Explore the vast range of titles available.

Sexual selection is a potent evolutionary force that can enhance adaptation and reduce mutational load, while simultaneously reducing survival, or causing sexual conflict that reduces fitness of one or both sexes. Many populations face extreme, short‐term stress events like heatwaves. The combined effects of sexual and environmental selection on population demography during and after such events remain poorly understood, even though such combined effects could be crucial for the persistence of small, endangered populations under climate change. In this study, we investigated how male aggression affects survival in a population during environmental stress. This was done by manipulating the expression of an aggressive male fighter morph in small populations of the male‐dimorphic mite Sancassania berlesei, using pheromonal cues from high‐density populations. We then exposed some of these populations to recurrent periods of extreme heat and monitored survival over eight generations. We found that heat exposure reduced survival, more severely in females than in males, and survival was lower in populations with higher fighter prevalence, but there was no interaction between temperature and fighter prevalence. Furthermore, survival declined across generations, and the decline was steeper in populations with lower prevalence of fighters, leading to the loss of their initial survival advantage by the last generation. Three populations exposed to heat went extinct from the reduced fighter expression regime. Our findings imply that despite its cost to individual survival, male aggression does not exacerbate population sensitivity to heatwaves over generations. Furthermore, we demonstrate that the mortality costs of male aggression are gradually compensated over successive generations, which could be a result of a more effective purging of inbreeding depression. Thus, while the additive effect of aggression and heatwaves on survival may increase demographic risks for bottlenecked populations in the short term, sexual selection may increase the resilience of populations to prolonged bottlenecks. This study examines how male aggression influences population survival under recurrent heat stress using experimental evolution in Sancassania berlesei. We show that while sexually selected tr initially reduce individual survival, they do not increase sensitivity to heatwaves and may enhance long‐term resilience to bottlenecks possibly by facilitating the purging of inbreeding depression.

Sexual selection and sexual antagonism are important drivers of eco-evolutionary processes. The evolution of traits shaped by these processes depends on their genetic architecture, which remains poorly studied. Here, implementing a quantitative genetics approach using diallel crosses of the bulb mite, Rhizoglyphus robini, we investigated the genetic variance that underlies a sexually selected weapon that is dimorphic among males and female fecundity. Previous studies indicated that a negative genetic correlation between these two traits likely exists. We found male morph showed considerable additive genetic variance, which is unlikely to be explained solely by mutation-selection balance, indicating the likely presence of large-effect loci. However, a significant magnitude of inbreeding depression also indicates that morph expression is likely to be condition-dependent to some degree and that deleterious recessives can simultaneously contribute to morph expression. Female fecundity also showed a high degree of inbreeding depression, but the variance in female fecundity was mostly explained by epistatic effects, with very little contribution from additive effects. We found no significant genetic correlation, nor any evidence for dominance reversal, between male morph and female fecundity. The complex genetic architecture underlying male morph and female fecundity in this system has important implications for our understanding of the evolutionary interplay between purifying selection and sexually antagonistic selection.

Hematophagous Spinturnix myoti mites and their host, the greater mouse-eared bat (Myotis myotis), were tested for the presence of Bartonella spp., Rickettsia spp., and Anaplasma phagocytophilum. In total, Bartonella spp. DNA was amplified in 28 % of 134 mite pools and in 25% of 59 bats tested by PCR targeting a fragment of citrate synthase gltA gen. Adult mites were at least threefold more frequently infected compared to immature stages. The overall infection prevalence among mite pools from cavedwelling bats was higher than for those collected from attic shelters. Three distinct genotypes were detected. The most prevalent genotype in mites and bats matched closely with Candidatus Bartonella hemsundetiensis identified in bats from Finland and was relatively distant from bat-borne Bartonella strains described in the UK and France. Importantly, most sequences were close to those reported in forest workers from Poland. The presence of identical genotype among S. myoti samples and M. myotis bats suggests that bartonellae can be shared between mites and their bat hosts. In this case, wing mites could serve as vectors, whereas their hosts as reservoirs. One blood sample was positive by PCR for the msp2 gene of A. phagocytophilum. Two mite pools yielded Rickettsia spp. DNA. Both sequences were distinct from any known species but can be classified as spotted fever group Rickettsia spp. Our findings expanded our knowledge on the role of spinturnicid mites in the ecology and epidemiology of bacterial infections associated with vespertilionid bats, especially regarding the genus Bartonella.

The evolution of costly traits such as deer antlers and peacock trains, which drove the formation of Darwinian sexual selection theory, has been suggested to both reflect and affect patterns of genetic variance across the genome, but direct tests are missing. Here, we used an evolve and resequence approach to reveal patterns of genome-wide diversity associated with the expression of a sexually selected weapon that is dimorphic among males of the bulb mite, Rhizoglyphus robini . Populations selected for the weapon showed reduced genome-wide diversity compared to populations selected against the weapon, particularly in terms of the number of segregating non-synonymous positions, indicating enhanced purifying selection. This increased purifying selection reduced inbreeding depression, but outbred female fitness did not improve, possibly because any benefits were offset by increased sexual antagonism. Most single nucleotide polymorphisms (SNPs) that consistently diverged in response to selection were initially rare and overrepresented in exons, and enriched in regions under balancing or relaxed selection, suggesting they are probably moderately deleterious variants. These diverged SNPs were scattered across the genome, further demonstrating that selection for or against the weapon and the associated changes to the mating system can both capture and influence genome-wide variation. Populations of a bulb mite that were experimentally selected for a male weapon showed reduced diversity across the genome, indicating that strong sexual selection increases the strength of purifying selection.

The risk of parasite infection grows with the size of host aggregations, which, in turn, may also depend on host sex and age and the quality of environmental resources. Herein, we studied the relationship between ectoparasitic infections with the wing mite (Spinturnix myoti) and the size of the breeding colonies, sex, age, and body condition index (BCI) of its host, the greater mouse-eared bat (Myotis myotis). The influence of environmental quality in the Carpathian Mountains (Poland) was also examined. We found significant differences in mite abundance and BCI between different breeding aggregations of the greater mouse-eared bat and also between the host sex/age categories. The most heavily infected bats were adult M. myotis females, while young males appeared to be the least infected. The BCI differed significantly between the sexes in young bats (males had a higher BCI than females) and also between colonies. No significant differences in the BCI were found for adult females. We did not find any relationship between the infestation rate of M. myotis, their colony size, the quality of environmental resources (percentage of forest cover around the colony), or the BCI. The prevalence of the various developmental stages of the mites did not differ between the host sex/age categories; however, differences were found in the sex ratios of deutonymphs and adult mites between adult M. myotis females. We predict that parasite load may not be dependent on colony size itself, but mainly on microclimatic factors, which are in turn directly correlated with colony size.

Sexually selected weapons used in intra‐sexual competition for mates are among the most striking animal features, but how their evolution affects life history traits closely correlated with fitness, and hence species' evolutionary trajectories, is not well understood. Here, we selected for or against male morphs carrying a lethal weapon in a male‐dimorphic mite Sancassania berlesei, and investigated how life histories evolve in populations with high vs. low proportion of weaponized, aggressive males called fighters and non‐weaponized, non‐aggressive males called scramblers. After 25 generations of experimental evolution, females from fighter‐selected lines showed higher early‐life fecundity compared to females from lines selected for non‐aggressive scrambler males. Furthermore, both sexes matured earlier in fighter‐selected lines compared to scrambler‐selected ones. Larvae‐to‐adult survivorship was not affected by such selection treatment. Finally, we investigated whether adult survivorship under temperature stress was influenced by such selection treatment, and we found no difference between fighter‐selected and scrambler‐selected lines. Our results demonstrate that composite selection pressures resulting from the prevalence of costly intra‐sexual aggression lead to an increase in key components of fitness, with likely consequences for population dynamics. However, we found no evidence that the response to such selection affects how individuals cope with environmental challenge. Using a soil mite system with dimorphic males, that is, aggressive, weaponized fighters and benign scramblers, we experimentally selected populations for higher proportion of fighter males for 25 generations. Populations with higher proportion of fighter males evolved faster juvenile development and higher early‐life fecundity. However, this evolution did not improve the survival of fighter populations in response to heat stress.

We studied variations in the abundance of parasitic spinturnicid mites in relation to the gender, age and body condition of bats living in different habitats. Populations of Spinturnix myoti Kolenati, 1856 (Acari: Spinturnicidae), an ectoparasite of the bat Myotis myotis (Borkhausen) (Mammalia: Chiroptera), were investigated in two types of roosts differing in microclimatic conditions: caves (low temperature and high humidity) and attics (high temperature and low humidity). Our data suggest that bats from cave nursery colonies harbour more parasites than those from attic colonies, irrespective of host sex or age. In underground colonies, adult females and their young differ in the mean abundance of parasites, whereas no such differences were found in attic colonies. Non-lactating females from underground roosts and lactating females from attic colonies had similar parasite loads, were lower than those of adult lactating females from caves. A negative correlation between the host body condition index and parasite load was found only in the most infected sex/age group of bats. In spite of significant differences in parasite load, the mean abundance of particular life stages of mites seems to be independent of the type of roost occupied by the host, its sex or age. However, in attic colonies the number of female deutonymphs was twice that of male deutonymphs, whereas in cave colonies the proportions of the sexes were similar. We suggest that the microclimate of the host's roosts may influence ectoparasite abundance through pressure on the sex ratio in the nymphal stages of mites.

The original version of this article published online (27 August 2018) unfortunately contained a mistake regarding an affiliation of Dr. Edyta Podsiadły, one of the authors.The original version of this article published online (27 August 2018) unfortunately contained a mistake regarding an affiliation of Dr. Edyta Podsiadły, one of the authors.

Sexual selection is a potent evolutionary force with complex effects. Strong sexual selection can enhance adaptation and reduce mutational load, while simultaneously reducing survival, or causing sexual conflict that reduces fitness for one or both sexes. Many populations today face not only gradual environmental changes but also extreme, short-term stress events like droughts or heatwaves. The combined effects of sexual and environmental selection on population demography during and after such events remain poorly understood, even though such combined effects could be crucial for the persistence of small, endangered populations under climate change. In this study, we investigated how sexual selection affects survival during environmental stress by manipulating the expression of an aggressive fighter morph in small populations of the male-dimorphic soil mite Sancassania berlesei, exposing some of these populations to recurrent periods of extreme heat and monitoring survival over eight generations. We found that heat exposure reduced survival, more severely in females than in males, and survival was lower in populations with higher fighter prevalence, but there was no interaction between temperature and fighter morph prevalence. Furthermore, survival declined across generations, and the decline was steeper in populations with lower prevalence of fighters, leading to the loss of their initial survival advantage by the last generation. T265625hree populations exposed to heat became extinct during the experiment, all from the reduced fighter expression treatment. Our findings imply that despite its cost to individual survival, sexual selection does not modulate population sensitivity to heatwaves over several generations. Furthermore, we demonstrate that these mortality costs of sexual selection are gradually compensated over successive generations, which could be a result of a more effective purging of inbreeding depression. Thus, while the additive effect of sexual selection and heatwaves on survival may increase demographic risks for bottlenecked populations in the short term, sexual selection may increase resilience of populations to prolonged bottlenecks.

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.Competing Interest StatementThe authors have declared no competing interest.Footnotes* https://doi.org/10.5281/zenodo.18242942* https://github.com/sebchm/sex_ratio_expEvolFunder Information DeclaredNational Science Centre, https://ror.org/03ha2q922, 2017/27/B/NZ8/00077