this predator effect appears to limit invasion success of A. albopictus in tree holes. There are many studies on predator-mediated coexistence in natural habitats but to our knowledge this is the first study to suggest differential predator-mediated coexistence between natural and man-made habitats. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The role of priority effects in limiting the success of the invasive tiger mosquito,Aedes albopictus

Priority effects (PE), wherein species colonizing a habitat early have a negative impact on later colonizers, can have profound and legacy effects on community organization. In temperate zones, larval mosquito habitats are emptied each year in the winter and recolonized in the spring. There are phenological differences among common species but the role of PE in these communities is largely unexplored. Aedes albopictus, the invasive tiger mosquito, is considered a superior competitor to resident species during the larval phase when conditions are initiated with same-staged heterospecific larvae. However in nature, Ae. albopictus hatches, and resumes activity, later in the spring than other species, suggesting it encounters larger later developed individuals, and denser populations, of species such as Aedes triseriatus. Additionally, despite their competitive inferiority, these species often coexist with Ae. albopictus in larval habitats, with Ae. albopictus often occurring at relatively low abundances in sylvan habitats. Using lab and near field experiments, we tested the hypothesis that PE with early hatching species reduces survivorship and population growth for the invasive Ae. albopictus. When Ae. albopictus larvae encountered larger, later developed heterospecific larvae at greater densities, under controlled lab conditions and in artificial and natural mesocosms, they experienced significant reductions in survival and estimated finite rate of population increase. Additionally, we found that intraguild predation of Ae. triseriatus on Ae. albopictus may be an important mechanism through which PE works. We conclude that PE is a potential mechanism for coexistence between invasive and resident mosquitoes and should be further explored.

     

Can the tortoise beat the hare? A possible mechanism for the coexistence of competing mosquitoes in bamboo groves

We studied interspecific competition between the larvae of the two mosquitoesAedes albopictus andTripteroides bambusa, which are predominantly found in water-filled bamboo stumps in northern Kyushu, south-western Japan, using microcosms with dead bamboo leaves in the laboratory. We compared short-term competition between single cohorts of the two species and long-term competition involving four cohorts of each species, which were introduced at 6-day intervals. In the single cohort experiment,A. albopictus grew faster thanT. bambusa. However, in the multiple cohort experiment, although the first cohort ofA. albopictus grew faster and began to pupate earlier than that ofT. bambusa, molting rates of later cohorts ofA. albopictus, that were introduced on the 12th and the 18th day, were lower than those ofT. bambusa. The survival rate ofA. albopictus became lower than that ofT. bambusa after the 18th day. The cumulative number of the pupatedT. bambusa individuals exceeded that ofA. albopictus on the 96th day. The final pupation success was higher inT. bambusa than inA. albopictus, especially when additional leaves were supplied on the 48th and the 96th days. The reversed outcomes between short- and long-term interspecific competition and the variation in the lifespans of small aquatic sites may contribute to the coexistence of the two mosquito species in bamboo groves.     

Habitat stability and the larval mosquito community in treeholes and other containers on a temperate Island

The temporal fluctuation of water levels and the presence of mosquito larvae were investigated for four types of small container habitats (treeholes, bamboo stumps, cemetery stone vases, and cemetery stone vessels) on Kabeshima Island in Kyushu, southwestern Japan. The probability that containers held water was positively correlated with the quantity of the preceding rainfall and with the depth and volume of the containers. It was estimated that dehydration occurred more regularly in autumn and winter than in summer. The probability that mosquito larvae were present in each type of container was positively correlated with habitat stability in terms of the probability of the existence of standing water and the coefficient of variation of the water level. Twelve species of mosquito larvae, including two rare predators, were found. Species composition differed between the different types of container. Although 4 to 10 species used each type of container, the median number of species per container was two for treeholes and bamboo stumps, and one for the others. The dominant species wasTripteroides bambusa in treeholes and bamboo stumps,Aedes albopictus in stone vases, andA. japonicus in stone vessels. The larval mosquito community, which lacked major predators, possessed the following features that may facilitate the coexistence of many species: (1) niche segregation amongst species in terms of their selection of container types; (2) an aggregated distribution of the individual species among containers of the same type; (3) high intraspecific mean crowding (and hence probably intense intraspecific competition) in the dominant species in each type of container; (4) independent species associations within the same type of container; and (5) low interspecific mean crowding (and hence probablynot intense interspecific competition) between species in the same type of container.     

Implications of saline concentrations for the performance and competitive interactions of the mosquitoes Aedes aegypti (Stegomyia aegypti) and Aedes albopictus (Stegomyia albopictus)

Aedes albopictus (Stegomyia albopictus) (Diptera: Culicidae) has probably supplanted Aedes aegypti (Stegomyia aegypti) throughout most of its historical range in the U.S.A., although Ae. aegypti still exists in large coastal cities in southern Florida. We measured salt concentrations in field containers along an axis perpendicular to the coast and examined intraspecific outcomes in these species under different salt concentrations in a factorial study using varying intra‐ and interspecific densities in different conditions of salinity to order to determine if salt could mitigate the documented competitive superiority of Ae. albopictus. Salt in field containers declined away from the coast, with maximal values similar to our lower salt concentrations. Egg hatching and short‐term survival of pupae and late instars were not affected by salt concentrations; survival of early instars of both species decreased at higher concentrations. In high salt conditions, Ae. aegypti achieved higher survival. In the longterm experiment, both species displayed longer development times. Salt did not affect interactions for either species; Ae. aegypti survived in the highest salt conditions, regardless of density. The tolerance of Ae. aegypti to high salt concentrations may allow it to use coastal containers, although because salt did not mediate interspecific interactions between Ae. aegypti and Ae. albopictus, the ultimate effects of salt on the coexistence of these species or exclusion of either species remain unknown.     

Ecological interactions in Aedes species on Reunion Island

Two invasive, container‐breeding mosquito species, Aedes aegypti (Stegomyia aegypti) and Aedes albopictus (Stegomyia albopicta) (Diptera: Culicidae), have different distribution patterns on Reunion Island. Aedes albopictus occurs in all areas and Ae. aegypti colonizes only some restricted areas already occupied by Ae. albopictus. This study investigates the abiotic and biotic ecological mechanisms that determine the distribution of Aedes species on Reunion Island. Life history traits (duration of immature stages, survivorship, fecundity, estimated finite rate of increase) in Ae. aegypti and Ae. albopictus were compared at different temperatures. These fitness measures were characterized in both species in response to competitive interactions among larvae. Aedes aegypti was drastically affected by temperature, performing well only at around 25 °C, at which it achieved its highest survivorship and greatest estimated rate of increase. The narrow distribution of this species in the field on Reunion Island may thus relate to its poor ability to cope with unfavourable temperatures. Aedes aegypti was also more negatively affected by high population densities and to some extent by interactions with Ae. albopictus, particularly in the context of limited food supplies. Aedes albopictus exhibited better population performance across a range of environmental conditions. Its ecological plasticity and its superior competitive ability relative to its congener may further enhance its invasion success on Reunion Island.     

<Emphasis Type="Italic">Aedes aegypti</Emphasis> and <Emphasis Type="Italic">Aedes albopictus</Emphasis> in Bermuda: extinction,invasion, invasion and extinction

We provide an analysis of the invasion and spread of the container inhabiting mosquitoes Aedes aegypti and Aedes albopictus in the Bermuda Islands. Considered eradicated in the mid-1960s, A. aegypti was redetected in 1997, and A. albopictus was first detected in 2000. Based on weekly ovitrap data collected during the early stages of the invasion, we mapped the spread of Aedes throughout the islands. We analyzed the effects of buildings and roads on mosquito density and found a significant association between density and distance to roads, but not to buildings. We discuss the potential role of human transport in the rapid spread in the islands. The temporal correlation in ovitrap collection values decreased progressively, suggesting that habitat degradation due to control efforts were responsible for local shifts in mosquito densities. We report a sharp decrease in A. aegypti presence and abundance after the arrival of A. albopictus in the year 2000. Possible mechanisms for this rapid decline at relatively low density of the second invader are discussed in the context of classical competition theory and earlier experimental results from Florida, as well as alternative explanations. We suggest that support for the competition hypothesis to account for the decline of A. aegypti is ambiguous and likely to be an incomplete explanation.     

Satellite observation to assess dengue risk due to Aedes aegypti and Aedes albopictus in a subtropical city of Argentina

Earth observation environmental features measured through remote sensing and models of vector mosquitoes species Aedes aegypti and Ae. albopictus provide an advancement with regards to dengue risk in urban environments of subtropical areas of Argentina. The authors aim to estimate the effect of landscape coverage and spectral indices (Normalized Difference Vegetation Index [NDVI], Normalized Difference Water Index [NDWI] and Normalized Difference Built-up Index [NDBI]) on the larvae abundance of Ae. aegypti and Ae. albopictus in Eldorado, Misiones, Argentina using remote satellite sensors. Larvae of these species were collected monthly (June 2016 to April 2018), in four environments: tire repair shops, cemeteries, dwellings and an urban natural park. The proportion of landscape coverage (water, urban areas, bare soil, low vegetation and high vegetation) was determined from the supervised classification of Sentinel-2 images and spectral indices, calculated. The authors developed spatial models of both vector species by generalized linear mixed models. The model's results showed that Ae. aegypti larvae abundance was better modelled by NDVI minimum values, NDBI maximum values and the interaction between them. For Ae. albopictus proportion of bare soil, low vegetation and the interaction between both variables explained better the abundance.     

Aedes albopictus oviposits with other Aedes species in artificial oviposition cups: a case study in Knox County,Tennessee, U.S.A.

Interspecific associations between two mosquito species can lead to effects such as competition, species displacement, and species stability. To better understand Aedes albopictus (Skuse) and other Aedes species, we monitored eggs in artificial oviposition cups (ovitraps) within Knox County, TN, U.S.A., during the 2016 and 2017 mosquito seasons. In 2016, one black and one white ovitrap were placed at 18 sites for 21 weeks, while in 2017 black and white ovitraps baited with grass‐infused or deionized water were placed at 11 sites for nine weeks. Eggs were identified to species and resulting counts were used to determine the degree of interspecific association using Cole's coefficients (C₇) and the degree of heterogeneity across space and time using generalized linear mixed models (GLMM). Here, Aedes mosquitoes are generally ovipositing in black cups with grass‐infused water, and Ae. albopictus eggs co‐occurred with other Aedes species more often than would be expected. Finding a positive significant interspecific association between Ae. albopictus and other Aedes eggs suggests that methods used to control Ae. albopictus may also control other Aedes mosquitoes. Finding that Ae. albopictus co‐occurs with other Aedes mosquitoes warrants additional research to evaluate outcomes associated with co‐occurrence within the study area.     

Temporal Patterns of Abundance of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) and Mitochondrial DNA Analysis of Ae. albopictus in the Central African Republic

The invasive Asian tiger mosquito Aedes albopictus (Diptera: Culicidae) was first reported in central Africa in 2000, in Cameroon, with the indigenous mosquito species Ae. aegypti (Diptera: Culicidae). Today, this invasive species is present in almost all countries of the region, including the Central African Republic (CAR), where it was first recorded in 2009. As invasive species of mosquitoes can affect the distribution of native species, resulting in new patterns of vectors and concomitant risk for disease, we undertook a comparative study early and late in the wet season in the capital and the main cities of CAR to document infestation and the ecological preferences of the two species. In addition, we determined the probable geographical origin of invasive populations of Ae. albopictus with two mitochondrial DNA genes, COI and ND5. Analysis revealed that Ae. aegypti was more abundant earlier in the wet season and Ae. albopictus in the late wet season. Used tyres were the most heavily colonized productive larval habitats for both species in both seasons. The invasive species Ae. albopictus predominated over the resident species at all sites in which the two species were sympatric. Mitochondrial DNA analysis revealed broad low genetic diversity, confirming recent introduction of Ae. albopictus in CAR. Phylogeographical analysis based on COI polymorphism indicated that the Ae. albopictus haplotype in the CAR population segregated into two lineages, suggesting multiple sources of Ae. albopictus. These data may have important implications for vector control strategies in central Africa.