Spider Communities Research Articles

The effect of thinning on ground spider diversity and microenvironmental factors of a subtropical spruce plantation forest in East Asia

Currently, information about the effect of forest management on biodiversity of subtropical plantation forests in Asia is quite limited. In this study, we compared the spider community structures and guild compositions of subtropical Cryptomeria japonica plantation forests receiving different degree of thinning (0, 25 and 50 %) in central Taiwan. The ground spider diversities and environmental variables were sampled/measured once every 3 months for 1 year before thinning and 2 years after thinning. Results showed that before thinning spider compositions did not differ significantly among three plantation forest types. Two years after thinning, spider species and family compositions of three plantation forest types differed significantly. In all three plantation forest types, the spider composition differed from year to year, indicating existence of temporal variations in spider diversity. Ground hunters (increased 200–600 % in thinned forests), sheet web weavers (increased 50–300 % in thinned forests) and space web weavers (decreased 30–50 % in thinned forests) were the major contributors of the observed spider composition differences among plantation forests receiving different treatments. The stands receiving thinning treatments also had higher illumination, litter decomposition rate, temperature and understory vegetation density. Thinning treatments might have changed the structures of understory vegetation and canopy cover and consequently resulted in abundance and diversity changes of these guilds. Moreover, the heterogeneity in understory vegetation recovery rate and temporal variation of spider composition might further generate spider diversity variations in subtropical forests receiving different degree of thinning.

Assessing spider diversity on the forest floor: expert knowledge beats systematic design

The design of sampling schemes affects the results of biodiversity inventories. As an approach for quantifying the implications of such effects, we compared data on spider communities sampled in a beech-dominated forest floor habitat by 1) a regular grid of pitfall traps (systematic design) and 2) an expert-based distribution of traps (stratified design). We tested whether the two designs would lead to similar conclusions about the diversity and composition of ground-dwelling spider communities. Estimates of species richness, rarefied species richness and activity density calculated per trap were significantly higher in the stratified than in the systematic design. The community composition based on the presence or absence of sampled species or based on log-transformed activity densities differed significantly. Most of the dissimilarity between the community estimates of the two designs was attributable to three species, with Pardosa saltans Topfer-Hofmann 2000 being more common in traps of the stratified design and Tenuiphantes zimmermanni (Bertkau 1890) and Walckenaeria cuspidata Blackwall 1833 being more frequently observed in traps of the systematic design. Our study suggests that a stratified sampling design is better suited for inventory surveys of spider communities of forest-floor habitats, as trap locations of this design reflect specific habitat needs. It is important to note that inventories are a major field for the application of such designs and that greater care is needed for the application of inferential statistics. For example, the non-randomness that is caused by expert selection of sampling sites may violate fundamental assumptions of simple linear models.

Dispatch from the field: ecology of ground-web-building spiders with description of a new species (Araneae, Symphytognathidae)

Crassignatha danaugirangensis sp. n. (Araneae: Symphytognathidae) was discovered during a tropical ecology field course held at the Danau Girang Field Centre in Sabah, Malaysia. A taxonomic description and accompanying ecological study were completed as course activities. To assess the ecology of this species, which belongs to the ground-web-building spider community, three habitat types were surveyed: riparian forest, recently inundated riverine forest, and oil palm plantation. Crassignatha danaugirangensis sp. n. is the most abundant ground-web-building spider species in riparian forest; it is rare or absent from the recently inundated forest and was not found in a nearby oil palm plantation. The availability of this taxonomic description may help facilitate the accumulation of data about this species and the role of inundated riverine forest in shaping invertebrate communities.

Ecomorphic organisation of the Ukraine steppe zone spider community

The conception of ecomorphes as ecological groups of living organisms has been developed by A. L. Belgard (1950) applicable for species of the highest plants of the southeast of a steppe zone of Ukraine. Conceptually close system of vital forms-biomorphs of animals and plants has been created by Mikhail Pavlovich Akimov (Akimov, 1955). A key task of an ecomorphic approach is the ecological analysis of ecosystems structure. The ecomorphic approach has been applied to various groups of animals: entomological fauna of wood plants (Apostolov, 1981), complexes of land arthropods (Barsov, 1996), communities of birds (Ponomarenko, 2002), soil mesofauna (Zhukov, 1996), coleoptera communities agrocoenosis (Sumarokov, 2007). To identify animal species as ecomorphes the expert approach was used: the expert in taxonomy group relying on the experience and knowledge of object identifies it ecomorphes. The algorithm of ecomorphes allocation of soil animals has been offered by Zhukov (Zhukov, 2009). With some changes this algorithm has been applied to allocation of spider species of the Dnepropetrovsk region (Prokopenko et al., 2011). A lack of the specified algorithm is that it yields satisfactory results only for abundant and frequent species in regional fauna. The shortcoming reason – it relies on parametrical statistics for which compliance of experimental data to the normal law of distribution is essentially important that actually can be established only for limited number of species. As result, for a number rather rare in regional fauna of species of spiders incorrect conclusions have been drawn on their ecological status which is known on data from spiders of regions more studied from the point of view of fauna. In our work nonparametric procedure of a multidimensional scaling which is tolerant to a statistical property of distribution of an abundance of types has been taken for a basis of ecomorphic classification of herpetobiont spiders. It including has allowed to integrate the data collected by various authors in a wide time and spatial span for the general analysis. Faunistic collection also differed and by a technique: the sizes of the traps, fixing liquid, number of traps, an exposition time. It is necessary to consider these circumstances objective as ecological classification of regional fauna should be based on considerable on coverage in time and space a material which cannot be collected on completely uniform procedure. The multidimensional scaling represents adaptive ordination procedure which assumes a choice of the final decision proceeding, first of all, ecological criteria, instead of especially mathematical. Such adaptability is reached by comparison of ordination decisions with markers of an ecological situation which are received at the biogeocoenosis description of places of sampling. These descriptions are presented in terms of typology of biogeocoenosis of Belgard (1950, 1971): their coenotic status, and also assessment of a mode of a fertility and humidity. The key material is received within the Prisamarsky biospheric station of the Dnepropetrovsk national university where within a monitoring profile reference types of wood biogeocenoses of a steppe zone of Ukraine are presented. Primary data of ecological-faunistic researches are represented in the form of matrixes (tables) where columns are presented by a species, and lines – sampling points. Sampling points may be ecologically processed on the basis of biogeocoenosis descriptions. If to find nature of compliance between sampling points and species, it is possible to make interpretation of the ecological status of species, i.e. to reveal key ecological groups (ecomorphes) and to establish belonging of species to them. The multidimensional scaling allows to estimate within one metric space an arrangement as species, and sampling points. Co-ordinates of sampling points in dimention of a multidimensional scaling are used as predictor of ecological characteristics of the environment in these points. Applying the obtained regression models it is possible to estimates of optimum conditions for species if in these models to use as predictor co-ordinates of species in those dimention of a multidimensional scaling. Species which are characterised by similar optimum values of ecological factors form ecological groups, or ecomorphes. Respectively for spiders we allocate coenomorphes, hygromorphes, trophocoenomorphes.

La comunidad de arañas Mygalomorphae (Araneae) de la Reserva Natural Sierra del Tigre, Tandilia, Buenos Aires, Argentina

We documented the specific richness, abundance and activity of the Mygalomorph spider community in the Natural Reserve Sierra del Tigre, Buenos Aires, Argentina. This hilly ecosystem is home for many endemic species and rich in native fauna and flora. Spider abundance was sampled monthly from May 2011 - May 2012 by hand capture and pitfall traps. The species recorded in the study area were Actinopus sp. 1 (Actinopodidae), Grammostola vachoni Schiapelli y Gerschman, 1960; Plesiopelma longisternale Schiapelli y Gerschman, 1942 and Catumiri argentinense (Mello-Leitão, 1941) (Theraphosidae). Grammostola vachoni was the dominant species in hand capture and Actinopus sp. 1 in pitfall traps. The seasonal variation, diversity, and abundance of the mygalomorph community are analyzed and discussed here. The Mygalomorphae of the Tandilia system comprises an important group of sedentary and cryptozoic spiders that seem to be dependent on habitat type and environmental factors.

Are Temperate Canopy Spiders Tree-Species Specific?

Arboreal spiders in deciduous and coniferous trees were investigated on their distribution and diversity. Insecticidal knock-down was used to comprehensively sample spiders from 175 trees from 2001 to 2003 in the Białowieża forest and three remote forests in Poland. We identified 140 species from 9273 adult spiders. Spider communities were distinguished between deciduous and coniferous trees. The richest fauna was collected from Quercus where beta diversity was also highest. A tree-species-specific pattern was clearly observed for Alnus, Carpinus, Picea and Pinus trees and also for those tree species that were fogged in only four or three replicates, namely Betula and Populus. This hitherto unrecognised association was mainly due to the community composition of common species identified in a Dufrene-Legendre indicator species analysis. It was not caused by spatial or temporal autocorrelation. Explaining tree-species specificity for generalist predators like spiders is difficult and has to involve physical and ecological tree parameters like linkage with the abundance of prey species. However, neither did we find a consistent correlation of prey group abundances with spiders nor could differences in spider guild composition explain the observed pattern. Our results hint towards the importance of deterministic mechanisms structuring communities of generalist canopy spiders although the casual relationship is not yet understood.

Spiders of Polanská Niva National Nature Reserve

Spiders of Polanská niva National Nature Reserve were investigated during 2013. Several capture methods were used from March to September. Altogether, 85 species from 14 families were recorded. The most interesting species are Arctosa maculata (Hahn, 1822) and Micaria nivosa L. Koch, 1866 (both are vunerable according to the Red List of threatened species in the Czech Republic). The other remarkable species were: Kaestneria pullata (O. P.- Cambridge, 1863), Donacochara speciosa (Thorell, 1875), Hylyphantes graminilola (Sundevall, 1830), Singa nitidula C. L. Koch, 1844 and Trochosa spinipalpis F. O. P.- Cambridge. Evaluation of spider community shows, that 8.2 % spider species prefer naturally like habitats.

Converting natural vegetation to farmland alters functional structure of ground-dwelling beetles and spiders in a desert oasis

A vast area of native shrub-dominated steppe at the margins of desert oases in arid regions of China had been reclaimed as farmland in the last century for grain production to feed growing human populations. This study evaluated the consequences of this land-use change on the activity density, taxa richness and composition of functional groups (herbivores, predators and detritivores) of ground-dwelling beetles and spiders, which include some important ecological groups of natural enemies of insect pests (e.g. predatory spiders and beetles), pollinators and decomposers (e.g. detritivorous beetles). Ground-dwelling beetles and spiders were collected using pitfall traps in native steppe habitats and adjacent irrigated farmland of different ages (cultivated either for 27 or at least for 90 years). It was found the conversion of native steppe to farmland, regardless of farmland age, led to a significant increase in activity density of predators, with a greater increase in 90-year-old farmland than in 27-year-old farmland, but did not affect their taxa richness. However, native steppe conversion to farmland, regardless of farmland age, led to significant declines in activity density and taxa richness of both detritivores and herbivores, with a much greater decrease of activity or richness in detritivores than in herbivores in both farmland types. We also observed taxa-specific responses to the land conversion within functional groups. The functional composition of the beetle and spider community shifted from a community dominated by detritivores in the native steppe sites to one dominated by predators in the irrigated farmland sites. Our results suggest that the different functional groups of ground-dwelling beetles and spiders responded in a different way to the land conversion. The remarkable increase in predators and the dramatic decline in detritivores by converting natural vegetation to agricultural land are expected to strongly affect the desert ecosystem services such as biological pest control, pollination and decomposition.

周边不同生境条件对茶园蜘蛛群落及叶蝉种群时空结构的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 周边不同生境条件对茶园蜘蛛群落及叶蝉种群时空结构的影响 DOI: 10.5846/stxb201308102054 作者: 作者单位: 广东省农业科学院饮用植物研究所;华南农业大学农业部热带农业环境重点实验室,广东省农业科学院饮用植物研究所,广东省农业科学院饮用植物研究所,广东省农业科学院饮用植物研究所,华南农业大学农业部热带农业环境重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点基础研究发展计划项目（2011CB100400）；国家科技支撑计划项目（2011BAD01B02-10）；国家茶叶产业技术体系专项（CARS-23）；广东省科技计划项目 （2010B031700029，2011B031400001，2012B040301041，2012B060500005） Effects of the surrounding habitat on the spider community and leafhopper population in tea plantations Author: Affiliation: Drinkable Plants Research Institute,Guangdong Academy of Agricultural Sciences;The Key Lab of Agro-Environment of Tropics, Agriculture Ministry of China, South China Agricultural University,Drinkable Plants Research Institute,Guangdong Academy of Agricultural Sciences,Drinkable Plants Research Institute,Guangdong Academy of Agricultural Sciences,Drinkable Plants Research Institute,Guangdong Academy of Agricultural Sciences,The Key Lab of Agro-Environment of Tropics,Agriculture Ministry of China,South China Agricultural University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为利用天敌实施害虫生态控制，田间调查了周边不同生境条件对茶园蜘蛛及叶蝉种群结构的影响。结果表明：小乔木生境茶园（Ⅰ）和相思树生境茶园（Ⅲ）影响下茶园蜘蛛及叶蝉聚集程度较强，茶园Ⅰ叶蝉聚集数最多，为692 头，但与其他生境茶园间差异不显著（P>0.05）；茶园Ⅲ蜘蛛聚集数量最多，为1155 头，并与稻田生境茶园（Ⅱ）、生活区生境茶园（Ⅳ）的差异达到显著水平（P<0.05）；从蜘蛛功能群聚集情况来看，结网型蜘蛛相对较少，为295 头；游猎型蜘蛛最多，为2957 头；其中，茶园Ⅰ与茶园Ⅲ蜘蛛多样性指数和丰富度数值较大，对叶蝉的跟随效应明显，并与Ⅱ、Ⅳ茶园有显著差异（P<0.05）。多元数据分析结果显示，茶园Ⅰ和茶园Ⅲ均能够明显提高蜘蛛群落聚集的时空分布水平；蜘蛛群落的聚集密度时空分布大小表现为：茶园Ⅰ > 茶园Ⅲ > 茶园Ⅳ > 茶园Ⅱ。由此可知周边生境结构植物丰富和相对稳定的茶园能通过和谐的生态过程影响蜘蛛和叶蝉的时空格局，提高蜘蛛对害虫叶蝉的自然控制能力。 Abstract:The issue of carbon emissions from tea plantations is currently the focus of global attention. The agricultural field ecosystem is a major factor in maintaining a balance, and plays a significant role in counteracting emissions. Our aim was to explore the aggregation indices, individual number, spatial distribution, dynamic occurrence, and principal component of arthropods, and their effects on tea plantations. Field experiments were conducted at the Drinkable Plants Research Institute, Guangdong Academy of Agricultural Sciences, Yingde County, Guangdong, China. Sampling was carried out continuously from January to December, 2009.In order to develop more effective pest control on tea plantations, four plantations were surveyed to quantify the effects of different surrounding habitats on both the pest (the leafhopper, Empoasca vitis Gothe) and predatory spider populations. No pesticides were used on the plantations. The results showed that: (1) The biggest aggregation occurred in the tea plantations surrounded by mixed natural woodland (plantation Ⅰ) or pure Acacia confusa communities (plantation Ⅲ). The greatest numbers of leafhoppers (692) occurred in plantation Ⅰ; however, this value was not significantly different from that found in the other three tea plantations (P>0.05). The number of predatory spiders in plantation Ⅲ (1155) was significantly higher than that found in the other three tea plantations (P<0.05). (2) Analysis of the behavior of all aggregated spider species showed that the number of spiders that remained in their webs was relatively small (295), which is significantly less than the 2957 spiders that were observed moving. The diversity index and species-rich value were both highest in plantations Ⅰ and Ⅲ. This had an obvious effect on leafhopper numbers, which were significantly higher than those found in plantations close to paddy fields (plantation Ⅱ) or to a village (plantation Ⅳ). Both predatory spiders and leafhoppers showed aggregated distribution, caused by their own biological habits and the common environment; different ways of managing habitats lead to significant differences in the size and diversity of the spider communities and the size of the leafhopper population. (3) Multivariate data analysis showed that the comprehensive distribution characteristics of the spider communities-both in time and space-had the potential for significant improvement in plantations Ⅰ and Ⅲ, over those in plantations Ⅱ and Ⅳ (P<0.05). These data enabled the behavior of predatory spiders in tracking their leafhopper prey to be examined. The aggregation density of spiders in the tea plantations was: plantation Ⅰ (close to mixed natural woodland) > plantation Ⅲ (close to pure Acacia confusa communities) > plantation Ⅳ (close to a village) > plantation Ⅱ (close to paddy fields). These results indicate that the habitat surrounding a tea plantation, being a relatively stable and complex structure, affects the spatial and temporal pattern of both leafhopper and spider populations through ecological processes. This leads to an increase in the quantity of spiders moving about on the tea trees, which creates a synergistic effect of leafhopper capture, hence improving the ability of predatory spiders to control leafhopper numbers. 参考文献 相似文献 引证文献

Effectiveness of sampling methods and further sampling for accessing spider diversity: a case study in a Brazilian Atlantic rainforest fragment

Abstract The current biodiversity crisis makes the quantification of the diversity and the description of organism distribution particularly pressing. Biological inventories are among the most effective ways to improve the knowledge about local biota, but they can be very time and money‐consuming. The determination of adequate sampling effort and the selection of cost‐effective collecting methods are critical issues. In this article, a spider diversity inventory in an Atlantic semi‐deciduous forest fragment in Brazil was used to compare the efficiency of three collecting methods in two different seasons in order to propose an optimised sampling protocol. The worthiness of increasing sampling effort in the target area and similar tropical ecosystems was estimated and evaluated in terms of its cost‐effectiveness. For a better sampling of the spider community, it is suggested that a proportion of 55, 29 and 16% of total sampling hours should be dedicated to nocturnal hand collecting (NHC), pitfall traps and beating trays, respectively, in the rainy season. If only one method can be applied, the most efficient in terms of species per sampling is the NHC. A completeness of 70% of the estimated spider species richness (as predicted by the Chao1 estimator) was observed in the complete inventory and increasing sampling effort in the studied area may be highly ineffective when the costs involved are considered. Other studies in similar tropical rainforest areas also presented completeness around 70%, which might be a threshold from which the sampling effort necessary to raise the observed species richness substantially starts to be ineffective.

Richness and composition of spiders in urban green spaces in Toledo, Ohio

Urbanization negatively affects biodiversity by increasing disturbance and habitat fragmentation. We compared three different urban habitats (vacant lots, gardens and forests) to examine differences in spider communities. We selected four sites of each habitat type and sampled spiders with pitfall traps. We collected a total of 547 individuals from 19 families. The most common families were Lycosidae, Corinnidae, Liocranidae, Cybaeidae, and Dictynidae. Spider activity-density overall and for males and females was higher in vacant lots than in forests, and female spiders had greater activity-density in gardens than in forests. Observed species richness did not differ with habitat type. Spider family composition differed significantly between urban habitat types, female morphospecies composition differed in forests and gardens and male morphospecies composition differed in forests and lots. The site characteristics differed significantly with habitat, and these habitat differences explained a large fraction (53.3% to 90.9%) of the variation in composition and richness. Yet, bare ground was the only factor that significantly correlated with declines in female richness. Thus, spider communities, aspects of specifically activity-density and composition, differ between habitats in urban green spaces with potentially important implications for conservation and trophic interactions within urban areas.

Richness and composition of spiders in urban green spaces in Toledo, Ohio

Urbanization negatively affects biodiversity by increasing disturbance and habitat fragmentation. We compared three different urban habitats (vacant lots, gardens and forests) to examine differences in spider communities. We selected four sites of each habitat type and sampled spiders with pitfall traps. We collected a total of 547 individuals from 19 families. The most common families were Lycosidae, Corinnidae, Liocranidae, Cybaeidae, and Dictynidae. Spider activity-density overall and for males and females was higher in vacant lots than in forests, and female spiders had greater activity-density in gardens than in forests. Observed species richness did not differ with habitat type. Spider family composition differed significantly between urban habitat types, female morphospecies composition differed in forests and gardens and male morphospecies composition differed in forests and lots. The site characteristics differed significantly with habitat, and these habitat differences explained a large fraction (53.3% to 90.9%) of the variation in composition and richness. Yet, bare ground was the only factor that significantly correlated with declines in female richness. Thus, spider communities, aspects of specifically activity-density and composition, differ between habitats in urban green spaces with potentially important implications for conservation and trophic interactions within urban areas.

Diversidad de Araneae en cultivos de &lt;i&gt;Citrus sinensis&lt;/i&gt; (Rutaceae) de la Provincia de Corrientes, Argentina

Spiders are predators that reduce insect pest populations in agroecosystems. In spite that the presence of spider assemblages has been described in different crop plants, no reports have been done for Citrus species in Argentina. We studied the spider community associated with cultures of Citrus sinensis in the province of Corrientes, Argentina, in two plots (AM1 irrigated and AM2 unirrigated) of 0.82 hectares each. Spiders were collected monthly by using pitfall traps, hand capture, agitation of foliage and sieving of soil litter. A total of 7174 specimens were collected (33 families, 44 genera and 200 species/morphospecies). The AM1 recorded 3811 individuals (33 families, 179 species/morphospecies) and AM2 3363 individuals (31 families, 174 species/morphospecies). November, December and January showed the highest abundance in both plots. A total of 70% of collected spiders were juveniles. Eight families were the most abundant and represented 75% of spiders collected in both plots, the largest being Lycosidae. We identified eight guilds in both plots, for which the ground runners resulted the most abundant (AM1 n = 1341, s=39, n=999 AM2, s = 33), followed by orb weavers (AM1 n = 637, s = 36; AM2 n = 552, s = 33), the stalkers (AM1 n = 471, s = 43, AM2 n = 453, s = 47) and the space web-builders (AM1 n = 446, s = 23; AM2 n = 342, s = 25). The analysis of alpha diversity in both plots (AM1H' = 4.161, J' = 0.802; AM2 H' = 4.184, J' = 0.811) showed no significant differences (t = 1.083 p = 0.279). The linear dependences model was the one with the best fit results, where the species observed were more than estimated. Clench model estimated 90.9% of the spiders observed in the unit with irrigation and 90.6% in the unit without irrigation.

Grassy margins along organically managed cereal fields foster trait diversity and taxonomic distinctness of arthropod communities

AbstractIt is not known if grassy margins contribute to the conservation of biodiversity if situated along organically managed cereal fields as the contrast in environmental conditions between fields and margins may be too small in absence of pesticide applications.Communities of spiders, ground beetles, true bugs and aphids were sampled in 2 years along transects from the centre of organically managed cereal fields into adjacent grassy margins. Based on species richness, abundances, ecological and body size traits of species and taxonomic distinctness between species, communities were compared between organically managed cereal fields and their grassy margins.The species richness, abundance and variation in taxonomic distinctness of true bugs were significantly higher in grassy margins. For spiders and ground beetles, these metrics were either higher in cereal fields or did not differ significantly. At the species level, spiders living under stones or in soil crevices, as well as phytophagous ground beetles and true bugs that overwinter as eggs benefited from grassy margins. True bug communities in cereal fields were dominated by a few abundant species, whereas communities in margins were rather dominated by a few large species.Our comprehensive analyses highlight the importance of accounting for species identities and biology in biodiversity studies. The traits that characterised arthropod species that benefited from margins are not characteristic for pest species. Grassy margins along organic fields therefore represent an important agri‐environmental scheme for the conservation of several arthropod taxa and margins should not be removed to increase the crop production area in organically managed cereal fields.

A Fungal Insecticide Engineered for Fast Per Os Killing of Caterpillars Has High Field Efficacy and Safety in Full-Season Control of Cabbage Insect Pests

Fungal insecticides developed from filamentous pathogens of insects are notorious for their slow killing action through cuticle penetration, depressing commercial interest and practical application. Genetic engineering may accelerate their killing action but cause ecological risk. Here we show that a Beauveria bassiana formulation, HV8 (BbHV8), engineered for fast per os killing of caterpillars by an insect midgut-acting toxin (Vip3Aa1) overexpressed in conidia has both high field efficacy and safety in full-season protection of cabbage from the damage of an insect pest complex dominated by Pieris rapae larvae, followed by Plutella xylostella larvae and aphids. In two fields repeatedly sprayed during summer, BbHV8 resulted in overall mean efficacies of killing of 71% and 75%, which were similar or close to the 70% and 83% efficacies achieved by commercially recommended emamectin benzoate but much higher than the 31% and 48% efficacies achieved by the same formulation of the parental wild-type strain (WT). Both BbHV8 and WT sprays exerted no adverse effect on a nontarget spider community during the trials, and the sprays did not influence saprophytic fungi in soil samples taken from the field plots during 4 months after the last spray. Strikingly, BbHV8 and the WT showed low fitness when they were released into the environment because both were decreasingly recovered from the field lacking native B. bassiana strains (undetectable 5 months after the spray), and the recovered isolates became much less tolerant to high temperature and UV-B irradiation. Our results highlight for the first time that a rationally engineered fungal insecticide can compete with a chemical counterpart to combat insect pests at an affordable cost and with low ecological risk.

Assessment of the probability of colonization of local spider communities in an experimental landscape

Establishment of communities is a dynamic process initiated by immigration. Therefore, movements of individuals within a metacommunity are important for maintaining and increasing species distribution. We present results of a small landscape-level experiment that manipulated habitat size and diversity. We examined the rates of colonization of spider species, and the richness, abundance and composition of foliage-dwelling spiders. Estimation of colonization rates was based on maximum likelihood. The experimental landscape was composed of five blocks with four patches (two large, 1 m 2 ; two small, 0.25 m 2 ). Less diverse patches had seedlings of one plant species, whereas more diverse patches had four species with diverse structures. Eight periodic censuses of spiders arriving in the patches were performed (average interval between censuses, 28 days). The initial composition of colonizers was significantly different from the final composition, but rates of colonization did not differ between sizes and diversities, or their interaction. Abundances of spiders were positively influenced by patch size. Compositions in each temporal sample were determined by differences in the species pool migrating and arriving at an experimental landscape irrespective of habitat size or diversity. Larger patches were more likely to receive more colonists representing a wider array of species than small patches. The probability of colonization was independent of patch size and diversity, which contradicts theoretical predictions. The results highlight the high colonization capacity of spiders on spatial and temporal scales.

Composición de la fauna de Araneae (Arachnida) de la Reserva provincial Iberá, Corrientes, Argentina

A survey of the spider community composition and diversity was carried out in grasslands and woods in three localities: Colonia Pellegrini, Paraje Galarza and Estancia Rinc6n (Iberá province Reserve). Pit fall traps, leaf litter sifting, foliage beating, hand collecting and sweep nets were used. Shannon's diversity index, evenness, Berger-Parker's dominance index, beta and gamma diversity were calculated, and a checklist of spider fauna was compiled. Species richness was estimated by Chao 1, Chao 2, first and second order Jack-knife. A total of 4,138 spiders grouped into 150 species from 33 families of Araneomorphae and two species from two families of Mygalomorphae were collected. Five species are new records for Argentina and eleven for Corrientes province. Araneidae was the most abundant family (39.8%), followed by Salticidae (10.9%), Anyphaenidae (7.9%), Tetragnathidae (7.4%), and Lycosidae (5.5%). The other families represented less than 5% of the total catch. The web-builder guild had the highest number of specimens and the highest richness index. The abundance, observed richness, Shannon diversity and evenness indexes were highest in Colonia Pellegrini woodland and Paraje Galarza grassland. Alpha diversity represented 89% of the gamma; the remaining 11% corresponded to beta diversity. According to the indexes, between 67% and 97% of the existing spider fauna was represented in the collected specimens from Iberá.

Arthropod assemblages in Norway spruce monocultures during a forest cycle – A multi-taxa approach

In an effort to understand processes accompanying aging of forest stands and to support management of commercial forests, population characteristics of epigeic arthropod assemblages (spiders, ground beetles, centipedes, millipedes and woodlice – suborder Oniscidea) were studied in spruce monoculture stands and compared with local environmental factors (litter, coarse and fine woody debris, canopy closure, and moss, herb and shrub cover). Arthropod sampling was conducted in 15 differently aged stands using pitfall traps, with environmental variables monitored concurrently. A total of 66 spider, 29 ground beetle, 12 centipede, 8 millipede and 3 woodlice species were determined. In general, litter depth, herb cover, canopy closure and the amount of coarse woody debris had the greatest influence on assemblage composition in all groups. Spider community composition, being more stenotopic than other arthropod groups, was affected by the highest number of factors. A closer association with site conditions in spiders and ground beetles was manifested by a marked differentiation in the occurrence of forest and open-habitat species in the youngest (open) and oldest (closed) stands, though neither the total species number nor abundance differed significantly throughout stand development. Contrary to arthropod assemblages, significant relationships between ecological groups and environmental variables were identified only in several cases. Centipede diversity (as defined by biodiversity indices) was significantly higher in 30–35-year-old stands. Appropriate intervention in homogenous spruce stands may help increase habitat availability for most epigeic arthropods, thus enhancing, or at least maintaining, biodiversity within such habitats.

Short and long-term effects of three neurotoxic insecticides on biological and behavioural attributes of the orb-web spider Alpaida veniliae (Araneae, Araneidae): implications for IPM programs

Soybean pest control in Argentina is done just by chemical control using broad-spectrum pesticides. Alpaida veniliae (Araneae, Araneidae) is one of the most abundant spider species of the orb web weaver guild in soybean, and it is considered a very important polyphagous predator, attacking different insects' families. The objective of this study was to determine if neurotoxic insecticides commonly used in soybean crops and a new active ingredient registered in Argentina (spinosad) adversely affected survival, prey consumption, mating behaviour, web building and reproductive capacity of A. veniliae females, under standard laboratory conditions. Spinosad was the most harmful insecticide due to high acute toxicity, even at lower concentrations than those registered for its field use and for its sublethal effects also. Cypermethrin caused several sublethal effects although its acute toxicity on spider was lower than other insecticides. It reduced prey consumption, affected web building, caused abnormalities in eggs sacs and decreased drastically the fecundity and fertility at sublethal concentrations. Endosulfan did not reduce prey consumption but it affected web building, caused abnormalities in eggs sacs and egg masses, and decreased the fecundity and fertility. Spinosad was also the compound with the most drastic effect on web building, it did not reduce prey consumption and fecundity, but fertility was reduced and abnormalities in egg sacs and egg masses were observed. The use of these insecticides in IPM programs according to their potential toxicity on spider communities is discussed.

Araneae communities associated with the canopies of chestnut trees in the northeastern part of Portugal: The influence of soil management practices

Chestnut (Castanea sativa Mill.) is one of the economically more important trees in the north of Portugal. Spiders, as generalist predators, are potential controlling agents of pests, yet the composition of the community of spiders associated with this crop is only poorly known. The objective of this study was to determine the spider communities in the canopies of chestnut trees subject to three different soil management practices in northeastern Portugal. Three chestnut groves each subject to a different agricultural practice (grazed, tilled or untilled) were studied in 2008 and 2009. The Araneae communities were sampled by beating the branches and the individuals collected were identified to family and species when possible. To investigate the structure of the spider community in each grove the abundance and family richness of spiders were calculated and compared between managements. In total, 4172 spiders were collected and, in both years, the three most abundant families were Araneidae, Philodromidae and Linyphiidae. In 2008, there was a greater abundance of spiders in the grazed, followed by the tilled and untilled groves, but no significant differences among groves. However, in 2009 there was a greater abundance of spiders in the tilled grove, followed by grazed and untilled groves and the differences between the untilled and the other two groves were significant. Araniella, Oxyopes and Anyphaena were the most abundant genera in the three groves. This study showed that soil management may influence the diversity of spiders, but the effects were weak and not consistent between years. The reduction or absence of a suitable habitat for spiders under the trees in the tilled treatment might have resulted in the spiders migrating up into the canopy. However, based on the weak effects on spider abundance recorded and its potentially adverse effects on soils, tillage is not recommended for managing the incidence of pests in chestnut groves.