Publications by authors named "Martin Sorg"

5 Publications

  • Page 1 of 1

Direct pesticide exposure of insects in nature conservation areas in Germany.

Sci Rep 2021 12 16;11(1):24144. Epub 2021 Dec 16.

Nature and Biodiversity Conservation Union (NABU), Charitéstraße 3, 10117, Berlin, Germany.

In Germany, the decline of insect biomass was observed in nature conservation areas in agricultural landscapes. One of the main causal factors discussed is the use of synthetic pesticides in conventional agriculture. In a Germany-wide field study, we collected flying insects using Malaise traps in nature conservation areas adjacent to agricultural land. We used a multi-component chemical trace element analysis to detect 92 common agricultural pesticides in ethanol from insect traps sampled in May and August 2020. In total, residues of 47 current use pesticides were detected, and insect samples were on average contaminated with 16.7 pesticides. Residues of the herbicides metolachlor-S, prosulfocarb and terbuthylazine, and the fungicides azoxystrobin and fluopyram were recorded at all sites. The neonicotinoid thiacloprid was detected in 16 of 21 nature conservation areas, most likely due to final use before an EU-wide ban. A change in residue mixture composition was noticeable due to higher herbicide use in spring and increasing fungicide applications in summer. The number of substances of recorded residues is related to the proportion of agricultural production area in a radius of 2000 m. Therefore, a drastic pesticide reduction in large buffers around nature conservation areas is necessary to avoid contamination of their insect fauna.
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http://dx.doi.org/10.1038/s41598-021-03366-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8677746PMC
December 2021

Reply to Redlich et al.: Insect biomass and diversity do correlate, over time.

Proc Natl Acad Sci U S A 2021 12;118(49)

Institute for Water and Wetland Research, Radboud University, 6525HP Nijmegen, The Netherlands.

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http://dx.doi.org/10.1073/pnas.2114567118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8673471PMC
December 2021

Pooling size sorted Malaise trap fractions to maximize taxon recovery with metabarcoding.

PeerJ 2021 5;9:e12177. Epub 2021 Oct 5.

Centre for Biodiversity Monitoring, Zoological Research Museum Alexander Koenig, Bonn, Germany.

Background: Small and rare specimens can remain undetected when metabarcoding is applied on bulk samples with a high specimen size heterogeneity. This is especially critical for Malaise trap samples, where most of the biodiversity is contributed by small taxa with low biomass. The separation of samples in different size fractions for downstream analysis is one possibility to increase detection of small and rare taxa. However, experiments systematically testing different size sorting approaches and subsequent proportional pooling of fractions are lacking, but would provide important information for the optimization of metabarcoding protocols. We set out to find a size sorting strategy for Malaise trap samples that maximizes taxonomic recovery but remains scalable and time efficient.

Methods: Three Malaise trap samples were sorted into four size classes using dry sieving. Each fraction was homogenized and lysed. The corresponding lysates were pooled to simulate unsorted samples. Pooling was additionally conducted in equal proportions and in four different proportions enriching the small size fraction of samples. DNA from the individual size classes as well as the pooled fractions was extracted and metabarcoded using the FwhF2 and Fol-degen-rev primer set. Additionally, alternative wet sieving strategies were explored.

Results: The small size fractions harboured the highest diversity and were best represented when pooling in favour of small specimens. Metabarcoding of unsorted samples decreases taxon recovery compared to size sorted samples. A size separation into only two fractions (below 4 mm and above) can double taxon recovery compared to not size sorting. However, increasing the sequencing depth 3- to 4-fold can also increase taxon recovery to levels comparable with size sorting, but remains biased towards biomass rich taxa in the sample.

Conclusion: We demonstrate that size fractionation of Malaise trap bulk samples can increase taxon recovery. While results show distinct patterns, the lack of statistical support due to the limited number of samples processed is a limitation. Due to increased speed and lower risk of cross-contamination as well as specimen damage we recommend wet sieving and proportional pooling of the lysates in favour of the small size fraction (80-90% volume). However, for large-scale projects with time constraints, increasing sequencing depth is an alternative solution.
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http://dx.doi.org/10.7717/peerj.12177DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8500090PMC
October 2021

Insect biomass decline scaled to species diversity: General patterns derived from a hoverfly community.

Proc Natl Acad Sci U S A 2021 01;118(2)

Institute for Water and Wetland Research, Radboud University, 6525HP Nijmegen, The Netherlands.

Reports of declines in biomass of flying insects have alarmed the world in recent years. However, how biomass declines reflect biodiversity loss is still an open question. Here, we analyze the abundance (19,604 individuals) of 162 hoverfly species (Diptera: Syrphidae), at six locations in German nature reserves in 1989 and 2014, and generalize the results with a model varying decline rates of common vs. rare species. We show isometric decline rates between total insect biomass and total hoverfly abundance and a scale-dependent decline in hoverfly species richness, ranging between -23% over the season to -82% at the daily level. We constructed a theoretical null model to explore how strong declines in total abundance translate to changing rank-abundance curves, species persistence, and diversity measures. Observed persistence rates were disproportionately lower than expected for species of intermediate abundance, while the rarest species showed decline and appearance rates consistent with random expectation. Our results suggest that large insect biomass declines are predictive of insect diversity declines. Under current threats, even the more common species are in peril, calling for a reevaluation of hazards and conservation strategies that traditionally target already rare and endangered species only.
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http://dx.doi.org/10.1073/pnas.2002554117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7812780PMC
January 2021

More than 75 percent decline over 27 years in total flying insect biomass in protected areas.

PLoS One 2017 18;12(10):e0185809. Epub 2017 Oct 18.

Radboud University, Institute for Water and Wetland Research, Animal Ecology and Physiology & Experimental Plant Ecology, PO Box 9100, 6500 GL Nijmegen, The Netherlands.

Global declines in insects have sparked wide interest among scientists, politicians, and the general public. Loss of insect diversity and abundance is expected to provoke cascading effects on food webs and to jeopardize ecosystem services. Our understanding of the extent and underlying causes of this decline is based on the abundance of single species or taxonomic groups only, rather than changes in insect biomass which is more relevant for ecological functioning. Here, we used a standardized protocol to measure total insect biomass using Malaise traps, deployed over 27 years in 63 nature protection areas in Germany (96 unique location-year combinations) to infer on the status and trend of local entomofauna. Our analysis estimates a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the 27 years of study. We show that this decline is apparent regardless of habitat type, while changes in weather, land use, and habitat characteristics cannot explain this overall decline. This yet unrecognized loss of insect biomass must be taken into account in evaluating declines in abundance of species depending on insects as a food source, and ecosystem functioning in the European landscape.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0185809PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5646769PMC
October 2017
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