Trait differences between and within ranges of an invasive legume species

Novel ecological interactions can drive natural selection in non-native species and trait evolution may increase the likelihood of invasion. We can gain insight into the potential role of evolution in invasion success by comparing traits of successful individuals in the invasive range with the traits of individuals from the native range in order to determine which traits are most likely to allow species to overcome barriers to invasion. Here we used Medicago polymorpha , a non-native legume species from the Mediterranean that has invaded six continents around the world, to quantify differences in life history traits among genotypes collected from the native and invasive range and grown in a common greenhouse environment. We found significant differences in fruit and seed production and biomass allocation between invasive and native range genotypes. Invasive genotypes had greater fecundity, but invested more energy into belowground growth relative to native genotypes. Beyond the variation between ranges, we found additional variation among genotypes within each range in flowering phenology, total biomass, biomass allocation, and fecundity. We found non-linear relationships between some traits and fitness that were much stronger for plants from the invasive range. These trait differences between ranges suggest that stabilizing selection on biomass, resource allocation, and flowering phenology imposed during or after introduction of this species may increase invasion success.

Increased opposite sex association is linked with fitness benefits, otherwise sociality is subject to stabilising selection in a wild passerine

Animal sociality, an individuals propensity to association with others, has consequences for fitness, and particularly mate choice. For example, directly, by increasing the pool of prospective partners, and indirectly through increased survival. Individuals benefit from both over the short-term as these benefits are associated with mating status and subsequent fecundity, but whether animal sociality also translates into fitness is unknown. Here, we quantified social associations and their link with annual and lifetime fitness, measured as the number of recruits and in de-lifed fitness. We measured this in birds visiting a feeding station over two non-breeding periods, using social network analysis and a multi-generational genetic pedigree. We find high individual repeatability in sociality. We found that individuals with an average sociality had the highest fitness, and that birds with more opposite-sex associates had higher fitness, but this did not translate to improved lifetime fitness. For lifetime fitness, we found evidence for stabilizing selection on between sex sociality measures, suggesting that such benefits are only short-lived in a wild population.

Indigenous Seeds, Seed Selection and Seed Bank for Sustainable Agriculture

Indigenous seeds are grown by the farmers over the years with a strong influence from local natural factors. Such seeds have a higher level of intrapopulation variations and the capacity of buffering the adverse factors. Understanding indigenous seeds along with their diversity are useful to diversify their uses, to assess conservation status, to know the factors making farming areas red zone, and to improve their performance. Selection is the simplest and most common method for the improvement of crop varieties. The variation must be created and maintained to impose selection. Different types of selection can be considered depending on the mode of reproduction of crops. Response to selection and correlated response are estimated to make the selection process more effective. Many different selection approaches can target either developing monomorphic or polymorphic varieties. There are five selection units and can be applied in five crop stages. Farmers’ criteria need to be considered during selection process. Based on the genotypic classes, there are three types of selection namely stabilizing selection, directional selection, and disruptive selection. The most simple and common selection methods are pure lines, mass selection, and class-bulking selection. Orthodox seeds in short, medium, and long-term storage facilities are conserved as a seed bank. Major types are household seed banks, community seed banks, national seeds, natural seed banks, and global seed banks. A seed bank is for assuring the availability of crop diversity for research, study, and production. The common works in seed banks are diversity collection, regeneration, characterization, multiplication, and distribution along with online database management.

Attracting pollinators vs escaping herbivores: eco-evolutionary dynamics of plants confronted with an ecological trade-off

A large number of plant traits are subject to an ecological trade-off between attracting pollinators and escaping herbivores. The interplay of both plant-animal interactions determines their evolution. Within a plant-pollinator-herbivore community in which interaction strengths depend on trait-matching, eco-evolutionary dynamics are studied using the framework of adaptive dynamics. We characterize the type of selection acting on the plant phenotype and the consequences for multispecies coexistence. We find that pollination favors stabilizing selection and coexistence. In contrast, herbivory fosters runaway selection, which threatens plant-animal coexistence. These contrasting dynamics highlight the key role of ecological trade-offs in structuring ecological communities. In particular, we show that disruptive selection is possible when such trade-offs are strong. While the interplay of pollination and herbivory is known to maintain plant polymorphism in several cases, our work suggests that it might also have fueled the diversification process itself.

The relative impact of evolving pleiotropy and mutational correlation on trait divergence

Both pleiotropic connectivity and mutational correlations can restrict the decoupling of traits under divergent selection, but it is unknown which is more important in trait evolution. To address this question, we create a model that permits within-population variation in both pleiotropic connectivity and mutational correlation, and compare their relative importance to trait evolution. Specifically, we developed an individual-based stochastic model where mutations can affect whether a locus affects a trait and the extent of mutational correlations in a population. We find that traits can decouple whether there is evolution in pleiotropic connectivity or mutational correlation, but when both can evolve, then evolution in pleiotropic connectivity is more likely to allow for decoupling to occur. The most common genotype found in this case is characterized by having one locus that maintains connectivity to all traits and another that loses connectivity to the traits under stabilizing selection (subfunctionalization). This genotype is favored because it allows the subfunctionalized locus to accumulate greater effect size alleles, contributing to increasingly divergent trait values in the traits under divergent selection without changing the trait values of the other traits (genetic modularization). These results provide evidence that partial subfunctionalization of pleiotropic loci may be a common mechanism of trait decoupling under regimes of corridor selection.

Directional selection at gene expression level contributes to the speciation of Asian rice cultivars

Differences in expression levels play important roles in phenotypic variation across species, especially those closely related species with limited genomic differences. Therefore, studying gene evolution at expression level is important for illustrating phenotypic differentiation between species, such as the two Asian rice cultivars, Oryza sativa L. ssp. indica and Oryza sativa L. ssp. japonica. In this study, we evaluated the gene expression variation at inter-subspecies and intra-subspecies levels using transcriptome data from seedlings of three indica and japonica rice and defined four groups of genes under different natural selections. We found a substantial of genes (about 79%) that are under stabilizing selection at the expression level in both subspecies, while about 16% of genes are under directional selection. Genes under directional selection have higher expression level and lower expression variation than those under stabilizing selection, which suggest a potential explanation to subspecies adaptation to different environments and interspecific phenotypic differences. Subsequent functional enrichment analysis of genes under directional selection shows that indica rice have experienced the adaptation to environmental stresses, and also show differences in biosynthesis and metabolism pathways. Our study provides an avenue of investigating indica-japonica differentiation through gene expression variation, which may guide to rice breeding and yield improvement.

How development affects evolution

How development affects evolution. A mathematical framework that explicitly integrates development into evolution has recently been derived. Here we use this framework to analyse how development affects evolution. We show that, whilst selection pushes genetic and phenotypic evolution uphill on the fitness landscape, development determines the admissible evolutionary pathway, such that evolutionary outcomes occur at path peaks, which need not be peaks of the fitness landscape. Development can generate path peaks, triggering adaptive radiations, even on constant, single-peak landscapes. Phenotypic plasticity, niche construction, extra-genetic inheritance, and developmental bias variously alter the evolutionary path and hence the outcome. Selective development, whereby phenotype construction may point in the adaptive direction, may induce evolution either towards or away landscape peaks depending on the developmental constraints. Additionally, developmental propagation of phenotypic effects over age allows for the evolution of negative senescence. These results help explain empirical observations including punctuated equilibria, the paradox of stasis, the rarity of stabilizing selection, and negative senescence, and show that development has a major role in evolution.

Integrating genomics and multivariate evolutionary quantitative genetics: a case study of constraints on sexual selection in Drosophila serrata

In evolutionary quantitative genetics, the genetic variance–covariance matrix, G , and the vector of directional selection gradients, β , are key parameters for predicting multivariate selection responses and genetic constraints. Historically, investigations of G and β have not overlapped with those dissecting the genetic basis of quantitative traits. Thus, it remains unknown whether these parameters reflect pleiotropic effects at individual loci. Here, we integrate multivariate genome-wide association study (GWAS) with G and β estimation in a well-studied system of multivariate constraint: sexual selection on male cuticular hydrocarbons (CHCs) in Drosophila serrata . In a panel of wild-derived re-sequenced lines, we augment genome-based restricted maximum likelihood to estimate G alongside multivariate single nucleotide polymorphism (SNP) effects, detecting 532 significant associations from 1 652 276 SNPs. Constraint was evident, with β lying in a direction of G with low evolvability. Interestingly, minor frequency alleles typically increased male CHC-attractiveness suggesting opposing natural selection on β . SNP effects were significantly misaligned with the major eigenvector of G , g max , but well aligned to the second and third eigenvectors g 2 and g 3 . We discuss potential factors leading to these varied results including multivariate stabilizing selection and mutational bias. Our framework may be useful as researchers increasingly access genomic methods to study multivariate selection responses in wild populations.

Temporal analysis of effective population size and mating system in a social wasp

Highly social species are successful because they cooperate in obligately integrated societies. We examined temporal genetic variation in the eusocial wasp Vespula maculifrons in order to gain a greater understanding of evolution in highly social taxa. First, we wished to test if effective population sizes of eusocial species were relatively low due to the reproductive division of labor that characterizes eusocial taxa. We thus estimated the effective population size of V. maculifrons by examining temporal changes in population allele frequencies. We sampled the genetic composition of a V. maculifrons population at three separate time points spanning a 13-year period. We found that effective population size ranged in the hundreds of individuals, which is similar to estimates in other, non-eusocial taxa. Second, we estimated levels of polyandry in V. maculifrons in different years in order to determine if queen mating system varied over time. We found no significant change in the number or skew of males mated to queens. In addition, mating skew was not significant within V. maculifrons colonies. Therefore, our data suggest that queen mate number may be subject to stabilizing selection in this taxon. Overall, our study provides novel insight into the selective processes operating in eusocial species by analyzing temporal genetic changes within populations.

Population differentiation of polygenic score predictions under stabilizing selection

1AbstractGiven the many loci uncovered by genome-wide association studies (GWAS), polygenic scores have become central to the drive for genomic medicine and have spread into various areas including evolutionary studies of adaptation. While promising, these scores are fraught with issues of portability across populations, due to the mis-estimation of effect sizes and missing causal loci across populations not represented in large-scale GWAS. The poor portability of polygenic scores at first seems at odds with the view that much of common genetic variation is shared among populations (Lewontin, 1972). Here we investigate one potential cause of this discrepancy: phenotypic stabilizing selection drives the turnover of genetic variation shared between populations at causal loci. Somewhat counter-intuitively, while stabilizing selection to the same optimum phenotype leads to lower phenotypic differentiation among populations, it increases genetic differentiation at GWAS loci and reduces the portability of polygenic scores constructed for unrepresented populations. We also find that stabilizing selection can lead to potentially misleading signals of the differentiation of average polygenic scores among populations. We extend our baseline model to investigate the impact of pleiotropy, gene-by-environment interactions, and directional selection on polygenic score predictions. Our work emphasizes stabilizing selection as a null evolutionary model to understand patterns of allele frequency differentiation and its impact on polygenic score portability and differentiation.