Biology subjects

Hoerren, T.

Publications and source records attributed to Hoerren, T..

6 recordsLinked to original sources

bioRxiv2023

Insect biomass of protected habitats under the impact of arable farming in Germany

Five years after the well-known study on insect biomass decline in nature protected habitats in Germany over three decades, the project DINA (Diversity of Insects in Nature protected Areas) has investigated the status of insects in 21 selected nature reserves across Germany in the years 2020 and 2021. We used the same methods and protocols for trapping and measuring the biomass of flying insects as in the mentioned study. Across two seasons, we accumulated a comprehensive data set of 1621 data points of two-week emptying intervals. The measured overall insect biomass remained at low levels and corresponds to the published latest figures from the years 2007-2016. There were no significant regional differences, but biomass was negatively correlated with agricultural production area within 2 km of nature reserves. Differences between the two consecutive years were very likely due to well-known natural fluctuations of insect populations, changes in agricultural cultivation and local weather events. The results show that protected habitats are essential for insects, but not sufficient in their function, and that further steps need to be taken for a better protection and sustainment of insects, which fulfil key functions in many ecosystems.

ecology↗

bioRxiv2022

Development of an insect sample fractionizer for biodiversity research

We describe a new mechanical tool for dividing mixed insects and other invertebrate samples into subsamples. The device enables the division to equal parts by means of a movable hemispherical bowl and a separating disc. Due to the complete stainless steel manufacturing, the sample divider is sterilizable by using chemicals or heating and thus suitable for DNA-based methods. The production of equally sized subsamples is of particular importance for biodiversity studies today, especially when using metabarcoding combined with insect homogenisation for species determination of mixed insect samples. The device allows sub-samples to be analyzed separately using the same or different methods, or getting archived for museal preservation and future research.

ecology↗

bioRxiv2022

It`s raining species: Rainwash eDNA metabarcoding as a minimally invasive method to assess tree canopy invertebrate diversity

O_LIForest canopies are a highly diverse ecosystem, but despite several decades of intense research, there remain substantial gaps in our knowledge of their biodiversity and ecological interactions. One fundamental challenge in canopy research is the limited accessibility of the ecosystem. Consequently, previous studies have relied on the application of either highly invasive methods such as chemical knockdown, or on time-consuming and expensive setups such as canopy walkways or cranes. Therefore, time- and cost-efficient, ideally minimally invasive yet comprehensive applications are required to help close this knowledge gap. High-throughput metabarcoding of environmental DNA (eDNA) collected from water, soil, or air provides a minimally invasive method for biodiversity assessment, yet its potential for canopy biodiversity monitoring has not been explored. C_LIO_LIHerein, we conducted metabarcoding of eDNA washed off the canopy via rainwater to explore its monitoring potential. We placed four 1 m2 rain samplers beneath the canopies of four different tree taxa prior to a major rain event, filtered eDNA from the collected rainwater, and performed cytochrome c oxidase subunit I (COI) metabarcoding to profile the invertebrate community. Additionally, we collected and identified all specimens present in the rainwater for verification. C_LIO_LIWe detected 50 invertebrate species by eDNA metabarcoding, of which 43 were not physically present in the water sample, thus likely representing true canopy biodiversity signals. Furthermore, we observed distinct species occurrence patterns corresponding to the four tree taxa, suggesting that ecological patterns such as host specificity can be assessed using the method. C_LIO_LIIn conclusion, our study provides a proof of principle that rainwash eDNA metabarcoding offers a minimally invasive and comprehensive method for tree canopy diversity monitoring. C_LI

molecular biology↗

bioRxiv2022

A universal insect trait tool (ITT, v1.0) for statistical analysis and evaluation of biodiversity research data

We present a unique data set of trait information for 586 insect families in Central Europe, covering the largest known part of described species (over 34,000 species). Life history information and major functional traits were evaluated with fuzzy coding and weighted according to the number of known species in Germany. An overall analysis of the German insect fauna is given and the data set is exemplarily applied to metabarcoding results of malaise trap samples. Due to the high functional and taxonomic diversity in insects, further developments and refinements of traits to be included will be an ongoing process with advancements of upcoming database versions to be subsequently published.

ecology↗

bioRxiv2022

Recommendations for tissue homogenisation and extraction in DNA metabarcoding of Malaise trap samples

With increased application of DNA metabarcoding in fast and high-resolution biodiversity assessment, various laboratory protocols have been optimised in recent years and their further evaluation is subject of current research. Homogenisation of bulk samples and subsequent DNA extraction from destructed tissue is one way of starting the metabarcoding process. This essential step in the protocol can either be conducted from wet sample material (e.g. bulk insect samples) soaked in fixative or from completely dried individuals. While the latter method appears to produce more consistent results, it is time consuming and more prone to cross-contamination. We tested both homogenisation approaches with regard to time efficiency and biodiversity assessment of complex arthropod bulk samples, in particular how the amount of processed tissue affects taxon recovery. Both approaches reveal similar taxa compositions and detect a similar total OTU diversity in a single extraction reaction. Increased amounts of tissue used in DNA extraction improved OTU diversity detection and recovered particularly specific low-biomass taxa, making this approach valuable for samples with high biomass and/or diversity. Due to less handling time and lower vulnerability for cross-contamination we recommend the processing of wet material when sample homogenisation is applied.

molecular biology↗

bioRxiv2020

Pooling size sorted malaise trap fractions to maximise taxon recovery with metabarcoding

O_LISmall and rare specimens can remain undetected when metabarcoding bulk samples with a high size heterogeneity of specimens. This is especially critical for malaise trap samples, where most of the biodiversity is often contributed by small specimens. How to size sort and in which proportions to pool these samples has not been widely explored. We set out to find a size sorting strategy that maximizes taxonomic recovery but remains highly scalable and time efficient. C_LIO_LIThree 3 malaise trap samples where size sorted into 4 size classes using dry sieving. Each fraction was homogenized and lysed. The corresponding lysates were pooled to simulate samples never sorted, pooled in equal proportions and in 4 different proportions favoring the small size fractions. DNA from the pooled fractions as well as the individual size classes were extracted and metabarcoded using the FwhF2 and Fol-degen-rev primer set. Additionally wet sieving strategies were explored. C_LIO_LIThe small size fractions harbored the highest diversity, and were best represented when pooling in favor of small specimens. Not size sorting a sample leads to a 45-77% decrease in taxon recovery compared to size sorted samples. A size separation into only 2 fractions (below 4 mm and above) can already double taxon recovery compared to not sorting. However, increasing the sequencing depth 3-4 fold can also increase taxon recovery to comparable levels, but remains biased toward biomass rich taxa in the sample. C_LIO_LIWe demonstrate that size fractionizing bulk malaise samples can increase taxon recovery. The most practical approach is wet sieving into two size fractions, and proportional pooling of the lysates in favor of the small size fraction (80-90% volume). However, in large projects with time constraints, increasing sequencing depth can also be an alternative solution. C_LI

molecular biology↗