Staphylinid Beetles Research Articles

The oldest Micropeplus (Coleoptera, Staphylinidae, Micropeplinae) species from mid-Cretaceous Burmese amber

The oldest species of Micropeplus Latreille (1809), Micropeplus pengweii Jiang, Peng & Wang sp. nov. is described from the mid-Cretaceous Burmese amber. The new species can be clearly attributed in the genus Micropeplus by sharing a lot of obviously similar characters with extant species. The new discovery enriched our knowledge of the biodiversity of staphylinid beetles in the Cretaceous.

Under pressure: force resistance measurements in box mites (Actinotrichida, Oribatida)

BackgroundMechanical defenses are very common and diverse in prey species, for example in oribatid mites. Here, the probably most complex form of morphological defense is known as ptychoidy, that enables the animals to completely retract the appendages into a secondary cavity and encapsulate themselves. The two groups of ptychoid mites constituting the Ptyctima, i.e. Euphthiracaroidea and Phthiracaroidea, have a hardened cuticle and are well protected against similar sized predators. Euphthiracaroidea additionally feature predator-repelling secretions. Since both taxa evolved within the glandulate group of Oribatida, the question remains why Phthiracaroidea lost this additional protection. In earlier predation bioassays, chemically disarmed specimens of Euphthiracaroidea were cracked by the staphylinid beetle Othius punctulatus, whereas equally sized specimens of Phthiracaroidea survived. We thus hypothesized that Phthiracaroidea can withstand significantly more force than Euphthiracaroidea and that the specific body form in each group is key in understanding the loss of chemical defense in Phthiracaroidea. To measure force resistance, we adapted the principle of machines applying compressive forces for very small animals and tested the two ptyctimous taxa as well as the soft-bodied mite Archegozetes longisetosus.ResultsSome Phthiracaroidea individuals sustained about 560,000 times their body weight. Their mean resistance was about three times higher, and their mean breaking point in relation to body weight nearly two times higher than Euphthiracaroidea individuals. The breaking point increased with body weight and differed significantly between the two taxa. Across taxa, the absolute force resistance increased sublinearly (with a 0.781 power term) with the animal’s body weight. Force resistance of A. longisetosus was inferior in all tests (about half that of Euphthiracaroidea after accounting for body weight). As an important determinant of mechanical resistance in ptychoid mites, the individuals’ cuticle thickness increased sublinearly with body diameter and body mass as well and did not differ significantly between the taxa.ConclusionWe showed the feasibility of the force resistance measurement method, and our results were consistent with the hypothesis that Phthiracaroidea compensated its lack of chemical secretions by a heavier mechanical resistance based on a different body form and associated build-up of hemolymph pressure (defensive trade-off).

No evidence for decline of carabid beetles in European and North-American arable fields; a meta-analysis

Recent studies have shown dramatic decline in the abundance and diversity of insects over the last decades, including pollinators, lepidopterans, flying insects, parasitoids or epigeal predators, such as carabid and staphylinid beetles. Many of these studies are based on regional data, therefore it is hard to draw a conclusion about the generality of the reported effects across multiple groups and regions. In this paper we focus on testing the hypothesis of insect decline in annual arable crops over a wide geographical range, using meta-analysis of data on carabid beetles as a model group. We extracted pitfall trap catches and observed species richness from 105 independent publications originating from Europe and North America. Data were from a variety of arable annual crops in 22 countries, and spanned a period of 42 years. As sampling effort varied notably across studies, we standardized catches by trapping effort, and explored different options for calculating trapping effort from data. The data over time did not show any evidence of a decline in carabid numbers nor species caught over the 42 years covered by the dataset. A possible explanation for this finding is that carabid beetles living in these habitats are adapted to periodical disturbance by either withstanding these disturbances on site or by periodically re-colonizing fields from adjacent habitats. Although local decreases in carabid populations are documented in the literature as a result of agricultural intensification or landscape simplification, at the broader geographical scale, such a decline is not supported by the data.

Sown wildflower strips as overwintering habitat for arthropods: Effective measure or ecological trap?

Wildflower strips (WFS) are increasingly commonly adopted measures to promote biodiversity in agro-ecosystems. While their effectiveness in providing floral and other food resources for pollinators and natural enemies has been relatively well studied, much less is known about the value of different types of WFS as overwintering habitat for different functional arthropod groups. Here, we examined arthropod overwintering in WFS of different age compared to winter wheat fields. Moreover, we addressed the largely unexplored question to what extent non-permanent WFS may act as sink or ecological trap, if they attract high numbers of overwintering arthropods but only a low proportion of them survive and successfully emerge due to ploughing of strips during overwintering.Overwintering of all studied arthropod groups including potential pest natural enemies spiders, carabid beetles, staphylinid beetles and different families of pollinating flies was higher in WFS compared to winter wheat crops. Overwintering increased in WFS compared to wheat fields irrespective of WFS age, except for 4 year old WFS in the case of carabid beetles and 1 year old WFS in the case of spiders. While WFS age positively affected spider overwintering, numbers of overwintering pollinating flies and staphylinid beetles did not change significantly with WFS age. Moreover, carabid beetles tended to decline in the four years old WFS compared to younger ones. Ploughing of annual WFS during overwintering significantly reduced the number of successfully emerging arthropods by 59% on average. Detrimental effects were strongest for carabid beetles and spiders (reductions by 67% and 69%, respectively) to their numbers in ploughed WFS being similar to winter wheat fields. Reductions were less severe for pollinating flies and staphylinid beetles (both 47%), with higher numbers emerging from annual WFS compared to winter wheat fields even after ploughing of WFS.We conclude that perennial WFS are valuable overwintering habitats for a range of arthropod taxa across functional groups in arable cropping systems. Distinct responses of different arthropod taxa to WFS age highlight the importance of managing perennial WFS of various successional stages in order to promote overwintering of a broad variety arthropods in agro-ecosystems. Our study raises concerns, however, that annual WFS ploughed during the overwintering period are poor overwintering habitats for arthropods and may even act as ecological traps.

Insects associated with an edible mushroom Pleurotus tuberregium (Basidiomycota): first fact-finding approach in Benin City, Nigeria

Mushroom growers are confronted with insect infestations in Benin City, where the composition of insect taxa associated with an edible mushroom Pleurotus tuberregium was examined for informed management decisions using standard method. Fifteen samples of insects were collected during the duration of sprouting to harvest of the mushroom. Twelve insect taxa were observed on P. tuberregium after being identified to their respective orders and families using an insect identification key. Following three non-parametric estimators (first and second order Jackknife, and Chao estimates), between 76% and 93% of the ‘true taxa richness’ of insects associated with the mushroom were estimated to have been encountered. Of these, Drosophila species (Diptera: Drosophilidae) were the most abundant insects followed by the Staphylinids (Coleoptera: Staphylinidae). Larvae of Drosophila were found feeding within the tissues of infested fruiting bodies of P. tuberregium. Some of the insects found on the mushroom can threaten its commercial farming and growers’ return on investment. The need to prioritise consumer-friendly pest management options as opposed to chemicals was discussed.Keywords: Drosophila species; staphylinid beetles; edible mushroom; insect pests

Behavior and exocrine glands in the myrmecophilous beetle Dinarda dentata (Gravenhorst, 1806) (Coleoptera: Staphylinidae: Aleocharinae).

The nests of advanced eusocial ant species can be considered ecological islands with a diversity of ecological niches inhabited by not only the ants and their brood, but also a multitude of other organisms adapted to particular niches. In the current paper, we describe the myrmecophilous behavior and the exocrine glands that enable the staphylinid beetle Dinarda dentata to live closely with its host ants Formica sanguinea. We confirm previous anecdotal descriptions of the beetle’s ability to snatch regurgitated food from ants that arrive with a full crop in the peripheral nest chambers, and describe how the beetle is able to appease its host ants and dull initial aggression in the ants.

Termitariophily: expanding the concept of termitophily in a physogastric rove beetle (Coleoptera: Staphylinidae)

1. Termitophily in some rove beetles is commonly attributed to the striking termite worker resemblance that is provided by the beetles' hypertrophic (‘physogastric’) abdomen. However, a termite nest may offer to a termitophile additional benefits, such as a continuously repaired shelter.2. This could apply to Corotoca melantho (Aleocharinae: Corotocini), a viviparous obligatory termitophile staphylinid beetle species. While conferring morphological congruence to its host worker termites, its physogastry may impair mobility, leading to vulnerability and the need for a secure environment. It seems plausible to hypothesise that physogastry in C. melantho would imply in interactions between this termitophile and its host termites as well as its host termitarium.3. This study provides evidence to build such a hypothesis by inspecting the morpho‐anatomical reproductive traits of this termitophile. It was found that a gradient of growth stages of embryos and larvae in the oviduct explains physogastry in females while pointing to iteroparity. The asynchronous development of oocytes in females, combined with a full developing sequence of sperm cells indicative of continuous spermatogenesis in males, suggests frequent matings.4. While improving guest–host similarity, physogastry and flightlessness should confer vulnerability to pregnant females, forcing C. melantho to seek close and sheltered environments. These could facilitate the frequent male–female contacts demanded by iteroparity. It is possible, therefore, that physogastry in C. melantho is not only associated with the termites themselves but also with the physical structure of the termitarium. Thus, C. melantho can be hypothesised to be a termitariophile in addition to being a termitophile.

Life as a fortress \u2013 structure, function, and adaptive values of morphological and chemical defense in the oribatid mite Euphthiracarus reticulatus (Actinotrichida)

BackgroundOribatid mites are among the primordial decomposer faunal elements and potential prey organisms in soil. Among their myriad morphological defenses are strong sclerotization and mineralization, cuticular tecta, and the “ptychoid” body-form, which allows to attain an encapsulated, seed-like appearance. Most oribatid mites possess a pair of exocrine glands that produce blends of hydrocarbons, terpenes, aromatics, alkaloids and cyanogenic compounds. Many species evolved “holistic” defensive strategies by combining several morphological and chemical traits.MethodsWe describe the morphological and chemical bases of defense in the ptychoid oribatid Euphthiracarus reticulatus. The functional morphology was investigated with synchrotron X-ray microtomography (SRμCT) and high-speed life-radiography. Gland secretions were collected from 20,000 adult specimens, purified and fractionated by preparative capillary gas chromatography (pcGC) and analyzed by gas chromatography / mass spectrometry (GC/MS), high-resolution mass spectrometry (HRMS), and nuclear magnetic resonance spectroscopy (NMR). The adaptive values of morphological and chemical defenses were estimated in bioassays against three predators: a similar-sized gamasid mite (Stratiolaelaps miles, ca. 0.8 mm, with slender chelicera for piercing membranous cuticular regions), and two larger staphylinid beetles, Stenus juno (ca. 7 mm, bearing a harpoon-like sticky labium and sickle-shaped mandibles) and Othius punctulatus (ca. 14 mm, bearing plesiomorphic chewing mandibles).ResultsThe secretions comprised two components: the diterpene β-springene and a novel compound with a mass of 276 g/mol – eventually elucidated as 2-(but-1-en-1-yl)-4-butylidene-3-(pent-2-en-1-yl)-pentanedial, to which we assign the trivial name δ-acaridial. Upon attacks by S. juno, E. reticulatus reacted quickly: within 150 ms from the first contact the encapsulation was almost completed – less time than the beetle needed to retract the labium and transfer the mite to the mandibles. Chemically-defended specimens of E. reticulatus effectively repelled all predators. After depletion of oil-gland reservoirs, however, O. punctulatus easily fed on the mites while S. miles and S. juno were not able to overcome the morphological barrier of strong cuticle and ptychoid body form.ConclusionSuch an effective, holistic defense strategy, involving both morphological and chemical traits, probably carries high resource-costs, but it allows adult euphthiracaroid mites to occupy an almost “enemy-free space” despite the high diversity of predators in soil.

Behavior and exocrine glands in the myrmecophilous beetle Lomechusoides strumosus (Fabricius, 1775) (formerly called Lomechusa strumosa) (Coleoptera: Staphylinidae: Aleocharinae).

To become integrated into an ant society, myrmecophilous parasites must overcome both the defenses and the communication system of their hosts. Some aleocharine staphylinid beetles employ chemical and tactile strategies to invade colonies, where they later consume ant brood and participate in parasitic trophallaxis with host ants. By producing compounds that both appease their hosts and stimulate adoption, the beetles are able to live in and deposit their own eggs in the well defended ant nest. In the current paper, previous findings on the myrmecophilous behavior and morphological features of the staphylinid beetle Lomechusoides (formerly Lomechusa) strumosus are reviewed and re-evaluated. Hitherto unpublished results concerning the beetles’ ability to participate in the social food flow of their host ants are reported. Furthermore, we present an analysis and documentation of the behavioral interactions between beetles and host ants during the adoption process, and we report new histological and scanning electron microscopic analyses of the exocrine glands and morphological adaptations that underlie the myrmecophilous behavior of L. strumosus. The main features of L. strumosus are compared with those of the staphilinid myrmecophile Lomechusa (formerly Atemeles) pubicollis. The paper concludes with a description of the life trajectory of L. strumosus and presents a brief history and discussion of the hypotheses concerning the evolution of myrmecophily in L. strumosus and other highly adapted myrmecophilous parasites.

Morphology and biology of the flower‐visiting water scavenger beetle genus Rygmodus (Coleoptera: Hydrophilidae)

AbstractHydrophilidae (water scavenger beetles) is well known as an aquatic beetle family; however, it contains ca. 1,000 secondarily terrestrial species derived from aquatic ancestors. The New Zealand endemic genus Rygmodus White is a member of the hydrophilid subfamily Cylominae, which is the early‐diverging taxon of the largest terrestrial lineage (Cylominae + Sphaeridiinae) within the Hydrophilidae. In this paper we report that Rygmodus beetles are pollen‐feeding flower visitors as adults, but aquatic predators as larvae. Based on analyses of gut contents and a summary of collecting records reported on museum specimen labels, adult Rygmodus beetles are generalists feeding on pollen of at least 13 plant families. Rygmodus adult mouthparts differ from those of other (saprophagous) hydrophilid beetles in having the simple scoop‐like apex and mola with roughly denticulate surface, resembling the morphology found in pollen‐feeding staphylinid beetles. Larvae were found along the sides of streams, under stones and in algal mats and water‐soaked moss; one collected larval specimen was identified using DNA barcoding of two molecular markers, mitochondrial cytochrome oxidase 1 (cox1) and nuclear histone 3 (H3). Larvae of two species, Rygmodus modestus and Rygmodus sp., are described in detail and illustrated; they closely resemble ambush‐type predatory larvae of the hydrophilid tribe Hydrophilini in the head morphology. Rygmodus is the only known hydrophilid beetle with adults and larvae inhabiting different environments.

Agri‐environmental schemes promote ground‐dwelling predators in adjacent oilseed rape fields: Diversity, species traits and distance‐decay functions

Abstract Rising demands for agricultural products and high environmental costs of intensive agriculture reinforce the need for ecological replacements in agricultural management. In Europe, agri‐environmental schemes (AES) are implemented to enhance species richness and provision of ecosystem services, but the effectiveness of different AES types and the spatial extent of possible beneficial effects are little understood. In this study, we assessed the effects of different AES types on diversity, species traits and distance‐decay functions of ground‐dwelling predators in adjacent crop fields. On 31 study sites with winter oilseed rape (OSR) adjacent to four types of AES differing in management intensity and habitat age, we recorded ground‐dwelling predators (carabid beetles, staphylinid beetles and spiders) during OSR growth from April to July. Effects of the AES on species richness, activity densities and different traits of these taxa were examined with transects of pitfall traps running along a continuous distance gradient from the AES across the habitat border into the OSR fields. Ground‐dwelling predator communities benefitted similarly from the different AES types. In adjacent OSR, activity densities, carabid species richness and the proportion of predatory carabid beetles declined from the field edge, while mean body size increased. Adjacent AES increased the proportion of predatory species and simultaneously decreased the proportion of granivorous or frugivorous species in adjacent OSR fields. Synthesis and applications. Our results indicate a beneficial effect of adjacent agri‐environmental schemes (AES) on ground‐dwelling predators in oilseed rape (OSR), mostly irrespective of agri‐environmental schemes type and therefore management intensity and habitat age. The short‐ranged distance‐decay effects on natural enemies in oilseed rape underpin that a strategic spatial placement of agri‐environmental schemes in agricultural landscapes is required to maximize biological pest control. This could help replace anthropogenic input in modern agriculture and secure adequate yields.

Cypha norvegica nov. sp. (Coleoptera, Staphylinidae) described from Norway.

A new staphylinid beetle, Cypha norvegica nov.sp., is described, illustrated and distinguished from similar species within the genus. The type specimens were collected, when swarming, before sunset in an extensively managed grassland in Vågå municipality, Oppland in Norway.

Habitat heterogeneity induces rapid changes in the feeding behaviour of generalist arthropod predators.

The “habitat heterogeneity hypothesis” predicts positive effects of structural complexity on species coexistence. Increasing habitat heterogeneity can change the diversity (number of species, abundances) and the functional roles of communities. The latter, however, is not well understood as species and individuals may respond very differently and dynamically to a changing environment.Here, we experimentally test how habitat heterogeneity affects generalist arthropod predators, including epigaeic spiders, carabid and staphylinid beetles, under natural conditions by assessing their diversity and directly measuring their trophic interactions (which provide a proxy for their functional roles). The experiment was conducted in spring barley fields in Southern Sweden where habitat heterogeneity was manipulated by increasing within‐field plant diversity.Increased habitat heterogeneity triggered rapid changes in the feeding behaviour of generalist predators characterized by lower trophic specialization at both network (H2’, degree of interaction specialization in the entire network) and species level (d’, degree of interaction specialization at the species level). We presume that this is because spatial separation resulted in relaxed competition and allowed an increased overlap in resources used among predator species. Predators collected from heterogenous habitats also showed greater individual‐level dietary variability which might be ascribed to relaxed intraspecific competition.Our results provide conclusive evidence that habitat heterogeneity can induce rapid behavioural responses independent of changes in diversity, potentially promoting the stability of ecosystem functions. A plain language summary is available for this article.

Tachyporus nitidulus (Fabricius, 1781) (Coleoptera, Staphylinidae, Tachyporinae): first record from the state of Florida, USA

The range of the staphylinid beetle Tachyporus nitidulus (Fabricius, 1781) (Coleoptera, Staphylinidae, Tachyporinae) is extended to include the state of Florida, USA. The record is based on a single female specimen collected via Malaise trap in a rural yard in Baker County, Florida in 2007.

Army imposters: diversification of army ant-mimicking beetles with their Eciton hosts

Colonies of neotropical army ants of the genus Eciton Latreille offer some of the most captivating examples of intricate interactions between species, with hundreds of associated species already described in colonies of Eciton burchellii Westwood. Among this plethora of species found with Eciton colonies, two genera of staphylinid beetles, Ecitomorpha Wasmann, and Ecitophya Wasmann, have evolved to mimic the appearance and parallel the colouration of the most abundant ant worker cast. Here, we study for the first time the association of these ant-mimicking beetles with their ant host in an evolutionary and population genetics framework. The central emphasis is on colonies of E. burchellii, the only Eciton species that harbours both genera of ant-mimicking beetles. Phylogenetic and population structure analyses using the same mtDNA COI region (802 bp) for ants and beetles indicated that speciation patterns of the myrmecophiles were congruent with specialization to a particular Eciton (sub)species. Therefore, current taxonomic treatments of Eciton and its Ecitomorpha and Ecitophya associates need revision. Molecular clock analyses suggested that diversification of the Eciton hosts pre-date that of their guests, with a possible earlier association of Ecitophya (found with a large number of Eciton species) than with Ecitomorpha (found only with E. burchellii colonies). Population-level analyses revealed that patterns of diversification for the myrmecophiles are also consistent with specialisation to a particular host across broad geographical areas but not at small geographical scales, with gene flow within each species found between host colonies, even across landscape features that are strong barriers for Eciton female-mediated gene flow.

Wood-inhabiting insects can function as targeted vectors for decomposer fungi

Abstract Most wood-inhabiting fungi are assumed to be dispersed primarily by wind, with the exception of a few species involved in mutualistic relationships with insects. In this study we tested whether several species of wood-inhabiting insects can function as dispersal vectors for non-mutualistic fungi, which would indicate that wood-inhabiting fungi can benefit from targeted animal-mediated dispersal. We sampled wood-inhabiting beetles (Coleoptera) from freshly felled wood experimentally added to forests and used DNA metabarcoding to investigate the fungal DNA carried by these insects. Staphylinid beetles rarely contained fungal DNA, while Endomychus coccineus, Glischrochilus hortensis and Glischrochilus quadripunctatus frequently carried fungal DNA with a composition specific to the insect taxon. A large proportion of the obtained fungal sequences (34%) represented decomposer fungi, including well-known wood-decay fungi such as Fomitopsis pinicola, Fomes fomentarius, Trichaptum abietinum and Trametes versicolor. Scanning electron microscopy further showed that some of the fungal material was carried as spores or yeast cells on the insect exoskeletons. Our results suggest that insect-vectored dispersal is of broader importance to wood-inhabiting fungi than previously assumed.

Riverine fen restoration provides secondary habitat for endangered and stenotopic rove beetles (Coleoptera: Staphylinidae)

Abstract Peatlands have undergone dramatic changes through anthropogenic activities in the last centuries, causing a substantial loss of fen‐specific biodiversity. Therefore, restoration of already degraded stands is an important conservation issue. The effectiveness of fen restoration was evaluated through rewetting in the valley of the river Peene, NE Germany, by comparing three fen types: drained fens, rewetted fens, and near‐natural fens. Rove beetles (Coleoptera: Staphylinidae) were used as indicators, comprising an ecologically important yet understudied insect group. 5,398 individuals from 121 staphylinid species were recorded by 30 pitfall traps per fen type, which were biweekly emptied between April and October 2012, and related to environmental parameters. Rove beetle assemblages differed markedly between fen types. Community structure was affected by peat degradation, the extent of organic matter, water level, and vegetation height. Fen rewetting favoured the establishment of a distinct, species‐rich beetle community within 15 years only, caused by an increase in hygrophilous wetland species partially replacing generalists. Nevertheless, this time span was not sufficient to restore communities characteristic for near‐natural fens, which harboured several particularly sensitive species that were not found on rewetted fens. Rewetting provided suitable habitats for a substantial number of stenotopic and threatened staphylinid beetles. Thus, the protection of pristine habitats along with restoration measures are both important strategies in peatland conservation.

Species trees, temporal divergence and historical biogeography of coastal rove beetles (Coleoptera: Staphylinidae) reveal their early Miocene origin and show that most divergence events occurred in the early Pliocene along the Pacific coasts.

We investigated the species trees, temporal divergence and historical biogeography of Emplenota Casey and Triochara Bernhauer (ET clade hereafter), subgenera of the Aleochara coastal staphylinid beetles, to determine their place of origin. We explored a multilocus dataset to infer gene trees and species trees based on traditional concatenated and multispecies coalescent-based approaches using both model- (maximum likelihood and Bayesian) and parsimony-based methods. The multilocus dataset comprised DNA sequences from five nuclear genes (ArgK, CAD, EF1-α, wg and 28S) and three mitochondrial genes (COI, COII and 16S). *BEAST analysis according to a coalescent-based approach resolved the following phylogenetic relationships: ((A.trisulcata (A.nubis+A.zerchei)) (A.obscurella ((A.pacifica (A.curtidens + A.litoralis)) (A.hayamai (A.yamato (A.fucicola (A.segregata+A.puetzi))))))). Using a relaxed molecular clock, we reconstructed a time-calibrated phylogeny for this group. Furthermore, to account for the historical biogeography of the ET clade at the ages of major divergences, we investigated the ancestral area based on a time-calibrated phylogeny. Biogeographical analyses suggested that the ancestor of the ET clade was widely distributed along the eastern and western Palearctic and the western Nearctic coasts in the early Miocene. According to reconstruction of the ancestral area, one dispersal and three vicariance events were required, and the analyses indicated that vicariance events were important in shaping its current distribution patterns. Most of the divergence events occurred in the late Miocene and early Pliocene along the Pacific coasts, and the East Asian seacoasts harboured the most species-rich fauna, including eight of the 13 species in the ET clade.

Attack and defense in a gamasid-oribatid mite predator-prey experiment – sclerotization outperforms chemical repellency

Oribatid mites represent a diverse group of soil micro-arthropods. They have evolved a broad range of defensive chemical and morphological traits (e.g. sclerotization, ptychoidy, biomineralization). Chemical defense, rather than sclerotization, can provide protection against large predators (staphylinid beetles) and many oribatid mite species are also well protected against gamasid soil mites using morphological traits (enemy-free-space hypothesis). However, since predatory mites and staphylinid beetles have different types of attacking and feeding, the adaptive values of chemical and morphological traits might differ accordingly. We used the oribatid model species Archegozetes longisetosus Aoki and the common gamasid mite Stratiolaelaps miles Berlese in a predator-prey experiment. We tested for effects of chemical defense (treatments with and without oil gland secretions) and sclerotization (treatments with unsclerotized tritonymphs and sclerotized adults) in an orthogonal design. In contrast to attacks by large predators, chemical defense was mostly ineffective against gamasid mites. Sclerotization, however, had a positive effect. Hence, in a natural environment with diverse types of predators, the enemy-free space seems only realizable by combinations of chemical and morphological protective traits.

Microhabitat heterogeneity promotes soil fertility and ground-dwelling arthropod diversity in Mediterranean wood-pastures

Mediterranean wood-pastures are extensive agroforestry systems that hold great ecological, social and cultural values, which consist of mixtures of grassland, scattered trees and shrubs, primarily used for livestock grazing. For centuries, low-intensity management in these landscapes has resulted in multiple microhabitats that favour biodiversity and are considered key elements for the long-term persistence of wood-pastures. However, the relative contribution of each microhabitat type to wood-pasture biodiversity and functioning remains poorly studied. We investigated the impact that different wood-pasture microhabitats have on soil chemical fertility and the decomposition food web. We analysed the two main microhabitats that make wood-pastures up – open grasslands and isolated trees – and three additional “litter-trapping” microhabitats – shrubs scattered in the grassland matrix, canopied shrubs and piles of pruning debris—in terms of soil chemical properties (organic matter content, total N, C:N ratio, available P, and exchangeable base cations), collembolan and dipteran (mostly detritivores) abundance, and carabid (seed-eaters and predators) and staphylinid (mostly predators) beetle abundance, body size, biomass, species richness and composition. Grasslands were the most different microhabitats, with the lowest soil nutrient content and particular carabid and staphylinid species composition. Trees had the highest soil fertility levels and abundance of Diptera and staphylinids, and held unique staphylinid assemblages. “Litter-trapping” microhabitats had medium to high soil nutrient values and shared a distinct staphylinid assemblage compared to grasslands and trees. Besides, scattered shrubs provided shelter for large-sized carabid and staphylinid predators, while canopied shrubs held the highest carabid abundance and biomass. “Litter-trapping” microhabitats retained tree leaves that would otherwise be lost to the wood-pasture, recovering nutrients to the system, and provided new habitat, shelter and food for detritivores and unique predator assemblages. “Litter-trapping” microhabitats thus enhanced soil fertility and the decomposition process, at the same time as increased the abundance and diversity of the communities of ground-dwelling detritivores and predators inhabiting wood-pastures. These findings confirmed that microhabitat heterogeneity resulting from low-intensity management is essential to maintain both the primary production and the biodiversity conservation value of wood-pastures.