Composition Of Arthropods Research Articles

Influence of local illumination and plant composition on the spatial and seasonal distribution of litter-dwelling arthropods in a tropical rainforest

Summary Using pitfall traps, we evaluated the spatial and seasonal variance in arthropod abundance, species richness, higher taxonomic and species composition, and guild structure within the ground litter of seven sites in a relatively undisturbed rainforest in Panama. We examined each of these five arthropod-dependent variables at two spatial scales (a few meters and a few hundred meters) and one temporal scale (a few months encompassing dry and wet periods), against environmental variables including local illumination and plant composition. Trap catches (9458 arthropods collected during 630 trap-days) were high compared to similar studies in temperate forests. We observed spatial and seasonal differences in abundance, species richness and composition of litter-dwelling arthropods. Often these differences appeared weakly related to geographical coordinates. They reflected forest structure (basal area) and local plant composition, and less so illumination patterns or seasonal changes in radiation. Seasonal variance was high and may relate to surrogate variables accounting for seasonal changes in litter moisture. The composition of higher taxa and species was often predicted by different independent variables at the three scales studied. Guild structure was difficult to predict. Our study lead us to expect that litter-dwelling arthropods may be more seasonal than soil microarthropods in tropical rainforests; and that tropical litter-dwelling arthropods may also be more spatially variable and seasonal than their temperate counterparts. We also recommend that conservation studies using pitfall traps in tropical rainforests should focus on: (1) taxonomic resolution to understand the functional complexity of soil organisms; (2) spatial replication to address subtle changes in plant composition throughout the study area; and (3) seasonal replicates to be commensurate with seasonal changes in litter moisture.

Arthropod Assemblages in Epiphyte Mats of Costa Rican Cloud Forests

ABSTRACTTropical cloud forests are functionally important ecosystems, but are severely threatened due to deforestation and fragmentation. Epiphyte mats, accumulations of live vegetation and dead organic matter on tree trunks and branches, are a conspicuous component of cloud forests and harbor diverse assemblages of meso‐ and microarthropods. We compared the morphospecies richness, composition, and abundance of arthropods in epiphyte mats between primary and secondary forests of Monteverde, Costa Rica, and at two nearby replicate sites. Epiphyte mats were thinner and less structurally diverse in secondary forest. We collected ca 36,000 micro‐ and mesoarthropods from epiphyte mats in the 2‐yr study. Whereas arthropod morphospecies richness did not differ among forest types, arthropod abundance was significantly higher in secondary forest due to larger numbers of ants, especially Solenopsis spp. Arthropod assemblages showed a high degree of taxonomic overlap both within and between primary and secondary forests (Jaccard abundance‐based similarity = 0.93–0.96). Although characteristics of the arthropod fauna proved to be similar among sites and between forest types, there was a significant temporal effect: arthropod morphospecies richness in epiphyte mats generally was lower in the dry season (February–May), when many taxa probably became dormant or sought shelter against desiccation in deeper portions of mats.

The use of ants and other soil and litter arthropods as bio-indicators of the impacts of rainforest clearing and subsequent land use

The present study investigated the impacts of rainforest clearance, and associated subsequent land␣use for pasture, on assemblages of soil and litter arthropods in eastern subtropical Australia. We assessed the utility of soil and litter arthropods as potential bio-indicators of cleared and forested habitats. Arthropods were sampled from 24 sites (12 sites each in rainforest and pasture) using two methods (extraction from litter, pitfall traps). Responses of taxa were analysed at various levels of taxonomic resolution, including ‘coarse’ arthropods (all arthropods sorted to Order/Class), ant genera and ant species. Multivariate analyses of arthropod composition indicated that an increase in the level of taxonomic resolution did not provide a commensurate increase in the sensitivity of assemblage response. Indicator values (IndVals), computed for each taxon, showed that a number of arthropod taxa may have potential as bio-indicators of habitat change. However the use of many of these, especially many ant species found in our study, may be unreliable because even after extensive numbers of sites were sampled, most species showed patchy distributions. To overcome this problem, we generated ‘composite indices’, by combining information from sets of indicator taxa. The utility of these composite indices is discussed.

Age and distance effects on the canopy arthropod composition of old-growth and 100-year-old Eucalyptus obliqua trees

Despite the anthropogenically-induced changes to forest tree demographics, few studies have examined the differences in arthropod species composition between the crowns of trees of different ages. We tested for differences in the taxonomic composition of the canopy arthropod faunas of 100 y.o. and old-growth trees, using eight pairs of trees in an Eucalyptus obliqua tall open-forest with a rainforest understorey in the Warra Long Term Ecological Research Site in southern Tasmania and compared these differences to those related to geographic distances. Sticky traps, hanging flight-intercept traps and bark funnel traps were used to sample the canopy arthropods in different placement situations. There were no significant differences between 100 y.o. and old-growth trees at the tree level, but several at the trap and placement levels. Ordination analyses and correlation analyses indicated that high inter-pair variability related to the geographic distance between trees was partially masking tree age effects. The age of E. obliqua does influence canopy arthropod species composition, but this effect was weaker than the geographic effect that was evident in a relatively uniform forest with a maximum distance between trees of only 324 m. This implied high beta diversity in the forest type has implications for the planning of conservation reserves. Further work is needed to see if age effects are stronger in forests of the ages created by silvicultural treatment.

Richness and species composition of arboreal arthropods affected by nutrients and predators: a press experiment

A longstanding goal for ecologists is to understand the processes that maintain biological diversity in communities, yet few studies have investigated the combined effects of predators and resources on biodiversity in natural ecosystems. We fertilized nutrient limited plots and excluded insectivorous birds in a randomized block design, and examined the impacts on arthropods associated with the dominant tree in the Hawaiian Islands, Metrosideros polymorpha (Myrtaceae). After 33 months, the species load (per foliage mass) of herbivores and carnivores increased with fertilization, but rarified richness (standardized to abundance) did not change. Fertilization depressed species richness of arboreal detritivores, and carnivore richness dropped in caged, unfertilized plots, both because of the increased dominance of common, introduced species with treatments. Herbivore species abundance distributions were more equitable than other trophic levels following treatments, and fertilization added specialized native species without changing relativized species richness. Overall, bird removal and nutrient addition treatments on arthropod richness acted largely independently, but with countervailing influences that obscured distinct top-down and bottom-up effects on different trophic levels. This study demonstrates that species composition, biological invasions, and the individuality of species traits may complicate efforts to predict the interactive effects of resources and predation on species diversity in food webs.

Geographic Variation and Succession of Arthropod Communities in Inflorescences and Infructescences of Xanthosoma (Araceae)1

ABSTRACTPhytotelmata, small aquatic ecosystems within different structures of terrestrial plants, occur in the inflorescescences and infructescences of Xanthosoma (Araceae). This study reports changes in composition and abundance of arthropods during the anthesis of inflorescences and in the developing infructescences of three species of Xanthosoma at three different geographic locations: (1) X. undipes in a tropical cloud forest of Costa Rica, Central America; (2) X. daguense in a tropical cloud forest in the central Andes of Colombia; and (3) X. poeppigii in the Peruvian Amazonas. All Xanthosoma species displayed similar interactions with the main pollinators, dynastine beetles. We observed a succession from terrestrial to aquatic arthropods as inflorescences aged and set fruit. However, community composition varied among different Xanthosoma species. Some arthropods recorded in Xanthosoma phytotelmata have also been reported as inflorescence visitors of the dynastine‐pollinated terrestrial genus Dieffenbachia and of vines from Philodendon and Syngonium. Further research may elucidate if phytotelmata similar to those described for Xanthosoma could occur among dynastine‐pollinated genera of Araceae, both in the understory and the canopy of Neotropical forests.

Arthropod responses to harvesting and wildfire: Implications for emulation of natural disturbance in forest management

Although natural disturbance has been widely adopted as a template for forest management that protects biodiversity, this hypothesis has not been adequately tested. We compared litter-dwelling arthropod assemblages (Coleoptera: Carabidae and Staphylinidae; Araneae) in aspen-dominated stands originating as clear-cuts or wildfires across three age classes (1–2, 14–15, and 28–29 years old) to test whether the post-harvest and post-fire assemblages converged following disturbances, and to compare faunal succession. These findings were compared to data about epigaeic arthropods in old and mature pyrogenic aspen stands (>70 years old) to determine whether diversity and community composition of arthropods from the younger age-classes approached what may have been typical pre-disturbance conditions. The resulting data-set of almost 27,000 arthropods and 230 species showed convergence in most taxa, and some general similarities between 28- and 29-year-old stands and old and mature stands. However, not all taxa responded similarly, and faunal succession following clear-cutting appeared to progress more rapidly than following wildfire. Rarefaction-estimated diversity was elevated in 1–2-year-old stands, compared to unharvested stands, reflecting a mix of closed-canopy and open-habitat species. Non-metric multi-dimensional scaling ordinations showed that samples from young wildfire disturbed stands (1–2 years old) included more variable assemblages than all other study sites, and contained species that may depend on unique post-fire habitat characteristics. The fauna of old and mature stands exhibited low diversity, but contained species with limited dispersal abilities, and species tied to old-growth habitats such as dead wood. Harvesting systems that do not allow adequate recovery following a first harvesting pass, or do not maintain microhabitat features associated with older fire-origin forests, may threaten persistence of some elements of boreal arthropod faunas.

The abundance and composition of arboreal arthropods in Acacia mangium and Paraserianthes falcataria plantations in South Sumatra, Indonesia

We investigated the abundance of arboreal arthropods in pure Acacia mangium and Paraserianthes falcataria plantations in South Sumatra, Indonesia, to evaluate the function of fast-growing tree plantations as wildlife habitats in the tropics. Two plots were established on each tree species,lplantation and insecticide fogging was conducted to sample arboreal arthropods. The mean number of arthropods collected was higher in the A. mangium plantation (230.9-268.0 ⁄ m2) than in the P. falcataria plantation (13.9-21.0 ⁄ m2). In all plots, Collembola was the most abundant order, comprising more than 50.4-56.2% and 82.5-89.2% of the total number of arthropods in the P. falcataria and A. mangium plantations, respectively. The predominance of Collembola in the A. mangium plantation resulted in lower diversity indices (Shannon-Wiener H’ and Simpson 1 ⁄ λ) than in the P. falcataria plantation. Compared to data in the literature, the abundance of arboreal arthropods in the A. mangium plantation was comparable to that of natural forests, although the low H’ in the A. mangium plantation and the low abundance in the P. falcataria plantation were extreme.

Phytophagous arthropods and silvertop levels associated with post-harvest residue treatments in three turfgrass species grown for seed

Silvertop, which is characterized by whitish, completely sterile seed heads produced on green tillers, is a common symptom in many perennial grasses. A 3-yr study of creeping bentgrass (Agrostis palustris), Kentucky bluegrass (Poa pratensis) and creeping red fescue (Festuca rubra subsp. rubra) grown for seed production was conducted at Saskatoon, Saskatchewan, to investigate the cause(s) of silvertop, the impact of residue management strategies on silvertop incidence, and the impact of silvertop on seed yield. Three residue management practices were applied in the fall of the first harvest year and again the next fall, as follows: (i) burned after harvest; (ii) clipped to 1–2 cm in height and the residue removed; or (iii) mowed to 20 cm and the residue retained. Arthropods in each plot were collected weekly from May until July by sweep sampling, counted, and identified to family level or lower, and the incidence of seed heads with and without silvertop were assessed. The majority of arthropods were thrips, leafhoppers, plant bugs, mites, or grass-dwelling flies. Grass species and residue treatment strongly affected the number of reproductive tillers and levels of silvertop. Levels of silvertop were lowest in creeping bentgrass in all 3 yr of the study, while they were similar for Kentucky bluegrass and creeping red fescue. Mown plots had fewer reproductive tillers, fewer heathy seed heads, and higher levels of silvertop than burned or clipped plots. However, arthropod species composition was generally similar across grass species and residue treatments. This indicates that a specific arthropod taxon may not be a critical factor in silvertop expression. The relationship between the number and composition of arthropods found and incidence of silvertop is discussed. Key words: Festuca rubra subsp. rubra, Poa pratensis, Agrostis palustris, seed production, arthropods, silvertop

Willow (Salix × rubens) invasion of the riparian zone in south‐eastern Australia: reduced abundance and altered composition of terrestrial arthropods

ABSTRACTThis study investigated the impact of invasion by an alien hybrid willow (the white‐crack willow, Salix × rubens) on the abundance and diversity of terrestrial arthropods along the lower Tarago River in south‐eastern Australia in spring and summer. Canopy arthropods were sampled by branch clippings, flying insects by sticky traps, and arthropod stream inputs by floating pan traps in willow‐invaded and uninvaded river sections. Willow‐invaded river sections had a significantly lower abundance and diversity of canopy arthropods, but the abundance and diversity of flying insects did not differ between willow‐invaded and native sections. Overall input of terrestrial arthropods was lower in willow‐invaded sections but this depended on sampling date. In general, differences in arthropod abundance between willow‐invaded and native river sections were greater in spring than summer, which may reflect seasonal changes in resource availability in native river sections. Morphospecies composition also differed significantly between willow‐invaded and native sections. These changes in abundance, diversity, and composition of terrestrial arthropods following plant invasion of the riparian zone may indirectly alter in‐stream food webs and have important effects on higher‐order consumers in the riparian zone.

Leaf ties as colonization sites for forest arthropods: an experimental study

Abstract. 1. Secondary colonization of leaf shelters constructed by caterpillars has been reported from a number of systems. Both the mechanism (larval or adult movement vs. oviposition) and the cues used by arthropods in locating leaf shelters, however, have received little attention.2. Artificial leaf shelters (i.e. leaf ties or pairs of leaves clipped together to form sandwiches) were constructed on understorey white oak (Quercus alba L.) trees and the abundance and species composition of arthropods colonizing and ovipositing on leaf pairs was examined in three treatments: occupied leaf ties (containing a leaf‐tying caterpillar), unoccupied leaf ties, and non‐tied control leaves.3. The density of arthropods present in the occupied and unoccupied leaf ties after two weeks was seven and four times greater respectively, than non‐tied controls. The guild composition of these early colonists differed among treatments, with the highest densities of leaf chewers, scavengers, and predators in occupied ties and the lowest densities in non‐tied controls.4. The densities of all arthropods ovipositing on leaf pairs in the occupied and unoccupied leaf tie treatments were four and three times greater than non‐tied controls. Leaf‐chewing insects (including leaf‐tiers and non‐tying inquiline species) and scavengers showed strong oviposition preferences for tied leaves. However, most species of leaf‐tying caterpillars and the psocids (Psocoptera) did not distinguish between occupied and unoccupied ties, suggesting that these groups do not use occupancy‐related cues in selecting oviposition sites.

Amino acid composition of some woodland arthropods and its implications for breeding tits and other passerines

Several studies on Parids have noted a peak in the provisioning of spiders to nestlings in the early stages of development. It has been suggested that spider proteins are rich in the sulphur‐containing amino acid (SAA) cysteine and that increased provisioning may serve to provide extra cysteine during rapid feather growth. Amino acid analyses were conducted on samples of arthropod groups known to feature in the diet of breeding tits. Cysteine and methionine (both SAA) levels were slightly higher in aranaea protein than in that of other arthropods. However, we argue that the increased level of SAA found in aranaea is insufficient to drive the observed diet selection and that the timing of peak aranaea provisioning does not support the feather growth hypothesis. Instead, we propose that observed patterns of provisioning are due to high levels of taurine present in aranaea and that taurine may be an essential nutrient during a critical stage of chick development.

Diversity and conservation of forest-floor arthropods on a small Seychelles island

Cousine Island, Seychelles, is of major conservation significance as it is in a biodiversity hotspot. Furthermore, it is relatively pristine, and is apparently the only tropical island over 20 ha with no alien invasive mammals. This study focuses on the island's log and litter arthropods, which were sampled by extraction methods from the dominant species, Pisonia grandis, Ficus spp. and Cocos nucifera. Stage of decomposition, and forest type in which the logs occurred, both significantly influenced the composition and structure of the arthropod assemblages. Young logs were significantly richer in species than older logs, possibly because they had the most resources and microhabitats. There were some significant changes in arthropod species richness, composition and abundance between species of young logs, but not old ones, because as logs decomposed, arthropod assemblages converged. Nevertheless, each old log species had some arthropod species not present in other log species, which has important implications for conservation. Arthropod assemblages in woody litter varied according to the forest type in which they occurred, and were different from those in logs in the same forest type. Cousine Island arthropod species richness, both in logs and litter, was comparable to figures from other tropical areas. As the logs, especially P. grandis, are home to many Seychelles endemic species, their conservation is essential. Furthermore, as the arthropods are also the main food of certain threatened Seychelles vertebrates, their conservation also underpins a food chain on this unique tropical island.

Seasonal changes in the canopy arthropod fauna in Rinorea beniensis in Budongo Forest, Uganda

Arthropods were collected by insecticidal tree fogging on the understorey tree species Rinorea beniensis Engler (Violaceae) in Budongo Forest, a seasonal rain forest in Uganda. Eight trees were fogged in adjacent plots of primary, selectively logged and swamp forest during the wet season and again in the dry season. In all forest types, Psocoptera, parasitoid Hymenoptera, and especially Formicidae and Auchenorrhyncha were more abundant during the dry season, while Ensifera, Heteroptera, Lepidoptera, Diptera, and Coleoptera were more abundant during the wet season. Seasonal change in arthropod composition was very low in the swamp forest located near a stream, where permanent water supply is crucial for the development of the distinct swamp vegetation, with comparatively constant microclimatic conditions all over the year. Seasonal change increased in the primary forest, and shows most significant changes of athropod abundance between dry and wet season in the selectively logged forest which also had the highest heterogeneity in forest structures. Especially small and soft bodied arthropods probably accumulate along a humidity gradient in the dense canopies of Rinorea during the dry season, when the forest floor outside the swamp forest is dry. This effect, which is also strongest in the selectively logged forest, leads to a much higher density of canopy dwelling arthropods during the dry season.

Importance of habitat structure to the arthropod food‐web in Douglas‐fir canopies

This study tested the hypothesis that habitat structure dictates the distribution and community composition of arboreal arthropods. A diverse arthropod assemblage of Douglas‐fir canopies, which included Araneae, Psocoptera, Collembola and Homoptera, was chosen as a model system. Habitat structural diversity, defined as needle density and branching complexity of Douglas‐fir branches, was manipulated in a four‐month experiment by needle removal, thinning and tying of branches. Abundance of canopy spiders declined significantly following needle density reduction and branch thinning, branch tying significantly increased spider abundance. Distinct habitat utilization patterns were found among individual spider guilds. Orb weavers (Araneidae) dominated spider assemblages in structurally simple habitats, whereas tied branches were colonized primarily by sheet‐web weavers (Linyphiidae) and nocturnal hunting spiders (Anyphaenidae and Clubionidae). Spider species richness and average body size of several spider species increased in structurally more complex habitats. Arboreal spiders appeared to be limited by strong bottom‐up effects in the form of habitat quality and, to a lesser degree, prey availability. Habitat manipulations did not affect densities or biomass of flying arthropod colonists in the branch vicinity. Needle removal and branch thinning led to a significant decline in the abundance of Psocoptera and Collembola. Tying of branches resulted in an eight‐fold increase in Collembola numbers, organisms most sensitive to habitat alterations. Canopy habitat structure modified vertical dispersal of Collembola from forest litter, which may have significant implications for arboreal consumers. Our results lend strong support to the importance of habitat structural diversity in explaining general patterns of arthropod abundance and diversity on plants.

Recovery of shrubland communities on abandoned farmland in southwestern Australia: soils, plants, birds and arthropods

Passive recovery of land formerly used for agricultural production may be an inexpensive and rapid method of ecosystem recovery, and may provide an alternative method to active revegetation. Passive recovery may also contribute to sustainable agriculture (soil salinity). For undisturbed and disturbed areas of the central wheatbelt of Western Australia, this paper reports the effects of farming history (clearing only, cultivation, duration of farming, and time since farming ceased) on the soil nutrient content, plant floristics (richness and composition) and structure, and the abundance, species richness and species composition of birds and arthropods. Only one site was cultivated for >6 years. We summarize as follows: (1) Previous clearing and cultivation has left no residual effects on the nitrogen or phosphorus content in the sandy soils. (2) There were no significant differences in terms of plant species richness but some differences in cover of woody plants, grass cover and plant species composition for farming history or time since farming ceased. (3) There were no significant differences in bird species richness but differences in species composition for time since farming ceased. (4) Arthropods showed few (and low) significant differences in their abundance, richness or species composition across different farming histories and time periods since farming ceased. Farming of these shrublands has left only minor changes in the composition and structure of the vegetation, and in the abundance, species richness and species composition of the passerine bird and arthropod assemblages. Abandoned parcels of land on the sandy soils which support shrubland may yield useful conservation benefits with relatively little input.

Post-Fire Arthropod Assemblages in Mediterranean Forest Soils in Israel

The presence of soil micro- and macroarthropod species was surveyed after severe fire in a mixed forest dominated by Aleppo pine on Mt. Carmel, Israel. Arthropods were sampled, and separated into 19 taxa (mainly orders or classes). The effects of 2nd-5th post-fire years, seasons, habitats (burned and unburned) and tree species (pine or oaks) on the relative abundance of soil arthropods were analyzed by linear redundancy analysis. Arthropod distribution along the first axis of the analysis was non-random, so all these factors influenced arthropod community composition. Arthropod composition in the 2nd and 3rd postfire years was different from later years, demonstrating outbreaks of pioneers. After five post-fire years arthropod populations were not completely recovered. Significant seasonal differences in population size were detected, indicating summer, and to lesser extent also winter, as unfavorable periods in that region, as was well demonstrated with Collembola. The resilience of arthropods under burned oaks differed from the arthropods sampled under burned pines. Seven taxa were highly correlated to the unburned zone and included the main microarthropod groups (Collembola, Protura, Acari, and Pauropoda) and Coleoptera, Thysanoptera and Chilopoda. Only two orders showed a distinct association with-the burned zone: Psocoptera and Homoptera; the latter was represented almost solely by specimens of a pioneer species, Rhizoicus sp. (Pseudococcidae).

Species composition, abundance, and activity of predatory arthropods in carrot fields, Canterbury, New Zealand

Pitfall trapping (November 1993 to April 1994) and Malaise trapping (January to June 1995) were carried out to study the predatory arthropod fauna in carrot fields at four sites in Canterbury, New Zealand. Staphylinidae (rove beetles), Linyphiidae (money spiders), Lycosidae (wolf spiders), Phalangiidae (harvestmen), and Carabidae (ground beetles) were the most abundant predators. At Lincoln, spiders, staphylinids, harvestmen, and carabids comprised 68, 13, 11, and 2.6 percent, respectively, of all total predaceous arthropods in pitfall traps. At Killinchy (30 km from Lincoln) these four taxa constituted 77, 8.5, 0.7, and 6.5 percent of the pitfall trap catches. Overall, a total of 33 staphylinid species was recorded, including one, Ocypus ater (Gravenhorst), which was new to New Zealand. The total number of predators caught in pitfall traps declined in March and April. In pitfall traps the abundant species were the staphylinids Amischa analis (Grav.), A. nigrofusca (Step.), Atheta fungi (Grav.), A. amicula (Step.), and Xantholinus linearis (Oliver); the carabids Meta‐glymma monilifer Bates and Holcaspis angustula Chaudoir; the spiders Lepthyphantes tenuis (Blackwall), Erigone spp. and ’Lycosa’ hilaris Koch; and the harvestman Phalangium opilio L. In Malaise traps, abundant staphylinid species were Tachyporus nitidulus (Fab.), Amischa decipiens (Sharp), and Atheta fungi (Grav.). The seasonal activity and abundance of the dominant species are described, and their potential importance in control of carrot rust fly (Psila rosae F.) and pests in other crops is discussed.

Spatiotemporal variation in body composition and cold tolerance of soil arthropods

Spatiotemporal variation in body composition and cold tolerance of soil arthropods

Aquatic Arthropods in California Rice Paddies: Effects of Water-Drainage Versus Continuous-Flood Regimes on Abundance and Species Composition

In conjunction with experiments to evaluate water drainage as a control method for the rice water weevil, Lissorhoptrus oryzophilus Kuschel, studies were performed to compare the abundance and species composition of aquatic arthropods in two sets of continuously flooded and temporarily drained but reflooded rice, Oryza sativa L., paddies. A total of 1,736 individuals representing 22 arthropod taxa was collected. Few differences in abundance were detected; however, Notonecta spp. were significantly more abundant in reflooded paddies. Percentage similarity (PS) between paired treatments was >0.50 on all but one date; relatively high PS values on the first sampling dates suggest that the aquatic arthropod community is able to recover rapidly following reflooding. Several taxa appear to possess traits that enhance survival in a rice paddy subjected to temporary drainage. Implications are discussed for the wide-scale use of drainage on California rice acreage.