Insects associated to ephemeral pools in Huentelauquén (29ºS Coquimbo Region, Chile)

In northern central Chile, ephemeral pools constitute shallow isolated water bodies with a favourable habitat for fauna adapted to seasonal changes. Based on the limited knowledge about the fauna—particularly insects—associated to these ecosystems, the objective of this study was to characterize the richness, composition, structure and similarity of the insect communities associated with ephemeral pools in Huentelauquén (29º S, Coquimbo Region, Chile). By using pitfall traps, 10,762 individuals were captured, represented by 7 orders, 27 families, and 51 species. Coleoptera and Hymenoptera were the best represented orders, with Neuroptera, Orthoptera and Plecoptera being poorly represented groups. The non-parametric estimators evaluated showed wealth values above those observed for all the studied pools, and their accumulation curves suggest the existence of an incomplete species inventory in the studied community. Additionally, the hierarchical and ordering analysis showed groupings of pools located in the northwest and southeast of Huentelauquén. Preliminarily we found a negative correlation between the area of the pools and the richness (species) and abundance of insects. Additional studies (on other arthropod groups and other seasons of the year) could provide a better understanding of the local processes of extinction and colonization of the species inhabiting these fragile coastal environments.

Vertical Stratification of Insect Species Developing in Water-Filled Tree Holes

Forest ecosystems have a distinct vertical dimension, but the structuring of communities in this three-dimensional space is not well understood. Water-filled tree holes are natural microcosms structured in metacommunities. Here, we used these microcosms as model systems to analyze how insect communities and the occurrence and abundance of individual species are influenced by biotic and abiotic microhabitat characteristics, the vertical position of the tree hole, and stand-scale habitat availability. We found that both the characteristics of water-filled tree holes and their insect communities differ significantly between canopy and ground level. Individual insect species showed contrasting responses to the vertical position of the tree holes when important environmental factors at the stand and the tree-hole scale were considered. While some species, such as the mosquito Aedes geniculatus and the beetle Prionocyphon serricornis, decreased in abundance with increasing tree-hole height, the biting midge Dasyhelea sp., the non-biting midge Metriocnemus cavicola and the hoverfly Myiatropa florea increased in abundance. Our results suggest that vertical stratification in forests is most likely driven not only by variation in tree-hole microhabitat properties, i.e., niche separation, but also by individual species traits, such as adult dispersal propensity, food preferences and mating behavior of adult stages, and interspecific competition of larval stages. Therefore, communities of insect species developing in tree holes are likely structured by competition–colonization trade-offs predicted by metacommunity theory.

Competition of insect decomposers over large vertebrate carrion: Necrodes beetles (Silphidae) vs blow flies (Calliphoridae)

Large carrion is inhabited by highly variable and interactive communities of insects. Positive interactions in carrion insect communities have been recently the focus in carrion ecology. By contrast, competition between carrion insects is rather undervalued. Here we provide evidence that blow flies (Calliphoridae) and Necrodes beetles (Silphidae), dominant decomposers of large carcasses in terrestrial habitats, compete over carrion. By reanalysing the results from 90 pig carcasses we demonstrated that the contribution of the flies and the beetles to the decay was negatively related. The greater part of the large carrion pool was monopolised by blow flies, whereas Necrodes beetles abundantly colonized carcasses, on which blow flies were less effective as decomposers. In behavioural assays, we found that adult beetles killed four times more frequently feeding than postfeeding third instar larvae of the flies, with the large decrease in the killing frequency after the larvae reached the age of early third instar. Therefore, adult Necrodes beetles preferentially killed the larvae that were before or in their peak feeding. The study provides evidence that the interaction between blow flies and Necrodes beetles is a combination of indirect exploitative effects of the flies and direct interference effects of the beetles (the mixed competition).

Evergreen Abundance Drives Ground Beetle Diversity And Density In Eastern Temperate Forests

Purpose: Soil insects mediate plant-soil interactions by fragmenting and decomposing litter that forms the base of soil food webs and through predator-prey interactions. Plant communities, in turn, shape soil insect communities via the quality, availability, and diversity of their litters. However, these drivers have rarely been examined in concert even though describing soil insect community patterns is critical for mitigating the effects of global environmental changes. Methods: Here, we evaluated the effects of tree diversity, density, and functional groups on ground beetle (Carabidae) diversity, density, and community composition in four eastern temperate forest sites in the National Ecological Observatory Network. Results Though we expected that higher tree diversity and density would, respectively, lead to higher diversity and density ground beetle communities, we found little evidence to support this hypothesis. Instead, evergreen tree abundance strongly shaped ground beetle diversity, density, and community composition. Specifically, evergreen plots as defined by National Land Cover Database hosted lower density ground beetle communities than deciduous plots. Similarly, ground beetle Shannon diversity and density decreased as the relative abundance of evergreen tree species increased. Conclusions: Although further study is needed to explicitly link litter quality with soil insect communities, the resource environments created by trees with varying leaf habits appear to be a dominant force driving ground beetle community diversity and density patterns.

Heat stress during development makes antlion larvae more responsive to vibrational cues

We investigated the effects of heat stress on the responsiveness to vibrational cues, our measure of perceptual ability, in Myrmeleon bore antlion larvae (Neuroptera: Myrmeleontidae). We reared these trap-building predatory larvae under two heat stress regimes (mild, 30 °C, and harsh, 36 °C), and after they progressed from one instar stage to another, we tested their perceptual ability in common unchallenging conditions. We hypothesized that exposure to the harsh heat stress regime would impose costs resulting in handicapped vibration responsiveness. We found that the harsh heat stress regime generated more stressful conditions for the larvae, as evidenced by increased mortality and postponed molting, and the loss of body mass among larger larvae. Furthermore, among the individuals who remained alive, those originating from the harsh heat stress regime were characterized by higher vibration responsiveness. Our results suggest two not mutually exclusive scenarios. Costly heat stress conditions can sieve out individuals characterized by poor perceptual ability, or surviving individuals can attempt to hunt more efficiently to compensate for the physiological imbalance caused by heat stress. Both of these mechanisms fit into the ongoing debate over how adaptation and plasticity contribute to shaping insect communities exposed to heat stress.

Temporal Variation Dominates in Local Carabid Beetle Communities in Korean Mountains

Spatial and temporal variation in ecological environments may result in spatial and temporal variation in communities. Temporal studies of biodiversity are essential for forecasting future changes in community structure and ecosystem function. Therefore, determining the mechanisms that drive temporal change in communities remains an important and interesting challenge in ecology. We quantified spatial and temporal variations in carabid beetle communities and site-specific environmental factors for 5 years at nine study sites on three mountains in the Baekdudaegan Mountain Range, Korea. Carabid beetle communities exhibited significant temporal variation, which was larger than spatial variations between and within mountains. Environmental factors mostly varied between sites within mountains. Community variation was only weakly associated with environmental factors at wide scales, i.e., between sites on three mountains, but was strongly associated at narrow spatial scales, i.e., between sites within one mountain. Our results indicate that temporal variation in communities occurs in response to variations in the local climate, and that the patterns of temporal variation differ between mountains. Thus, temporal surveys of insect communities and climates at local scales are important for predicting temporal changes in the communities.