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1.
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.  相似文献   

2.
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.  相似文献   

3.
We studied the seasonal occurrence and the distribution patterns of larval mosquitoes in a bamboo grove in northern Kyushu, Japan. The number of pools was large from June to August and was small in winter. Deep stumps and semi-closed-type stumps held water more persistently than shallow and open-type stumps, respectively. Open-type stumps trapped more leaves than semi-closed-type stumps and the number of leaves trapped in the open-type stump was positively correlated with the area of the pool. The incidences ofTripteroides bambusa andAedes albopictus were low early in their breeding season and gradually increased thereafter. In August, the density ofT. bambusa larvae per pool was higher in the old (>2 months) pools than in the new pools and was positively correlated with the depth of the stumps. In contrast, the density ofA. albopictus did not differ significantly between the new-and old pools and was not significantly correlated with the depth of the stump. The density ofA. albopictus was positively correlated with the number of leaves that had been trapped in the stump, whereas the density ofT. bambusa was not. In addition to the seasonal fluctuation in habitat-patch availability, the variations in habitat persistence and resource input among bamboo stumps may facilitate the coexistence of the two mosquitoes that were differentially limited by these factors.  相似文献   

4.
We surveyed the distribution of a mosquito, Tripteroides bambusa (Yamada), among patchily distributed bamboo groves from 1994 to 1997 in an area of 4 km × 4 km in Saga, south-western Japan. In the study area, this mosquito uses mainly water-filled bamboo stumps as its larval habitat. In 1994, a year with little rainfall in the summer, T. bambusa larvae were found in 30 of the 60 groves that contained water-filled bamboo stumps. By 1997, the number of occupied groves increased to 64, and the number of groves with water-filled stumps increased to 109. Tripteroides bambusa was found frequently in the area covered by an orange orchard where bamboo groves were dense, and rarely in the open land where bamboo groves were sparse. Colonization of T. bambusa occurred in groves in the orchard and the open land which were less than 0.57 km away from the nearest occupied grove. Large groves were more likely to be occupied, and extinction occurred only in small groves ( 0.104 ha). Groves without water-filled stumps in 1994 were less likely to be occupied in the following period than those with water-filled stumps in 1994. These findings suggest that the T. bambusa metapopulation will not extend its distribution into all of the bamboo groves in the study area, but will not become extinct because of some highly persistent populations.  相似文献   

5.
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.  相似文献   

6.
Understanding mechanisms fostering coexistence between invasive and resident species is important in predicting ecological, economic, or health impacts of invasive species. The mosquito Aedes aegypti coexists at some urban sites in southeastern United States with invasive Aedes albopictus, which is often superior in interspecific competition. We tested predictions for three hypotheses of species coexistence: seasonal condition-specific competition, aggregation among individual water-filled containers, and colonization–competition tradeoff across spatially partitioned habitat patches (cemeteries) that have high densities of containers. We measured spatial and temporal patterns of abundance for both species among water-filled resident cemetery vases and experimentally positioned standard cemetery vases and ovitraps in metropolitan Tampa, Florida. Consistent with the seasonal condition-specific competition hypothesis, abundances of both species in resident and standard cemetery vases were higher early in the wet season (June) versus late in the wet season (September), but the proportional increase of A. albopictus was greater than that of A. aegypti, presumably due to higher dry-season egg mortality and strong wet-season competitive superiority of larval A. albopictus. Spatial partitioning was not evident among cemeteries, a result inconsistent with the colonization-competition tradeoff hypothesis, but both species were highly independently aggregated among standard cemetery vases and ovitraps, which is consistent with the aggregation hypothesis. Densities of A. aegypti but not A. albopictus differed among land use categories, with A. aegypti more abundant in ovitraps in residential areas compared to industrial and commercial areas. Spatial partitioning among land use types probably results from effects of land use on conditions in both terrestrial and aquatic-container environments. These results suggest that both temporal and spatial variation may contribute to local coexistence between these Aedes in urban areas.  相似文献   

7.
The mosquitoes Aedes albopictus (Stegomyia albopicta) (Skuse) and Culex quinquefasciatus (Say) (Diptera: Culicidae) are common inhabitants of tyres and other artificial containers, which constitute important peridomestic mosquito breeding habitats. We tested the hypotheses that interspecific resource competition between the larvae of these species is asymmetrical, that the concentration of chemicals associated with decomposing detritus affects the competitive outcomes of these species, and that wild and colonized strains of Cx. quinquefasciatus are affected differently by competition with Ae. albopictus. We conducted two laboratory competition experiments wherein we measured survivorship and estimated population growth (λ′) in both species under multiple mixed‐species densities. Under varying resource levels, competition was asymmetrical: Ae. albopictus caused competitive reductions or exclusions of Cx. quinquefasciatus under conditions of limited resources. In a second experiment, which used both wild and colonized strains of Cx. quinquefasciatus, organic chemical compounds associated with decomposing detritus did not affect the competitive outcome. The colonized strain of Cx. quinquefasciatus had greater survivorship and adult mass, and faster development times than the wild strain, but both strains were similarly affected by competition with Ae. albopictus. Competition between these species may have important consequences for vector population dynamics, especially in areas in which tyres and artificial containers constitute the majority of mosquito breeding habitats.  相似文献   

8.
Aedes albopictus (Skuse) is an invasive mosquito species found across the southern U.S. with range expansion into many northern states. Intra‐ and interspecific larval competition have been evaluated for Ae. albopictus with respect to subsequent adult size, immature and adult survivability, and its capacity to vector pathogens as an adult. However, limited data are available on egg production as related to larval rearing conditions. Because Ae. albopictus is a container‐inhabiting mosquito that oviposits in resource‐limited habitats, it is found under variable density‐dependent conditions. Therefore, we examined the impact of specific rearing conditions on Ae. albopictus clutch size and adult body size; comparing the egg production values and wing lengths from known developmental densities to those from field‐collected populations. Field populations varied significantly among collection sites in mean clutch size (23 to 46). These clutch sizes were comparable to the mean clutch sizes of females reared at the larval densities of nine (20 eggs) and three (53 eggs) larvae per 3 ml of water in the laboratory. Field populations experienced density‐dependent effects impacting adult mosquito size. Mosquitoes from the four sample sites had mean wing lengths of 1.99, 2.47, 2.51, and 2.54 mm, which were less than the mean wing length of mosquitoes reared at larval densities of three larvae per 3 ml of water (2.57 mm).  相似文献   

9.
Aedes albopictus (Diptera: Culicidae) was first reported in Central Africa in 2000, together with the indigenous mosquito species Aedes aegypti (Diptera: Culicidae). Because Ae. albopictus can also transmit arboviruses, its introduction is a public health concern. We undertook a comparative study in three Cameroonian towns (Sahelian domain: Garoua; equatorial domain: Douala and Yaoundé) in order to document infestation by the two species and their ecological preferences. High and variable levels of pre‐imaginal Ae. aegypti and Ae. albopictus infestation were detected. Only Ae. aegypti was encountered in Garoua, whereas both species were found in Douala and Yaoundé, albeit with significant differences in their relative prevalence. Peridomestic water containers were the most strongly colonized and productive larval habitats for both species. No major differences in types of larval habitat were found, but Ae. albopictus preferentially bred in containers containing plant debris or surrounded by vegetation, whereas Ae. aegypti tended to breed in containers located in environments with a high density of buildings. These findings may have important implications for vector control strategies.  相似文献   

10.
When a species is introduced into a new location, it may escape, at least temporarily, from its natural enemies. In field surveys, we found that when the exotic, invasive mosquito, Aedes albopictus, invades new sites, it initially experiences reduced infection by its gut parasite, Ascogregarina taiwanensis. To determine the effect of this escape from parasitism on the competitive ability of A. albopictus, we performed a laboratory competition experiment in which infected and uninfected A. albopictus larvae were reared in microcosms alone and in competition with larvae of the native mosquito, Ochlerotatus triseriatus. We analyzed the effect of parasitism by A. taiwanensis on A. albopictus performance when subjected to intra- and interspecific competition across a range of larval densities, as well as the effect of A. albopictus parasitism by A. taiwanensis on the competitive impact of A. albopictus on O. triseriatus. At a density of 30 O. triseriatus larvae, O. triseriatus survivorship was significantly reduced by the addition of 30 unifected A. albopictus, but not by addition of 30 infected A. albopictus, and not by addition of 15 A. albopictus whether infected or uninfected. Although estimated finite rate of population increase (') showed similar trends, and was significantly affected by treatments, no pairwise differences in rate of increase were significant. Infection by A. taiwanensis also significantly prolonged A. albopictus female development time and reduced the intraspecific competitive effect of increased density of A. albopictus, but did not affect A. albopictus survivorship, mass, or estimated finite rate of population increase. Thus, when A. albopictus escapes from this parasite as it colonizes new sites, this escape may give it a small, but significant, added competitive advantage over O. triseriatus, which may facilitate range expansion of A. albopictus and enhance A. albopictus's initial impact on resident species.  相似文献   

11.
12.
Interactions between invasive species can have important consequences for the speed and impact of biological invasions. Containers occupied by the invasive mosquito, Aedes albopictus Skuse, may be sensitive to invasive plants whose leaves fall into this larval habitat. To examine the potential for interactions between invasive leaf species and larval A. albopictus, we conducted a field survey of leaf material found with A. albopictus in containers in Palm Beach County, Florida and measured density dependent responses of A. albopictus larvae to two invasive and one native leaf species in laboratory experiments. We found increased diversity of leaf species, particularly invasive species, in areas further from the urbanized coast, and a significant positive association between the presence of Schinus terebinthifolious (Brazilian pepper) and the abundance of A. albopictus. In laboratory experiments, we determined that larval growth and survivorship were significantly affected by both larval density and leaf species which, in turn, resulted in higher population performance on the most abundant invasive species (Brazilian pepper) relative to the most abundant native species, Quercus virginiana (live oak). These results suggest invasive leaf species can alleviate density dependent reductions in population performance in A. albopictus, and may contribute to its invasion success and potential to spread infectious disease.  相似文献   

13.
Allochthonous leaf litter is often the main resource base for invertebrate communities in ephemeral water-filled containers, and detritus quality can be affected by hydrologic conditions. The invasive mosquito Aedes albopictus utilizes container habitats for its development where it competes as larvae for detritus and associated microorganisms with the native Aedes triseriatus. Different hydrologic conditions that containers are exposed to prior to mosquito utilization affect litter decay and associated water quality. We tested the hypothesis that larval competition between A. albopictus and A. triseriatus would be differentially affected by prior hydrologic conditions. Experimental microcosms provisioned with Quercus alba L. litter were subjected to one of three different hydrologic treatments prior to the addition of water and mosquito larvae: dry, flooded, and a wet/dry cycle. Interspecific competition between A. albopictus and A. triseriatus was mediated by hydrologic treatment, and was strongest in the dry treatment vs. the flooded or wet/dry treatments. Aedes triseriatus estimated rate of population change (λ'') was lowest in the dry treatment. Aedes albopictus λ'' was unaffected by hydrologic treatment, and was on average always increasing (i.e., > 1). Aedes triseriatus λ'' was affected by the interaction of hydrologic treatment with interspecific competition, and was on average declining (i.e., < 1.0), at the highest interspecific densities in the dry treatment. Dry treatment litter had the slowest decay rate and leached the highest concentration of tannin-lignin, but supported more total bacteria than the other treatments. These results suggest that dry conditions negatively impact A. triseriatus population performance and may result in the competitive exclusion of A. triseriatus by A. albopictus, possibly by reducing microbial taxa that Aedes species browse. Changing rainfall patterns with climate change are likely to affect competition between A. triseriatus and A. albopictus, probably enhancing negative competitive effects of A. albopictus on A. triseriatus in areas that experience drought.  相似文献   

14.
The proposed expansion of biofuels production may cause unintended land‐use changes and potentially alter ecosystem services. This study evaluated the impact of first‐generation (corn) and second‐generation (switchgrass and Miscanthus) biofuel crops on production and oviposition site selection by two vector mosquitoes, the yellow fever mosquito Aedes aegypti and the Asian tiger mosquito Aedes albopictus. Larvae of the two species were reared at varying conspecific and heterospecific densities in senescent leaf infusions prepared from one of the three biofuel crops and their survival and development time to adulthood determined. The effects of the three leaf infusions on water chemistry and oviposition site selection by the two mosquito species were also determined. Ae. albopictus females deposited significantly fewer eggs in Miscanthus than in corn infusion while Ae. aegypti females deposited significantly fewer eggs in Miscanthus than in both corn and switchgrass infusion. Survival to adulthood for both mosquito species was significantly lower in corn than in switchgrass and Miscanthus infusions; was consistently lower at high‐ (0:40 and 20:20) than at low density treatments in both switchgrass and Miscanthus infusions; and significantly lower at high intraspecific density (40:0 and 0: 40) than at high interspecific density (20:20) in Miscanthus infusion. Development time to adulthood was positively related to larval density, but was not influenced by biofuel leaf treatment. Corn infusion had lower pH values and higher salinity, conductivity, total dissolved solids (TDS), and temperature values than switchgrass and Miscanthus infusions. These findings demonstrate the potential for biofuel crops to modify the chemistry of aquatic habitats in ways that may influence mosquito production and thereby the risk of exposure to mosquito‐borne diseases.  相似文献   

15.
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.  相似文献   

16.
Native predators are postulated to have an important role in biotic resistance of communities to invasion and community resilience. Effects of predators can be complex, and mechanisms by which predators affect invasion success and impact are understood for only a few well-studied communities. We tested experimentally whether a native predator limits an invasive species’ success and impact on a native competitor for a community of aquatic insect larvae in water-filled containers. The native mosquito Aedes triseriatus alone had no significant effect on abundance of the invasive mosquito Aedes albopictus. The native predatory midge Corethrella appendiculata, at low or high density, significantly reduced A. albopictus abundance. This effect was not caused by trait-mediated oviposition avoidance of containers with predators, but instead was a density-mediated effect caused by predator-induced mortality. The presence of this predator significantly reduced survivorship of the native species, but high predator density also significantly increased development rate of the native species when the invader was present, consistent with predator-mediated release from interspecific competition with the invader. Thus, a native predator can indirectly benefit its native prey when a superior competitor invades. This shows the importance of native predators as a component of biodiversity for both biotic resistance to invasion and resilience of a community perturbed by successful invasion.  相似文献   

17.
Invasive arthropods that vector pathogens have the potential to influence pathogen transmission both directly, by becoming a novel pathogen vector, or indirectly, by interacting with native vectors. Adult mosquito size is influenced by food availability in the larval stage, and smaller, nutrient-deprived mosquitoes are, in some studies, more efficient viral vectors in the laboratory. This is the first study to examine the indirect impacts that larval competition between Aedes albopictus, an introduced mosquito species, and Ochlerotatus triseriatus, a native mosquito species and the primary vector for La Crosse virus (LACV) in the US, has on native mosquito larval survival, adult size, and vector competence. A. albopictus presence decreased Oc. triseriatus larval survival, but surviving Oc. triseriatus females were larger, potentially owing to a release from intraspecific competition. These larger, native females were more likely to develop both midgut and disseminated LACV infections than females emerging from monospecific treatments. Collectively, these results suggest a need to better understand the ecology of both native and invasive vector species, their interactions, and the potential for those interactions to alter vector-borne disease transmission.  相似文献   

18.
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.  相似文献   

19.
1. Predation risk affects interspecific competition by decreasing foraging activity and relative competitive ability. Predation risk is determined by predators' prey choice and prey responses, both of which can be influenced by temperature. Temperature is especially important for larval prey and can result in a trade‐off between predator‐induced decreases in foraging activity and growth. Interspecific competition must also be examined in relation to intraspecific density‐dependent competition; weaker interspecific competition leads to coexistence of competitors. 2. This study explored how temperature (15 and 25 °C) could affect a focal species, larvae of the mosquito Culex quinquefasciatus, by examining prey choice in a shared predator (mosquitofish; Gambusia holbrooki) and the effects of predation risk on interspecific competition with Limnodynastes peronii tadpoles. Intraspecific density‐dependent competition in C. quinquefasciatus at these temperatures was also examined. 3. At 25 °C, G. holbrooki consumption of both C. quinquefasciatus and L. peronii increased; however, the effects of interspecific competition on mosquito survival did not decrease with L. peronii exposure to predation risk. The relationship between intraspecific density‐dependent competition and interspecific competition was temperature‐dependent, with competitive dominance of L. peronii at 25 °C. Male and female mosquitoes had different temperature‐dependent responses, indicating sex‐specific intrinsic responses to starvation and differential selection pressures. At 25 °C, females were susceptible to interspecific competition by L. peronii, while males were susceptible to intraspecific competition. 4. The use of competitors as biological controls has implications for mosquito disease transmission, and these results suggest that control effectiveness may be modified by climate change.  相似文献   

20.
This study assessed the risk of larval displacement of the eastern treehole mosquito, Aedes triseriatus, and the northern house mosquito, Culex pipiens, by Aedes albopictus, the Asian tiger mosquito, during the establishment and successional stages of novel larval mosquito treehole and ground‐container habitats in the state of New Jersey, U.S.A. Culex pipiens and Culex restuans were the first mosquito species to colonize ground‐container habitats and were the dominant larval species throughout the study period, whereas Ae. albopictus was late to colonize ground habitats and accounted for less than 15% of weekly larval collections once established. Ae. albopictus had a much stronger community presence within treehole ovitraps; however, Ae. albopictus never reached the average larval densities of the expected primary colonizer, Ae. triseriatus. Throughout the study period, the weekly abundances of Ae. triseriatus and Ae. albopictus were positively correlated and there were no significant differences between the abundances of each species. The larval dominance of Ae. triseriatus appears to be enhanced by the presence of Toxorhynchites rutilus septentrionalis, a large predatory mosquito species. When Tx. rut. septentrionalis was present, mature larvae (3rd–4th instar) of Ae. albopictus were also present in only 16.7% of collections, whereas mature larvae of Ae. triseriatus were collected concurrently with Tx. rut. septentrionalis in 53.8% of collections. These data suggest that Ae. triseriatus is at a greater risk of displacement by Ae. albopictus than are Cx. pipiens and Cx. restuans.  相似文献   

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