Understanding how environmental variation influences even cryptic traits is important to clarify the roles of selection and developmental constraints in past evolutionary divergence and to predict future adaptation under environmental change. Female yellow dung flies (Scathophaga stercoraria) typically have three sperm storage compartments (3S), but occasionally four (4S). More spermathecae are thought to be a female adaptation facilitating sperm sorting after mating, but the phenotype is very rare in nature. We manipulated the flies' developmental environment by food restriction, pesticides, and hot temperatures to investigate the nature and extent of developmental plasticity of this trait, and whether spermatheca expression correlates with measures of performance and developmental stability, as would be expected if 4S expression is a developmental aberration. The spermathecal polymorphism of yellow dung fly females is heritable, but also highly developmentally plastic, varying strongly with rearing conditions. 4S expression is tightly linked to growth rate, and weakly positively correlated with fluctuating asymmetry of wings and legs, suggesting that the production of a fourth spermatheca could be a nonadaptive developmental aberration. However, spermathecal plasticity is opposite in the closely related and ecologically similar Scathophaga suilla, demonstrating that overexpression of spermathecae under developmental stress is not universal. At the same time, we found overall mortality costs as well as benefits of 4S pheno- and genotypes (also affecting male siblings), suggesting that a life history trade-off may potentially moderate 4S expression. We conclude that the release of cryptic genetic variation in spermatheca number in the face of strong environmental variation may expose hidden traits (here reproductive morphology) to natural selection (here under climate warming or food augmentation). Once exposed, hidden traits can potentially undergo rapid genetic assimilation, even in cases when trait changes are first triggered by random errors that destabilize developmental processes.

The biodiversity of agricultural land is usually measured via indicator species that can be recorded time- and cost-efficiently. Behind this approach lies the seldom-questioned assumption that these groups of organisms are good at reflecting the overall species diversity of a habitat. We tested this assumption by comparing the diversity of cow-dung insects with that of grasshopper, butterfly, vascular plant and nearby moss and snail communities on 24 pastures on the Swiss Central Plateau. The diversity of the vascular plants and mosses increased with that of the (often herbivorous) butterflies, grasshoppers and snails, both on the sites examined in our study and on those in the wider vicinity. By contrast, the diversity of the dung insects (flies and parasitic wasps) did not correlate with other groups of organisms. Consequently, vascular plants, grasshoppers, butterflies, mosses and snails can represent one another well. This is not, however, the case for dung insects: they, and hence most likely their functions in decomposing dung, are scarcely represented by the commonly used indicators.

Environmental stressors can have unintended negative effects on beneficial organisms. Testing environmental effects of pharmaceutical residues is therefore often mandated in form of single-species ecotoxicological laboratory tests, yet differential sensitivity of species can ultimately disturb the entire community. A more realistic approach is to directly assess toxicity in the field to account for spatio-temporal variation in climate and habitat. We conducted the first field study at the landscape scale, replicated al 24 Swiss farms north of the Alps, to test the impact of a realistically low concentration (6,6 mu g/kg fresh dung) of the popular parasiticide ivermeain on the beneficial cow dung insect community over the season, We found a graded negative impact of ivermectin on many but not all species, with significant reductions in ca. one third of 32 evaluated fly (Diptera) and wasp (Hymenoptera) taxa, No taxon benefited from ivermectin presence. Small hymenopteran parasitoids particularly decreased in numbers (62%), with large dipteran predators (38%) being reduced more than primary coprophagous dung consumers (234), This supports theoretical expectations that the [op trophic levels of a community are particularly vulnerable to environmental disturbance because their numbers tend to be low and their body size large, hut also because pollutants can biomagnify in the food chain. Sensitivity to pollutants may further exhibit a phylogenetic signal. Ivermectin residues thus generally reduced the biodiversity of the dung insect community, but impact varied among farms, years and over the season, being lowest in autumn. We conclude that spatio-temporal replication of such higher-tier field studies is advised to capture the full extent of effects in realistic natural settings, as even low concentrations of a pharmaceutical can have varying impact on the different organisms comprising an ecosystem.

Veterinary medical product residues can cause severe damage in the dung ecosystem. Depending on the manner of application and the time after treatment, the excreted concentration of a given pharmaceutical varies. The popular anthelmintic drug ivermectin can be applied to livestock in several different ways and is fecally excreted over a period of days to months after application. In a field experiment replicated in summer and autumn, the authors mixed 6 ivermectin concentrations plus a null control into fresh cow dung to assess the reaction of the dung insect community. Taxon richness of the insect dung fauna emerging from the dung, but not Hill diversity ((1) D) or the total number of individuals (abundance), decreased as ivermectin concentration increased. Corresponding declines in the number of emerging insects were found for most larger brachyceran flies and hymenopteran parasitoids, but not for most smaller nematoceran flies or beetles (except Hydrophilidae). Parallel pitfall traps recovered all major dung organism groups that emerged from the experimental dung, although at times in vastly different numbers. Ivermectin generally did not change the attractiveness of dung: differences in emergence therefore reflect differences in survival of coprophagous offspring of colonizing insects. Because sample size was limited to 6 replicates, the authors generally recommend more than 10 (seasonal) replicates and also testing higher concentrations than used in the present study as positive controls in future studies. Results accord with parallel experiments in which the substance was applied and passed through the cow's digestive system. In principle, therefore, the authors' experimental design is suitable for such higher-tier field tests of the response of the entire dung community to pharmaceutical residues, at least for ivermectin. Environ Toxicol Chem 2016;35:1947-1952. © 2015 SETAC.

Elevational gradients influence the distribution and abundance of species drastically and can lead to variation in community composition. Although coprophagous flies are of ecological and economic importance, their biodiversity and distribution are largely neglected. We studied the impact of steep elevational gradients and geography on the distribution of sepsid flies in the Swiss Alps. Sepsidae are a family of acalyptrate flies strongly associated with decaying organic matter and vertebrate dung, and characterised by a high extent of sympatry in their breeding substrates. Historical, haphazardly sampled specimens from 116 locations covering an elevational range from 200 to 2000 m were available in ethanol collections of various Swiss museums. Nineteen species encompassing all native genera (Meroplius, Nemopoda, Saltella, Sepsis and Themira) were recorded. Local species richness increased linearly with elevation, while area‐corrected regional species richness of elevational belts increased asymptotically. Species occurring at higher altitudes had lower wing loadings and greater elevational ranges than lowland species, supporting Rapoport's elevational rule. Despite compositional similarities, the sepsid communities of the northern lowlands differed significantly from the alpine sepsid fauna. The southern lowlands were particularly differentiated in community composition due to a number of presumably thermophilic species that predominantly occur south of the Alps. Relative abundances of several species were thus strongly affected by elevation and climatic variables. We illustrate the impact of elevational gradients and geography on a community of closely related, often sympatric species, and discuss potential mechanisms of niche partitioning via temporal succession, thermal adaptation and differential resource use.

Summary The mechanistic basis for and adaptive significance of variation in female sperm storage organs are important for a range of questions concerning sexual selection and speciation, as such variation influences the evolutionary trajectories of male fertilization related traits and may facilitate speciation through its effects on gamete recognition. Female yellow dung flies (Scathophaga stercoraria) usually develop three sperm storage compartments, and this subdivision may be an adaptation for sorting sperm during postcopulatory choice. Using lines artificially selected to express four spermathecae (4s), we explored the fitness consequences of the novel phenotype relative to the naturally prevalent three‐spermatheca (3s) phenotype by manipulating the opportunity for postcopulatory sexual selection (females mated either with three or only one male prior to oviposition). In addition, we examined the developmental plasticity of spermathecal number in response to different larval food environments and estimated its genetic correlation with growth rate. Mating treatments with and without the opportunity for postcopulatory sexual selection revealed no significant fitness differences between alternative spermathecal phenotypes within selection lines despite overall benefits associated with multiple mating, and moderate egg‐to‐adult survival costs in response to artificial selection for 4s. Manipulations of the larval food environment revealed that the expression of 4s is highly plastic and tightly linked to environmental conditions promoting fast somatic growth and development. Likewise, siblings with fast intrinsic (genetic) growth were more likely to express 4s within and across food environments. The present results highlight a great potential for rapid evolutionary change in female sperm storage morphology through indirect selection on life‐history traits, and further suggest genetic assimilation as a potential mechanism facilitating phylogenetic transitions in spermatheca number as frequently observed within the Dipterans.

To register veterinary medicinal products (VMPs) as parasiticides on pastured animals, legislation in the European Union requires an environmental risk assessment to test the potential nontarget effects of fecal residues on dung-dwelling organisms. Products with adverse effects in single-species laboratory tests require further, higher-tier testing to assess the extent of these effects on entire communities of dung-dwelling organisms under more realistic field or semifield conditions. Currently, there are no documents specifically written to assist researchers in conducting higher-tier tests or to assist regulators in interpreting the results of such tests in an appropriate context. Here we provide such a document, written by members of the SETAC Advisory Group DOTTS (Dung Organism Toxicity Testing Standardization) with research experience on dung fauna in central and southern Europe, Canada, Australia, and South Africa. This document briefly reviews the organisms that make up the dung community and their role in dung degradation, identifies key considerations in the design and interpretation of experimental studies, and makes recommendations on how to proceed.

A standardized bioassay using the yellow dung fly, Scathophaga stercoraria L. (Diptera: Scathophagidae), was developed to test the lethal and sublethal toxicity of parasiticide residues in livestock dung. The repeatability of the bioassay was assessed for the parasiticide ivermectin in 13 tests performed by seven laboratories in Germany, the United Kingdom, Switzerland, and Canada. Test results had an acceptable range of heterogeneity. The calculated median effective concentration for 50% (EC50) egg-to-adult mortality was 20.9 +/- 19.1 microg ivermectin/kg dung fresh weight (FW) (mean +/- standard deviation; range, 6.33-67.5 microg/kg). Mortality was not observed below a calculated no-observable-effect concentration (NOEC) of 8.1 +/- 7.7 microg/kg FW. However, prolonged development time (and, in a subset of tests, reduced body size) was observed above a calculated NOEC of 0.8 +/- 0.8 microg/kg FW. An oviposition site choice test revealed that yellow dung fly females do not discriminate among dung of different ivermectin concentrations. Thus, the yellow dung fly is suitably sensitive, and the methods are sufficiently repeatable, to support use of this standardized bioassay by the international community in the registration of new veterinary pharmaceuticals.