Interplay between vertebrate adaptive immunity and bacterial infectivity genes: Bank vole MHC versus Borrelia afzelii OspC.

Coevolution of parasites with their hosts may lead to balancing selection on genes involved in determining the specificity of host-parasite interactions, but examples of such specific interactions in wild vertebrates are scarce. Here, we investigated whether the polymorphic outer surface protein C (OspC), used by the Lyme disease agent, Borrelia afzelii, to manipulate vertebrate host innate immunity, interacts with polymorphic major histocompatibility genes (MHC), while concurrently eliciting a strong antibody response, in one of its main hosts in Europe, the bank vole. We found signals of balancing selection acting on OspC, resulting in little differentiation in OspC variant frequencies between years.

Ivermectin decreases parasite load, testosterone, and potentially antler length in a group of captive red deer males (Cervus elaphus).

Secondary sex traits (SSTs) can favour males in intra-sexual competition, allowing females to reliably assess their quality. They can also be connected to other aspects of fitness, such as resistance to parasites and pathogens, as parasites have negative effects on the development of SSTs. Antlers are one of the most recognizable examples of SSTs whose development is regulated by testosterone and reflects the actual condition of the bearer.

Understanding the joint evolution of dispersal and host specialisation using phytophagous arthropods as a model group.

Theory generally predicts that host specialisation and dispersal should evolve jointly. Indeed, many models predict that specialists should be poor dispersers to avoid landing on unsuitable hosts while generalists will have high dispersal abilities. Phytophagous arthropods are an excellent group to test this prediction, given extensive variation in their host range and dispersal abilities.

Integration of the immune memory into the pathogen-driven MHC polymorphism hypothesis.

Major histocompatibility complex (MHC) genes (referred to as human leukocyte antigen or HLA in humans) are a key component of vertebrate immune systems, coding for proteins which present antigens to T-cells. These genes are outstanding in their degree of polymorphism, with important consequences for human and animal health. The polymorphism is thought to arise from selection pressures imposed by pathogens on MHC allomorphs, which differ in their antigen-binding capacity.

Sexually selected male weapon increases the risk of population extinction under environmental change: an experimental evidence.

Exaggerated sexually selected traits (SSTs), occurring more commonly in males, help individuals to increase reproductive success but are costly to produce and maintain. These costs on the one hand may improve population fitness by intensifying selection against maladapted males, but on the other hand, may increase the risk of extinction under environmental challenges. However, the impact of SSTs on extinction risk has not been investigated experimentally.

Small-scale genetic structure of populations of the bulb mite Rhizoglyphus robini.

Bulb mites are an economically significant pest of subterranean parts of plants and a versatile laboratory animal. However, the genetic structure of their populations remains unknown. To fill this gap in our knowledge of their biology, we set up a field experiment in which we allowed mites to colonize onion bulbs, and then determined the genetic structure of colonisers based on a panel of microsatellite loci.

The quest for good genes: Epigamic traits, fitness, MHC and multilocus heterozygosity in the guppy.

The 'good genes' hypothesis for the evolution of male secondary sexual traits poses that female preferences for such traits are driven by indirect genetic benefits. However, support for the hypothesis remains ambiguous, and, in particular, the genetic basis for the benefits has rarely been investigated. Here, we use seminatural populations of Trinidadian guppies to investigate whether sexually selected traits (orange, black and iridescent colouration, gonopodium length and body size) predict fitness measured as the number of grandoffspring, a metric that integrates across fitness components and sexes.

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.

Effective specialist or jack of all trades? Experimental evolution of a crop pest in fluctuating and stable environments.

Understanding pest evolution in agricultural systems is crucial for developing effective and innovative pest control strategies. Types of cultivation, such as crop monocultures versus polycultures or crop rotation, may act as a selective pressure on pests' capability to exploit the host's resources. In this study, we examined the herbivorous mite (commonly known as wheat curl mite), a widespread wheat pest, to understand how fluctuating versus stable environments influence its niche breadth and ability to utilize different host plant species.

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.

Long term patterns of association between MHC and helminth burdens in the bank vole support Red Queen dynamics.

Major histocompatibility complex (MHC) genes encode proteins crucial for adaptive immunity of vertebrates. Negative frequency-dependent selection (NFDS), resulting from adaptation of parasites to common MHC types, has been hypothesized to maintain high, functionally relevant polymorphism of MHC, but demonstration of this relationship has remained elusive. In particular, differentiation of NFDS from fluctuating selection, resulting from changes in parasite communities in time and space (FS), has proved difficult in short-term studies.

What do orange spots reveal about male (and female) guppies? A test using correlated responses to selection.

Female preferences for male ornamental traits can arise from indirect benefits, such as increased attractiveness or better viability of progeny, but empirical evidence for such benefits is inconsistent. Artificial selection offers a powerful way to investigate indirect effects of male ornaments. Here, we selected for the area of orange spots on male guppies, a trait subject to female preferences in our population, in replicated up- and down-selected lines.

Functional immunogenetic variation, rather than local adaptation, predicts ectoparasite infection intensity in a model fish species.

Natural host populations differ in their susceptibility to infection by parasites, and these intrapopulation differences are still an incompletely understood component of host-parasite dynamics. In this study, we used controlled infection experiments with wild-caught guppies (Poecilia reticulata) and their ectoparasite Gyrodactylus turnbulli to investigate the roles of local adaptation and host genetic composition (immunogenetic and neutral) in explaining differences in susceptibility to infection. We found differences between our four study host populations that were consistent between two parasite source populations, with no indication of local adaptation by either host or parasite at two tested spatial scales.

Expansion of frozen hybrids in the guppy ectoparasite, Gyrodactylus turnbulli.

Hybridization is one of the major factors contributing to the emergence of highly successful parasites. Hybrid vigour 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.

Balancing selection versus allele and supertype turnover in MHC class II genes in guppies.

Selection pressure from parasites is thought to be a major force shaping the extreme polymorphism of the major histocompatibility complex (MHC) genes, but the modes and consequences of selection remain unclear. Here, we analyse MHC class II and microsatellite diversity in 16 guppy (Poecilia reticulata) populations from two islands (Trinidad and Tobago) that have been separated for at least 10 ky. Within-population MHC diversity was high, but allele sharing was limited within islands and even lower between islands, suggesting relatively fast turnover of alleles.

RNA-Seq analysis of the guppy immune response against Gyrodactylus bullatarudis infection.

Gyrodactylids are ubiquitous ectoparasites of teleost fish, but our understanding of the host immune response against them is fragmentary. Here, we used RNA-Seq to investigate genes involved in the primary response to infection with Gyrodactylus bullatarudis on the skin of guppies, Poecilia reticulata, an important evolutionary model, but also one of the most common fish in the global ornamental trade. Analysis of differentially expressed genes identified several immune-related categories, including IL-17 signalling pathway and Th17 cell differentiation, cytokine-cytokine receptor interaction, chemokine signalling pathway, NOD-like receptor signalling pathway, natural killer cell-mediated cytotoxicity and pathways involved in antigen recognition, processing and presentation.

Sexual and ecological selection on a sexual conflict gene.

Sexual selection and conflict can act on genes with important metabolic functions, potentially shaping standing genetic variance in such genes and thus evolutionary potential of populations. Here, using experimental evolution, we show how reproductive competition intensity and thermal environment affect selection on phosphogluconate dehydrogenase (6Pgdh)-a metabolic gene involved in sexual selection and conflict in the bulb mite. The S allele of 6Pgdh increases male success in reproductive competition, but is detrimental to S-bearing males' partners.

Sexually selected male weapon is associated with lower inbreeding load but higher sex load in the bulb mite.

Elaborate sexually selected ornaments and armaments are costly but increase the reproductive success of their bearers (usually males). It has been postulated that high-quality males can invest disproportionately more in such traits, making those traits honest signals of genetic quality. However, genes associated with such traits may have sexually antagonistic effects on fitness.

Gene duplications, divergence and recombination shape adaptive evolution of the fish ectoparasite Gyrodactylus bullatarudis.

Determining the molecular basis of parasite adaptation to its host is an important component in understanding host-parasite coevolution and the epidemiology of parasitic infections. Here, we investigate short- and long-term adaptive evolution in the eukaryotic parasite Gyrodactylus bullatarudis infecting Caribbean guppies (Poecilia reticulata), by comparing the reference genome of Tobagonian G. bullatarudis with other Platyhelminthes, and by analysing resequenced samples from local Trinidadian populations.

Mating preferences can drive expansion or contraction of major histocompatibility complex gene family.

Major histocompatibility complex (MHC)-based mating rules can evolve as a way to avoid inbreeding or to increase offspring immune competence. While the role of mating preference in shaping the MHC diversity in vertebrates has been acknowledged, its impact on individual MHC diversity has not been considered. Here, we use computer simulations to investigate how simple mating rules favouring MHC-dissimilar partners affect the evolution of the number of MHC variants in individual genomes, accompanying selection for resistance to parasites.

Advances in the Evolutionary Understanding of MHC Polymorphism.

Proteins encoded by the classical major histocompatibility complex (MHC) genes incite the vertebrate adaptive immune response by presenting peptide antigens on the cell surface. Here, we review mechanisms explaining landmark features of these genes: extreme polymorphism, excess of nonsynonymous changes in peptide-binding domains, and long gene genealogies. Recent studies provide evidence that these features may arise due to pathogens evolving ways to evade immune response guided by the locally common MHC alleles.

Evolution of major histocompatibility complex gene copy number.

MHC genes, which code for proteins responsible for presenting pathogen-derived antigens to the host immune system, show remarkable copy-number variation both between and within species. However, the evolutionary forces driving this variation are poorly understood. Here, we use computer simulations to investigate whether evolution of the number of MHC variants in the genome can be shaped by the number of pathogen species the host population encounters (pathogen richness).

Major histocompatibility complex class I diversity limits the repertoire of T cell receptors.

Major histocompatibility complex (MHC) genes encode proteins that initiate adaptive immune responses through the presentation of foreign antigens to T cells. The high polymorphism found at these genes, thought to be promoted and maintained by pathogen-mediated selection, contrasts with the limited number of MHC loci found in most vertebrates. Although expressing many diverse MHC genes should broaden the range of detectable pathogens, it has been hypothesized to also cause deletion of larger fractions of self-reactive T cells, leading to a detrimental reduction of the T cell receptor (TCR) repertoire.

infection can bias estimates of intralocus sexual conflict.

Males and females share most of their genome and develop many of the same traits. However, each sex frequently has different optimal values for these shared traits, creating intralocus sexual conflict. This conflict has been observed in wild and laboratory populations of insects and affects important evolutionary processes such as sexual selection, the maintenance of genetic variation, and possibly even speciation.