Biology subjects

Konczal, M.

Publications and source records attributed to Konczal, M..

11 recordsLinked to original sources

bioRxiv2026

Experimental evolution under biased sex ratios: phenotypic and genomic responses in the bulb mite, Rhizoglyphus robini

Sexual selection may increase population fitness by favouring high-condition individuals and accelerating the purging of deleterious alleles. However, it can also reduce population fitness through intra- and interlocus sexual conflict by promoting male-benefit traits that harm females and maintain polymorphism at sexually antagonistic loci. The balance between these opposing forces remains unresolved, yet it has major consequences for how sexual selection shapes population fitness and genome-wide variation. To explore the genomic and phenotypic effects of sexual selection and sexual conflict, we evolved replicated bulb mite (Rhizoglyphus robini) lines for 28 generations under male- versus female-biased sex ratios and combined phenotypic assays with whole-genome resequencing. Female fecundity and inbreeding depression did not differ between treatments, and genomic analyses revealed no treatment effect on the loss of rare, putatively deleterious SNPs. Contrary to expectations, males from male-biased lines were less harmful to stock females than males from female-biased lines. Genome-wide nucleotide diversity declined similarly across generations in both treatments, although synonymous exonic diversity declined more slowly in male-biased lines. While only a few SNPs diverged consistently between treatments, we identified large treatment-specific haplotype blocks indicating that multiple genomic regions were involved in response to sex-ratio manipulation. Overall, our results indicate that sex ratio manipulation drives evolution of male harm to females and widespread haplotype frequency changes without clear evidence for enhanced purging or maintenance of genetic diversity. The response thus appears to reflect adaptation to altered level of reproductive competition, but without measurable consequences for population fitness and genetic diversity. Significance statementSexual selection is often proposed to improve population fitness by removing deleterious mutations, yet it can also favour traits that harm the opposite sex; consequently, it remains unclear whether stronger reproductive competition reliably enhances population viability. By evolving bulb mite populations under strongly male- or female-biased sex ratios, we found that male-biased populations did not purge genetic load more effectively, while the genomic response to sex-ratio bias was highly polygenic. In contrast to our predictions, males from male-biased lines were less harmful to females than males from female-biased lines. Overall, our results show that sex-ratio bias can reshape male phenotypes and generate patterns of genomic divergence, but without any significant effect on population fitness. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=152 SRC="FIGDIR/small/701246v1_ufig1.gif" ALT="Figure 1"> View larger version (61K): org.highwire.dtl.DTLVardef@15afcf7org.highwire.dtl.DTLVardef@95ef16org.highwire.dtl.DTLVardef@183c405org.highwire.dtl.DTLVardef@1ba3159_HPS_FORMAT_FIGEXP M_FIG C_FIG

genomics↗

bioRxiv2026

Genomic basis of adaptation to constant and fluctuating environments in a global pest of cereals

In agricultural systems, spatially and temporally heterogeneous environments are expected to favour the evolution of generalist pests and pathogens, yet the genomic mechanisms underlying niche-breadth expansion remain poorly understood. Here, we address this gap by assembling one of the smallest known eukaryotic genomes--from the global cereal pest Aceria tosichella--and by resequencing generalist and specialist populations which evolved in the lab on constant versus fluctuating hosts. A previous study demonstrated that generalist populations retained a wider niche, including the ability to exploit a refuge host, compared to specialist populations that showed a narrowing of the ecological niche. Genomic scans identified 640 SNPs that significantly differed in frequency between treatments, including a single highly differentiated 120-kbp region containing 13 genes. Allele-frequency shifts across many SNPs in this region paralleled phenotypic divergence in the ability to utilise refuge hosts, and gene annotations suggested their roles in starvation resistance and nutrient signalling. However, experimental validation of the top candidate gene did not support its strong direct effect on survival on the refuge host, implying a more complex, likely polygenic basis for adaptation. Consistent with this interpretation, numerous significant SNPs occurred outside the focal region, with enrichment for genes involved in xenobiotic transport, detoxification pathways, and ABC transporters. Together, these results indicate that generalism in A. tosichella relies on complex molecular mechanisms that enable survival on suboptimal or refuge hosts, relying to a considerable extent on the ability to deal with stress arising, for example, from toxic compounds present in suboptimal hosts.

evolutionary biology↗

bioRxiv2025

A key regulator of missing-self innate immunity is polymorphic and under diversifying selection

Host-parasite co-evolution drives the diversification of host immune genes involved in the recognition of pathogen antigens and molecular patterns. In contrast, the immune genes involved in self-recognition and inhibition of immune responses against self-cells (missing-self immunity) are expected to be evolutionarily constrained. However, many pathogens, such as the Lyme disease agent Borrelia, hijack these genes to evade the immune system and may therefore select for their diversification. How these contrasting but concurrent selective forces shape the evolution of missing-self regulators is not clearly understood. To fill this gap, we investigated polymorphism and molecular signatures of selection acting on a missing-self regulator, the Complement Factor H (CFH), in bank vole populations, which are an important wild reservoir for Borrelia. We then compared the geographic structuring in the CFH domain interacting with Borrelia (CCP 20) against a genomic background represented by RAD-seq markers. We found signals of positive and diversifying selection at CCP 20, suggesting that CFH evolved in response to pressures from pathogens. Additionally, we found other innate immunity genes within the alternative complement pathway, which is regulated by CFH, under diversifying selection, highlighting its involvement in host-parasite coevolution. This study demonstrates that an innate missing-self sensor in a wild vertebrate is under diversifying selection, likely driven by pathogens.

evolutionary biology↗

bioRxiv2025

Immune Signatures of Gastrointestinal Helminth Infection in Transcriptomes of European Bison

Understanding the genes and molecular pathways that shape host responses to infection is essential for advancing our knowledge of host-parasite interactions and their ecological and evolutionary implications. Such insights are especially valuable for conserving endangered species that may be vulnerable to emerging or novel pathogens. Here, we investigated the impact of the recently introduced gastrointestinal nematode Ashworthius sidemi on gene expression in its novel host, the European bison (Bison bonasus). We analyzed abomasal transcriptomes (n = 45) from individuals characterized by a wide range of infection intensities (0-8,620 parasites per host). Despite substantial variation in parasite burden, differential expression analyses detected no individual genes significantly associated with infection intensity. However, gene set enrichment analyses based on p-value distributions revealed multiple immune-related gene ontology categories, including B and T cell activation, neutrophil chemotaxis, inflammatory responses, and regulation of IL-6 production. These findings indicate that European bison mount a clear yet subtle transcriptional response to A. sidemi infection and highlight molecular pathways potentially involved in mediating host defense against this emerging parasite.

immunology↗

bioRxiv2025

Maternal antibody-mediated elimination of a Puumala hantavirus outbreak in a bank vole colony

Bank voles (Myodes glareolus syn. Clethrionomys glareolus) are frequently used as an animal model in ecological and biomedical studies, and are important reservoir of viral and bacterial zoonotic pathogens, e.g. of Puumala hantavirus (PUUV). Here we describe an accidental PUUV outbreak in a large bank vole laboratory colony by incursion of infected wild-trapped bank voles, and a successful eradication of the virus. The eradication plan was based on results of previous studies, which showed that maternal antibodies (MatAb) protect the young from infection for up to 40 days after the weaning, four weeks longer than the estimated duration of maintaining infectivity of PUUV in the environment. After ensuring that most animals are infected, 620 pairs were mated on the same day. Only females that showed PUUV-specific antibodies and gave offspring within 26 days after the mating were retained. All individuals of the parental generation were euthanized before the last weaning. The weaned offspring was moved to individually ventilated cages (IVC) and repeatedly tested for the presence of PUUV-specific antibodies and RNA. A few infected and suspicious animals were euthanised. Then the animals were mated (in IVC) and after producing grand-offspring euthanised and tested for PUUV RNA in lungs. No PUUV RNA was detected, and no animals showed PUUV-specific antibodies in next generations. The successful clearance confirmed the protective efficiency of PUUV-specific MatAb. The procedure for clearance of PUUV in the bank vole colony may represent a blueprint for similar approaches in precious colonies of other rodents infected by similar pathogens. Author SummaryIn 2006 we started a unique long-term experiment on the bank vole, a common European rodent. Our goal was to study how animals can adapt to different challenges - a process called adaptive radiation. We established 16 vole lines: four control lines and others selected for specific behavioural and physiological traits. Over the years, this colony became an important model for studying evolution, physiology, and behaviour. Unfortunately, the colony became infected with Puumala hantavirus. The virus is mild for voles but can cause serious zoonotic illness in humans, without specific medical treatment available. At first, it seemed that the entire colony would have to be destroyed - a loss of thousands of animals and many years of research. However, we used a natural advantage: young voles born to infected mothers are temporarily protected by maternal antibodies. By carefully planning breeding, isolation, and testing, we created conditions where the virus lost its strength before the young lost their protection. This simple yet challenging approach worked - we saved the colony. Because many animals respond to viruses in a similar way, our method can help rescue other valuable research populations without complex procedures like embryo transfer or cross-fostering.

zoology↗

bioRxiv2025

Interplay between purging and admixture shapes genetic load in an invasive guppy population

Demographic history can shape the genetic load of populations by influencing the efficacy of selection, levels of heterozygosity, and the incorporation of new variants via gene flow. Understanding these dynamics is crucial for identifying threats to population viability and predicting evolutionary trajectories of invasive populations translocated by humans into non-native environments. We investigate these processes in Trinidadian guppies (Poecilia reticulata) by estimating genetic loads across multiple populations, with a particular focus on a single expanding population in which translocated individuals have rapidly spread and replaced native individuals. Overall, we observe the expected negative relationship between neutral genetic diversity and relative genetic load. In the translocated population, patterns differ between strongly and weakly deleterious mutations. Strongly deleterious alleles are purged at the isolated translocation site but tend to accumulate along the expansion front. In contrast, the genetic load estimated based on weakly deleterious variants declines along the expansion gradient. These differing patterns can be explained by admixture with native populations (which carried fewer weakly deleterious mutations) reducing the overall genetic load of the population at the expansion front. However, admixture has also increased genetic diversity and introduced new strongly deleterious alleles, thereby reversing the purging effect. Together, our findings illustrate the complex interactions determining genetic load in subdivided populations, offering important insights into the evolutionary aspects of biological invasions.

evolutionary biology↗

bioRxiv2025

Fighting to persist: Genetic rescue increases long-term fitness despite elevated genetic load

Genetic rescue (GR) can restore fitness in small genetically depauperate populations, however, long-term effectiveness, impact of rescuer quality and introduced deleterious load on population persistence remains uncertain. Using a male-dimorphic mite we tested whether a condition-dependent sexually selected trait influences GR. Genome-wide diversity and genetic load increased similarly for both morphs, while population fitness trajectories differed, suggesting that genetic quality is associated with the trait. Overall, GR sustained fitness benefits over 20 generations. The benefits persisted under thermal stress lowering extinction risk regardless of the rescuers morph and introduced load indicating their minimal importance. These results provide experimental evidence that maximising genome-wide variation via GR can yield lasting benefits, even when many deleterious mutations are introduced to populations facing environmental change.

evolutionary biology↗

bioRxiv2024

Sex-specific recombination landscape in a species with holocentric chromosomes

The rate and chromosomal positioning of meiotic recombination significantly affects the distribution of the genetic diversity in eukaryotic genomes. Many studies have revealed sex-specific recombination patterns, with male recombination typically biased toward chromosome ends, while female recombination is more evenly distributed along chromosomes, or concentrated in pericentromeric region. It has been proposed that such patterns in females may counteract meiotic drive caused by selfish genetic elements near centromeres and should not occur in species devoid of clearly defined centromeres, but evidence for this expectation is scarce. Here, we constructed a sex-specific genetic map of a species with holocentric chromosomes, the bulb mite (Rhizoglyphus robini), a model organism for sexual selection studies with heritable alternative male reproductive phenotypes. We found a similar recombination landscape in both males and females, with a consistent pattern of increased rates towards both chromosome ends, and a higher recombination rate in females than in males. Recombination rate was positively correlated with repeat density and negatively with gene density. Our results are consistent with the meiotic drive hypothesis and suggest that the evolution of recombination patterns is closely linked to chromosome features.

genomics↗

bioRxiv2023

Has recombination changed during the recent evolution of the guppy Y chromosome?

Genome sequencing and genetic mapping of molecular markers has demonstrated Y-linkage across most of the guppy (Poecilia reticulata) XY chromosome pair. However, they also revealed exchanges with the X, consistent with classical genetic observations of occasional exchanges of factors controlling visible male-specific phenotypic traits. It remains unclear whether this fish species has an extensive sex-determining region without crossing over (whose suppressed recombination could have evolved under selection created by sexually antagonistic effects of male coloration factors), or whether the fully Y-linked region is very small, perhaps within a single gene. Population genomic data support cytogenetic results indicating that it is within the terminal 5 Mb of the 26.5 Mb chromosome 12, just proximal to a highly recombining pseudo-autosomal region, PAR1. Using molecular markers, we studied recombination, focusing on this region of the XY pair. Despite assembly errors in the small terminal PAR1, our mapping identifies very similar genetic PAR boundaries in sires from four populations, suggesting that their crossover patterns have not changed. Our results also confirmed occasional crossovers proximal to the male-determining region, defining a second pseudo-autosomal region, PAR2, recombining much more rarely than PAR1. The crossover positions suggest that the male-determining factor is within a repetitive region near 21 Mb in the female assembly. A sex-reversed XX male had few crossovers in PAR2, suggesting that this regions low crossover rate depends on the phenotypic, not the genetic, sex. Thus rare sex changes, and/or occasional crossovers in males can explain the failure to detect fully Y-linked variants.

genetics↗

bioRxiv2021

Social hosts evade predation but have deadlier parasites

Parasites exploit hosts to replicate and transmit, but overexploitation kills host and parasite (1): predators may shift this cost-benefit balance by consuming hosts (2-4) or changing host behavior, but the strength of these effects remains unclear. Modeling both, we find a primary, strong effect: hosts group to defend against predators (5), increasing parasite transmission, thus multiple infections, and therefore favoring more exploitative, virulent, parasites (6). Indeed, among 18 Trinidadian Gyrodactyus spp. parasite lines, those collected from high predation guppy populations were more virulent in common garden than those from low predation populations. Our model accurately predicted this result when parametrized with our experimentally demonstrated virulence-transmission trade-off, implicating the behavioral effects of predation. Broadly, our results indicate that reduced social contact selects against parasite virulence. One-Sentence SummaryOur theory and data show predators cause increased host social grouping; the resulting transmission favors parasite virulence.

ecology↗

bioRxiv2020

Expansion of frozen hybrids in guppy ectoparasite, Gyrodactylus turnbulli

Hybridization is one of the major factors contributing to the emergence of highly successful parasites. Hybrid vigor can play an important role in this process, but subsequent rounds of recombination in the hybrid population may dilute its effects. Increased fitness of hybrids can, however, be frozen by asexual reproduction. Here, we identify invasion of a "frozen hybrid" genotype in natural populations of Gyrodactylus turnbulli, a facultatively sexual ectoparasitic flatworm that causes significant damage to its fish host. We re-sequenced genomes of these parasites infecting guppies from six Trinidad and Tobago populations, and found surprisingly high discrepancy in genome-wide nucleotide diversity between islands. The elevated heterozygosity on Tobago is maintained by predominantly clonal reproduction of hybrids formed from two diverged genomes. Hybridization has been followed by spread of the hybrids across the island, implying a selective advantage compared to native genotypes. Our results thus highlight that a single outcrossing event may be independently sufficient to cause pathogen expansion.

evolutionary biology↗