蜘蛛飞航习性观察

蜘蛛是农田多种害虫的重要天敌,保蛛治虫不但已为人们认识,且已应用于生产实际,并收到了良好的效益。了解蜘蛛的各种习性,对认识蜘蛛和保蛛治虫都有重要意义。蜘蛛无翅能飞航,有关资料均有所述,但飞航行为的具体细节特别是蛛丝在飞航中的作用却所见不多,作者出于兴趣,对     

江西广丰铜钹山自然保护区蜘蛛资源报告

江西广丰铜钹山自然保护区地处118°12’00”～118°21’36”E,28°03’30”---28°10’33”N,位于江西省东北部,与福建省浦城县毗邻,总面积1．08万hm2。蜘蛛是农林生态系统害虫天敌的主要类群,也常作为生态系统稳定的指示生物。作者等人通过对铜钹山自然保护区蜘蛛资源及区系分布进行野外调查、标本采集和分类鉴定等,发现该保护区有蜘蛛32科123属313种,其中54种为江西新记录种,115种为未确定种。     

江西井冈山国家级自然保护区蜘蛛资源调查

江西井冈山国家级自然保护区地处114° 04′～114°16′E,26° 28′～26°40′N,位于江西省西南部,东边江西泰和、遂川两县,南邻湖南炎陵县,西靠湖南茶陵县,北接江西永新县.蜘蛛是农林生态系统害虫天敌的主要类群,也常作为生态系统稳定的指示生物.作者等人通过对井冈山白然保护区蜘蛛资源及区系分布进行野外调查、标本采集和分类鉴定等,发现该保护区有蜘蛛18科48属73种,其中6种为江西新记录种,18种为未确定种.     

豇豆田生态系统中主要害虫及天敌的生态位研究

对武汉地区春播和夏播豇豆田生态系统中主要害虫、天敌的种类及空间、时间生态位进行了调查研究。结果表明,春播和夏播豇豆中,瓢虫、蜘蛛和捕食蝽同主要害虫的生态位重叠较大,跟随作用强,具保护利用价值;害虫生态位宽度以蚜虫LipaahiserysimiKaltenbach、蓟马ThripspalmiKarny、豆野螟MarucatestulalisGeyer较宽,天敌生态位春播田中瓢虫较宽,夏播田中蜘蛛较宽。     

江西宁都凌云山自然保护区蜘蛛资源初报

凌云山自然保护区位于江西省赣州市宁都县西北部边境,属雩山山脉中段。其地理坐标为东经115°50′16″-116°1′40″,北纬26°50′42″-27°2′11″,总面积11260hm^2。蜘蛛是农林生态系统害虫天敌的主要类群,也常作为生态系统稳定的指示生物。作者等人通过对凌云山自然保护区蜘蛛资源及区系分布进行野外调查、标本采集和分类鉴定等,发现该保护区有蜘蛛32科96属165种,其中,有5个江西新记录科,1个中国新记录种,29种江西新记录种和33未确定种。     

蜘蛛的生态进化

蜘蛛随着其生活环境的多种多样,在生活习性方面也可看到各种各样的变化。从地下到地表、落叶层、洞穴、草间、树上、树间、建筑物,直到水中,生活场所广泛,在各个环境中生活着;还有其他动物所不能模仿的静止在空中的生活,以及利用蜘丝在空中飘荡飞航借以扩散。     

土壤微藻的种类及其功能研究进展

微藻作为土壤生态系统中重要的生物类群之一,数量和种类非常可观,在生态学研究、农业生产、环境保护和治理、新资源开发利用等领域具有重要的理论研究意义和经济开发价值。介绍了土壤微藻的种类,影响其生长和分布的主要生态因子,以及固氮蓝藻、丝状蓝藻、集胞藻和硅藻等几种重要的土壤微藻类群的生态功能和应用价值。     

沈阳地区稻田节肢动物群落结构及群落生态研究

通过对沈阳地区稻田生态系统节肢动物群落结构及群落生态研究。共查得。属昆虫纲的有10个目的29科66种,其中天敌昆虫种类有7目20科51种,属蜘蛛纲的有蜘蛛目10科20种。用空间及时间生态位分析了害虫与天敌两个营养阶层间的关系。稻田生态系统节肢动物的多样性指数、均匀度与优势度分析表明,各类群落受外界干扰都很敏感,且表现一致性。依据节肢动物群落的结构及规律,结合沈阳地区水稻生长、栽培条件,用最优分割方法将稻田群落分为4个阶段,并提出了不同阶段害虫群落特点及害虫防治对策。     

农田常见微蛛的鉴别

微蛛科(Micryphantidae)的蜘蛛在农田蜘蛛中占有重要的地位。微蛛的个体虽小,但它们的数量多,繁殖力强,分布广,有飞航习性,利于迁移。且因个体小,便于荫蔽在稻丛基部或棉桃苞叶等处,甚至可钻进虫苞猎食害虫。在利用天敌蛛蜘消灭害虫方面,微蛛无疑是一类重要的研究对象。目前,农田中的微蛛已引起不少人的重视,本文介绍五种常见的农田蜘蛛,以供有关同志参考。     

中国西南喀斯特地区土壤动物生态学研究进展

中国西南喀斯特地区生态环境十分脆弱,在人为活动和自然因素的严重干扰下,该区生态系统遭到严重的破坏。土壤动物是喀斯特地区生态系统能量流动和物质循环至关重要的生物驱动因子,在保护和改善土地资源、防控该地区生态退化中有着重要意义。该区土壤动物类群组成丰富,具有明显的表聚性;随石漠化程度的加重,土壤动物类群数有减少的趋势;生境越复杂、扰动越小,土壤动物群落结构也越复杂、个体密度和类群数越高;不同海拔的土壤动物群落结构存在异质性。当前,中国西南喀斯特地区土壤动物生态学研究中存在分类水平不高、生态服务功能研究较少、对自然因素和人为因素响应的研究不够深入等问题。未来中国西南喀斯特地区土壤动物生态学研究应在生物指示作用、生态服务功能、微生态调控与作用机制及对当今热点环境问题的响应等方面展开深入研究。     

Fluid mechanic constraints on spider ballooning

Summary Early investigations point to ballooning as an important mechanism for the dispersal of spiders. Most studies, however, have focused on collecting and interpreting observations with the aim of establishing the statistical characteristics of the dispersed population and their relation to biotic factors. With few exceptions, important physical factors that mechanically constrain the ballooning activity have been neglected or simply ignored. Especially important are various fluid mechanics phenomena that affect the initiation and maintenance of the ballooning activity. By reference to a simple mechanical model that simulates the essential drag characteristics of the ballooning spider-filament system, a region is defined, in terms of the relevant physical parameters, within which the ballooning activity can be initiated. Extension of the model allows a numerical investigation of the influence of vertical wind oscillations on the velocities and trajectories of ballooning spider-filament systems. Results are presented and discussed to illustrate the relative importance to ballooning of drag on the spider's body and on the silk filament to which it is attached.     

Larval dispersal of the invasive fall armyworm,Spodoptera frugiperda,the exotic stemborer Chilo partellus,and indigenous maize stemborers in Africa

Larval dispersal either through ballooning or crawling results in a redistribution of the insect population and infestations within and between plants. In addition, invasive species, such as the fall armyworm (FAW), Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), and the exotic stemborer Chilo partellus (Swinhoe) (Lepidoptera: Crambidae), may displace indigenous stemborers on maize in Africa. To test whether larval dispersal activity may play a role in the displacement of indigenous stemborers, larval dispersal was compared between FAW, C. partellus, and the indigenous species Busseola fusca (Fuller) and Sesamia calamistis (Hampson) (both Lepidoptera: Noctuidae). Twenty potted maize plants were infested with one batch of eggs either from stemborers (B. fusca, S. calamistis, or C. partellus) or from FAW and monitored in the greenhouse for ballooning activities. After egg hatching, both ballooning and non-ballooning larvae were identified according to species and counted. FAW neonate larvae had greater potential for ballooning off than stemborers, irrespective of species. For each species, more females dispersed than males, and their survival rate was higher than that of non-ballooning larvae. In addition, plant-to-plant larval movements were studied using 6.25-m² plots of caged maize in a completely randomized design with five replicates. FAW was found to have wider dispersal and plant damage potential than any of the stemborer species. In conclusion, in contrast to C. partellus, the invasive characteristic of FAW can be explained, in part, by its higher larval dispersal activity compared to stemborers. This difference in larval dispersal might also be considered in sampling plans for monitoring pest density in the field.     

Low propensity for aerial dispersal in specialist spiders from fragmented landscapes

Aerial dispersal by ballooning is a passive flight, by which wind drag generates an upward lift on a silk thread. It is likely to reflect an aerial lottery, in which the absence of flight direction control is a serious cost for long-distance dispersal in a fragmented landscape. For species occurring in one patchily distributed habitat type, dispersal should evolve in a different way from morphological traits, directly linked to active dispersal. Therefore, we expect that if the risk of landing in an unsuitable habitat is lower than the probability of reaching a suitable habitat, selection should benefit a well-developed ballooning behaviour. We investigated interspecific variation in the ballooning-initiating tiptoe behaviour as it is linked to spider dispersal performance. Our results indeed indicate that ballooning performance is negatively related to habitat specialization in spiders from patchy grey dunes, so habitat specialists are characterized by poorly developed dispersal behaviour. These findings are concordant with recent insights that dispersal is selected as risk spreading in generalists, while it is selected against in specialist species.     

Effects of Predator and Prey Dispersal on Success or Failure of Biological Control

Biological control, defined as the reduction of pest populations by natural enemies, is often a component of integrated pest management strategies. Augmentation of natural enemy numbers by planned releases is a common biological control method, the successes and failures of which have been extensively reviewed. The effectiveness of biological control is influenced by how populations of predators and prey (or hosts and parasitoids) disperse in patchy environments. Here, we address the question of whether such dispersal leads to beneficial or detrimental pest control outcomes by developing a simple predator-prey model with constant releases of natural enemies in a two-patch environment. Theoretical and numerical results for all possible cases indicate that population dispersal has significant effects on the persistence of pests. For some ranges of dispersal rates or parameter space, dispersal is beneficial for pest control measures but this is not so for other ranges when it is detrimental. Therefore, knowledge of pest and natural enemy dispersal is crucial for understanding the effectiveness of biological control in a patchy environment. Finally, the model is generalised for multi-patch systems.     

Starvation affects pre-dispersal behaviour of Erigone spiders

Population studies often focus on demographic and genetic consequences of dispersal strategies, generally within an evolutionary framework. Adaptive investment in dispersal is generally assessed from single types of (pre-)dispersal behaviour that are presumed to reliably reflect the dispersal strategy adopted. Various spider families show a striking and quantifiable display, known as tiptoe behaviour that prepares individuals for take-off prior to (passive) aerial dispersal (ballooning). The lack of efficient control mechanisms during ballooning prevents individuals from actively selecting a suitable habitat for landing. Ballooning dispersal is therefore often regarded as a wind lottery preceded by individual-based risk assessment. Our laboratory experiments showed that the duration of tiptoe behaviour can be used as an indicator of silk thread length, which is related to the potential dispersal distance. For two related species, Erigone arctica and E. dentiplapis, tiptoe duration decreased independently of sex after starvation, while more complex reaction norms were observed for tiptoe frequency.

Because these two aspects of dispersal behaviours show different responses towards a simple stress-factor (starvation) in two related spider species, we conclude that the level of plasticity in dispersal investment can be subject to selective forces affecting different dispersal properties in different ways. Our results, hence, plead for a more holistic approach when addressing evolutionary and applied questions related to dispersal.     

Population genetic structure of the winter moth,Operophtera brumata Linnaeus,in the Orkney Isles suggests long‐distance dispersal

1. The application of population genetic analysis and molecular ecological approaches allows us to examine the invasion of species in the wild. In particular, we can gain an insight into the role of dispersal, a key determinant of the invasion and population dynamics of important pest species. Since the 1980s, severe outbreaks of the winter moth, Operophtera brumata (Linnaeus), have caused extensive damage to heather moorlands in the Orkney Isles. The population genetic structure of O. brumata in Orkney was examined in order to establish whether the widely dispersed outbreaking populations are connected. 2. Amplified fragment length polymorphism (AFLP) analysis showed a high level of genetic diversity within subpopulations. This is consistent with an initial mass colonisation event and/or continuing dispersal between populations of O. brumata in Orkney. 3. Genetic differentiation among populations is low, and although some weak isolation by distance is detectable, no effect of isolation as a result of a sea barrier was found. High gene flow between populations is consistent with the low genetic differentiation observed, although there is evidence to suggest that the populations are not panmictic. 4. Given the limited dispersal of adults, the present results suggest that larvae may disperse over considerable distances by ballooning on strong winds across the Orkney Isles.     

Ballooning dispersal in arthropod taxa with convergent behaviours: dynamic properties of ballooning silk in turbulent flows

We present a new model of ballooning behaviour in arthropods in which draglines are regarded as being extendible and completely flexible. Our numerical simulations reveal that silk draglines within turbulent flows can become twisted and stretched into highly contorted shapes. Ballooners are therefore predicted to have little control over their aerodynamic drag and their dispersal within the atmospheric boundary layer. Dragline length is crucial only at lift-off. This prediction runs counter to that of Humphrey who suggested that the length of rigid draglines can be used to control dispersal. In contrast with Humphrey's model, the new model accounts naturally for the large distances travelled by some ballooners.     

Repeatability of dispersal behaviour in a common dwarf spider: evidence for different mechanisms behind short‐ and long‐distance dispersal

Abstract 1. The response of dispersal towards evolution largely depends on its heritability for which upper limits are determined by the trait’s repeatability. 2. In the Linyphiid spider E. atra, we were able to separate long‐ and short‐distance dispersal behaviours (respectively ballooning and rappelling) under laboratory conditions. By performing repeated behavioural trials for females, we show that average dispersal trait values decrease with increasing testing days. By comparing mated and unmated individuals during two periods (before and after mating for the mated group, and the same two periods for the unmated group), we show that mating has no effect on the mean displayed dispersal behaviour or its within‐individual variation. Repeatabilities were high and consistent for ballooning motivation, but not for rappelling. 3. Ballooning motivation can be regarded as highly individual‐specific behaviour, while general pre‐dispersal and rappelling behaviours showed more individual variation. Such difference in repeatability between long‐ and short‐distance dispersal suggests that short‐ and long‐distance dispersal events are triggered by different ecological and evolutionary mechanisms.     

Sex-biased dispersal and a density-independent mating system in the Australian brushtail possum, as revealed by minisatellite DNA profiling

Natal dispersal can have important effects on mammal population structure and dynamics following a local population crash. Such dispersal is of practical importance when applied to the control of pest species because dispersal may significantly, and undesirably, reduce the population recovery time following a control operation. The relative dispersal rate of the sexes is also critical because that too will affect the rate of population increase. Here, we describe a field experiment in which we reduce the density of two populations of the Australian brushtail possum, and use genetic similarity, as estimated by minisatellite DNA profiles, to investigate dispersal in the original (undisturbed) and recovering populations. Our results show that the genetic similarity within the undisturbed populations was lower between males than between females. Conversely, the genetic similarities between males and females in the two recovering populations were not significantly different, while relatedness among males was significantly higher in the recovering populations when compared with those in the pre-removal populations. These data indicate two important characteristics of dispersal in possums: (i) that dispersal in established populations is sex biased towards males; and (ii) that within the first 3 years following population control, 'the vacuum effect', whereby individuals from areas adjacent to a control area expand their home range and invade the depopulated area, is the most important factor in the re-colonization process for possums. We found no evidence that the mating system, which is polygynous, varied when the density was markedly reduced. These results indicate that drastic reductions in population density by conventional control will not affect the rate of spread of biological control agents that rely on sexual transmission for dissemination.     

Rapid spread agents may impair biological control in a tritrophic food web with intraguild predation

The augmentation of natural enemies against agricultural pests is a common tactic undertaken to minimize crop damage without the use of chemical pesticides. Failures of this strategy may result from (i) Allee effects acting on biological control agent; (ii) trophic interactions between the released control agent and native species in the local ecosystem; (iii) excessively rapid spreading agents. To investigate the interplay of these mechanisms in pest biocontrol efficiency in the context of intraguild predation (IGP), we develop a one-dimensional dynamical model of a spatial, tritrophic food web with intraguild predation. We show that the agent’s diffusivity (i.e., agent’s dispersal speed), and intraguild predator’s addition of alternative food sources are important factors in determining the success or failure of pest biocontrol. These results are obtained for spatially explicit models by considering the speed of dispersal of the control agent and the pest. Feedback from theoretical models as the one constructed in this work can provide useful guidelines for practitioners in biological control.