Biology subjects

Pettrich, L. C.

Publications and source records attributed to Pettrich, L. C..

3 recordsLinked to original sources

bioRxiv2026

Panagrolaimus einhardi sp. nov. and two sisters of fortune

Identifying nematodes to the species level is known to be complicated due to their morphological plasticity and limited number of taxonomically important characters. This is especially apparent in the genus Panagrolaimus, which comprises many cryptic species that are morphologically difficult to distinguish but differ genetically. These roundworms are particularly notable for their adaptation to extreme environments that are inhospitable to many other forms of life. Traditional morphological identification methods often fail at distinguishing genetically divergent populations due to high morphological plasticity in Panagrolaimus, limiting the efficacy of species discovery. High-quality genome assemblies overcome these challenges, offering a comprehensive blueprint of an organisms genetic structure that can be used for species identification. The analysis of ultra-conserved elements across multiple loci harvested from genome assemblies provides robust phylogenetic resolution. In this study, we integrate genome sequencing, ultra-conserved element analysis, and morphological assessment to identify and describe three novel species: Panagrolaimus einhardi sp. nov., formerly Panagrolaimus sp. ES5 from Germany; Panagrolaimus shuimeiren sp. nov. from the Namib Desert; and Panagrolaimus nebliphilus sp. nov. from the Atacama Desert. P. einhardi sp. nov. is named after Prof. Einhard Schierenberg, a renowned expert in roundworm development and cherished member of the nematode community, who isolated this species himself. All three species originate from different geographical locations, and their respective identification are supported by high-quality genome assemblies from either PacBio HiFi or Oxford Nanopore long-read data. The P. einhardi sp. nov. genome was scaffolded using Hi-C technology, which resulted in a 116 Mb collapsed assembly composed of 44 scaffolds (N50: 28 Mb). P. shuimeiren sp. nov. has an assembly size of 69 Mb with 49 scaffolds and a N50 of 13 Mb. P. nebliphilus sp. nov. assembly is 70 Mb with 24 scaffolds (N50: 13 Mb). The capacity of Panagrolaimus to adapt to extreme environments is driving research into their survival mechanisms, requiring comprehensive genomic resources. By combining morphology and genomics, we can gain a more comprehensive understanding of the rich biological diversity in lineages with numerous cryptic species, such as the Panagrolaimidae, thereby clarifying relationships where morphological data alone are ambiguous or confounded.

zoology↗

bioRxiv2025

Influence of geography, seasonality and experimental selection on Chironomus riparius recombination rates

BackgroundUnderstanding recombination rates is crucial in evolutionary biology, as recombination shapes genetic diversity, natural selection, and adaptation. We investigated recombination rate variation in Chironomus riparius across different latitudes, seasons, and experimental treatments using Pool-seq data from five studies and the ReLERNN neural network-based method. We examined its relationship with genetic diversity, GC content, and FST, assessing causality through structural equation modeling. ResultsIn natural populations, recombination rates showed no clear latitudinal pattern, likely due to interactions between climate-driven selection and regional environmental heterogeneity. However, seasonal variation was evident, with higher recombination rates in autumn than winter, possibly due to temperature-induced plasticity or seasonal bottlenecks. A cold snap in March 2018 triggered a sharp recombination increase, potentially suggesting a stress-induced adaptive response. In experimental populations, thermal regimes had no direct effect on recombination, but adaptation to lab conditions was significant. Environmental stressors produced distinct responses: microplastic exposure reduced recombination genome-wide, likely due to stress-induced DNA repair prioritizing genome integrity, while cadmium exposure generally suppressed recombination. ConclusionsOur findings reveal recombination as a highly dynamic process influenced by environment, selection, and genetic background, underscoring the importance of the context in shaping genomic architecture under both natural and experimental conditions.

evolutionary biology↗

bioRxiv2024

The interplay of recombination landscape, a transposable element and population history in European populations of Chironomus riparius

Genome resolution is often constrained for non-model species. This can be challenging for population genomic studies as estimations are highly dependent on the quality of the reference genome. This is the case for population history inferences where accuracy relies on the correct detection of single-nucleotide polymorphisms (SNPs) and accurate recombination rates. Here, we utilize a novel long-read genome assembly of Chironomus riparius with high resolution at a chromosome-scale and reanalyse Illumina resequencing data of five European populations. With the model MSMC2, new population demographies were inferred and compared to an older study based on a fragmented genome. Assembly contiguity and completeness led to an increase in accuracy of past demography, suggesting the onset of divergence of an ancestral population between late Pleistocene and early Holocene. These estimates are additionally supported by paleotemperature data, which reveal significant climate shifts in Central Europe during these times. Recombination severely influences population history estimates. With the new reference genome, it was possible to resolve the recombination landscape on the genome-wide scale across different populations using the tool iSMC. Recombination and the dispersal of transposable elements (TEs) in the genome are suspected to influence each other. One TE, known as Cla-element, is suspected to be involved in the divergence of the different C. riparius populations. As it seems to be highly dynamic in the genome, its potential impact on the recombination landscape was explored. No global pattern could be detected which demonstrated a higher resistance of the recombination landscape to the impact of repetitive elements on genome integrity.

genomics↗