Michael Heethoff

Technische Universität Darmstadt | TU · Animal Evolutionary Ecology

Significance Hydrogen cyanide (HCN) is highly volatile and among the most toxic substances known, being lethal to humans at a dosage of 1–2 mg/kg body weight. HCN blocks the respiratory chain and prevents aerobic organisms from using oxygen. In nature, HCN is produced by numerous plants that store it mainly as glycosides. Among animals, cyanogenesi...

Compositional data are commonly used in chemical ecology to describe the biological role of chemical compounds in communication, defense or other behavioral modifications. Statistical analyses of compositional data, however, are challenging due to several constraints (e.g., constant sum constraint). We use an ontogenetic series of defensive gland s...

Morphological and chemical defences are widespread anti-predator mechanisms in most domains of life, and play an important role in understanding predator–prey interactions. Classical concepts of dynamical protection (‘inducible defence’) include the morphological changes in certain crustaceans or the production of chemicals in many plants. Permanen...

There is a long-standing controversial about how parthenogenetic species can be defined in absence of a generally accepted species concept for this reproductive mode. An integrative approach was suggested, combining molecular and morphological data to identify distinct monophyletic entities. Using this approach, speciation of parthenogenetic lineag...

Insects evolved various modifications to their mouthparts, allowing for a broad exploration of feeding modes. In ants, workers perform non-reproductive tasks like excavation, food processing, and juvenile care, relying heavily on their mandibles. Given the importance of biting for ant workers and the significant mandible morphological diversity acr...

Chewing with the mandibles is a food processing behavior observed in most current insect lineages. Mandible morphology has an essential role in biting behavior and food processing capacity. However, the mandible cuticle can have regional differences in its mechanical properties, associated or not with the accumulation of elements that increase cuti...

Climate change is enhancing the annual mean temperature and the risk for droughts and natural disasters. Hot and dry summers not only have a negative impact on forest performance, but also affect fundamental ecosystem processes such as litter decomposition and nutrient cycling and the organisms involved. Oribatid mites are sexually or parthenogenet...

Intensive land use has been shown to alter the composition and functioning of soil communities. Due to their low dispersal ability, oribatid mites are particularly vulnerable to land-use intensification and species which are not adjusted to management-related disturbances become less abundant. We investigated how different land-use parameters in fo...

We present Biomedisa, a free and easy-to-use open-source online platform developed for semi-automatic segmentation of large volumetric images. The segmentation is based on a smart interpolation of sparsely pre-segmented slices taking into account the complete underlying image data. Biomedisa is particularly valuable when little a priori knowledge i...

Temperature influences all biochemical and biophysiological processes within an organism. By extension, it also affects those ecological interactions that are mediated by gland-produced chemical compounds, such as reservoir-based chemical defense. Herein, we investigate how environmental temperature affects the regeneration of defensive secretions...

The ability to synthesize simple aromatic compounds is well known from bacteria, fungi and plants, which all share an exclusive biosynthetic route—the shikimic acid pathway. Some of these organisms further evolved the polyketide pathway to form core benzenoids via a head-to-tail condensation of polyketide precursors. Arthropods supposedly lack the...

The fatty acid (FA) composition of lipids in animals is influenced by factors such as species, life stage, availability and type of food, as well as the ability to synthesize certain FAs de novo. We investigated the effect of starvation on the neutral lipid (NLFA) and phospholipid (PLFA) fatty acid patterns of the oribatid mite Archegozetes longise...

One of the largest species in its genus, Odontomachus davidsoni Hoenle, Lattke & Donoso, sp. nov. is described from workers and queens collected at lowland forests in the Chocó-Darién bioregion in coastal Ecuador. The workers are characterized by their uniform red coloration, their large size (16–18 mm body length), and their frontal head striation...

Numerous animal species use defense mechanisms such as chemical secretion to defend against attacks of predators. Although defense mechanisms have the potential to considerably change the dynamics and stability of a system, few theoretical studies exist. In this paper, we focus on predator-prey systems with reservoir-based chemical defense, which i...

Food webs in soil differ fundamentally from those above ground; they are based on inputs from both living plants via root exudates, and from detritus, which is a complex mixture of fungi, bacteria and dead plant remains. Trophic relationships are difficult to disentangle due to the cryptic lifestyle of soil animals and inevitable microbial contribu...

The rove beetle genus Stenus has experienced a tremendous radiation, comprising > 3000 species widely distributed throughout the world. Its evolutionary success can be partly attributed to specific morphological features, two of which will be in the focus of this contribution: (1) the labium, or lower lip, is modified into a prey-capture apparatus...

Background Trait based functional and community ecology is en vogue. Most studies, however, ignore phenotypical diversity by characterizing entire species considering only trait means rather than their variability. Phenotypical variability may arise from genotypical differences or from ecological factors (e.g., nutritionally imbalanced diet), and t...

Size scaling phenomena occur on different levels, from organisms to ecosystems. In predictive ecology, empirical data on body size relation have been used for decades to explain large-scale temporal and spatial patterns. More recently, community ecologists have started to use abundance-weighted mean body sizes as a tool to predict changes in specie...

Background The use and partitioning of trophic resources is a central aspect of community function. On the ground of tropical forests, dozens of ant species may be found together and ecological mechanisms should act to allow such coexistence. One hypothesis states that niche specialization is higher in the tropics, compared to temperate regions. Ho...

Table S3. Principal component analysis and Envfit of ant species × baits × NLFAs in Brazil and Germany.

Fig. S1. Incidence of ant species in baits and pitfalls in Brazil (a) and Germany (b). Incidence means the number of sample points where a species was recorded using each method. The dashed lines indicate similar expected incidences, taking into account the total number of incidences for each method (mBR = 1.4, mGE = 0.8).

Table S2. SIMPER analysis for ant fatty acids in Brazil and Germany. NLFAs are ordered by decreasing contribution towards dissimilarity between sites (Bray-Curtis). Asterisks indicate statistically significant differences.

Bait composition and display.

Table S1. Incidence of species recorded in this work and labels used in plots.

Background Oribatid 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...

Oribatid mites are abundant and diverse decomposers in almost all terrestrial microhabitats, especially in temperate forests. Although their functional importance in the decomposition system in these forests has been investigated, spatio-temporal patterns of oribatid mite communities inhabiting different microhabitats have largely been neglected. T...

Species abundances (individuals/kg dry weight) in the microhabitats moss, dead wood (dw) and litter from January to December 2016

Humidity niche of 55 oribatid mite taxa Numbers in brackets indicate the months of occurrence. Symbols denote means, while error bars stand are the standard deviation (SD). Red line indicates the annual mean air temperature. Asterisks indicate different significant levels: *, P < 0.05, **, P < 0.01; ***, P < 0.001.

Statistical results of the temperature occurrence niche analysis μi(ϑ), environmental occurrence niche for air temperature; SD, standard deviation of μi(ϑ).

Statistical results of the humidity occurrence niche analysis μi (RH), environmental occurrence niche for air humidity; SD, standard deviation of μi (RH).

Dry weights (gram) for ten replicates of dead wood, moss and litter from January to December 2016

Digitization of natural history collections is a major challenge in archiving biodiversity. In recent years, several approaches have emerged, allowing either automated digitization, extended depth of field (EDOF) or multi-view imaging of insects. Here, we present DISC3D: a new digitization device for pinned insects and other small objects that comb...

The parthenogenetic trhypochthoniid oribatid mite Archegozetes longisetosus serves as a model organism. Numerous studies have investigated different aspects of its life history and nutritional biology, yet several results remain contradictive. To clarify effects of nutrition on life history parameters, we set up a large scale experiment with ten fo...

Most oribatid mites are opportunistic feeders with a broad variety of different food sources. However, preferences for certain food such as dark pigmented fungi, led to the 'choosy generalist'-hypothesis. The mechanisms behind this idea and whether oribatid mites have an innate or learned preference for food are unknown. We used Archegozetes longis...

This study investigates sex ratios of oribatid mite species and oribatid mite assemblages in different forest microhabitats (dead wood, grass sod, moss, lichen litter, tree bark) to identify possible factors driving sex ratio dynamics. We considered 46,320 individuals belonging to 47 species, and analyzed data on numbers of sexual and parthenogenet...

Diplo-diploid parthenogenesis (thelytoky) is a widespread phenomenon in the mite taxon Sarcoptiformes, and is unusually frequent in the suborder Oribatida, where it characterizes almost 10% of extant species, including whole genera and families. Based on molecular and cytological data, terminal fusion automixis with an inverted meiotic sequence bas...

Reservoir-based chemical defense (= reducible defense) is a widespread mechanism to repel predators in many invertebrates. We investigated the influence of macronutrients on the availability and regeneration of defensive secretions and parametrize a theoretical functional response model for reducible defense to predict nutritional effects on predat...

Modern applications for analysing 2D/3D data require complex visual output features which are often based on the multi-platform OpenGL® API for rendering vector graphics. Instead of providing classical workstations, the provision of powerful virtual machines (VMs) with GPU support in a scientific cloud with direct access to high performance storage...

At the basis of a trophic web, coprophagous animals like dung beetles (Scarabaeoidea) utilize resources that may have advantages (easy gain and handling) as well as drawbacks (formerly processed food). Several studies have characterized the nutrients, e.g. C/N ratios and organic matter content, for specific types of dung. However, a comparative app...

Beamtime and resulting SRμCT data are a valuable resource for researchers of a broad scientific community in life sciences. Most research groups, however, are only interested in a specific organ and use only a fraction of their data. The rest of the data usually remains untapped. By using a new collaborative approach, the NOVA project (Network for...

Biomarkers (e.g. fatty acids, amino acids, stable isotopes, and molecular barcodes) have become increasingly important for investigating food web structure and nutrient flow in soil ecosystems. While the biomarker function of fatty acids has been investigated for some soil animal taxa (e.g. collembolans and nematodes), their role in soil-dwelling o...

Modern applications for analysing 2D/3D data require complex visual output features which are often based on the multi-platform OpenGL® API for rendering vector graphics. Instead of providing classical workstations, the provision of powerful virtual machines (VMs) with GPU support in a scientific cloud with direct access to high performance storage...

Background: Trophic interactions are a fundamental aspect of ecosystem functioning, but often difficult to observe directly. Several indirect techniques, such as fatty acid analysis, were developed to assess these interactions. Fatty acid profiles may indicate dietary differences, while individual fatty acids can be used as biomarkers. Ants are am...

The ecological interactions that occur in and with soil are of consequence in many ecosystems on the planet. These interactions provide numerous essential ecosystem services, and the sustainable management of soils has attracted increasing scientific and public attention. Although soil ecology emerged as an independent field of research many decade...

The Biomedical Image Segmentation App (Biomedisa) was developed as a semi-automatic tool for improving and accelerating the tedious manual segmentation of computed x-ray tomographic images. It is based on a parameter-free and highly scalable diffusion algorithm, making it easy to use and facilitating the analysis of even large tomographic data sets...

The so-called “glandulate Oribatida” (including Astigmata) possess large opisthonotal oil glands, which produce semiochemicals as potent agents for chemical defence against predators (allomones) as well as for intraspecific communication (pheromones). The oil gland reservoirs and their contents remain with shed exuviae, so secretions need to be syn...

Members of the genus Stenus (Coleoptera, Staphylinidae) possess a unique adhesive labial prey-capture apparatus as an adaptation to their predatory behaviour. In order to examine the relationships between the morphology of the prey-capture apparatus, its adhesive performance and the prey-capture success, we combined force measurements, morphologica...