Biology subjects

Berger, D.

Publications and source records attributed to Berger, D..

5 recordsLinked to original sources

bioRxiv2018

Sexual selection, environmental robustness and evolutionary demography of maladapted populations: a test using experimental evolution in seed beetles.

Whether sexual selection impedes or aids adaptation has become a pressing question in times of rapid environmental change and parallels the debate about how the evolution of individual traits impacts on population dynamics and viability. The net effect of sexual selection on population viability results from a balance between genetic benefits of \"good genes\" effects and costs of sexual conflict. Depending on how these facets of sexual selection are affected under environmental change, extinction of maladapted populations could either be avoided or accelerated. Here, we evolved seed beetles under three alternative mating regimes (polygamy, monogamy and male-limited selection) to disentangle the contributions of sexual selection, fecundity selection and male-female coevolution to individual reproductive success and population fitness. We compared these contributions between the ancestral environment and two new stressful environments (temperature and host plant shift). Evolution under polygamy resulted in the highest individual reproductive success in competitive context for both sexes. Moreover, females evolving only via sexual selection on their male siblings in the male-limited regime had similar reproductive success and higher fertility than females evolving under monogamy, suggesting that sexual selection on males had positive effects on female fitness components. Interestingly, male-limited sexual selection resulted in males that were robust to stress, compared to males from the two evolution regimes applying fecundity selection. We quantified the population-level consequences of this sex-specific adaptation and found evidence that costs of socio-sexual interactions were higher in male-limited lines compared to polygamous lines, and that this difference was particularly pronounced at elevated temperature to which males from the male-limited regime were more robust compared to their conspecific females. These results illustrate the tension between individual-level adaptation and population-level viability in sexually reproducing species and suggest that sex-specific selection can cause differences in environmental robustness that may impact population demography under environmental change.

evolutionary biology↗

bioRxiv2018

Effects of host species and environmental factors on the prevalence of Batrachochytrium dendrobatidis in northern Europe

The fungal pathogen Batrachochytrium dendrobatidis (Bd) is a major threat to amphibian populations. Here we asked if the prevalence of Bd differs between amphibian species and whether it is related to local environmental factors in breeding habitats as well as landscape variables measured at three scales (500, 2000 and 5000 m radius) in southernmost Sweden. We sampled 947 anurans from six species in 31 ponds. Canopy cover, pond perimeter, pH and temperature were treated as local scale pond characteristics. Number of surrounding ponds, area of arable land, area of mature forest and number of resident people were treated as landscape variables. Bufo bufo and Rana temporaria had a prevalence of 0.5-1.0% which differed strongly from the other four species (Bombina bombina, Bufotes variabilis, Epidalea calamita, Rana arvalis) showing 13-64% prevalence. Bd prevalence in these four species was higher in ponds with higher pH, surrounded by a landscape with less mature forest and few wetlands. Our results show that the infection dynamics of Bd are complex and depend on local pond characteristics, host community composition and the spatial scale under investigation. Information on environmental factors associated with Bd and species differences in susceptibility may mitigate further spread of the disease through public information and guide conservational action plans, especially for the most threatened species.

ecology↗

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↗

bioRxiv2018

A Universal Temperature-Dependence of Mutational Fitness Effects

Adaptation in new environments depends on the amount and type of genetic variation available for evolution, and the efficacy by which natural selection discriminates among this variation to favour the survival of the fittest. However, whether some environments systematically reveal more genetic variation in fitness, or impose stronger selection pressures than others, is typically not known. Here, we apply enzyme kinetic theory to show that rising global temperatures are predicted to intensify natural selection systematically throughout the genome by increasing the effects of DNA sequence variation on protein stability. We tested this prediction by i) estimating temperature-dependent fitness effects of induced random mutations in seed beetles adapted to ancestral or warm temperature, and ii) calculating 100 paired selection estimates on mutations in benign versus stressful environments from a diverse set of unicellular and multicellular organisms. Environmental stress per se did not increase the mean strength of selection on de novo mutation, suggesting that the cost of adaptation does not generally increase in new environments to which the organism is maladapted. However, elevated temperature increased the mean strength of selection on genome-wide polymorphism, signified by increases in both mutation load and mutational variance at elevated temperature. The theoretical predictions and empirical data suggest that this increase may correspond to a doubling of genome-wide selection for a predicted 2-4{degrees}C climate warming scenario in ectothermic organism living at temperatures close to their thermal optimum. These results have important implications for global patterns of genetic diversity and the rate and repeatability of evolution under climate change. Impact StatementNatural environments are constantly changing so organisms must also change to persist. Whether they can do so ultimately depends upon the reservoir of raw genetic material available for evolution, and the efficacy by which natural selection discriminates among this variation to favour the survival of the fittest. Here, the biochemical properties of molecules and proteins that underpin the link between genotype and phenotype can exert a major influence over how the physical environment affects the expression of phenotypes and the fitness consequences of DNA sequence polymorphism. Yet, the constraints set by these molecular features are often neglected within eco-evolutionary theory trying to predict evolution in new environments. Here we combine predictions from existing biophysical models of protein folding and enzyme kinetics with experimental data from ectothermic organisms across the tree of life, to show that rising global temperatures are predicted to increase the mean strength of selection on DNA sequence variation in cold-blooded organisms. We also show that environmental stress per se generally does not increase the mean strength of selection on new mutations, suggesting that genome-wide natural selection is not stronger in new environments to which an organism is maladapted. Theoretical predictions and data suggest that an expected climate warming scenario of a 2-4{degrees}C temperature raise within the forthcoming century will result in roughly a doubling of genome-wide selection for organisms living close to their thermal optima. However, our results also point to substantial variability in the temperature-dependence of selection on different proteins within and between organisms, suggesting scope for compensatory adaptation to shape this relationship. These results bear witness to and extend the universal temperature dependence of biological rates and have important implications for global patterns of genetic diversity and the rate and repeatability of genome evolution under environmental change.

evolutionary biology↗

bioRxiv2017

Improving the annotation of the Heterorhabditis bacteriophora genome

Genome assembly and annotation remains an exacting task. As the tools available for these tasks improve, it is useful to return to data produced with earlier instances to assess their credibility and correctness. The entomopathogenic nematode Heterorhabditis bacteriophora is widely used to control insect pests in horticulture. The genome sequence for this species was reported to encode an unusually high proportion of unique proteins and a paucity of secreted proteins compared to other related nematodes. We revisited the H. bacteriophora genome assembly and gene predictions to ask whether these unusual characteristics were biological or methodological in origin. We mapped an independent resequencing dataset to the genome and used the blobtools pipeline to identify potential contaminants. While present (0.2% of the genome span, 0.4% of predicted proteins), assembly contamination was not significant. Re-prediction of the gene set using BRAKER1 and published transcriptome data generated a predicted proteome that was very different from the published one. The new gene set had a much reduced complement of unique proteins, better completeness values that were in line with other related species genomes, and an increased number of proteins predicted to be secreted. It is thus likely that methodological issues drove the apparent uniqueness of the initial H. bacteriophora genome annotation and that similar contamination and misannotation issues affect other published genome assemblies.

bioinformatics↗