A sexually selected male weapon characterized by strong additive genetic variance and no evidence for sexually antagonistic polyphenic maintenance.

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.

Genomic evidence that a sexually selected trait captures genome-wide variation and facilitates the purging of genetic load.

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.

Correction to: Bartonella and Rickettsia Infections in Haematophagous Spinturnix myoti Mites (Acari: Mesostigmata) and their Bat Host, Myotis myotis (Yangochiroptera: Vespertilionidae), from Poland.

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

Bartonella and Rickettsia Infections in Haematophagous Spinturnix myoti Mites (Acari: Mesostigmata) and their Bat Host, Myotis myotis (Yangochiroptera: Vespertilionidae), from Poland.

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 cave-dwelling 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.

Kin selection promotes female productivity and cooperation between the sexes.

Hamilton's theory of kin selection explains the evolution of costly traits that benefit other individuals by highlighting the fact that passing genes to offspring is not the only way of increasing the representation of those genes in subsequent generations: Genes are also shared with other classes of relatives. Consequently, any heritable trait that affects fitness of relatives should respond to kin selection. We tested this core prediction of kin selection theory by letting bulb mites (Rhizoglyphus robini) evolve in populations structured into groups of relatives or nonrelatives during the reproductive phase of the life cycle. In accordance with predictions derived from kin selection theory, we found that evolution in groups of relatives resulted in increased female reproductive output. This increase at least partly results from the evolution of male traits that elevate their partners' fecundity. Our results highlight the power and universality of kin selection.

Is parasite load dependent on host aggregation size? The case of the greater mouse-eared bat Myotis myotis (Mammalia: Chiroptera) and its parasitic mite Spinturnix myoti (Acari: Gamasida).

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.

Differences between populations of Spinturnix myoti (Acari: Mesostigmata) in breeding and non-breeding colonies of Myotis myotis (Chiroptera) in central Europe: the effect of roost type.

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.