Biology subjects

Brehm, G.

Publications and source records attributed to Brehm, G..

7 recordsLinked to original sources

bioRxiv2026

UV photogrammetry for transparent and composite surfaces

Transparent and composite surfaces pose a fundamental challenge for stereo photogrammetry: optically smooth glass produces no detectable surface features under visible illumination, making three-dimensional reconstruction impossible without surface preparation. This excludes optical components such as lenses and cover glasses, composite assemblies, and semi-translucent biological specimens from non-contact geometric measurement. Here we show that coherent speckle illumination at 266 nm overcomes this limitation by exploiting wavelength-dependent scatter enhancement, generating sufficient backscattered signal on surfaces that are entirely invisible under visible illumination. We developed a multispectral stereo system and evaluated three illumination modalities under identical acquisition conditions. On transparent glass, both visible modalities produce complete reconstruction failure, recovering only non-transparent holder structures. Ultraviolet speckle illumination at 266 nm enables dense reconstruction of the same surfaces. We demonstrate recovery of an uncoated plano-convex lens with a fitted radius of 30.946 mm and point-cloud standard deviation of 106.5 {micro}m, defect detection on a transparent cover glass without surface preparation, and reconstruction of a semi-translucent biological specimen. On metrology-grade reference objects, ultraviolet speckle achieves a standard deviation of 116 {micro}m and completeness exceeding 93%, approaching the performance of optimised visible structured illumination. These results establish ultraviolet speckle photogrammetry as an enabling approach of optical metrology to otherwise uncooperative surfaces, with relevance to optical manufacturing inspection and biological surface analysis.

biophysics↗

bioRxiv2026

Host-specific and common core microbiota in adult butterflies across continents

1 Abstract The assembly of host-specific microbiota is critical for health and functioning of many insect pollinators. While social pollinators maintain core microbiota through social transmission, the factors driving microbiota assembly in solitary pollinators remain poorly understood. Lepidoptera are an important group of pollinators, but microbiome research has largely focused on their larval stage, while nectar-feeding adults have been widely ignored. Field-based studies of the adult butterfly microbiota are rare and geographically and taxonomically restricted. Here, we characterize the microbiota of adult butterflies from natural environments along elevational and seasonal gradients across two continents spanning the Neotropical and Palearctic realms. Microbiota diversity and composition were primarily explained by host taxonomic identity, whereas geographic location and temperature had little effect. We found high microbial titers and a common core microbiota across seven butterfly subfamilies from temperate and tropical regions. A comparison with sympatric wild bees revealed partial taxonomic overlap but marked distinctions in lactic acid bacteria between Lepidoptera and Hymenoptera. Together, our results demonstrate that host taxonomic identity, rather than environmental drivers, is the dominant force structuring the microbiota of adult butterflies. This highlights that the host-filtering capacity of solitary species has been largely underestimated, challenging previous assumptions that the microbiota of this important pollinator group is primarily environmentally driven and of limited functional significance.

ecology↗

bioRxiv2025

Improving allometric models to estimate the proboscis length of tropical bees

The proboscis length of bees is a key morphological trait shaping communities, pollination networks, and likely their responses to habitat loss. Despite its importance, it is rarely considered in ecological studies because of logistic limitations in obtaining accurate measurements across many different species. In two previous studies, the proboscis length of temperate bee species was estimated based on body size and bee family. However, bee taxa partially occurring in the tropics might deviate from this allometric relationship due to different functional constraints. Thus, we tested if equations developed for temperate bees can accurately predict the proboscis length in Meliponini, Euglossini (both Apidae), and Augochlorini (Halictidae), three ubiquitous and highly important tribes of tropical bees. We measured the intertegular distance (as a proxy of body size measurement) and the proboscis length of 892 specimens of 105 tropical species. We used these measurements to evaluate the previous model and found that its estimations lacked accuracy when applied to tropical bees, particularly to Meliponini and Euglossini. We developed new allometric equations estimating the proboscis length based on the intertegular distance, using (sub-) genera as an additional predictive variable to refine the estimations. We tested our approach by creating a test model for Meliponini, trained with only 80 % of the data, and evaluated this model using the remaining 20 %, resulting in a high accuracy of estimates. Our results shed additional light on the nature of the proboscis length-body size allometric relationship in tropical bees and provide a tool for future studies on the functional ecology of bees and their interactions with plants.

zoology↗

bioRxiv2025

Is blue the most attractive color for bees? Exploring the attractiveness of colors in vane traps

Bees play important roles in shaping ecosystems through processes like pollination. However, their populations are in decline due to habitat degradation and unsustainable agriculture. This study assesses the effectiveness of color traps for bee monitoring in two distinct yet geographically close habitats in "Jenaer Forst" natural reserve in Germany. Over a 23-week period in spring and summer 2023, we tested six trap colors (blue, yellow, white, violet, blue-yellow, and violet-white) and analyzed their performance in terms of bee abundance, diversity, and species composition. Our results indicate that violet and blue-yellow traps captured the highest bee abundance and species richness. While overall bee community composition did not differ significantly between trap colors, specific species showed color preferences. The blue-yellow trap emerged as a versatile option, potentially capturing a diverse range of species through its contrasting colors. Moreover, despite the close proximity of the two sites, differences in community composition suggest that habitat-specific factors influence bee color preferences. Minor habitat changes significantly impacted trap effectiveness, emphasizing the importance of tailored trap designs. These findings highlight the importance of considering both color contrast and habitat context when designing bee monitoring strategies and understanding bee foraging behavior. This study contributes valuable insights to improve trap designs and enhance our understanding of the interactions between bees and their environments.

zoology↗

bioRxiv2025

Do camera light traps for moths provide similar data as conventional funnel light traps?

O_LIInsects are of crucial importance for terrestrial ecosystems but many populations decline rapidly. Conventional collecting methods are usually time-consuming, resulting in a low temporal, spatial and taxonomic resolution of data. Automated camera light traps (CLT) allow non-lethal monitoring of species-rich moths (Lepidoptera) and other nocturnal insects, but so far little is known about their performance compared to conventional collecting methods. C_LIO_LIBy observing the behaviour of moths in previous field work, we hypothesized that CLT perform well in moth groups in which species tend to sit down quietly after approaching the lamp (such as Geometridae) but worse in moth groups in which species are persistently active (such as Sphingidae). C_LIO_LIWe tested the performance of two CLTs, equipped with Sony alpha 7II (24 megapixel sensor) cameras that resulted in images with approx. 420 dpi resolution. The study was carried out in a forested area near Bielefeld in NW Germany for 196 nights in a row from April to September 2023, and photos were taken every two minutes during the night. All macromoths recognizable in the photos were identified and counted individually. We directly compared the data from the CLTs with moth samples obtained from conventional funnel light traps (FLTs) during 12 nights which were spread across the flight season. C_LIO_LIThe resulting 420 dpi images from the CLTs allowed reliable species identification of all observed macromoths with only few exceptions due to technical problems. In direct comparison during 12 nights, CLTs recorded 39 species exclusively, FLTs recorded 48 species exclusively, and 53 species were recorded by both methods equally. During the whole sampling period of 196 nights in a row, a total of 225 moth species were recorded by CLTs. CLTs tended to record Geometridae better than FLTs whereas Sphingidae tended to be undersampled by the new method. Familes differed in the length to which they remained on the screen of the CLTs. C_LIO_LIOur study is the first to systematically compare the methods and it shows that CLTs perform overall very well. Results from CLTs differ to a certain extent from conventional trapping methods because they seem to perform worse in groups with highly active species and perform better in calmer groups like geometrid moths. CLTs are promising devices for insect monitoring since they deliver data with high resolution in time, space and taxonomy. The use of artificial intelligence (AI) for the analysis of images is intended as the next logic step. C_LI

ecology↗

bioRxiv2025

Stratification along tropical forest succession enhances pollinator diversity via functionally unique canopies

Vertical stratification is a prominent driver of biodiversity in forests. As the proportion of successional forests increases worldwide and canopies are lost at a fast pace, it is crucial to understand the role of stratification as a driver of community recovery and ecological processes during succession, particularly for important plant mutualist groups essential for forest recovery. Within a well-resolved chronosequence in the northwestern Ecuadorian rainforest, we compiled an extensive database of over 20,000 diurnal and nocturnal pollinators and 2,000 interactions with plants and examined the interacting effects of recovery age and stratification on pollinator community and interaction network reassembly. In late successional and old-growth forests, stratification was a stronger predictor of pollinator abundance, alpha-diversity, functional richness and beta-diversity than forest legacy. While most groups were strongly associated with canopies (moths, social bees, and nocturnal bees), orchid bees exhibited an inverse pattern, also presenting the strongest functional response to stratification and recovery status. Within the entire chronosequence (0-38 years of recovery, plus old-growth forests), recovery status and stratification, alongside landscape features, acted synergistically as predictors of pollinator community parameters. Although structurally stable across the chronosequence and between strata, Interaction networks were richer and most distinct in canopies, while the highest pollinator and interaction diversity were found in old-growth canopies. In successional forests, networks were only comparable in size to active disturbances and early recovery with both strata combined, whereas complete networks in old-growth forests were more than twice as large as those in other recovery statuses. Our study underlines the importance of stratification in leveraging pollinator diversity during forest succession. By serving as havens for canopy-adapted species, tropical canopies may thus help safeguard pollination processes in disturbed landscapes.

ecology↗

bioRxiv2020

The Coding And Small-Non-Coding Hippocampal Synaptic RNAome

Neurons are highly compartmentalized cells that depend on local protein synthesis. Thus, messenger RNAs (mRNAs) have been detected in neuronal dendrites and more recently also at the pre- and postsynaptic compartment. Other RNA species, such as microRNAs, have also been described at synapses where they are believed to control mRNA availability for local translation. Nevertheless, a combined dataset analyzing the synaptic coding and non-coding RNAome via next-generation sequencing approaches is missing. Here we isolate synaptosomes from the hippocampus of young wild type mice and provide the coding and non-coding synaptic RNAome. These data are complemented by a novel approach to analyze the synaptic RNAome from primary hippocampal neurons grown in microfluidic chambers. Our data show that synaptic microRNAs control almost the entire synaptic mRNAome and we identified several hub microRNAs. By combining the in vivo synaptosomal data with our novel microfluidic chamber system, we also provide evidence to support the hypothesis that part of the synaptic microRNAome may be supplied to neurons via astrocytes. Moreover, the microfluidic system is suitable to study the dynamics of the synaptic RNAome in response to stimulation. In conclusion, our data provide a valuable resource and hint to several important targets for future experiments.

neuroscience↗