Litter Arthropods Research Articles

Influence of edaphic factors along an altitudinal gradient on a litter arthropod community in an Abies-Quercus forest in Mexico

Elevational gradients can serve as natural experiments to study how species are restricted spatially according to environmental conditions. The variation in resources and conditions that habitats experience in relation to the seasons can be useful for understanding why the abundance and distribution of the species change temporarily. In this study, we evaluated the influence of an altitudinal gradient and seasonality on the composition, richness (S), diversity (Hʹ), and density of arthropod community associated with litter in a conserved Abies-Quercus forest in Central Mexico. We defined five altitudinal ranges in an altitudinal gradient that oscillated between 2570 and 2770 m, in which edaphic factors [pH, organic matter (OM), carbon (C), total nitrogen (N), total phosphorous (P), C/N, C/P, N/P ratios] and environmental temperature were characterized. Litter arthropods were collected through this vertical gradient in dry and rainy season. We identified 163 species belonging to 22 orders. Arthropods composition on each elevation zone is significantly different from one another in both seasons. The highest abundance and S values through altitudinal gradient were registered in the rainy season; in contrast, H’ values were higher during the dry season. We detected a significant negative effect related to the altitude on S, Hʹ and abundance of litter arthropods during the dry season and total data. An exception was the rainy season in which we did not detect any pattern. The community similarity reduces as altitude increases. Surprisingly, the intermediate altitudinal range showed the higher density values in the rainy season. On the other hand, OM, C/N and C/P ratios had a negative influence on litter community parameters analyzed in the rainy season and total data. In contrast, P shows a positive influence on S of litter arthropods in the same period. Edaphic characteristics recorded along the altitudinal gradient can explain differences in litter arthropod communities.

Effects of rainfall manipulations versus a natural aridity gradient on plant litter arthropods in desert and Mediterranean ecosystems

Predicting responses of litter arthropods to future variation in precipitation is critical for understanding decomposition processes under global climate change. A field experiment on litter arthropods extracted from litterbags using Berlese-Tullgren funnels was conducted under simulated drought and increasing precipitation treatments at a semiarid site and a Mediterranean site, and along a natural climatic gradient from arid to mesic Mediterranean ecosystems during three consecutive years. Our objective was to examine the effects of variation in water availability on the abundance of litter arthropods along the aridity gradient. The results demonstrated positive responses of total abundances, including Acari abundance, but negative responses of taxonomic richness to experimentally increased precipitation at the semiarid site and the Mediterranean site. Collembolan abundance responded positively while the Shannon index responded negatively to experimental precipitation at the Mediterranean site only. However, total abundance and collembolan abundance were found to decrease across a mean annual precipitation (MAP) gradient from the arid site to the mesic Mediterranean site. Quantile regression for linear mixed-effects models demonstrated a negative effect of MAP on Acari abundance at the medium level of Acari abundance but weak positive effects of MAP on taxonomic richness and the Shannon index. In conclusion, we found that the distribution of abundance was a poor proxy for predicting the response of the studied litter arthropod assembly to spatial variation in precipitation.

Who gives a flux? Synchronous flowering ofCoffea arabicaaccelerates leaf litter decomposition

AbstractCoffee (Coffea arabica) flowers synchronously and flowers are only open for a few days before senescing. Flower petals often decompose easily, containing higher concentrations of nutrients relative to other plant tissues. Thus, a pulse of petals into the detrital pool could be beneficial for the decomposer community and accelerate decomposition processes. Our research assessed the magnitude of the pulse of petals within a shaded coffee farm, and the impact of petals on the litter arthropod community and on the rate of leaf litter decomposition. Three plots of 12 coffee plants were monitored throughout the flowering period to estimate the magnitude of the bloom. Pitfall traps were used to assess the litter arthropod community before and after flowering. Finally, litterbags withC. arabicaleaves alone andC. arabicaleaves with flower petals were used to compare the effect of petals on decomposition rates. The average number of flowers open per plant at the peak of the bloom was 792 flowers. When scaling to obtain an estimate per hectare in a year, our results indicate flower petals could contribute 26.27 kg of nitrogen, 2.03 kg of phosphorus, and 26.7 kg of potassium. The leaf litter community did not change during our sampling, suggesting that any community effects may be acting on a longer time scale or smaller spatial scale. Leaf litter decomposed nearly three times as quickly in litterbags that included flower petals, relative to litterbags with onlyC. arabicaleaf litter in the first month and twice as fast in the second month. The rate of decomposition with petals exceeded the rate of decomposition without petals and was highest after one month, though the benefit continued after two months. Our results demonstrate that the presence of flower petals can accelerate short‐term decomposition processes.

Applied nucleation facilitates tropical forest recovery: Lessons learned from a 15‐year study

Abstract Applied nucleation, mostly based upon planting tree islands, has been proposed as a cost‐effective strategy to meet ambitious global forest and landscape restoration targets. We review results from a 15‐year study, replicated at 15 sites in southern Costa Rica, that compares applied nucleation to natural regeneration and mixed‐species tree plantations as strategies to restore tropical forest. We have collected data on planted tree survival and growth, woody vegetation recruitment and structure, seed rain, litterfall, epiphytes, birds, bats and leaf litter arthropods. Our results indicate that applied nucleation and plantation restoration strategies are similarly effective in enhancing the recovery of most floral and faunal groups, vegetation structure and ecosystem functions, as compared to natural regeneration. Seed dispersal and woody recruitment are higher in applied nucleation and plantation than natural regeneration treatments; canopy cover has increased substantially in both natural regeneration and applied nucleation treatments; and mortality of planted N‐fixing tree species has increased in recent years. These trends have led to rapid changes in vegetation composition and structure and nutrient cycling. The applied nucleation strategy is cheaper than mixed‐species tree plantations, but there may be social obstacles to implementing this technique in agricultural landscapes, such as perceptions that the land is not being used productively. Applied nucleation is likely to be most effective in cases where: planted vegetation nuclei enhance seed dispersal and seedling establishment of other species; the spread of nuclei is not strongly inhibited by abiotic or biotic factors; and the approach is compatible with restoration goals and landowner preferences. Synthesis and applications. Results from our 15‐year, multi‐site study show that applied nucleation can be a cost‐effective strategy for facilitating tropical forest regeneration that holds promise for helping to meet large‐scale international forest restoration commitments.

Impacts of Forest and Agricultural Land Use on Soil and Litter Arthropod Assemblages in Southern Province of Rwanda

To assesseffects of land use change on soil and litter arthropods, a research was conducted inexotic and native tree species at the Artboretum of Ruhande and in varieties of coffee andbanana plantations at the Rubona agricultural research station, in southern Rwanda. Datawere collected by pitfall traps, hand sorting, and Berlese-Tullgren funnels. Collectedspecimens of soil and litter arthropods were morphologically identified under microscope,and classified to the family level by using dichotomous keys. Fourteen orders and 20 familiescomprising 2135 individuals were identified. The family of Formicidae was more abundantcompared to the other identified families, and occurred in all land uses. High abundance anddiversity of soil and litter arthropods werefound under plots of native tree species and bananaplantations compared to exotic tree species and coffee plantations. Research concluded thatnative tree species offer suitable habitats for soil and litter arthropods.It recommendedfurtherstudies in other land uses and ecological zones of Rwanda to generalize the findings.Key words: arthropod, fauna, land use change, soil and litter

Exotic tree and shrub invasions alter leaf-litter microflora and arthropod communities.

Approximately 90% of all annual net primary productivity in temperate deciduous forests ends up entering the detritus food web as leaf litter. Due to chemical and physical differences from native litter, inputs from invasive species may impact the litter-dwelling community and ecosystem processes. We compared leaf-litter nutritional quality and decomposition rates from two invasive shrubs, Lonicera maackii and Rhamnus davurica, and the invasive tree Ailanthus altissima to litter from native oak-hickory forest in the Shenandoah Valley of Virginia, USA. We sampled litter from both invaded and uninvaded habitats and conducted litter colonization experiments to test for effects on microflora and the litter-dwelling arthropod communities. Litter from all three invasive species decomposed more rapidly than native litter, with native habitats averaging two to nearly five times as much litter by June. Invasive litter had higher nitrogen concentration and lower C:N ratios than native litter. Invasive litter supported greater growth of bacteria and fungi. Higher numbers of arthropods colonized invasive litter than native litter, but litter arthropod numbers on the forest floor of invaded habitats dropped in the early summer as litter decomposed. Litter had no effect on arthropod richness. Over short time scales, our results indicate that these invasive species represent beneficial, novel resources for the litter-dwelling community. However, the short-lived nature of this resource resulted in a crash in the abundance of the litter-dwelling organisms once the litter decomposed. As a whole, native habitat seems to support a larger, more stable litter-dwelling community over the course of a growing season.

Effects of Chinese privet (Ligustrum sinense) invasion on decomposition and litter-dwelling invertebrates in Southeastern U.S. floodplain forests

Chinese privet (Ligustrum sinense) is one of the most problematic invasive plants in many parts of the world where it often dominates the shrub layer in riparian forests. We aimed to evaluate the role of privet invasion on litter inputs, rates of litter decomposition and litter-dwelling arthropods in the Southeastern United States. To do this we: (1) evaluated the relative contribution of privet to total litter-fall, (2) compared breakdown of artificial leaves (filter paper) in plots which had or had not been subjected to experimental privet removal, and (3) compared litter breakdown and arthropod communities among the following litter types: (a) native sweetgum, (b) invasive Chinese privet, and (c) a mixed sweetgum–privet litter treatment. Privet accounted for 10% of annual litter-fall at our study sites and leaf fall phenology differed from native species. Filter paper decomposed about twice as quickly in reference compared to removal plots but there were no differences between plot types in litter decomposition. This difference may relate to flooding during the litter bag experiment. In both plot types, privet litter decomposed faster than sweetgum or mixed litter but there were no differences in decay rates between the latter two litter types, suggesting that sweet gum may slow the rate of decomposition in mixed bags. There were no differences among litter or plot types in invertebrate community composition or overall abundances, but detritivores were marginally more abundant in the reference plots. Our findings suggest that flooding may affect the impact of privet invasion on litter decay rates and associated invertebrate communities.

Cohabitation and niche overlap in the occupation of twigs by arthropods in the leaf litter of Brazilian Atlantic Forest

In tropical forests, twigs are the nesting resources most frequently occupied by ants in the leaf litter. During occupation, this resource may be shared among different arthropods, such as ants or non-ant arthropods, but the mechanisms that promote cohabitation in this context are poorly known. In this study, we examined if twig structure influences species cohabitation. Additionally, we calculated co-occurrence and niche overlap metrics for ant species and non-ant arthropods occupying the same twigs in the leaf litter. We collected 52 species of ants and 82 morphospecies of non-ant arthropods inside 575 twigs from fragments of Brazilian Atlantic Forest. Thirty-six ant species cohabited with non-ant arthropods, which were primarily Isopoda and Coleoptera. We observed that the twigs most commonly shared by ants and non-ant arthropods were wider, longer, and had a larger number of holes. We also found that cohabiting ants and non-ant arthropods had higher co-occurrence and niche overlap scores. We suggest that twig diameter is an important factor determining occupation by ants and other arthropods. When the twig is occupied by more than one ant species, our results show that niche overlap and cohabitation with non-ant arthropods are less common. We conclude that examining twig structure is important to better understand arthropod species cohabitation in leaf litter twigs and to study coexistence in ant assemblages that use twigs.

Short term effects of Bacillus thuringiensis and diflubenzuron aerial applications on non-target arthropods in a Mediterranean Forest

Several products are widely used to control gypsy moth (Lymantria dispar) populations. The main purpose of the present study is to evaluate the aerial application effects of B. thuringiensis and diflubenzuron on non-target arthropods in a Mediterranean holm-oak forest. The density of gypsy moth population at the time of application of treatments was the same in the three forests and the defoliation levels in the three holm-oak forests were between level 0 (no apparent defoliation) and level 1 (small defoliations of new leaf). Sampling litter, soil, ground-dwelling, and epiphytic arthropods showed that the holm-oak forests treated with diflubenzuron had a better quantitative faunal outcome than the Control, whereas the highest taxonomic diversity was found in the site treated with B. thuringiensis. These results could probably be explained by a temporary competitive decrease due to the huge number of gypsy moth caterpillars on plants, as well as the enormous accumulation of their excrements in the soil during a prolonged period of time.

Litter Spider Communities and their Effects on Invertebrate Fauna and Decomposing Rates in Nanjenshan Rain Forest, Taiwan

Spiders are among the most important predators in forest litter layer that control food chain and decomposition process. However, little is known about the changes in litter-spider communities from wind-exposed to wind-shielded areas during monsoon seasons, and their roles in litter arthropod distribution and decomposition processes. In the present study, the densities and diversities of the spider communities in litter were examined at the two locations in monsoon and non-monsoon seasons in southern Taiwan. Enclosures with/without the spider Ctenus yaeyamensi were set up to compare litter arthropod distribution and decomposition rates in litterbags in different sampling units. It was found that the mean density of litter spiders was significantly greater in wind-shielded area than wind-exposed area. There was a marked impact of structure and depth of litter layers on guild composition, but not on the diversity indices of the litter spider communities. The litter invertebrates and decomposition rates did not differ between enclosures with/without spiders. However, there was a marked difference in litter arthropod abundance between monsoon and non-monsoon seasons in wind-exposed areas. The decomposition rate was remarkably greater in non-monsoon seasons than in monsoon seasons, whereas there were no marked differences between wind-shielded and wind-exposed locations. It was concluded that litter arthropod distribution and related decomposition were affected by variation of monsoon seasons but not by spider presence/absence in Nanjenshan Rain Forest.

Mechanisms of Convergent Egg Provisioning in Poison Frogs.

Parental provisioning of offspring with physiological products (nursing) occurs in many animals, yet little is known about the neuroendocrine basis of nursing in non-mammalian species. Within amphibians, maternal provisioning has evolved multiple times, with mothers of some species feeding unfertilized eggs to their developing offspring until tadpoles complete metamorphosis [1-3]. We conducted field studies in Ecuador and Madagascar to ask whether convergence at the behavioral level provides similar benefits to offspring and relies on shared neural mechanisms in dendrobatid and mantellid poison frogs. At an ecological level, we found that nursing allows poison frogs to provide chemical defenses to their tadpoles in both species. At the neural level, nursing was associated with increased activity in the lateral septum and preoptic area, demonstrating recruitment of shared brain regions in the convergent evolution of nursing within frogs and across vertebrates [4]. In contrast, only mantellids showed increased oxytocin neuron activity akin to that in nursing mammals [5], suggesting evolutionary versatility in molecular mechanisms. Our findings demonstrate that maternal provisioning provides similar potential benefits to offspring and relies on similar brain regions in poison frog species with convergently evolved toxicity and maternal care. VIDEO ABSTRACT.

Impacts of rainfall extremes predicted by climate-change models on major trophic groups in the leaf litter arthropod community.

Arthropods in the leaf litter layer of forest soils influence ecosystem processes such as decomposition. Climate-change models predict both increases and decreases in average rainfall. Increased drought may have greater impacts on the litter arthropod community. In addition to affecting survival or behaviour of desiccation-sensitive species, lower rainfall may indirectly lower abundances of consumers that graze drought-stressed fungi, with repercussions for higher trophic levels. We tested the hypothesis that trophic structure will differ between the two rainfall scenarios. In particular, we hypothesized that densities of several broadly defined trophic groupings of arthropods would be lower under reduced rainfall. To test this hypothesis, we used sprinklers to impose two rainfall treatments during three growing seasons in roofed, fenced 14-m2 plots and documented changes in abundance from initial, pre-treatment densities of 39 arthropod taxa. Experimental plots were subjected to either LOW (fortnightly) or HIGH (weekly) average rainfall based upon climate models and the previous 100years of regional weekly averages. Unroofed open plots, our reference treatment (REF), experienced higher than average rainfall during the experiment. The two rainfall extremes produced clear negative effects of lowered rainfall on major trophic groups. Broad categories of fungivores, detritivores and predators were more abundant in HIGH than LOW plots by the final year. Springtails (Collembola), which graze fungal hyphae, were 3× more abundant in the HIGH rainfall treatment. Taxa of larger-bodied fungivores and detritivores, spiders (Araneae), and non-spider predators were 2× more abundant under HIGH rainfall. Densities of mites (Acari), which include fungivores, detritivores and predators, were 1.5× greater in HIGH rainfall plots. Abundances and community structure of arthropods were similar in REF and experimental plots, showing that effects of rainfall uncovered in the experiment are applicable to nature. This pattern suggests that changes in rainfall will alter bottom-up control processes in a critical detritus-based food web of deciduous forests. Our results, in conjunction with other findings on the impact of desiccation on arthropods and fungal growth, suggest that drier conditions will depress densities of fungal consumers, causing declines in higher trophic levels, with possible impacts on soil processes and the larger forest food web.

Hemiparasites drive heterogeneity in litter arthropods: Implications for woodland insectivorous birds

AbstractProviding fruit, nectar, leaves and litter, mistletoes represent important resources for many organisms, linking above‐ground patterns with below‐ground processes. Here, we explore how mistletoe litter affects arthropod availability, especially those taxa preferentially consumed by ground‐feeding insectivorous birds, a group that has undergone widespread declines. We estimated the influence of mistletoe on arthropod occurrence by sampling arthropod communities beneath infected and uninfected trees with pit‐fall traps. Then, we experimentally isolated direct effects of mistletoe litter on arthropods with a litterbag study. Soil arthropod communities beneath infected trees had consistently greater abundance and biomass – total arthropods and the subset of arthropods preferentially consumed by ground‐foraging insectivores – compared to otherwise comparable uninfected trees. Arthropods showed a weak response to litter addition, with maximum abundances recorded from bags with low mistletoe litter, significantly lower abundances associated with higher mistletoe fractions and pure tree litter (after 5 months). Our findings confirm that mistletoe occurrence has a significant positive impact on arthropod availability, especially on those preferred by ground‐foraging bird insectivores. However, only a minor part of this impact is due to the direct, short‐term effects of mistletoe litter, which suggests that additional mistletoe‐mediated effects (e.g. local changes in structural or microclimatic factors, cumulative effects over multiple years) play significant roles. By altering arthropod assemblages within leaf litter and increasing the heterogeneity of resource availability on forest floors, mistletoe plays an important role in improving habitat quality for declining insectivores.

Molecular physiology of chemical defenses in a poison frog.

Poison frogs sequester small molecule lipophilic alkaloids from their diet of leaf litter arthropods for use as chemical defenses against predation. Although the dietary acquisition of chemical defenses in poison frogs is well documented, the physiological mechanisms of alkaloid sequestration has not been investigated. Here, we used RNA sequencing and proteomics to determine how alkaloids impact mRNA or protein abundance in the little devil frog (Oophaga sylvatica), and compared wild-caught chemically defended frogs with laboratory frogs raised on an alkaloid-free diet. To understand how poison frogs move alkaloids from their diet to their skin granular glands, we focused on measuring gene expression in the intestines, skin and liver. Across these tissues, we found many differentially expressed transcripts involved in small molecule transport and metabolism, as well as sodium channels and other ion pumps. We then used proteomic approaches to quantify plasma proteins, where we found several protein abundance differences between wild and laboratory frogs, including the amphibian neurotoxin binding protein saxiphilin. Finally, because many blood proteins are synthesized in the liver, we used thermal proteome profiling as an untargeted screen for soluble proteins that bind the alkaloid decahydroquinoline. Using this approach, we identified several candidate proteins that interact with this alkaloid, including saxiphilin. These transcript and protein abundance patterns suggest that the presence of alkaloids influences frog physiology and that small molecule transport proteins may be involved in toxin bioaccumulation in dendrobatid poison frogs.

Use of Soil and Litter Ants (Hymenoptera: Formicidae) as Biological Indicators of Soil Quality Under Different Land Uses in Southern Rwanda.

The use of soil and litter arthropods as biological indicators is a way to assess environmental changes, where ant species in particular may serve as important indicators of soil quality. This study aimed at relating the abundance of soil and litter ant species to soil parameters under different tree species, both native and exotic, and varieties of coffee and banana plantations. Variations were found in soil physicochemical parameters. A total of 30 species belonging to 14 genera, and four subfamilies, the Formicinae, Dorylinae, Myrmicinae, and Ponerinae were identified. Higher abundance was found in coffee plantations compared to banana plantations, exotic and native tree species. Species of Camponotus cinctellus and Odontomachus troglodytes occurred in all land uses which is a sign of tolerance to a wide range of soil properties. In addition, these species, together with Myrmicaria SP02, Phrynoponera gabonensis, Camponotus SP06, Myrmicaria opaciventris, Pheidole SP03, Tetramorium simillimum, Pheidole SP01, and Tetramorium laevithorax were not strongly correlated with soil physicochemical parameters. Species of Pheidole SP02 and Camponotus SP05 were restricted to specific soil physicochemical properties, while species of Tetramorium zonacaciae and Bothroponera talpa discriminated between native tree species, coffee plantations, soil organic carbon, sandy soil texture, and aggregate stability. We concluded that these ant species can differently indicate the soil quality depending on the land use. We recommended further studies in order to generalize these findings.

Foraging connections: Patterns of prey use linked to invasive predator diel movement.

Invasive predators can profoundly impact native communities, especially in insular ecosystems where functionally equivalent predators were evolutionarily absent. Beyond direct consumption, predators can affect communities indirectly by creating or altering food web linkages among existing species. Where invasive predators consume prey from multiple distinct resource channels, novel links may couple the dynamics of disjunct modules and create indirect interactions between them. Our study focuses on invasive populations of Eleutherodactylus coqui (Anura: Leptodactylidae) on Hawaii Island. Coqui actively forage in the understory and lower canopy at night but return to the forest floor and belowground retreats by day. Recent dietary studies using gut contents and naturally occurring stable isotopes indicate higher than expected consumption of litter arthropods, which in these Hawaiian forests are primarily non-native species. We used laboratory studies to observe diurnal and nocturnal foraging behavior, and experimental field additions of C4 vegetation as a litter tracer to distinguish epigaeic sources from food web pools in the C3 canopy. Lab trials revealed that prey consumption during diurnal foraging was half that consumed during nocturnal foraging. Analysis of δ13C isotopes showed incorporation of C4 carbon into litter arthropods within one month, and Bayesian mixing models estimated that 15–25% of the carbon in coqui tissue was derived from litter sources. These results support recent findings that E. coqui are not quiescent diurnally but instead actively forage. Such activity by a mobile invasive predator may introduce a novel linkage that integrates detrital and foliar resource pools, potentially distributing influences of invasive litter arthropods through the broader system to amplify impacts on native species.

Managed Fire Frequency Significantly Influences the Litter Arthropod Community in Longleaf Pine Flatwoods.

Frequent prescribed burns are essential to pine forest restoration and management. Research studies have assessed effects of prescribed fire and burn frequency on plants and vertebrates, but impacts of fire on terrestrial invertebrate communities are still poorly understood. This case study investigated effects of burning frequency on species richness and community composition of social insects (ants, Hymenoptera: Formicidae and termites, Blattodea: Isoptera) in fire-managed Southern longleaf pine flatwoods in central Florida. Community response to different fire frequencies was assessed: burned annually, every 2 yr, or every 3 yr, 30 yr unburned and 75 yr unburned. Richness was similar across all treatments, but ant community composition and species density significantly differed between frequently burned (1, 2, and 3 yr) and long-unburned (30 and 75 yr) treatments. Long-unburned treatments had higher ant abundance, but the species present were less characteristic of open canopy longleaf pine habitat than ants in frequently burned treatments. The annual burn treatment differed from 2-yr burn in species density, but to a lesser degree. Exotic species abundance was highest in frequently burned sites; only native species were detected in the 75-yr unburned plot. The red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), was detected in all regularly burned plots but not in long-unburned sites. Frequent burning at this site increased habitat suitability for ant species adapted to the sunny, open canopy, and diverse niches characteristic of longleaf pine forest; however, regular fire disturbance also increased the likelihood of exotic ant species establishment.

Behavioral interactions between terrestrial salamanders and spiders: competition or intraguild predation?

Several studies suggest that small terrestrial salamanders are important regulators of leaf litter arthropod communities, and likely contribute to ecosystem processes such as decomposition and nutrient cycling. Despite the recognition that salamanders have the potential to strongly affect ecosystem function through both direct and indirect pathways, little is known regarding the nature of interactions between small vertebrates and the large, predatory arthropods with which they share both microhabitat and prey. Our study was designed to explore interactions between Eastern Red-backed Salamanders, Plethodon cinereus, and spiders in the genus Wadotes in an eastern North American temperate forest ecosystem. We were particularly interested in teasing apart behaviors such as territoriality and intraguild predation in an attempt to determine specifically which interaction is most likely responsible for the observed negative relationship between salamander and spider abundance at our field site. Field data indicate that P. cinereus and large syntopic spiders exhibit negative spatial associations in the microhabitat beneath cover objects, a possible indication of interspecific territoriality. In our laboratory experiments, resident salamanders displayed agonistic postures similarly toward both intruding conspecifics and spiders, suggesting that salamanders may perceive large intruding spiders as competitors. Finally, we observed no injuries to individual P. cinereus or adult spiders even though occasional chases and bites by both were recorded during the behavioral trials. We found no evidence that adults or juveniles of P. cinereus were envenomated by adult Wadotes spp., and there were no instances of intraguild predation in this study. Multiple lines of evidence from this study, and others, suggest that the primary interaction between individuals of P. cinereus and large spiders is competitive in nature rather than predatory. We suggest that the cost associated with intraguild predation on salamanders with noxious skin secretions may preclude them from being preyed upon by spiders.

Competence of Litter Ants for Rapid Biodiversity Assessments

Rapid Biodiversity Assessment approaches associated with focusing taxa have overcome many of the problems related to large scale surveys. This study examined the suitability of litter ants as a focusing taxon by checking whether diversity and species assemblages of litter ants reflect the overall picture of arthropod diversity and assemblages in leaf litter in two vegetation types: secondary forest and pine plantation in Upper Hanthana forest reserve, Sri Lanka. In each vegetation type, arthropods were sampled using three sampling methods (Winkler extraction, hand collection, and pitfall traps) along three 100 m line transects. From the two sites, 1887 litter ants (34 species) and 3488 litter arthropods (52 species) were collected. Species assemblages composition of both ants and other arthropods differed significantly between the two sites (ANOSIM,p=0.001) with both groups generating distinct clusters for the two sites (SIMPROF,p=0.001). But there was no significant correlation (p>0.05) between abundance and richness of litter ants and those of other arthropods in both vegetation types. The overall finding suggests that the litter ants do not reflect the holistic picture of arthropod diversity and assemblages in leaf litter, but the quality of the habitat for the survival of all litter arthropods.

Tree functional diversity affects litter decomposition and arthropod community composition in a tropical forest

AbstractDisturbance can alter tree species and functional diversity in tropical forests, which in turn could affect carbon and nutrient cycling via the decomposition of plant litter. However, the influence of tropical tree diversity on forest floor organisms and the processes they mediate are far from clear. We investigated the influence of different litter mixtures on arthropod communities and decomposition processes in a 60‐year‐old lowland tropical forest in Panama, Central America. We used litter mixtures representing pioneer and old growth tree species in experimental mesocosms to assess the links between litter types, decomposition rates, and litter arthropod communities. Overall, pioneer species litter decomposed most rapidly and old growth species litter decomposed the slowest but there were clear non‐additive effects of litter mixtures containing both functional groups. We observed distinct arthropod communities in different litter mixtures at 6 mo, with greater arthropod diversity and abundance in litter from old growth forest species. By comparing the decay of different litter mixtures in mesocosms and conventional litterbags, we demonstrated that our mesocosms represent an effective approach to link studies of litter decomposition and arthropod communities. Our results indicate that changes in the functional diversity of litter could have wider implications for arthropod communities and ecosystem functioning in tropical forests.