Spider Abundance Research Articles

Diversity, Composition and Distribution Patterns of Spiders (Arachnida: Araneae) in Sand Forest, South Africa

ABSTRACTSpiders are the dominant representative of the top predator guild in many terrestrial ecosystems, but their diversity and distribution in forests in South Africa are still understudied. This study aimed to determine ground‐dwelling spider diversity, composition and distribution patterns in both sand forest and savanna (and their ecotone) using pitfall traps and to provide a spider species checklist for these three habitats in Phinda Private Game Reserve. A total of 410 individuals from 64 species and 21 families were recorded from the three habitat types. The Lycosidae family and Pardosa crassipalpis were the most dominant family and species. Spider abundances were similar between sand forest and the ecotone, but lower in savanna. However, species richness was similar across habitats. Spider species assemblages were similar between sand forest and the ecotone, but differed from the species assemblages in savanna. Spiders play an important role in food webs both below‐ and aboveground. Therefore, determining their diversity and distribution contributes to the overall understanding of the ecosystem in addition to promoting conservation efforts of key habitats such as the critically endangered sand forest.

Temperate alley‐cropping agroforestry improves pest control potential by promoting spider abundance and functional diversity

Temperate alley‐cropping agroforestry improves pest control potential by promoting spider abundance and functional diversity

Composition and Diversity of Spiders in the Lian-huo Highway (Shangqiu Section) Shelter Forest and Campus Habitat of Henan Province, China

Background: Spider assemblages, which are easily sampled, are useful indicators that can be used to compare the biodiversity of various environments and assess the effects of disturbances on diversity. Because spiders are generally found in forests in high abundance, they form some good model taxa for biodiversity studies. Methods: The present study compares the composition and diversity of spiders in the Lian-Huo highway (Shangqiu section) shelter forest (HS) and campus habitat (CH) of Henan province, China. Sampling were collected from April to June 2018 and fourth time a month, a total of twenty-four samples were collected. Within each habitat type there were eight sites surveyed which represented a wide geographical spread of the habitats. Result: A total of 3725 individual spiders were collected from the two sites, representing 14 families and 23 species. Guild structure analysis of the collected spiders revealed 4 feeding guilds viz, web weavers, Sheet web weavers, Foliage hunter’s spider and Ambush hunters. The abundance of spiders in the campus habitat is significantly higher than that in Lian-Huo highway (Shangqiu section) shelter forestand the Shannon-Wiener index (H’) (HS=3.3827, CH=2.2007), Simpson index (D) (HS=0.8710, CH=0.7391), Evenness index (J) (HS=2.8391, CH=1.7088) and Richness index (E) (HS=0.7462, CH=0.6362) are significantly higher in the campus habitat than in the Lian-Huo highway (Shangqiu section) shelter forest. These results suggest that increasing the complexity of habitat structure and reducing anthropogenic disturbance is a meaningful way to conserve and restore Spiders diversity.

Arthropod traits as proxies for abundance trends in the Azorean Islands

Human activities drive ecological transformation, impacting island ecosystems from species diversity to ecological traits, mainly through habitat degradation and invasive species. Using two unique long‐term datasets we aim to evaluate whether species traits (body size, trophic level, dispersal capacity and habitat occupancy) can predict temporal variations in the abundance of endemic, indigenous (endemic and native non‐endemic) and exotic arthropods in the Azores Islands. We found that body size is crucial to predict arthropod abundance trends. Small‐bodied herbivorous arthropods showed a decrease in abundance, while large‐bodied indigenous arthropods increased in abundance, mainly in well‐preserved areas. Also, large‐bodied exotic arthropods increased in abundance across the entire archipelago. Moreover, endemic canopy dwellers increased in abundance, while endemic ground‐dwellers decreased in abundance. Simultaneously, exotic arthropods showed the opposite result, increasing in abundance in the ground while decreasing in abundance in the canopy. Finally, habitat influenced both endemic and exotic spider abundance trends. Endemic spiders that occupy solely natural habitats experienced a decline in abundance, while exotic spiders in the same habitats increased in abundance. Our study underscores the significance of arthropod species traits in predicting abundance changes in island ecosystems over time, as well as the importance of monitoring species communities. Conservation efforts must extend beyond endangered species to protect non‐threatened ones, given the increased extinction risk faced by even common species on islands. Monitoring and restoration programs are essential for preserving island ecosystems and safeguarding endemic arthropod populations.

Биотопическое распределение пауков-кругопрядов (Aranei: Araneidae) острова Аскольд (залив Петра Великого, Приморье)

The article presents the data on the species composition, abundance, spatial and biotopical distribution of orb-weaver spiders on Askold Island, located in Russia's Far East, in the Peter the Great Gulf (Primorsky Krai). The material was collected from 21 key sites of 3 x 25 m, by entomological sweeping and manually. A total of 507 spiders, belonging to 13 species from 8 genera, were captured. Of these, one species - Singa hamate - is indicated for the first time. On the island the most widespread spiders are of the genus Araneus, living in 11 out of 13 types of biotopes. For this genus, the most favorable are forest habitats, dominated by A. ishisawai and A. ventricosus. In open meadow biotopes, 8 species of spiders from 6 genera were recorded, with Neoscona adianta dominating: reaching the density of 29 specimens per 100 m2 in open plant communities with predominance of Artemisia gmelinii. In various parts of the island within linden and broad-leaved multi-species forests, the greatest diversity and abundance of orb-weaver spiders is recorded. There spiders from 3 genera (5 species of each) were caught. Their total density is 42.5 specimens per 100 m2. Stony beaches, stretching along the entire coast of the island, are characterized by the poorest faunal composition. One species encountered was Araneus ventricosus (4 specimens per 100 m2). For the Askold Island, a series of schematic distribution maps for the common species of orb-weaver spiders (A. ishisawai, A. ventricosus, A. macacus, Argiope bruennichi, Neoscona adianta, Plebs sachalinensis) has been compiled for the first time.

Assessment of biodiversity and seasonal dynamics of spiders in maize crops of Punjab, Pakistan

Spiders contribute significantly to natural pest control in agriculture. Here, we investigated the biodiversity, population dynamics and predatory activities of spiders in the maize-growing districts (Kasur and Lahore) of Punjab, Pakistan during 2018–2019. Various collecting methods including pitfall and yellow pan traps, manual hand-picking, beat sheet, and sweep nets were used to collect spiders on a biweekly basis. The collected 12,894 individuals represented 45 different species, 27 genera, and 13 families. The major families recorded were Araneidae (32.92%), Lycosidae (20.43%) and Salticidae (11.12%) comprising >64% of the overall abundance. Neoscona theisi (Araneidae) was found to be most dominant species (11.61%). Moreover, the species Macracantha hasselti (Araneidae) and Atypena formosana are reported for the first time from Pakistan. Besides, the estimated species diversity from both districts was 97%. The Margalef's index was highest in Kasur (D = 5.08) and lowest in Lahore (D = 4.95). The values of the Shannon-Wiener and species evenness indices were similar in Kasur and Lahore suggesting similar diversity levels and an even distribution. Spider abundance was highest in April and lowest in June and July. These findings will help to develop effective Integrated Pest Management strategies in maize growing areas across the world.

Changes in community composition and prey capture of web-building spiders during rice field development

Understanding the effects of microhabitat changes on arthropod predator communities and their prey in agroecosystems is essential for field management and biocontrol. Few studies have investigated the trait composition of web-building spider communities in rice ecosystems. Here, we examined how temporal changes during the rice field development affect the abundance and traits of orb-web spiders, and how these effects consequently influence captured prey number and prey composition in irrigated rice ecosystems in southern Thailand. We used structural equation models to evaluate direct and indirect, spider-mediated effects of rice field development on captured prey numbers in each different guild. We found that the number of horizontal web-building spiders decreased during the rice field development, whereas there was no significant change in number of vertical web-building spiders. The number of captured detritivorous insects was positively related to the numbers of horizontal and vertical web-building spiders, while phytophagous insects and others were positively related only to the numbers of vertical web-building spiders. Moreover, the prey number captured by vertical web-building spiders seems to be indirectly increased through the decreasing number of horizontal web-building spiders in the late rice season. A fourth-corner analysis showed that spider species identity, spider traits (web type, web height and web diameter), vegetation height, and water level generally influenced the prey captured by web-building spiders. Horizontal web-building spider species with lower web placement during the flooding phase captured high numbers of detritus-feeding insects, while vertical web-building spider species with higher web placement captured high numbers of rice pests, predators and others. Our results suggest that the field development acted as an environmental factor that determined the species identity and traits of web-building spider communities. The findings of this study can help to predict the ecosystem services provided by the web-building spider community in rice ecosystems.

Nature-based solutions to increase rice yield: An experimental assessment of the role of birds and bats as agricultural pest suppressors in West Africa

Rice is widely consumed as a staple food, being cultivated worldwide. However, in West Africa, production is not enough to satisfy demand. Rice often suffers intensive damage by herbivorous arthropods that affect quality and quantity of the grain. Birds and bats have been shown to suppress arthropod pests, potentially enhancing rice productivity and food security. However, the degree to which these taxa provide nature-based solutions for mitigating pest-induced rice losses is poorly known, especially in West Africa. Here, we used experimental exclosures to investigate whether birds and bats reduce plant damage and boost rice yield by suppressing arthropod abundance. In a rural area in northern Guinea-Bissau, we established 14 sets of paired control and experimental exclosures parcels, precluding access of birds and bats to rice plants. We then quantified how the absence of birds and bats influenced arthropod communities, plant damage, and rice yield over a full rice production cycle (six months). Arthropod numbers in exclosures (10.1 ± 9.1 ind./plot) were nearly double those in control plots (5.8 ± 3.0 ind./plot), a result mostly due to a lower spider abundance in the controls. The percentage of leaf and grain damage showed no difference between exclosure and control. Using Structural Equation Models, we uncovered that the exclusion of birds and bats boosted arthropod abundance but had only marginal effects on rice damage and no detectable effect on yield. The exclusion of flying vertebrates led to a marked increase in spider abundance, suggesting an effect of mesopredator release, which in turn likely helped maintaining pest abundance low and potentially contributing to the small overall effect on rice damage and yield. Enhancing the abundance of birds and bats is an interesting option to suppress agricultural pests, but our results highlight the need for a better understanding of ecological interactions in agricultural landscapes in West Africa. We stress the need for more research to inform evidence-based policies using nature-based solutions that foster the natural consumption of pests by vertebrates, as a means to improve food security.

Foliage and ground spiders respond differently to a semi‐natural habitat‐vineyard gradient

AbstractNatural vegetation in and around crops effectively increases predators. Semi‐natural habitats (SNHs; non‐crop vegetation) surrounding crops provide refuge and resources. However, the function of SNHs may depend on several factors, and the response of natural predators may vary among crops and regions. Here, we examined the spider community in a SNH and at an adjacent vineyard in a semi‐arid region of Argentina. We collected spiders in a gradient from an adjacent SNH, towards the vineyard at three distances from the SNH using two techniques: beating and pit‐fall traps. We collected spiders in December and February during two consecutive years at two strata: in vegetation and on the ground. In vegetation, spider abundance significantly decreased from SNH towards the interior of the vineyard at 80 m. On the ground, spider abundance was also significantly higher in SNH. However, after decreasing at the 5 and 20 m sites inside the vineyard, the abundance increased at 80 m. For foliage spiders, species richness followed the same pattern as abundance, whereas ground spider richness significantly increased from SNH to the interior of the vineyard. Species composition also showed different tendencies between foliage and ground spiders. The foliage spider community differed between SNH vs. all the vineyard sites. Contrarily, at the ground stratum, SNH was similar in composition to the edge of the vineyard, and they both differed from the other vineyard sites. We found that the adjacent SNH influenced the spider community in the vineyard and that this effect depended on the distance from that habitat and the association of the community to various strata. These results highlight the importance of studying the whole community of spiders when aiming to increase predator abundance to enhance biological control in this kind of crop. In addition, we found species that may act as indicators of native vegetation which has important implications for the management of natural habitats in this region.

Effects of insecticide spray drift on arthropod prey resources of birds in grasslands in Minnesota

AbstractSoybean aphid (Aphis glycines) insecticides are used throughout the Upper Midwest and Great Plains regions of North America, including the farmland region of Minnesota, USA, to combat insect pests. These broad‐spectrum, foliar spray insecticides have the potential to drift beyond target fields into nearby grassland cover where birds and other insectivores forage. Arthropods serve important roles in grassland ecology and are susceptible to mortality and sublethal effects from exposure to these pesticides. Our objective was to assess effects of soybean aphid insecticides on grassland arthropods, especially those that are important in grassland bird diets. We measured the abundance, consumable biomass, and family richness of insects and spiders in grasslands adjacent to soybean fields in an agricultural landscape. Soybean fields were treated with chlorpyrifos and lambda‐cyhalothrin, which were the 2 most common foliar pesticides used to control soybean aphids in Minnesota. We compared measures at focal sites to samples collected at reference sites adjacent to corn fields not sprayed for aphids during 3 periods in mid‐to‐late summer: 1–3 days before spraying, 3–5 days post‐spraying, and 19–21 days post‐spraying. The abundance of arthropods in focal grasslands was lower 3–5 days after pesticide applications. Coleoptera family richness at focal sites was also lower than at reference sites 3–5 days after pesticide applications. These measures 19–21 days after application were similar to pre‐spraying levels, indicating that arthropod populations rebounded during this period. Measures of consumable dry biomass, bird prey abundance, bird prey biomass, family richness of Araneae, family richness of Hemiptera, and family richness of Orthoptera were not different between focal and reference sites after spraying. Our results reveal that reductions in arthropod food abundance for grassland birds are associated with pesticide applications up to 5 days after spraying. We suggest that natural resource managers factor proximity to row crop fields and susceptibility to pesticide drift into decisions about where to add grassland cover to landscapes.

Tundra wolf spider (Araneae: Lycosidae) abundance and phenology shift with distance from a northern highway

Abstract Climate change is disproportionately impacting the North, and northern arthropods are particularly vulnerable to disturbances. The Dempster Highway is a gravel road that crosses the northern Yukon Territory in Canada, and wolf spiders (Araneae: Lycosidae) are the top arthropod predators on the tundra in this region. We investigated the effects of the Dempster Highway on subarctic tundra wolf spider abundance, phenology, and community composition by actively sampling 8 paired plots near (20 m) and far (200 m) from the road. Species richness did not differ with distance from the road, but total wolf spider abundance was much lower near the road, and this was driven by decreased abundance of the dominant tundra wolf spider species, Pardosa lapponica (Thorell, 1872). The overall proportion of females carrying egg sacs was higher near the road, suggesting advanced phenology in response to increased temperatures near the road. Together, these results indicate that the Dempster Highway impacts tundra wolf spider communities, which may have important consequences for food web dynamics and ecosystem function. Les changements climatiques ont un impact plus important sur le Nord, et les arthropodes nordiques sont particulièrement vulnérables aux perturbations. La route Dempster est une route de gravier qui traverse le nord du territoire du Yukon au Canada, et les araignées-loups (Araneae: Lycosidae) sont d’importants prédateurs d’arthropodes de la toundra de cette région. Nous avons étudié les effets de la route Dempster sur l’abondance, la phénologie et la composition de la communauté des araignées-loups de la toundra subarctique en échantillonnant activement huit parcelles appariées proches (20 m) et éloignées (200 m) de la route. La richesse des espèces ne différait pas avec la distance par rapport à la route, mais l’abondance totale d’araignées-loups était inférieure près de la route, et cela peut être attribué à une diminution de l’abondance de l’espèce dominante d’araignées-loups de la toundra, Pardosa lapponica (Thorell, 1872). La proportion globale des femelles portant des cocons était plus élevée près de la route, suggérant une phénologie avancée en réponse à l’augmentation des températures près de la route. Ces résultats indiquent que, globalement, la route Dempster a un impact sur les communautés d’araignées-loups de la toundra, ce qui peut avoir des conséquences importantes sur la dynamique du réseau trophique et le fonctionnement de l’écosystème.

Spider–Plant Interaction: The Role of Extrafloral Nectaries in Spider Attraction and Their Influence on Plant Herbivory and Reproduction

Spiders, abundant and diverse arthropods which occur in vegetation, have received little attention in studies investigating spider–plant interactions, especially in plants which have extrafloral nectaries (EFNs). This study examines whether spiders attracted to EFNs on the plant Heteropterys pteropetala (Malpighiaceae) function as biological protectors, mitigating leaf herbivory and positively impacting plant fitness, through manipulative experiments. Spiders are attracted to EFNs because, in addition to consuming the resource offered by these structures, they also consume the herbivores that are attracted by the nectar. At the same time, we documented the reproductive phenology of the plant studied and the abundance of spiders over time. Our results revealed that the plant’s reproductive period begins in December with the emergence of flower buds and ends in April with the production of samarids, fruits which are morphologically adapted for wind dispersal, aligning with the peak abundance of spiders. Furthermore, our results demonstrated that spiders are attracted to plants that exude EFNs, resulting in a positive impact on reducing leaf area loss but with a neutral effect on protecting reproductive structures. By revealing the protective function of spiders’ vegetative structures on plants, this research highlights the ecological importance of elucidating the dynamics between spiders and plants, contributing to a deeper understanding of ecosystems.

Abundance and Diversity of Spiders in Agroecosystems of Jabalpur

The fauna of spiders which is a significant part of agriculture ecosystem was observed in 8 crop fields during the kharif. The spiders were caught from June-October, using sweep nets. The total numbers of spider species were 37 representing 12 families. Araneidae was the most abundant family, followed by Thomisidae, Salticidae, Oxyopidae, Tetragnathidae, Clubionidae, Dictynidae, Gnaphosidae, Lycosidae, Sparassidae, Theridiidae and Ulboridae. The species diversity index (H`) was 4.98 and the Equitability index (EH) was 0.95. An ordination of correspondence analysis demonstrated a bunching of the spiders commencing to paddy fields was more as compared to other crops. Thus, paddy seemed to give better natural niche for the spiders than other field crops. Increasing use of pesticides is the main menace to the several species and their survival in agroecosystem.

Overview of Predators in Shallots Plantation in Peatland, Landasan Ulin South Borneo

Species abundance and diversity of predatory arthropods are important information for developing biological pest control strategies. A study that aims to determine the abundance of predators (Coccinellidae and Araneae) in peatlands planted with shallots in Tegal Arum Village, Landasan Ulin District, Banjarbaru City, South Borneo has been carried out. The method used is purposive sampling method. Selecting plots with uniform growth and plant height of shallots in one plot or beds measuring 3 x 20 m and six plots were observed using three methods: direct sampling, swing nets, and pitfall traps. Observations on species abundance of spiders and predatory coccinellids were carried out to describe the number of species and the abundance of insects in shallot cultivation on peatlands. Predators from the order Coleoptera of the Coccinellidae family observed belong to (Menochilus sexmaculatus, Micrapsis sp, Coccinella novemnotata and Scymnus sp. with 143 individuals and the highest population was found by Micrapsis sp (128 individuals). Meanwhile, there were 6 species of spiders (Araneae) from 5 different families (Oxyopidae, Tetragnatidae, Lyniphiidae, Thomisidae, and Lycosidae) with the most individuals being Oxyopes variabilis (Araneidae: Oxyopidae). The distribution index of species diversity (E) shows E> 0.6, indicating that the evenness of species on the land is uneven

Flying to greener pastures: Spider ballooning in the city

Abstract Spider ballooning is a phenomenon in which spiders employ silk threads to travel through the air for dispersal. While this behaviour has been extensively studied in agricultural areas, limited research has been conducted in urban environments, where green spaces are highly fragmented. However, in cities, aerial dispersal can be advantageous for spiders as it allows them to move to suitable habitat patches. This study aimed to investigate how the urban landscape affects spider ballooning. We collected ballooning spider samples using sticky traps in 10 urban sites within different landscape contexts. By using generalised linear models, we analysed the influence of vegetation cover at both local and landscape scales on spider abundance and family richness. Family composition was similar across the city regardless of the landscape context. More individuals were collected dispersing aerially in areas with low landscape‐level green cover. However, a higher local percentage of vegetation cover led to a substantial increase in aerial dispersal in areas with high landscape‐level green cover. Our findings highlight the significance of the interaction between vegetation cover at these two scales on aerial spider abundance. Our results support the hypothesis that generalist spiders exhibit increased ballooning in highly fragmented landscapes, actively seeking suitable habitats despite the elevated associated risk. Higher aerial dispersal in areas with greater local vegetation cover suggests an increase in short‐distance dispersal, indicating spiders' active search for better habitats nearby upon arrival at a site with potentially greater habitat availability.

Local Habitat Complexity and Its Effects on Herbivores and Predators in Urban Agroecosystems.

In urban community gardens, cultivated vegetation provides variable levels of habitat complexity, which can suppress pests by promoting predator diversity and improving pest control. In this study, we examine three components of the structural complexity of garden vegetation (cover, diversity, and connectivity) to investigate whether higher garden vegetation complexity leads to fewer herbivores, more predators, and higher predation. We worked in eight community gardens where we quantified vegetation complexity, sampled the arthropod community, and measured predation on corn earworm eggs. We found that plots with high vegetation cover supported higher species richness and greater abundance of predatory insects. High vegetation cover also supported a greater abundance and species richness of spiders. In contrast, high vegetation diversity was negatively associated with predator abundance. While high predator abundance was positively associated with egg predation, greater predator species richness had a negative impact on egg predation, suggesting that antagonism between predators may limit biological control. Community gardeners may thus manipulate vegetation cover and diversity to promote higher predator abundance and diversity in their plots. However, the species composition of predators and the prevalence of interspecific antagonism may ultimately determine subsequent impacts on biological pest control.

Diversity and ecological dynamics of ground and understory arachnid spiders from a lowland tropical forest in Sumber Pawon, Kediri, East Java

Spiders have significantly contributed to the dynamics of terrestrial ecosystems and play an essential role as appropriate bio-indicators to monitor habitat changes. We aim to determine the composition and local scale diversity of spiders in the understory and ground layers and to determine habitat preferences regarding the distribution of spiders in the interior forests and riparian forests. Sampling was conducted at a protected forest area in Sumber Pawon Kediri, covering an area of 12.45 Ha during the wet season (January-March). The study’s results found 340 individuals consisting of 15 families and 63 species. Family Araneidae and species Hamadruas superba are the most common taxa groups in the interior forests, while Hippasa holmerae are in riparian forests. More individuals and species are found understorey shrubs in forest interiors. Soil temperature, relative humidity, and litter thickness positively correlate with spider abundance. Resource partitioning observation showed that leaf litter and herbaceous plants contain more potential prey for spiders. Forest habitat management programs must consider the spatial variation of spiders between strata, as well as the response of the spiders to the seasons. A better understanding of spider ecological dynamics will support the sustainable management of forest ecosystems.

Inverted Soil Mounding as a Restoration Approach of Seismic Lines in Boreal Peatlands: Implications on Plant and Arthropod Abundance and Diversity

In northern Alberta, Canada, much of treed boreal peatlands are fragmented by seismic lines—linear disturbances where trees and shrubs are cleared for the exploration of fossil fuel reserves. Seismic lines have been shown to have slow tree regeneration, likely due to the loss of microtopography during the creation of seismic lines. Inverted soil mounding is one of the treatments commonly applied in Alberta to restore seismic lines and mitigate the use of these corridors by wildlife and humans. We assessed the effects of mounding on understory plants and arthropod assemblages three years after treatment application. We sampled five mounded and five untreated seismic lines and their adjacent treed fens (reference fens). Compared to reference fens, mounded seismic lines showed on average lower bryophyte (6.5% vs. 98.1%) and total understory cover (47.2% vs. 149.8%), ground-dwelling spider abundance (226.0 vs. 383 individuals), richness (87.2 vs. 106.4 species) and diversity (19.0 vs. 24.6 species), rove beetle abundance (35.2 vs. 84.8 individuals), and ant richness (9.0 vs. 12.9 species). In contrast, rove beetle and ground beetle richness (39.0 and 14.5 species, respectively) and diversity (16.8 and 7.8 species, respectively) were higher on mounded seismic lines compared to reference fens (richness: 18.0 and 7.5 species, respectively; diversity: 7.0 and 3.8 species, respectively). This is one of the first studies to assess arthropod responses to restoration efforts in the context of oil and gas disturbances in North America, and our results highlight the need to incorporate multiple taxa when examining the impact of such treatments.

Seasonal Diversity of Spiders (Arachnida: Araneae) and Collection Methods in Barpeta District, Assam, India

Barpeta district, Assam, India covers an area of 2754 square kilometers. The Spider specimens were collected by visual search method and the collection methods adopted were Aerial hand collection, Ground hand collection and Beat sheet method. 70 spider species from the different habitats of Barpeta District were documented. The study shows the difference in quantity and quality of spider fauna concerning the seasons and collection method. The spider species were more active in the post-monsoon season and some were inactive during winter. Almost 75% of spider species were collected by the beat sheet method which shows that it is more significant than all other trapping techniques. The spider species richness and spider abundance were significantly affected by seasons, studied by Simpson’s diversity index and Shannon – Weiner’s diversity index. However, further study needs to be carried out for the effective conservation of these species.

Ants offset bottom-up control of spiders in Amazonian savanna trees

Community trophic structure is shaped by concurrent bottom-up (resources) and top-down effects (predators), but the extent to which they interact remains uncertain. The Exploitation Ecosystems Hypothesis predicts that predators should offset increases in herbivore abundance with plant productivity, which is supported by data. However, the extent to which interactions within trophic levels (e.g. competition, intraguild predation) have similar effects is less clear. Ants and spiders are abundant in vegetation and consume similar arthropod prey (occasionally each other) and plant exudates, with ants generally showing competitive dominance over spiders. We tested whether ants could shape the trophic structure of tree-dwelling macroarthropod communities by offsetting increases in spider abundance with insect prey. We performed three surveys of the macroarthropod community of 97 trees from two sites in the savanna of Northern Amazonia. Together, ants and spiders represented 74% of the sampled individuals per tree. Insect prey abundance increased with tree crown volume and crown flower cover, consistent with bottom-up limitation. Likewise, both ants and spiders increased with insect prey abundance, with ant abundance also varying with tree species, suggesting reliance on both animal and plant resources. However, as predicted, the positive relationship between spider abundance and insect prey abundance disappeared as ant abundance increased. Our results suggest that agonistic interactions within trophic levels can strongly shape community structure and size by modifying bottom-up effects as much as interactions across trophic levels.