Diversity Of Arthropod Communities Research Articles

Aeolian fallout on recently deglaciated terrain in the high Arctic

In the absence of autochthonous inputs, it has been hypothesised that winds operate as an important vector for the nutritional subsidisation of pre-vegetative sites on deglaciated terrain (the aeolian subsidisation hypothesis). Aerial deposition of passively transported organic matter (non-flying Collembola and Acari; organic detritus) was measured on the proglacial region of the Midtre Lovenbre glacier, Kongsfjorden, West Spitsbergen during June and July 2003. Passive fallout, in terms of both biomass and rates of accumulation, was insufficient to explain the abundance and relative functional diversity of arthropod communities on such nutritionally depauperate sites. The role of wind as a passive vector for nutrient introduction is far overshadowed by the allochthonous inputs provided by the active dispersal to and/or colonisation of recently deglaciated habitats by arthropods.

Effects of transgenic cotton carrying Cry1A+CpTI and Cry1Ac genes on diversity of arthropod communities in cotton fields in North China

The effects of insect-resistant transgenic cotton on the diversity of arthropod communities in cotton fields in North China were investigated during 2000–2001. The field experiments were conducted in non-insecticide treated plots of transgenic cotton lines (SGK321, a transgenic cotton variety carrying Cry1A+CpTI genes; GK12, a transgenic cotton variety carrying the Cry1Ac gene) and their conventional parent varieties (Shiyuan 321 and Shimian 3, respectively), and in sprayed plots of the parent varieties where pyrethroid insecticides were used regularly against the cotton bollworm. All the arthropods were sucked up using a portable suction device and identified to species wherever possible. They were later sorted into guilds (pests, natural enemies and neutral arthropods) for diversity analysis using the method of Shannon's index. The diversity of arthropod communities in transgenic cotton plots was similar to that in conventional cotton fields without spraying, but Shannon's index for total arthropod community and the neutral arthropod guild in Bt cotton fields were significantly higher than those in sprayed plots in the mid and late growing stages of cotton. It is concluded that planting of Bt cotton could increase the stability of arthropod communities in cotton ecological systems and benefit the management of insect pests in cotton.

Arthropod Diversity and Community Structure in Relation to Land Use in the Mekong Delta, Vietnam

Declining biodiversity in agro-ecosystems, caused by intensification of production or expansion of monocultures, is associated with the emergence of agricultural pests. Understanding how land-use and management control crop-associated biodiversity is, therefore, one of the key steps towards the prediction and maintenance of natural pest-control. Here we report on relationships between land-use variables and arthropod community attributes (for example, species diversity, abundance and guild structure) across a diversification gradient in a rice-dominated landscape in the Mekong delta, Vietnam. We show that rice habitats contained the most diverse arthropod communities, compared with other uncultivated and cultivated land-use types. In addition, arthropod species density and Simpson’s diversity in flower, vegetable and fruit habitats was positively related to rice cover in the local landscape. However, across the landscape as a whole, reduction in heterogeneity and the amount of uncultivated cover was associated, generally, with a loss of diversity. Furthermore, arthropod species density in tillering and flowering stages of rice was positively related to crop and vegetation richness, respectively, in the local landscape. Differential effects on feeding guilds were also observed in rice-associated communities with the proportional abundance of predators increasing and the proportional abundance of detritivores decreasing with increased landscape rice cover. Thus, we identify a range of rather complex, sometimes contradictory patterns concerning the impact of rice cover and landscape heterogeneity on arthropod community attributes. Importantly, we conclude that that land-use change associated with expansion of monoculture rice need not automatically impact diversity and functioning of the arthropod community.

The effects of urbanization on ant assemblages (Hymenoptera: Formicidae) associated with the Molson Nature Reserve, Quebec

AbstractUrbanization causes the fragmentation of natural habitats into isolated patches surrounded by anthropogenic habitats. Fragment size and the intensity of human disturbance have been shown to affect both composition and diversity of arthropod communities, but most groups have been understudied. We investigated effects of urbanization on ant assemblages (Hymenoptera: Formicidae) in and around the Molson Reserve, a preserved maple-beech forest surrounded by residential properties near Montréal, Quebec. We studied how local ant assemblages differed in terms of composition, abundance, and species richness, depending on whether they were situated in the interior forest, in adjacent residential backyards, or at the edge between these two habitats. We also compared an intact forest interior with a younger and moderately disturbed forest (“buffer zone”) between the urban matrix and the interior forest. Few differences were detected between the buffer zone and the intact forest interior. Extrapolated estimates of species richness suggest that it is lowest in the forest interior and highest in urban zones. Community composition, as investigated with ordination analysis, revealed a clear difference between the fauna of urban sites and the fauna of edges and forest interiors, and analyzing the relative abundance of ants showed residential backyards to contain the most ants. Urban assemblages were characterized by several competitively dominant species, including one introduced or “tramp” species. The occurrence of aggressive and dominant species in urban sites and at the edges of the Molson Reserve could potentially interfere with the dispersal and immigration of ground-dwelling arthropods and negatively affect local diversity or community composition in isolated forest reserves in urban centres.

Effects of transgenic cotton carrying <I>Cry1A</I>+<I>CpTI</I> and <I>Cry1Ac</I> genes on diversity of arthropod communities in cotton fields in North China

Effects of transgenic cotton carrying <I>Cry1A</I>+<I>CpTI</I> and <I>Cry1Ac</I> genes on diversity of arthropod communities in cotton fields in North China

Arthropod Predator Occurrence and Performance ofGeocoris uliginosus(Say) on Pest-Resistant and Susceptible Turfgrasses

Interactions between host plant resistance and biological control may be advantageous or disadvantageous for pest management. Turfgrass cultivars have rarely been tested for extrinsic resistance characteristics such as occurrence and performance of beneficial arthropods on plants with resistance to known turf pests. Among six turfgrass cultivars tested, the bigeyed bug, Geocoris uliginosus (Say) nymphs varied in ability to reduce numbers of fall armyworm, Spodoptera frugiperda (J. E. Smith), larvae. The six grasses tested (Sea Isle 1 and 561-79 seashore paspalum, Paspalum vaginatum Swartz; TifSport and TifEagle bermudagrass, Cynodon dactylon [L.] x C. transvaalensis [Burtt-Davy]; and Cavalier and Palisades zoysiagrass Zoysia japonica von Steudel and Z. matrella [L.] Merrill) represented a range in resistance to S. frugiperda. In the laboratory, the greatest reduction in S. frugiperda larvae by a low density of G. uliginosus occurred on the resistant Cavalier zoysiagrass. A 7-fold difference in weight of 10-d-old larvae between those feeding on susceptible versus resistant grasses suggested that on the resistant grass larvae remained for a longer period in a size range susceptible to predation. Results of laboratory studies were not directly translated to the field, in which a diverse predatory arthropod community varied in composition depending on turfgras cultivar. In the field, the greatest reduction in S. frugiperda larvae by a low density of G. uliginosus occurred on Sea Isle 1 and 561-79 seashore paspalum grass. In the field, vacuum samples indicated that predaceous Heteroptera were most abundant in paspalum grasses and bermudagrasses, while Carabidae, Staphylinidae, and Araneae were more common in zoysiagrasses. In contrast, pitfall traps indicated that carabids were more common in bermudagrasses, Araneae and Staphylinids were similar among grass taxa, and Cicindellidae were most common in paspalum grasses and bermudagrasses. Predation was never significantly decreased on resistant turfgrass cultivars in any of the experiments described in this work, indicating no negative tritrophic interactions.

Diversity of Arthropod Communities in Transgenic Bt Cotton and Nontransgenic Cotton Agroecosystems

Abstract In a 3-yr field experiment, possible effects of Bt transgenic cotton plants expressing cry1A(c) gene from Bacillus thrungiensis Berliner variety kurstaki on diversities of arthropod communities and pest and natural enemy sub-communities were assessed in insecticide treated and untreated cotton fields, as measured by the Shannon-Weaver diversity index. The treatments included: 1) nontransgenic cotton with no insecticide treatment (nontransgenic), 2) nontransgenic cotton with insecticide treatments (nontransgenic+insecticide), 3) transgenic Bt-cotton with no insecticide treatment (Bt-cotton), and 4) transgenic Bt-cotton with insecticide treatments (Bt-cotton+insecticide). The results indicated that Bt-cotton increased the diversity of arthropod communities and pest sub-communities; however, it decreased the diversities of natural enemy sub-communities. Insecticide treatments increased diversities of communities and sub-communities of arthropods in both transgenic Bt-cotton and nontransgenic cotton ...

CHARACTERISTICS OF ARTHROPOD COMMUNITY AND THEIR DIVERSITY RESTORATION IN LEAFY VEGETABLE FIELDS

Abstract The effect of chemical insecticides on the structure and diversity of arthropod communities in various vegetable fields and the restoration of their biodiversity after stopping application of chemical insecticides were studied. The results showed that the effect of chemical insecticides on the arthropods in vegetable fields could be characterized the species structure, the diversity index and the evenness of species distribution. Components of arthpod species depended closely on the species number of insect pests, predatory natural enemies and spiders. Investigations showed that the numbers of species in the vegetable fields managed with chemical insecticides were obviously reduced, and their diversity indices were lower comparing with that without chemical insecticides. When the applications of chemical insecticides were stopped in vegetable fields, the index of population trend (I) of dominant insect pests decreased greatly, the control effect of natural enemies on major insect pests increased, and the diversity index of arthropod increased at the same time. Thus, limiting the application of chemical insecticides, resuming the environment of vegetable fields destroyed by using chemical insecticides, escalating the control ability of natural enemies on main insect pests will play an important role in the ecological control of insect pests in vegetable fields.

Arboreal antics

The canopies of tropical lowland rainforests host some of the most diverse arthropod communities on Earth. But whereas the crowns of boreal trees usually teem with free-feeding and slow-moving lepidopteran caterpillars, such creatures are all but lacking from many canopies in the lowland tropics. In their absence, the quick-moving nymphs of Hemiptera (bugs) or Orthoptera (katydids, crickets and grasshoppers) dominate the youth scene. Why this difference? Some studies have emphasized the fact that fogging samples from lowland rainforest canopies often abound with ants. If these animals all had a taste for insect flesh, they would certainly exert a high predation pressure on any caterpillars slow enough for them to catch.

A trophic cascade in a diverse arthropod community caused by a generalist arthropod predator.

We tested the hypothesis that a generalist arthropod predator, Tenodera sinensis Saussure, could trigger a trophic cascade in an old-field ecosystem. These mantids had relatively weak effects on abundance and biomass of other carnivorous arthropods as a group. The effect of mantids on herbivores was stronger than on carnivores, mainly concentrated in Homoptera and Diptera. Herbivore load was reduced by mantids with the consequence that overall plant biomass (mainly grasses) was increased. Percapita interaction strengths between mantids and other arthropod taxa were, for the most part, weakly negative. Our study demonstrates that a significant trophic cascade can be triggered by a generalist predator even within the framework of a diverse community with relatively diffuse interactions.

Arthropods in no-tillage soybean agroecosystems: Community composition and ecosystem interactions

Sampling data are provided and concepts discussed regarding soil and foliage arthropod communities in conventional and no-tillage soybean agroecosystems Soil arthropod communities from the two cropping systems were also compared with that from an adjacent old field. Biweekly arthropod samples were collected from conventional, no-tillage, and old-field systems Soil arthropods were sampled by quadrat and pitfall trap methods, foliage arthropods were collected by sweep net Quadrat sampling revealed that ground beetle number, species diversity, and biomass were significantly higher (P<0.05) in no-tillage than in conventional tillage systems. Pitfall trap data indicated higher densities and species diversity for most major soil macro-arthropod guilds Foliage arthropod guilds from no-tillage treatments showed higher species diversity throughout the growing season than those of conventional tillage, possibly because of greater structural diversity provided by weeds and litter in notillage systems No-tillage systems supported a larger and more diverse arthropod community than conventionally grown soybeans, suggesting a need for pest management strategies that simultaneously consider many variables. Both foliar grazing and leaf nitrogen content were higher in conventional than in no-tillage systems, indicating a possible causal connection between soil tillage and insect herbivory rates

Soil Arthropod Response to Prairie Burning

Soil arthropod response to altered litter production in a Wisconsin prairie was examined after a long established biennial spring burning program was modified by substituting raking for burning in some experimental blocks, and substituting no disturbance for burning in others. Very few species were favored by increased surface litter in undisturbed blocks. After two biennial burnings or rakings, a drop in species numbers, density of individuals, and diversity of herbivore—decomposers occurred in undisturbed, and to a lesser extent, in raked blocks. Predatory soil arthropod species showed no response. These results suggest that soil detritus levels dropped slowly in response to decreased plant productivity in undisturbed blocks. The drop in soil arthropod community diversity which occurred in undisturbed blocks indicates a direct productivity—diversity relationship. Other field experiments show the same direct productivity—diversity relationship among consumers or terrestrial producers, but an inverse relationship among aquatic producers.