Vector competence of Australian Culex gelidus Theobald (Diptera: Culicidae) for endemic and exotic arboviruses

The recent recognition of established populations of the mosquito, Culex gelidus Theobald, in Australia has raised concerns about local transmission of arboviruses. The vector competence of a mainland population of Cx. gelidus was investigated for two local alphaviruses, Ross River (RRV) and Barmah Forest (BFV) viruses, and three flaviviruses, Japanese encephalitis (JEV), Kunjin (KUNV) and Murray Valley encephalitis (MVEV) viruses. Colonised mosquitoes were exposed to virus via blood-soaked pledgets and transmission was tested using a capillary-tube method. The important Australian vectors, Aedes vigilax (Skuse) and Culex annulirostris Skuse, were used as internal controls for the alphaviruses and flaviviruses, respectively. Overall, Cx. gelidus was a more efficient vector of flaviviruses than alphaviruses. Culex gelidus was refractory to infection with BFV, and nearly 25% transmitted RRV, which was comparable to Ae. vigilax . Culex gelidus was susceptible to all three flaviviruses, with transmission rates of 96%, 95% and 41% for JEV, KUNV and MVEV, respectively. JEV transmission rates in Cx. annulirostris were unexpectedly low and this was possibly due to differences in susceptibility to JEV genotypes I and II. Considering the high susceptibility to the flaviviruses demonstrated here, and the natural infections with RRV and JEV that have been detected from northern Australian populations, the establishment of the exotic mosquito, Cx. gelidus , in Australia is potentially a significant public health concern.     

The Changing Epidemiology of Murray Valley Encephalitis in Australia: The 2011 Outbreak and a Review of the Literature

Murray Valley encephalitis virus (MVEV) is the most serious of the endemic arboviruses in Australia. It was responsible for six known large outbreaks of encephalitis in south-eastern Australia in the 1900s, with the last comprising 58 cases in 1974. Since then MVEV clinical cases have been largely confined to the western and central parts of northern Australia.In 2011, high-level MVEV activity occurred in south-eastern Australia for the first time since 1974, accompanied by unusually heavy seasonal MVEV activity in northern Australia. This resulted in 17 confirmed cases of MVEV disease across Australia. Record wet season rainfall was recorded in many areas of Australia in the summer and autumn of 2011. This was associated with significant flooding and increased numbers of the mosquito vector and subsequent MVEV activity. This paper documents the outbreak and adds to our knowledge about disease outcomes, epidemiology of disease and the link between the MVEV activity and environmental factors.Clinical and demographic information from the 17 reported cases was obtained. Cases or family members were interviewed about their activities and location during the incubation period.In contrast to outbreaks prior to 2000, the majority of cases were non-Aboriginal adults, and almost half (40%) of the cases acquired MVEV outside their area of residence. All but two cases occurred in areas of known MVEV activity.This outbreak continues to reflect a change in the demographic pattern of human cases of encephalitic MVEV over the last 20 years. In northern Australia, this is associated with the increasing numbers of non-Aboriginal workers and tourists living and travelling in endemic and epidemic areas, and also identifies an association with activities that lead to high mosquito exposure. This outbreak demonstrates that there is an ongoing risk of MVEV encephalitis to the heavily populated areas of south-eastern Australia.     

Container-breeding mosquitoes and predator community dynamics along an urban-forest gradient: The effects of habitat type and isolation

Environmental disturbances such as deforestation, urbanization or pollution have been widely acknowledged to play a key role in the emergence of many infectious diseases, including mosquito-borne viruses. However, we have little understanding of how habitat isolation affects the communities containing disease vectors. Here, we test the effects of habitat type and isolation on the colonization rates, species richness and abundances of mosquitoes and their aquatic predators in water-filled containers in northwestern Thailand. For eight weeks water-filled containers were monitored in areas containing forest, urban and agricultural habitats and mixtures of these three. Mosquito larvae of the genera Aedes and Culex appeared to be differentially affected by the presence of the dominant predator; Toxorhynchites splendens (Culicidae). Therefore, a predation experiment was conducted to determine predator response to prey density and its relative effects on different mosquito prey populations. Colonization rates, species richness and abundances of mosquito predators were strongly related to forest habitat and to the distance from other aquatic habitats. Areas with more tree cover had higher predator species richness and abundance in containers. Containers that were close to surface water were more rapidly colonized than those further away. In all habitat types, including urban areas, when predators were present, the number of mosquito larvae was much lower. Containers in urban areas closer to water-bodies, or with more canopy cover, had higher predator colonization rates and species richness. T. splendens (Culicidae) preyed on the larvae of two mosquito genera at different rates, which appeared to be related to prey behaviour. This study shows that anthropogenic landscape modification has an important effect on the natural biological control of mosquitoes. Vector control programmes and urban planning should attempt to integrate ecological theory when developing strategies to reduce mosquito populations. This would result in management strategies that are beneficial for both public health and biodiversity.     

Anthropogenic ecological change and impacts on mosquito breeding and control strategies in salt-marshes, Northern Territory, Australia

Darwin, in the tropical north of Australia, is subject to high numbers of mosquitoes and several mosquito-borne diseases. Many of Darwin's residential areas were built in close proximity to tidally influenced swamps, where long-term storm-water run-off from nearby residences into these swamps has led to anthropogenic induced ecological change. When natural wet-dry cycles were disrupted, bare mud-flats and mangroves were transformed into perennial fresh to brackish-water reed swamps. Reed swamps provided year-round breeding habitat for many mosquito species, such that mosquito abundance was less predictable and seasonally dependent, but constant and often occurring in plague proportions. Drainage channels were constructed throughout the wetlands to reduce pooled water during dry-season months. This study assesses the impact of drainage interventions on vegetation and mosquito ecology in three salt-marshes in the Darwin area. Findings revealed a universal decline in dry-season mosquito abundance in each wetland system. However, some mosquito species increased in abundance during wet-season months. Due to the high expense and potentially detrimental environmental impacts of ecosystem and non-target species disturbance, large-scale modifications such as these are sparingly undertaken. However, our results indicate that some large scale environmental modification can assist the process of wetland restoration, as appears to be the case for these salt marsh systems. Drainage in all three systems has been restored to closer to their original salt-marsh ecosystems, while reducing mosquito abundances, thereby potentially lowering the risk of vector-borne disease transmission and mosquito pest biting problems.     

A comparison of Aedes vigilax larval population densities and associated vegetation categories in a coastal wetland,Northern Territory,Australia

Darwin's northern suburbs border an extensive coastal reed and upper mangrove wetland recognized as an important larval habitat for Aedes vigilax (Skuse), the northern salt marsh mosquito, an established vector for Ross River and Barmah Forest viruses and an appreciable pest species. We sought to identify the most important vegetation categories associated with Ae. vigilax breeding to maximize the efficiency of mosquito control efforts. Using a generalized linear model with negative binominal distribution and log link, this study compares larval densities, determined by focused dipping, between 13 discernable vegetation categories. The incidence rate ratios (RR) generated can be used to compare the magnitude of larval densities for each vegetation category, compared with the reference category. Aedes vigilax larval densities were almost ten times greater in artificial drainage areas (RR=9.82), followed by tide‐affected reticulate (Sporobolus/Xerochloa) areas (RR=8.15), then Schoenoplectus/mangroves (RR=2.29), compared with the reference vegetation category “lower mangroves.” Furthermore, larval densities were highest in May, due to tidal inundation, for drainage areas and tide‐affected reticulates (RR=12.2, 11.7, respectively) compared with March, the reference month. Thus, to maximize the efficiency of aerial salt marsh mosquito control operations in this wetland, larval control is best accomplished by concentrating on drains, Schoenoplectus/mangroves, and tide‐affected reticulate areas, commencing early after the wet season. These results should apply to other areas of salt marsh mosquito breeding across northern Australia.     

Meteorological factors affecting physical comfort (with special reference to Alice Springs,Australia)

The concept of effective temperature appears to have certain advantages for indoor use and is applied as an example to the climatological data for Alice Springs, Australia. Average values of effective temperature for the hottest hour of the day are compared with those for certain Australian and overseas locations and it is concluded that, although Alice Springs is uncomfortable for a substantial part of the warm season, the climate is more comfortable than the tropical north of Australia and some overseas arid areas. The larger diurnal range at Alice Springs means more comfortable nights than in areas near the tropical coast. It is stressed that mean values can be misleading, and for adequate treatment it is necessary to examine the distribution of daily values.

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Zusammenfassung Das Konzept der effektiven Temperatur scheint gewisse Vorteile für die Anwendung im geschlossenen Raum zu besitzen und wird als Beispiel für die klimatologischen Daten von Alice Springs angewandt. Durchschnittswerte der effektiven Temperatur für die heisseste Stunde des Tages werden mit denen für bestimmte australische und überseeische Orte verglichen.Es wird gefolgert,dass,obwohl Alice Springs für einen bestimmten Teil der warmen Jahreszeit ein unbekömmliches Milieu hat, das Klima trotzdem bekömmlicher ist als der tropische Norden Australiens und einige aride Gebiete in Übersee. Die grössere Tagesschwankung in Alice Springs ist gleichbedeutend mit bekömmlicheren Nächten, als sie in den Gebieten nahe der tropischen Küste vorhanden sind. Es muss gefolgert werden, dass Mittelwerte zu falschen Deutungen führen und dass es für einen genauen Vergleich notwendig ist,die Verteilung der täglichen Werte hinzuzuziehen.

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Resume Le concept de la température effective semble présenter certains avantages pour caractériser le climat intérieur des habitations. Il est appliqué ici par exemple aux données climatologiques d'Alice Springs (Australie). On compare des valeurs moyennes de la température effective des heures les plus chaudes de la journée avec des valeurs similaires provenant d'autres lieux d'Australie ou d'ailleurs. On en conclut bien qu'à Alice Springs le climat soit peu propice durant une bonne partie de la saison chaude; mais il est, en général, moins éprouvant que dans le nord tropical de l'Australie ou que dans des régions arides d'autres continents. La grande variation diurne que l'on observe à Alice Springs rend les nuits plus supportables que dans le voisinage de la côte tropicale. Il faut en conclure que les valeurs moyennes peuvent conduir à de fausses interprêtations et que, pour établir des comparaisons valables, il faut tenir compte aussi de la répartition des valeurs journalières.

     

A review of the role of fish as biological control agents of disease vector mosquitoes in mangrove forests: reducing human health risks while reducing environmental risk

The saltwater mosquito, Aedes vigilax, is prolific in coastal wetlands including mangroves and saltmarshes. Ae. vigilax is a vector for arboviruses such as Ross River and Barmah Forest viruses, with significant consequences for human health and economic productivity. In Australia the dominant form of mosquito control is chemicals. For mangroves, this is because there is a critical lack of knowledge supporting alternative approaches, such as environmental modification or biological control using larvivorous fish. This review examines the potential of fish as biological agents for the control of mosquito larvae in mangroves. We consider two key aspects: how larvivorous fish use mangroves; and can larvivorous fish reduce larval mosquito populations sufficiently to provide effective mosquito control? The link between fish and mangroves is reasonably well established, where mangroves act as refuge habitat for small and juvenile fish. Also, research has established that fish can be significant predators of mosquitoes, and therefore may be effective control agents. However, studies of fish activity within mangroves are limited to study of the fringe of the mangroves and not the internal structure of mangrove basins and as a result, fish populations within these areas remain unstudied. Also, until recently there was little appreciation of the mangrove-mosquito habitat relationship and, as a consequence, the importance of the mangrove basin as the key mosquito habitat has also been overlooked in the literature. Similarly, the predator/prey relationships between fish and mosquitoes within mangrove basin environments also remain unstudied, and therefore the importance of fish for mosquito management in mangrove basins is not known. There are substantial knowledge gaps regarding the potential of fish in controlling larval mosquitoes in mangroves. The gaps include: understanding of how larvivorous fish use mangrove basins; the nature of the fish-mosquito predator/prey relationship in mangrove basins; and whether larvivorous fish are effective as a mosquito control option in mangroves.     

Ecological limitations on aquatic mosquito predator colonization in the urban environment.

Urban malaria cases are becoming common in Africa as more people move into cities and industrialization proceeds. While many species of Anopheles mosquitoes vector malaria in rural areas, only a few are found within cities. The success of anthropophilic species in cities, such as members of the An. gambiae complex, may be explained by limitations on colonization by predator species in urban environments. Habitats that are temporal or structurally simple have lower predator survivorship in a variety of ecosystems, but these have not been investigated previously in an urban area. Areas within and around the Kenyan coastal town of Malindi were previously sampled for the presence of standing water using a geographic sampling strategy with probability proportional to size sampling of planned well-drained, unplanned poorly-drained, planned poorly-drained, unplanned well-drained, and peri-urban locations. Standing aquatic habitats in these areas were reassessed. During monthly sampling, presence/absence of mosquitoes and predator taxa were noted, as were ecological habitat variables: structural complexity and presence of water. Lambda statistics were calculated to associate predator guilds, habitat types, location variables, and ecological variables. All predator guilds found in habitats were strongly associated with habitat type, as were the structural complexity and temporal nature of the habitats. Types of habitat were heterogeneously distributed throughout Malindi, with swimming pools as a common habitat type in planned urban areas and tire track pools a common habitat type in peri-urban areas of Malindi. Predator colonization of aquatic habitats in Malindi was strongly influenced by habitat type, and not associated with location characteristics. Ecological variables were affected by the type of habitats, which are co-associated with planning and drainage in Malindi. While habitat types are distributed heterogeneously within Malindi, habitats with low predation pressure are available for mosquito colonization in both urban and peri-urban areas. The temporal, peri-urban tire track pools and the structural simplicity of urban swimming pools may discourage predator colonization, thereby increasing the probability of malaria vectors in these areas of Malindi. Future studies should evaluate habitats for use in malaria surveillance and experimentally test the effects of structural complexity and temporal nature of urban habitats on the densities of mosquito larvae and their aquatic predators.     

Identifying habitat linkages to maintain connectivity for corridor dwellers in a fragmented landscape

Anthropogenic habitat fragmentation typically precedes conservation planning; maintaining remaining linkages among core habitat areas can thus become a key conservation objective. Identifying linkages for dispersal and ensuring those linkages have long-term protection and management are challenging tasks for wildlife managers. These tasks can be especially daunting for smaller species with low mobility, termed corridor dwellers, which must maintain sustainable populations within corridors. Between May 2007 and June 2009, we collected occurrence locations for a corridor dweller, the Palm Springs pocket mouse (Perognathus longimembris bangsii), from museums, previous research, and our own field sampling. We used those data to model their suitable niche space and then identify suitable linkages between proposed conservation areas. We used a partitioned Mahalanobis D² statistic to create a spatially explicit niche model describing the distribution of a suitable niche space, and we validated the model statistically, with live trapping and with burrowing owl (Athene cunnicularia) diets. Our model identified soil characteristics, topographic ruggedness, and vegetation as variables delimiting Palm Springs pocket mouse habitat; sand content of the soils was an especially important characteristic. Our historic distribution model identified 120,000–90,000 ha as historically potential Palm Springs pocket mouse habitat; roughly 39% of that has been lost to more recent development. Most of the remaining suitable habitat occurred in the northwestern portion of the valley. We modeled habitat within core reserves as well as within proposed linkages between those reserves as having high similarity to known occupied habitats. Live trapping in areas with high (≥0.95) Habitat Suitability Index (HSI) values resulted in captures at 66% of those locations and, along with burrowing owl diets, refined a qualitative model as to what constituted a suitable Palm Springs pocket mouse corridor. While most corridor analyses have focused on mobile species which may traverse corridors in hours, days, or weeks, linkages for corridor dwellers must include habitat for sustaining multi-generational populations. This requires evaluating whether continuous suitable habitat exists within proposed corridors. Our research demonstrates how niche modeling can provide a landscape-scale view of the distribution of suitable habitat to evaluate conservation objectives for connectivity. © 2011 The Wildlife Society.     

Managing mosquitoes without destroying wetlands: an eastern Australian approach

Recognising both the importance of intertidal wetlands and their role in mosquito-borne disease we discuss wise management to conserve wetland values and to reduce vector borne disease health risks. First we summarise the mosquito-borne diseases associated with intertidal wetlands in sub-tropical and tropical Australia. We consider the Ramsar Strategic Plan, its reflection in some key Australian statutes and the relationship between environment-focussed legislation and health legislation. This is followed by a brief overview of mosquito control and its impact on human health. Using a salt marsh example of an integrated process, we describe the development of what was, in the 1980s in Australia, a novel method of habitat modification (runnelling) for mosquito control. Runnelling modifies the tidal water flow on salt marshes, reducing mosquito larval numbers and minimising environmental impacts. The approach is related to two of the Ramsar goals (wise use and institutional capacity and effectiveness). We then describe the extension of its rationale to a complex mangrove system. Finally, with a concept model, we consider the convergence between minimal habitat modification for wetland conservation and human health protection using an interdisicplinary approach involving multiple stakeholders.     

Urban nectarivorous bird communities in Cape Town,South Africa,are structured by ecological generalisation and resource distribution

Biological communities are increasingly faced with novel urban habitats and their response may depend on a combination of biological and habitat traits. The response of pollinator species to urban habitats are of particular importance because all species involved in the pollination mutualism may be affected. Nectarivorous bird communities worldwide show varying tolerances to urban areas, but studies from Africa are lacking. We investigated nectarivorous bird communities in a medium‐sized South African city and asked which biological and garden traits best predict the community assembly of specialist and opportunistic nectarivorous birds. Information was collected on garden traits and the frequency of nine nectarivorous bird species for 193 gardens by means of a questionnaire. Information on biological traits of birds was obtained from published literature. Habitat generalism and tree nesting were identified as the most important biological traits influencing bird occurrence in gardens. A greater diversity of indigenous bird‐pollinated plants and the presence of sugar water feeders increased the numbers of nectar specialist birds and species richness of nectarivorous birds. While bird baths increased the species richness of nectar specialist birds, opportunistic birds’ urban adjustment was further facilitated by large vegetated areas in gardens and limited by the distance to the nearest natural habitat. In conclusion, though some biological traits and dispersal barriers seem to limit urban adjustment, a combination of natural and artificial nectar resource provisioning could facilitate this adjustment.     

Potential distribution of the Asian disease vector Culex gelidus Theobald (Diptera: Culicidae) in Australia and New Zealand: a prediction based on climate suitability

Abstract  Culex gelidus has a wide distribution throughout Asia, where it is a vector of Japanese encephalitis. It was first detected in Australia in 1999, with archived material revealing an introduction sometime prior to 1994. It is currently widely distributed throughout northern and particularly north-eastern Australia. Using climate matching software (CLIMEX Version 1.1) and the known distribution of Cx. gelidus throughout Asia, a predicted distribution for Australasia based on current climate was developed. A potentially wide distribution throughout coastal Australia, particularly in tropical and subtropical areas, was revealed. Few inland locations were suitable, except in tropical areas of the Northern Territory and Queensland. The predicted distribution presented here is concordant with most recent collection records of Cx. gelidus in Australasia. However, there are a small number of exceptions which highlight some of the limitations of this approach for predicting mosquito distributions. The presence of Cx. gelidus in a large artificial swamp in Alice Springs is one such example. The predicted Cx. gelidus distribution incorporates highly populated areas, in which people may experience an increased risk of mosquito-borne viral encephalitis should this mosquito spread throughout its entire predicted range.     

基于过程视角的城市地区生物保护规划——以浙江台州为例

生境破碎化和生物过程的阻断是城市区域生物多样性面临的主要威胁。当前以物种为中心的生物保护规划对区域生境格局关注不足,而景观导向的思路缺乏生物过程考虑。随着保护生物学、景观生态学及景观规划的发展,将物种生物过程与生境格局相结合的综合方法日益得到认可。台州是中国东南沿海快速城市化区域,具备丰富的生物资源,但近年的分散城市化和大规模基础设施建设造成严重的生境破坏和物种丧失问题。本文以2种鸟类作为指示物种,将其生物过程信息与区域景观格局设计相结合:黑嘴鸥作为典型迁徙候鸟,季节性停留于当地泥质滩涂,其生物行为可视作一种垂直生境选择过程;白茎长尾雉作为本地重要留鸟,其生物过程兼有垂直生境选择和水平迁移。利用景观适宜性和景观安全格局方法从垂直和水平过程对指示物种适宜生境进行判别,并叠加构建城市区域综合生物保护基础结构,为类似地区提供参考。     

Are invasive species drivers of native species decline or passengers of habitat modification? A case study of the impact of the common myna (Acridotheres tristis) on Australian bird species

Habitat modification and invasive species are significant drivers of biodiversity decline. However, distinguishing between the impacts of these two drivers on native species can be difficult. For example, habitat modification may reduce native species abundance, while an invasive species may take advantage of the new environment. This scenario has been described as the driver‐passenger model, with ‘passengers’ taking advantage of habitat modification and ‘drivers’ causing native species decline. Therefore, research must incorporate both habitat modification and invasive species impact to successfully investigate native species decline. In this paper, we used the common myna (Acridotheres tristis) as a case study to investigate the driver‐passenger model. We investigated changes in bird abundance, over 2 years, in relation to different habitat types and common myna abundance. We hypothesized that the common myna is both a passenger of habitat change and a driver of some bird species decline. Our results indicated that the abundance of many native species is greater in high tree density nature reserves, while the common myna was uncommon in these areas. Common myna abundance was almost three times higher in urban areas than nature reserves and declined rapidly as tree density in nature reserves increased. Our findings indicated that the common myna is primarily a passenger of habitat change. However, we also observed negative associations between common myna abundance and some bird species. We stress the importance of simultaneously investigating both invasive species impact and habitat modification. We suggest habitat restoration could be a useful tool for both native species recovery and invasive species control. Understanding the drivers of native species decline will help inform impact mitigation and direct further research.     

珠江源区生境质量对土地利用变化的时空响应

生境质量评估给探究土地利用变化与生物多样性之间的关联机制提供了有效接口。采用InVEST模型评估2000—2020年间珠江源区生境质量时空演变特征,衡量土地利用变化对生境质量的影响。结果表明: 研究期间,建设用地变化幅度最大,面积增加321.48 km²,草地面积降低最显著。珠江源区生境质量整体处于较高水平,呈小幅下降趋势,低值区集中于城镇中心和农业主产区,南部和北部山地生境质量高。生境质量变化的冷点在南盘江沿岸曲沾坝子的聚集效应最显著,热点数量少且分布零散。在各类自然保护地中,会泽驾车自然保护区生境质量最低,珠江源自然保护区生境质量有轻微降低态势,主要原因是局部地区草地向耕地的转变。土地功能变化驱使的生境质量退化贡献率是改善贡献率的5.6倍,城乡建设空间侵占草地生态空间和农业生产空间是珠江源区生境质量降低的主导因素。建设用地扩张的贡献度从2000—2010年的69.9%降为2010—2020年的46.7%,2010—2020年间来自耕地扩张的退化威胁超过路网建设成为次要威胁源。珠江源区仍需加大自然保护地的管控力度,严格落实土地用途管制,以保障生态系统的无净损失和完整性。     

Why might roadside mulgas be better mistletoe hosts?

We tested the hypothesis that roads in arid central Australia modify roadside hydrology and nutrient patterns creating better habitat for mistletoes (Loranthaceae). In two areas of mulga woodland near Alice Springs where mulgas (Acacia aneura) are the principal mistletoe host, we compared mistletoe abundance, and host foliar water and nutrient content between roadside and interior (100 m from the road) sites. Mistletoes were significantly more abundant close to roadsides than at interior sites and mulgas had significantly higher foliar water contents at roadside compared to interior sites. Mulga foliar P and N levels were not, however, significantly different between roadside and interior sites. We conclude that roads exert a strong influence on the adjacent biota in arid central Australia primarily through facilitating water infiltration at roadside sites.     

Urban Wet Environment as Mosquito Habitat in the Upper Midwest

Sampling of Culex larval habitat plays an important role in West Nile virus surveillance and control programs. Although many cities have established mosquito sampling programs and abatement districts, there is relatively little information describing the extent and ecology of urban surface waters and stormwater systems in different geographic areas and how these parameters affect mosquito communities and control strategies. An aerial survey of the city of Madison, Wisconsin revealed 521 above-ground wet sites. These included both constructed stormwater systems (ditches, retention ponds, detention ponds) and natural wetlands (marshes, flood areas, creeks, and rivers). Repeat sampling of 351 of these sites was conducted during 2004 and 2005. The majority of sites, 58% in 2004 and 72% in 2005, yielded no mosquito larvae, suggesting that physical and biological features of these wet sites limit the development of mosquito larvae. For both years, analysis of the positive samples revealed that less than 25% of sites produced Culex spp. while a small number of ditches and detention ponds were consistent “superproducers” of Culex larvae from year to year. This information will facilitate comparisons across geographical areas and provides insight into local variation in the public health risk due to mosquito transmission of human disease agents. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

生境质量对城镇化的时空响应——以长春市为例

生境质量是评价区域生态安全的重要指标,掌握其对城镇化发展的时空响应,有利于新型城镇化的深入推行。本研究基于土地利用数据,在综合利用空间分析及生态模型分析基础上,从网格尺度对长春市景观格局、生境质量及其样带进行时空特征分析,并进一步探讨生境质量在城镇化发展过程中的响应状况。结果表明: 长春市景观斑块密度、边缘密度及Shannon多样性指数低值多分布在西部平原地带,聚合度指数高值区则在市域东部及南部呈现片状格局。2000—2015年,长春市生境质量呈退化趋势且空间异质性显著,大致呈现出“东高西低”分布态势,建设用地扩张及交通基础设施建设对区域生境质量退化起到主导作用;不同样带内生境质量变化存在显著差异性,水域整体变化相对较小,而山脉、城市扩张及交通的变化频度及幅度处于较高水平。坡度及高程等自然因素基本塑造了长春市生境质量整体分布格局,而人口密度、国内生产总值、夜间灯光指数等城镇化要素与生境质量总体呈负相关关系。为缓解城镇化带来的生态压力、促进生境质量的回升,本研究提出防止大黑山脉林区滥砍乱伐、以生态手段修复生境退化地区,提升城镇建成区土地利用效率、促进城镇“精明增长”,设定丘陵地带耕地红线、加强生态基础设施建设等差异化发展策略。     

Conservation and conflict between endangered desert fishes

Conservation of naturally sympatric endangered species requires unique considerations. While impacts of invasive species garner much attention, interactions between endangered species must also be managed. The endangered Leon Springs pupfish, Cyprinodon bovinus, has suffered a population decline due to decreasing natural habitat. As breeding habitat is lost, C. bovinus is also adversely affected by the sympatric, endangered Pecos gambusia, Gambusia nobilis. Here, we document interactions between these species, finding significantly more G. nobilis accumulated at pupfish spawning events than randomly distributed on breeding grounds in the absence of spawning. As a known egg predator, our results suggest that G. nobilis presence at spawnings may further decrease pupfish numbers while also altering the evolutionary dynamics of C. bovinus breeding tactics. Habitat restoration may decrease Gambusia concentrations or influence C. bovinus breeding behaviour and increase the number of territorial males resulting in viable population sizes for both critically endangered fishes.     

Examining Landscape Factors Influencing Relative Distribution of Mosquito Genera and Frequency of Virus Infection

Mosquito-borne infections cause some of the most debilitating human diseases, including yellow fever and malaria, yet we lack an understanding of how disease risk scales with human-driven habitat changes. We present an approach to study variation in mosquito distribution and concomitant viral infections on the landscape level. In a pilot study we analyzed mosquito distribution along a 10-km transect of a West African rainforest area, which included primary forest, secondary forest, plantations, and human settlements. Variation was observed in the abundance of Anopheles, Aedes, Culex, and Uranotaenia mosquitoes between the different habitat types. Screening of trapped mosquitoes from the different habitats led to the isolation of five uncharacterized viruses of the families Bunyaviridae, Coronaviridae, Flaviviridae, and Rhabdoviridae, as well as an unclassified virus. Polymerase chain reaction screening for these five viruses in individual mosquitoes indicated a trend toward infection with specific viruses in specific mosquito genera that differed by habitat. Based on these initial analyses, we believe that further work is indicated to investigate the impact of anthropogenic landscape changes on mosquito distribution and accompanying arbovirus infection.