THE ECOLOGY OF ANISOPUS FENESTRALIS SCOP. (DIPTERA) IN SEWAGE BACTERIA BEDS

The assessment of populations of Anisopus fenestrate (Scopoli, 1763) in sewage bacteria beds by the trapping of adults at the surface has been previously proved to be unsatisfactory. Methods were therefore developed for determining the numbers of egg masses, larvae and pupae as well as the total organic matter in a unit volume of bed. The relative larval populations of three areas under investigation were related to the loading of the beds as measured by the sewage strength and rate of application. In the upper 2 ft. 6 in. the numbers of larvae and pupae per unit volume of bed decreased with depth. There was no evidence of any vertical migration of the larvae before pupation. The horizontal distribution of larvae was found to be affected by the method of distribution. In beds served with fixed spray jets larvae are more abundant nearer the jets than at some distance away. In beds served with travelling distributors the larvae are more abundant in the zones below the jets than in the drier intermediate zones. In both cases relatively higher percentages of pupae in the drier zones might indicate a horizontal migration of larvae before pupating or of the pupae themselves.
The incidence of the larvae throughout 1949 in all three beds showed recurring peaks. In the following year a more intensive investigation on one area showed that this was due to successive generations of the fly; the proximity of the peaks is determined mostly by temperature and their size by the amount of food available in the bed during the larval grazing phase.
In the area not treated with insecticide intraspecific competition during a period when food was limiting, due to depletion by the previous generation, resulted in a natural reduction in the population. In the area treated with insecticide the food was retained and this natural control was thereby delayed.     

A STUDY OF THE BIOLOGY AND CONTROL OF ANISOPUS FENESTRALIS (SCOPOLI, 1763), A FLY ASSOCIATED WITH SEWAGE FILTERS

In work on the control of the sewage fly Anisopus fenestralis (Scopoli, 1763), it was shown that the larval phase was considerably lengthened by limiting the food supplied. The effects of food supply and temperature are considered in relation to the incidence of the adult fly in the filters. The assessment of the fly population of sewage filters by tray traps, as previously used by other workers, was investigated. Both light and temperature were found to affect the number of A. fenestralis entering the trays: it is concluded that although the trays do not accurately assess the A. fenestralis population of a bed, nor measure the rate of emergence from the bed, they are of value in assessing the relative effect of different control measures. In the filters the period of maximum abundance was during the spring, followed by a period of reduced numbers throughout the summer, with a recovery in the autumn giving relatively high numbers throughout the winter. Emergence of A. fenestralis from the filters is influenced by climatic factors, especially temperature and light; a diurnal variation in the rate of emergence was also observed. Because of this effect of temperature on emergence, the flies were only present above the filters in the warmer periods of the year; and because of the reduced numbers in the filters in the summer, the flies were only abundant above the beds during the spring and early summer and in the autumn. BHC applied as a water-dispersible powder was more effective than in the form of an emulsion. It was also most effective when used against the larval phase.     

The ecology and function of Protozoa in sewage purification

Seasonal recording of the Protozoa in various sewage disposal units has shown that, together with changes correlated with the degree of purification of the sewage, fluctuations occur as a result of the interplay of seasonal non-specific factors and local specific factors. The incidence and abundance of Protozoa in each disposal plant would seem to be controlled by sewage 'strength' and characteristic local drainage. Fluctuations of the population, however, are limited by different factors in different seasons.
In the bacteria bed investigations a 'weak' sewage shows a decrease of a generally rich fauna during the periods of sloughing, a 'strong' acid sewage during sloughing shows an increase in an otherwise restricted fauna and where the sewage is medium in 'strength' and supports an abundant insect population the fluctuations of the Protozoa are dominated by the more active insect populations of summer and by temperature in winter. In this last-named environment a significant inverse correlation between ciliate and insect frequency throughout the summer indicates the thoroughness with which the insect larvae devour the film; this may explain the summer reductions in certain groups of Protozoa.
In activated sludge channels conditions favour a uniform population which may vary in composition according to the purity of the sewage. Flocculation is most pronounced when protozoan populations comprise a restricted variety of ciliates and would seem to depend on a protozoan fauna since cultures of bacteria obtained from sewage did not flocculate unless Protozoa, free from or contaminated with bacteria, were added.
The protozoan populations of the two systems of disposal are compared in discussion.     

AN ECOLOGICAL STUDY OF THE ENCHYTRAEID WORM POPULATION OF SEWAGE BACTERIA BEDS LABORATORY EXPERIMENTS

This paper records the results of the experimental phase of an ecological study of the enchytraeid population of the sewage beds of the Huddersfield Corporation. The sewage in this drainage area is heavily charged with chemical wastes which have a marked effect on the fauna. Enchytraeus albidus Henle was the dominant worm while Lumbricillus lineatus Mull., the common bacteria bed-worm, was relatively scarce. The ability of these two worms to complete their life cycles in the sewage before and after treatment in particular beds was examined.
The crude Huddersfield sewage proved toxic to both E. albidus and L. lineatus but the former was much more resistant. After treatment in the beds the degree of toxicity was much reduced and the final sewage was harmless to all stages of E. albidus but the eggs of L. lineatus were still unable to develop in it.
The eggs of both species were less resistant to the toxic substances than the young worms; the adults were most resistant. High temperatures lowered toxicity by reducing the duration of the more susceptible early stages.
There was no evidence of physiological adaptation of L. lineatus to conditions in the Huddersfield beds. Wastes from both the main chemical works in the drainage area were examined and shown to be toxic; the domestic sewage was non-toxic. Both the distillate and residue of one of the chemical wastes proved toxic, especially the latter.
The toxicity could be entirely removed from the treated sewage by standing it over activated carbon for a few hours, or permitting slow oxidation for some weeks. The eggs of L. lineatus were used for these tests.
The Huddersfield sewage was very acid from time to time and the acidity reached was sufficient to kill young worms and adults of both species. But this factor was not considered important in the beds owing to the persistent effects of the toxic sewage.     

THE EFFECTS OF INSECTICIDE TREATMENT ON THE MACROFAUNA POPULATIONS, FILM ACCUMULATION AND EFFICIENCY OF SEWAGE PERCOLATING FILTERS

In an attempt to replace the laborious method of assessing macrofauna populations of sewage filters, which involves the separation of the macro-organisms from unit volumes of stone samples excavated from the filters, it was found that the numbers of Anisopus fenestrate (Scopoli, 1763) larvae taken weekly during 1951 in baited traps placed in the filters were greatly affected by the amount of available food within the filter. A method involving separation by flotation was, however, evolved for the rough estimation of Collembola.     

中国北方黄土地层中的哺乳动物群及在磁性地层中的位置

本文研究了中国黄土地层中有确切层位的哺乳动物化石记录,并进行了生物地层学与磁性地层学对比,将黄土地层中的动物化石归纳成如下哺乳动物群：早更新世（2．50─0．73Ma）：午城动物群（2．50─1．20Ma）、公王岭动物群（1．20─1．10Ma）和阳郭动物群（1．10─0．90Ma）、中更新世（0．73─0．13Ma）：陈家窝子动物群（0．73─0．40Ma）;晚更新世（0．13─0．01Ma）：柔远─靖远动物群（0．13─0．01Ma）;全新世（0．01Ma─Rec）:半坡动物群。结果表明：早更新世许多森林习性的化石动物虽然反映出气候较第三纪的寒冷,但比后期温暖湿润。中更新世出现了较多的草原、干旱草原习性的动物,气候更为寒冷干旱,森林逐渐减少或消失,草原或干旱草原得到发展;晚更新世出现的沙鼠、跳鼠等动物,表明气候更加寒冷、干旱,部分地区甚至沙化。     

Genetic variation tracks ecological segregation in Pacific island black flies

Geographic isolation is widely viewed as a key component of insular radiations on islands. However, strong ecological affinities may also reinforce isolation and promote genetic divergence. The black fly fauna in the Society Islands French Polynesia is notable for the number of closely related endemic species (31), and the morphological and habitat diversity of the larvae. Here, we measure ecological and morphological differences within and between two closely related species, Simulium oviceps and Simulium dussertorum and relate these differences to genetic distance. Phylogenetic analyses of a 920 bp fragment of the cytochrome oxidase I (COI) gene revealed a well-supported, ecologically divergent S. oviceps clade (larvae found in rivers instead of cascades) that shows little morphological differentiation. For both S. oviceps and S. dussertorum, genetic distance among populations is related to larval habitat, with cascade populations showing greater isolation from each other than river populations. Our data support the hypothesis that larval ecological shifts have played a role in the radiation of this black fly fauna.     

Gene transfer and plasmid instability within pilot-scale sewage filter beds and the invertebrates that live in them

The environmental plasmid pQKH6 was transferred conjugatively between strains of Pseudomonas putida at mean frequencies of up to 8.4x10(-4) within pilot-scale sewage filter beds. This frequency was 10-fold higher than that reported previously for this environment and was probably due to seasonal temperature changes. Many (45%) of the plasmids isolated subsequently from the filter beds had restriction fragment length polymorphism (RFLP) profiles that differed from that expected for pQKH6. RFLP analysis revealed structural rearrangements occurring within a particularly restriction-site-rich region of the plasmid. Although no evidence was obtained showing the indigenous invertebrate populations within the filter beds to influence the rate of gene transfer, pQKH6 was transferred with frequencies of up to 1.6x10(-2) within the guts of the filter-bed-dwelling Sylvicola fenestralis larvae during laboratory experiments. This transfer was strongly influenced by donor to recipient ratios. Laboratory experiments also showed that Serratia fonticola survived better within invertebrate guts than P. putida. This evidence, along with experiments showing that S. fonticola could participate in pQKH6 transfer within filter-bed biofilm, identify this bacterium as a better model than P. putida for examining the effect of invertebrates on gene transfer.     

Environmental stress and the evolution of dioecy: Wurmbea dioica (Colchicaceae) in Western Australia

Stressful ecological conditions have been implicated in the evolution of separate sexes in plants. Gender dimorphic species are often found in drier habitats than their sexually monomorphic relatives, and gynodioecious populations appear closer to a dioecious state as resources, particularly water, become limiting. This pattern could result if dry conditions decrease the relative seed fitness of cosexual plants, allowing female plants to become established in monomorphic populations. We studied geographical variation in gender expression and biomass allocation among 12 monomorphic and dimorphic populations of Wurmbea dioica along a latitudinal precipitation gradient in southwestern Australia to provide insight into mechanisms by which aridity might favor transitions between sexual systems. Plants in monomorphic and dimorphic populations exhibited contrasting gender expression and patterns of biomass allocation in areas with different levels of precipitation. Among dimorphic populations, lower precipitation was associated with a higher frequency of female plants, and reduced allocation to female function by hermaphrodites during flowering. In contrast, stress conditions had no effect on female allocation at flowering in monomorphic populations. Across latitudes, unisexuals and cosexuals exhibited consistent differences in above ground traits, with cosexuals having larger leaves, taller stems and larger flowers. Although all plants were smaller under drier conditions, cosexuals decreased above ground allocation to vegetative and reproductive structures with decreasing latitude. In contrast, unisexuals increased allocation to reproduction in drier areas at the expense of below ground size. Aridity was associated with reduced flower size among all gender classes, but not with changes in flower number. These data do not support the hypothesis that resource limitation of female allocation in cosexual populations favors the establishment of gender dimorphism in W. dioica. Alternative hypotheses, involving higher selfing rates and enhanced survival of unisexuals relative to cosexuals under resource-limited conditions, are discussed as possible explanations for the origin of dioecy in W. dioica. This revised version was published online in August 2006 with corrections to the Cover Date.     

横断山区昆虫区系初探

1981—1984年,中国科学院青藏高原科学考察队在我国西南部的横断山区进行了大规模的多学科综合考察,收集昆虫标本17万多号.横断山区特殊的自然地理条件孕育着独特的昆虫区系.种类繁庶、成分复杂,特有种,尤其高山特有种相当丰富,物种分化显著,并具有地域上的狭布性,构成本区昆虫区系特征.作者根据古北、东洋、高山特有三种主要成分的分布,试提出古北、东洋两大区系在本区的分异界线.典型东洋区系成分一般限于海拔2,800—3,000m以下地区,约与亚热带常绿阔叶林分布上线一致.     

SYMPATRIC SEA SHELLS ALONG THE SEA'S SHORE: THE GEOGRAPHY OF SPECIATION IN THE MARINE GASTROPOD TEGULA

Uncertainty and controversy surround the geographical and ecological circumstances that create genetic differences between populations that eventually lead to reproductive isolation. Two aspects of marine organisms further complicate this situation: (1) many species possess planktonic larvae capable of great dispersal; and (2) obvious barriers to movement between populations are rare. Past studies of speciation in the sea have focussed on identifying the effects of past land barriers and on biogeographical breakpoints. However, assessing the role such undeniable barriers actually play in the initial divergence leading to reproductive isolation requires phylogenetic studies of recent radiations living in varying degrees of sympatry and allopatry to see which barriers (if any) tend to separate sister species. Here I infer phylogenetic relationship between 23 species of the marine snail Tegula using DNA sequences from two regions of the mitochondrial genome: cytochrome c oxidase I (COI) and the small ribosomal subunit (12S) These snails possess planktonic larvae with moderate dispersal capabilities and have speciated rapidly with over 40 extant species arising since the genus first appeared in the mid-Miocene (about 15 M.Y.B.P.). Trees constructed from the COI and 12S regions (which yielded 205 and 137 phylogenetically informative sites, respectively) were robust with respect to tree-building method, bootstrapping, and the relative weightings of transitions, transversions, and gaps Within clades where all extant species have been sampled, five of six identified sister species pairs broadly coexist on the same side of biogeographical boundaries. These data suggest strong geographical barriers to gene flow may not always be required for speciation in the sea; transient allopatry or even ecological barriers may suffice. A survey of the geographic distributions of marine radiations suggests that coastal distributions may favor the sympatry of sister taxa more than island distributions do.     

THE EFFECT OF CERTAIN PREDATORS ON THE NUMBERS OF CABBAGE ROOT FLY (ERIOISCHIA BRASSICAE (BOUCHÉ)) AND ON THE SUBSEQUENT DAMAGE CAUSED BY THE PEST

To determine the importance of beetle predators on the natural control of cabbage root fly, experiments were carried out in 1958 and 1959 using various types of barriers to obtain different levels of beetle populations on cauliflower plots. A barrier of DDT-treated straw, placed in the soil around some plots, decreased the numbers of beetles within them and allowed a greater number of eggs and larvae of cabbage root fly to survive than on the untreated plots, resulting in a greater crop damage. Another type of barrier allowed the beetles to enter plots but made it difficult for them to leave. On these, fewer cabbage root-fly eggs and larvae survived and the crop damage was much less than on the plots surrounded by straw barriers. Where plants were treated with insecticide the root-fly population was reduced to a minimum and crop yields were considerably increased. The insecticide, however, caused a reduction in the numbers of predatory beetles.     

海南岛尖峰岭热带山地雨林采伐迹地更新群落的初步分析

 海南岛西南部热带山地雨林采伐迹地上的更新群落大多数是以闽粤栲占优势的森林植被。本文以尖峰岭为例,对热带山地雨林不同采伐方式迹地上更新的群落进行了群落数量特征、种群年龄结构的分析。同时从林业生产的角度,评定了群落的更新质量,并提出了热带山地雨林适宜的采伐方式和群落更新的抚育管理方法。     

长江中游宜昌江段鱼类早期资源现状及水文影响条件

为了解长江中游鱼类的早期资源现状, 2017年和2018年5—7月在长江干流宜都断面开展鱼类早期资源调查, 采样网具包括弶网和圆锥网。调查期间共采集鱼卵21120粒和仔鱼2123尾。利用形态学和分子生物学等方法, 鉴定鱼类5目9科37种。其中, 鱼卵有29种, 仔鱼有27种。2017年和2018年通过宜都断面的鱼卵径流量分别为124.45×108粒和101.07×108粒, 优势种为四大家鱼和贝氏?(Hemiculter bleekeri); 仔鱼径流量分别为16.43×108尾和8.29×108尾, 优势种为贝氏?和寡鳞飘鱼(Pseudolanbuca engraulis)。根据发育期和流速分析, 四大家鱼鱼卵来源于三峡大坝下游至宜都断面之间的产卵场, 仔鱼来源于三峡大坝以上的产卵场。与2009—2010年相比, 2017—2018年通过宜都断面的鱼卵径流量增大了85.3%, 尤其是四大家鱼的鱼卵径流量与2005—2012年相比增加了约13倍。冗余分析(Redundancy Analysis, RDA)结果显示, 流量和流量日变化对产漂流性鱼卵密度有影响。研究结果表明, 2017—2018年仍有大量的鱼卵和仔鱼补充到长江中游江段。与历史数据相比, 三峡大坝下游宜昌江段鱼类产卵规模有明显的增加, 可能与长江中游四大家鱼亲鱼增殖放流和生态调度等保护措施的实施有关。为了更加有效地保护长江中游的鱼类资源, 建议除了已经逐步实施的长江全面禁渔措施之外, 还应恢复江湖连通, 保护和修复长江中游河漫滩生境, 继续开展重要经济鱼类亲本放流, 以及开展生态调度。     

长江安庆段仔稚鱼群落特征调查研究

安庆江段是长江下游重要渔业资源水域之一, 为了解该江段仔稚鱼群落特征及与环境因子的关系, 于2016年4月17日至8月15日对安庆江段仔稚鱼进行了逐日调查。结果显示: 研究共采集仔稚鱼个体92160尾, 鉴定90457尾, 隶属于7目11科49种, 其中鲤科(Cyprinidae)种类数居第一, 32种, 尾数占比为90.16%; 鰕虎鱼科(Gobiidae)居第二, 3种, 尾数占比为5.71%。在生态类型及产卵方式上, 淡水定居性鱼类和产漂流性卵鱼类数量占比最大, 分别为87.57%和88.30%。贝氏?(Hemiculter bleekeri)是该江段第一优势种, 数量占比44.53%, 其余优势种为?(Hemiculter leucisculus, 占比14.21%)、银鲴(Xenocypris argentea, 占比8.11%)、子陵吻鰕虎(Rhinogobius giurinus, 占比5.60%)、飘鱼(Pseudolaubuca sinensis, 占比4.75%)、似鳊(Pseudobrama simoni, 占比4.13%)、寡鳞飘鱼(Pseudolaubuca engraulis, 占比4.50%)、鳊(Parabramis pekinensis, 占比2.63%)、刀鲚(Coilia nasus, 占比1.89%)、鲢(Hypophthalmichthys molitrix, 占比1.57%)。仔稚鱼丰度出现4次明显的高峰时期, 第一次在5月1日, 后面三次集中出现在6月中下旬, 分别为1127.00、1608.44、1568.35 和1202.94 ind./100 m3。通过冗余分析(RDA)表明, 影响安庆江段仔稚鱼丰度的主要环境因子为水流量、水位、透明度(P<0.05), 大多数仔稚鱼丰度与水流量、水位呈现负相关, 与透明度呈现正相关, 可能与该年份过高的水流量、水位有关。研究表明, 安庆江段的仔稚鱼种类较丰富, 但主要以小型鱼类为主, 且经济性仔稚鱼类占比小。研究初步探明了安庆江段的仔稚鱼资源状况, 其结果为安庆鱼类早期资源进一步研究提供基础资料, 同时也为渔业资源保护策略制定提供科学依据。     

Antarctic reptant decapods: more than a myth?

The impoverished Antarctic decapod fauna is one of the most conspicuous biodiversity phenomena in polar science. Although physiological and ecological approaches have tried to explain the reason for the low decapod biodiversity pattern in the Southern Ocean, the complexity of this problem is still not completely understood. The scant records of crabs south of the Polar Front were always considered as exceptional, and have mostly been ignored by marine biologists world-wide, creating one of the most dogmatic paradigms in polar science. We herein review the record of both adults and larvae of reptants from the Southern Ocean. At present, several species of only lithodid crabs maintain considerable adult populations in circum-Antarctic waters, although they remain absent from the high-Antarctic shelves.     

九龙江口底栖生物生态研究

本文研究了九龙江口底栖生物种类组成、数量分布、季节变化及其与环境因子的关系等生态特点。结果表明,九龙江口底栖生物种类丰富(计440种)。其分布具有三种生态类型:河口种、海水种和近岸广盐种。平均总生物量为56.17克/米~2,平均栖息密度为358个/米~2。底栖生物与环境因子的关系密切:河口区底栖生物种群和数量的分布趋势是随着盐度的增高而增多;局部区域的水动力特点以及不同的沉积物类型也影响底栖生物种类和数量的分布。     

我国南方第四纪哺乳动物群的划分和演变

到目前为止,通过调查和研究已认识到,在我国南方第四纪存在四个主要的哺乳动物群,即:元谋动物群、柳城巨猿动物群、大熊猫-剑齿象动物群和现代哺乳动物群。本文对这四个主要的哺乳动物群的进一步划分和演变进行讨论。元谋动物群、柳城巨猿动物群、建始高坪动物群和柳州笔架山动物群均属早更新世。元谋组发现的动物群似乎可以分为两个不同的层位:早期以森林中生活的动物为主,其时代似可划归晚上新世;晚期的动物则反映出以森林—疏林草原为主的生态环境。早更新世的元谋动物群以元谋组上部(3—4段)发现者为代表。柳城巨猿动物群中现生种类比元谋动物群中多,似较后者为晚。柳城巨猿动物群和大熊猫-剑齿象动物群有较密切的关系,可以说前者是后者的原始类型。建始高坪动物群和柳州笔架山动物群代表柳城巨猿动物群和大熊猫-剑齿象动物群之间的过渡类型。大熊猫-剑齿象动物群的地质时代为中-晚更新世,根据动物群的组合情况可分为四个不同的发展阶段:(1)含第三纪残留种类或古老种类;(2)含中更新世典型种类;(3)含早期智人化石;(4)含晚期智人化石或相当于这一阶段的人类制造的文化遗物。我国南方现代哺乳动物群奠基于大熊猫-剑齿象动物群,大体上形成于晚更新世后期。在全新世早期可能有个别更新世残留下来的种类,稍后可能还有个别绝灭种或绝灭亚种;而地理分布改变的种类,在全新世较长的时期内还有所残留。我国南方第四纪哺乳动物表现出土生土长的特点。动物群大致经历过三次较大的变化。和华北地区比较,我国南方第四纪哺乳动物群显示出三大特点:(1)古老种类延续时期较长;(2)现生种类出现较早;(3)动物群的变化不及华北那么明显。     

THE FUNCTIONAL BASIS OF NATURAL SELECTION FOR VERTEBRAL TRAITS OF LARVAE IN THE STICKLEBACK GASTEROSTEUS ACULEATUS

Previous studies have demonstrated selective predation for vertebral traits of larvae in the stickleback Gasterosteus aculeatus. I tested the hypothesis that this selection results from a direct functional advantage to particular vertebral phenotypes by direct measurement of the burst swimming performance of larvae. Within a narrow window of lengths, burst speed did depend on vertebral phenotype. As in the previous predation experiments, performance was related more directly to the ratio of abdominal to caudal vertebrae (VR) than to the total number of vertebrae (VN), and the optimal VR decreased as larval length increased. Changes with length in the vertebral phenotype frequencies of wild larvae provided evidence of selection for VR and for VN in the wild. Larvae with particular VR increased in frequency in the wild at just those lengths when their relative performance was superior in the laboratory. The observed pattern of length-dependent selection for vertebral number provides an explanation for the widespread trends in vertebral number that occur among populations of related fishes.     

Diet composition of post-metamorphic bullfrogs (Rana catesbeiana) in the Zhoushan archipelago, Zhejiang Province, China

Bullfrogs (Runa catesbeiana) are listed as one of the 100 worst invasive alien species in the world.They are generalist predators and thus may affect native species through predation.In previous studies,the food contents of bullfrogs were mostly examined at a single site.In the present study,the diet composition of post-metamorphic bullfrogs on eight islands (Daishan,Liuheng,Xiushan,Fodu,Taohua,Xiashi,Cezi,and Putuoshan) in the Zhoushan Archipelago,Zhejiang Province of China,were examined by using the stomach flushing method from June 30 to August 11 in 2005.A total 0f391 individual frogs were measured,including 113 adults and 278 juveniles.The analysis of the stomach contents shows that,for adult bullfrogs,the most important prey (by diet volume) overall were Decapoda,Coleoptera,Odonata,Mesogastropoda,Raniformes,and Cypriniformes.For juvenile bullfrogs,these were Decapoda,Coleoptera,Cypriniformes,Odonata,Orthoptera,Hymenoptera,Lepidoptera larvae,Mesogastropoda,and Raniformes.Moreover,the prey size and diet volume increased with the body size of both adult and juvenile bullfrogs.The diet composition of primary preys of bullfrogs was significantly different among the islands.The results indicate that bullfrogs exert different predatory influences on native fauna at different sites and that bullfrogs are generalist predators with extensive ecological impacts on native fauna.