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Influence of geography, seasonality and experimental selection on Chironomus riparius recombination rates
Summary
Researchers studied how geography, season, and experimental conditions affect genetic recombination rates in the midge Chironomus riparius, an organism commonly used in ecotoxicology studies including microplastic research. Using pooled DNA sequencing and neural network analysis, they found that experimental conditions in the lab had a much larger effect on recombination rates than natural factors like latitude or season. The findings highlight how laboratory conditions can introduce genetic changes that may complicate the interpretation of toxicology experiments.
ABSTRACT Background Understanding 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 F ST , assessing causality through structural equation modeling. Results In 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. Conclusions Our 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.