Biology subjects

Toepfer, S.

Publications and source records attributed to Toepfer, S..

3 recordsLinked to original sources

bioRxiv2024

Unraveling genetic load dynamics during biological invasion: insights from two invasive insect species

Many invasive species undergo a significant reduction in genetic diversity, i.e. a genetic bottleneck, in the early stages of invasion. However, this reduction does not necessarily prevent them from achieving considerable ecological success and becoming highly efficient colonizers. Here we investigated the purge hypothesis, which suggests that demographic bottlenecks may facilitate conditions (e.g., increased homozygosity and inbreeding) under which natural selection can purge deleterious mutations, thereby reducing genetic load. We used a transcriptome-based exome capture protocol to identify thousands of SNPs in coding regions of native and invasive populations of two highly successful invasive insect species, the western corn rootworm (Chrysomelidae: Diabrotica virgifera virgifera) and the harlequin ladybird (Coccinelidae: Harmonia axyridis). We categorized and polarized SNPs to investigate changes in genetic load between invasive populations and their sources. Our results differed between species. In D. virgifera virgifera, although there was a general reduction in genetic diversity in invasive populations, including that associated with genetic load, we found no clear evidence for purging of genetic load, except marginally for highly deleterious mutations in one European population. Conversely, in H. axyridis, the reduction in genetic diversity was minimal, and we detected signs of genetic load fixation in invasive populations. These findings provide new insights into the evolution of genetic load during invasions, but do not offer a definitive answer to the purge hypothesis. Future research should include larger genomic datasets and a broader range of invasive species to further elucidate these dynamics.

evolutionary biology↗

bioRxiv2022

Laboratory and field trials reveal the potential of a gel formulation of entomopathogenic nematodes as biocontrol against the fall armyworm (Spodoptera frugiperda)

1.The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae) can cause tremendous yield losses in maize. Its invasion into Africa and Asia has led to an enormous influx of insecticides into maize agro-ecosystems. Safe, effective and readily available alternatives are desperately needed. Entomopathogenic nematodes (EPN) are commonly used against soil insect pests, but can also control some above-ground pests. We explored the possibility to control FAW by incorporating EPN into a formulation that can be easily applied into the whorl of maize plants, where the caterpillars mostly feed. We tested this approach in laboratory cage experiments as well as in field trials. In the laboratory, treating maize plants with a low dose of EPN in a carboxymethyl cellulose (CMC) gel formulation (about 3000 infective juveniles per plant), caused 100% mortality of FAW caterpillars and prevented plant damage considerably, whereas EPN applied in water or a surfactant-polymer-formulation (SPF) caused 72% and 94% mortality, respectively. Under field conditions, one-time treatments with EPN applied in water, SPF or CMC gel were all able to prevent significant plant damage, but only the EPN-gel formulation significantly reduced FAW infestation. Notably, the gel formulation was as effective as a standard dose of cypermethrin, an insecticide commonly used against FAW. Repeated applications may be needed to reduce re-infestations by FAW across a whole cropping season depending on the local maize phenology and pest dynamics. These findings demonstrate that EPN are excellent candidates for the biological control of FAW and are a safe and sustainable alternative to chemical insecticides. HighlightsO_LIEntomopathogenic nematodes are highly lethal to fall armyworm caterpillars. C_LIO_LIAppropriate formulation of the nematodes is crucial for above-ground application. C_LIO_LIA gel formulation of entomopathogenic nematodes was as effective as chemical insecticides. C_LIO_LIEntomopathogenic nematodes can be used for the control of fall armyworm in maize. C_LI

ecology↗

bioRxiv2020

Ultra-precise quantification of mRNA targets across a broad dynamic range with nanoreactor beads

Precise quantification of molecular targets in a biological sample across a wide dynamic range is a key requirement in many diagnostic procedures, such as monitoring response to therapy or detection of measurable residual disease. State of the art digital PCR assays provide for a dynamic range of four orders of magnitude. However digital assays are complex and require sophisticated microfluidic tools. Here we present an assay format that enables ultra-precise quantification of RNA targets in a single measurement across a dynamic range of more than seven orders of magnitude. The approach is based on hydrogel beads that provide for microfluidic free compartmentalization of the sample as they are used as digital nanoreactors for reverse transcription, PCR amplification and combined real time and digital detection of gene transcripts. We have applied these nanoreactors for establishing an assay for the detection and quantification of BCR-ABL1 fusion transcripts. The assay has been characterized for its accuracy and linear dynamic range. A comparison of the new method against the current clinical standard procedure with clinical samples from patients with chronic myeloid leukemia (CML) revealed good agreement between the results obtained with the respective method.

molecular biology↗