Biology subjects

Rueffler, C.

Publications and source records attributed to Rueffler, C..

10 recordsLinked to original sources

bioRxiv2026

Sex-specific dominance maintains multilocus polymorphism and can resolve sexual conflict

Sexually antagonistic selection arises when females and males favour different phenotypes but share their genetic basis. Beneficial sex-specific dominance can alleviate this conflict by allowing each allele to be more dominant in the sex in which it is beneficial. Whether the coevolution of dominance and allelic diversity can generate and maintain polymorphism across a polygenic trait remains unclear. We investigate a quantitative trait encoded by multiple diploid loci, with allelic effects shared between the sexes and evolving sex-specific promoter affinities determining dominance. We show that sex-specific dominance can generate polymorphism across many loci, including under weak or asymmetric selection. Whereas additive allelic effects lead to the concentration of polymorphism at a single major locus, evolving dominance allows polymorphism to become distributed across loci. This distributed polygenic architecture generates sexual dimorphism while reducing within-sex phenotypic variance: increasing the number of polymorphic loci, as well as allelic diversity within loci, allows female and male phenotypes to approach their respective optima with lower segregation load. Sufficiently strong selection can instead cause polymorphism to collapse toward a single major locus, but the selection strength required for this transition increases sharply with the number of contributing loci. Thus, evolving sex-specific dominance can make widespread genetic polymorphism part of the resolution of sexual conflict.

evolutionary biology↗

bioRxiv2026

The flaws of fitness functions in changing environments

When predicting species responses to changing environments, one can use mathematical functions that describe how individual fitness components depend on the environment, or a single "composite" function that directly links fitness to the environmental state. The former approach is a cornerstone of process-based modelling, but the latter remains standard for developing fundamental theory and making ecological predictions. Yet, fitness is not a single instantaneous trait, but an integrated outcome of multiple underlying processes accruing throughout an organisms life. We show that by ignoring the distinct environmental dependence of the underlying processes, predictions from composite fitness functions become inherently flawed in variable environments. We explore the magnitude of this error by leveraging empirical thermal reaction norms for four important life-history processes in an insect pest, the seed beetle Callosobruchus maculatus. We parameterize two fitness functions: one explicitly modelling the temperature-dependence of the four life-history traits independently (the "ground truth") and one composite function, which treats fitness as a single, instantaneous outcome of the environment. By combining these two functions with hourly temperature data, we projected demographic responses under different warming scenarios across 300 sites over three beetle population origins (California, USA; Yemen; Brazil). We show that the composite function over- or underestimates fitness depending on subtle climatic differences and whether fitness is assumed to accumulate additively or multiplicatively, highlighting the problems of applying composite fitness functions to variable conditions. We conclude that explicitly modeling trait-specific processes will become increasingly important for accurate eco-evolutionary forecasting under future environmental change.

ecology↗

bioRxiv2024

Central place foragers, prey depletion halos, and how behavioral niche partitioning promotes consumer coexistence

Many seabirds congregate in large colonies for breeding, a time when they are central place foragers. An influential idea in seabird ecology posits that competition during breeding results in an area of reduced prey availability around colonies, a phenomenon known as Ashmoles halo, and that this limits colony size. This idea has gained empirical support, including the finding that species coexisting within a colony might be able to do so by foraging on a single prey species but at different distances. Here, we provide a comprehensive mathematical model for central place foragers exploiting a single prey in a two-dimensional environment, where the prey distribution is the result of intrinsic birth and death, movement in space and mortality due to foraging birds (we also consider a variant tailored toward colonial social insects). Bird predation at different distances occurs according to an ideal free foraging distribution that maximizes prey delivery under flight and search costs. We fully characterize the birds ideal free distribution and the prey distribution it generates. Our results show that prey depletion halos around breeding colonies are a robust phenomenon and that the birds ideal free distribution is sensitive to prey movement. Furthermore, coexistence of several seabird species on a single prey easily emerges through behavioral niche partitioning whenever trait differences between species entail trade-offs between efficiently exploiting a scarce prey close to the colony and a more abundant prey far away. Such behavioral-based coexistence-inducing mechanism should generalize to other habitat and diet choice scenarios. Significance statementThis study presents a mathematical model to explore the distribution of foraging trips among seabirds breeding on isolated islands, providing insight into the emergence of prey depletion halos around colonies. Our findings reveal that such halos are a robust feature of central place foraging, independent of prey dynamics. Additionally, the model shows that trait-mediated niche partitioning promotes coexistence among species through behavioral segregation into different circular zones around the island. This partitioning occurs despite a shared preference to forage close to the island, where flight costs are lowest. The study advances understanding of ecological coexistence mechanisms and suggests broader applicability to other predator-prey systems beyond seabird ecology, offering a new perspective on community assembly under shared preferences.

ecology↗

bioRxiv2024

Sex-specific dominance and its effects on allelic diversity in sexually antagonistic loci

Sexually antagonistic (SA) selection can promote genetic diversity. Current theory predicts biallelic polymorphism in SA loci primarily under strong selection or dominance reversal between the sexes. Yet, selection is often weak, several candidate SA loci harbour more than two alleles, and the prevalence of dominance reversal remains unclear. We present a model in which allelic effects at a quantitative-trait locus coevolve with sex-specific promoter affinities that determine allelic dominance, under distinct female and male phenotypic optima. We show that gradual coevolution between allelic values and promoter affinities can generate a positive feedback between beneficial sex-specific dominance and allelic divergence. Importantly, this feedback does not require an established balanced polymorphism, but can be initiated during selective sweeps, during evolutionarily transient protected polymorphism, or from variation maintained by mutation-selection-drift balance. Under weak or asymmetric selection, repeated diversification can generate polyallelic polymorphism, with several alleles forming dominance hierarchies that reduce segregation load. These results hold for both autosomal and X-linked loci and do not require complete dominance reversal. To assess these findings, we analyse segregating genetic variation in three insect populations and find stronger signals of polyallelic polymorphism in candidate SA loci and those showing sex-specific dominance, while genes with the strongest signals are enriched for functions associated with known SA phenotypes.

evolutionary biology↗

bioRxiv2022

Foraging for locally and spatially varying resources: Where exploitation competition, local adaptation and kin selection meet

In patch- or habitat-structured populations different processes can lead to diversity at different scales. While spatial heterogeneity generates spatially disruptive selection favoring variation between patches, local competition can lead to locally disruptive selection promoting variation within patches. So far, almost all theory has studied these two processes in isolation. Here, we use mathematical modelling to investigate how resource variation within and between habitats influences the evolution of variation in a consumer population where individuals compete in finite patches connected by dispersal. We find that locally and spatially disruptive selection typically act in concert, favoring polymorphism under a significantly wider range of conditions than when in isolation. But when patches are small and dispersal between them is low, kin competition inhibits the emergence of polymorphism, especially when driven by local competition. We further use our model to clarify what comparisons between trait and neutral genetic differentiation (Qst/Fst comparisons) can tell about the nature of selection. Overall, our results help understand the interaction between two major drivers of diversity: locally and spatially disruptive selection; and how this interaction is modulated by the unavoidable effects of kin selection under limited dispersal.

evolutionary biology↗

bioRxiv2022

Consequences of life-cycle complexity to the potential for evolutionary branching

Complex life-cycles - that is, organismal development that unfolds across ecological niches - are pervasive in nature. In this work we set out to investigate the effects of complex life-cycles on the potential for diversification via evolutionary branching. We did this by analyzing a mathematical model of a consumer with two life-stages, each of which is characterized by a specific feeding efficiency trait that undergoes evolutionary change in response to ecological conditions such as resource competition. We find (i) that life-cycle complexity can favor diversification when compared to simple life-cycles, as there is a larger potential for evolutionary branching in the trait of the life-stage that has a higher population density; (ii) that evolution favors character displacement to minimize intra-stage resource competition; and (iii) that under certain parameters more than one evolutionary branching event can occur.

evolutionary biology↗

bioRxiv2020

Invasion and maintenance of spore killing in ascomycete fungi

Meiotic drivers are selfish genetic elements that are able to become over-represented among the products of meiosis. This transmission advantage makes it possible for them to spread in a population even when they impose fitness costs on their host organisms. Whether a meiotic driver can invade a population, and subsequently reach fixation or coexist in a stable polymorphism, depends on the one hand on the biology of the host organism, including its life-cycle, mating system, and population structure, and on the other hand on the specific fitness effects of the driving allele on the host. Here, we present a population genetic model for spore killing, a type of drive specific to fungi. We show how ploidy level, rate of selfing, and efficiency of spore killing affect the invasion probability of a driving allele and the conditions for its stable coexistence with the non-driving allele. Our model can be adapted to different fungal life-cycles, and is applied here to two well-studied genera of filamentous ascomycetes known to harbor spore killing elements, Neurospora and Podospora. We discuss our results in the light of recent empirical findings for these two systems.

evolutionary biology↗

bioRxiv2020

The components of directional and disruptive selection in heterogeneous group-structured populations

We derive how directional and disruptive selection operate on scalar traits in a heterogeneous group-structured population for a general class of models. In particular, we assume that each group in the population can be in one of a finite number of states, where states can affect group size and/or other environmental variables, at a given time. Using up to second-order perturbation expansions of the invasion fitness of a mutant allele, we derive expressions for the directional and disruptive selection coefficients, which are sufficient to classify the singular strategies of adaptive dynamics. These expressions include first- and second-order perturbations of individual fitness (expected number of settled offspring produced by an individual, possibly including self through survival); the first-order perturbation of the stationary distribution of mutants (derived here explicitly for the first time); the first-order perturbation of pairwise relatedness; and reproductive values, pairwise and three-way relatedness, and stationary distribution of mutants, each evaluated under neutrality. We introduce the concept of individual k-fitness (defined as the expected number of settled offspring of an individual for which k - 1 randomly chosen neighbors are lineage members) and show its usefulness for calculating relatedness and its perturbation. We then demonstrate that the directional and disruptive selection coefficients can be expressed in terms individual k-fitnesses with k = 1, 2, 3 only. This representation has two important benefits. First, it allows for a significant reduction in the dimensions of the system of equations describing the mutant dynamics that needs to be solved to evaluate explicitly the two selection coefficients. Second, it leads to a biologically meaningful interpretation of their components. As an application of our methodology, we analyze directional and disruptive selection in a lottery model with either hard or soft selection and show that many previous results about selection in group-structured populations can be reproduced as special cases of our model.

evolutionary biology↗

bioRxiv2018

The evolution and maintenance of extraordinary allelic diversity

AbstractThe majority of highly polymorphic genes are related to immune functions and with over 100 alleles within a population, genes of the major histocompatibility complex (MHC) are the most polymorphic loci in vertebrates. How such extraordinary polymorphism arose and is maintained is controversial. One possibility is heterozygote advantage (HA), which can in principle maintain any number of alleles, but biologically explicit models based on this mechanism have so far failed to reliably predict the coexistence of significantly more than ten alleles. We here present an eco-evolutionary model showing that evolution can result in the emergence and maintenance of more than 100 alleles under HA if the following two assumptions are fulfilled: first, pathogens are lethal in the absence of an appropriate immune defence; second, the effect of pathogens depends on host condition, with hosts in poorer condition being affected more strongly. Thus, our results show that HA can be a more potent force in explaining the extraordinary polymorphism found at MHC loci than currently recognized.

evolutionary biology↗

bioRxiv2018

The efficacy of sexual selection under environmental change

Sexual selection can promote adaptation if sexually selected traits are reliable indicators of genetic quality. Moreover, stronger sexual selection in males, as often reported in empirical studies, may help purge deleterious alleles at a low cost to population productivity. However, to what extent this remains true when a changing environment affects sexual selection dynamics has been debated. Here, we show that even if sexually selected traits remain honest signals of male quality in new environments, the efficacy of sexual selection will often be reduced under stress. We model the strength of sex-specific selection under different levels of environmental stress in a population in which males compete with each other for fertilization success and in which females experience fecundity selection. We observe that the strength of sexual selection is reduced relative to fecundity selection, resulting in a lowered potential for selection on males to aid adaptation under environmental change.

evolutionary biology↗