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44 results for “natural selection and evolution”
Data from: Natural selection and repeated patterns of molecular evolution following allopatric divergence
Background: Geographic speciation is a major force in generating biodiversity. However, how genomes diverge over time after geographic isolation has halted gene flow has remained unclear. We examine genome-wide divergence of putatively single-copy orthologous genes (POGs) from transcriptomes in 20 allopatric species/variety pairs from diverse angiosperm clades. Sixteen of these pairs reflect the well-known eastern Asia – eastern North America floristic disjunction; these species have been isolated for different lengths of time, from the Miocene to Pleistocene. Results: Molecular evolutionary analyses revealed that >90% of the genes examined are under purifying selection and <10% are under positive selection, and this pattern was observed for all taxon pairs, despite differences in divergence time. The divergence level at synonymous sites shared by most POGs in each taxon pair predicts the divergence time between the species/varieties. Divergence time estimates were positively correlated with abundance of genes under moderate purifying selection, but negatively correlated with abundance of genes under strong purifying selection. We identified 200 genes under strong positive selection across the species pairs, with 14 shared by 10-15 pairs and one shared by all taxon pairs. An additional 15 loci annotated to biological processes responding to various stimuli were present in 1-3 pairs.Conclusions: Our results suggest a common "most genes conserved–few genes adaptive" genomic architecture for the taxon pairs, which may be a key for maintaining a balance between the ability to conserve ancestral functions and the ability to evolve new features beneficial for new adaptations. As geographic isolation proceeds through time, the evolutionary trajectory of some genes changed from strong purifying selection to more relaxed selection. The allopatric divergence of these taxon pairs involved both neutral and adaptive evolution of functional genes.
Data from: Natural selection and repeated patterns of molecular evolution following allopatric divergence
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Data from: Population genomics of rapid evolution in natural populations: polygenic selection in response to power station thermal effluents
Background: Examples of rapid evolution are common in nature but difficult to account for with the standard population genetic model of adaptation. Instead, selection from the standing genetic variation permits rapid adaptation via soft sweeps or polygenic adaptation. Empirical evidence of this process in nature is currently limited but accumulating. Results: We provide genome-wide analyses of rapid evolution in two Fundulus heteroclitus populations subjected to recently elevated temperatures due to coastal power station thermal effluents. Bayesian and multivariate analyses of population genomic structure reveal a substantial portion of genetic variation that is most parsimoniously explained by selection at the site of thermal effluents. An FST outlier approach in conjunction with additional conservative requirements identify significant allele frequency differentiation that exceeds neutral expectations among exposed and closely related reference populations. Genomic variation patterns near these candidate loci reveal that individuals living near thermal effluents have rapidly evolved from the standing genetic variation through small allele frequency changes at many loci in a pattern consistent with polygenic selection on the standing genetic variation. Conclusions: While the ultimate trajectory of selection in these populations is unknown, our findings suggest that polygenic models of adaptation may play important roles in large, natural populations experiencing recent selection due to environmental changes that cause broad physiological impacts.
Natural selection drives genome-wide evolution via chance genetic associations
<p>Understanding selection's impact on the genome is a major theme in biology. Functionally-neutral genetic regions can be affected indirectly by natural selection, via their statistical association with genes under direct selection. The genomic extent of such indirect selection, particularly across loci not physically linked to those under direct selection, remains poorly understood, as does the time scale at which indirect selection occurs. Here we use field experiments and genomic data in stick insects, deer mice and stickleback fish to show that widespread statistical associations with genes known to affect fitness cause many genetic loci across the genome to be impacted indirectly by selection. This includes regions physically distant from those directly under selection. Then, focusing on the stick insect system, we show that statistical associations between SNPs and other unknown, causal variants result in additional indirect selection in general and specifically within genomic regions of physically linked loci. This widespread indirect selection necessarily makes aspects of evolution more predictable. Thus, natural selection combines with chance genetic associations to affect genome-wide evolution across linked and unlinked loci and even in modest-sized populations. This process has implications for the application of evolutionary principles in basic and applied science.</p>
Exploring the interplay between natural and intersexual selection on the evolution of a cognitive trait
<p><span>There has been an increased focus on the role of natural and sexual selection in shaping cognitive abilities, but the importance of the interaction between both forces remain largely unknown. Intersexual selection through female mate choice might be an important driver of the evolution of cognitive traits, especially in monogamous species, where females may obtain direct fitness benefits by choosing mates with better cognitive abilities. However, the importance given by females to male cognitive traits might vary among species and/or populations according to their life-history traits and ecology. To disentangle the effects of natural and sexual selection, here we use an agent-based simulation model and compare the model's predictions when females mate with the first randomly encountered male (i.e. under natural selection) versus when they choose among males based on their cognitive trait values (i.e. under natural and intersexual selection). Males and females are characterized, respectively, by their problem-solving ability and assessment strategy. At each generation, agents go through (1) a choosing phase during which females assess the cognitive abilities of potential mates until eventually finding an acceptable one, and (2) a reproductive phase during which all males compete for limited resources that are exploited at a rate which depends on their cognitive abilities. Because males provide paternal care, the foraging success of mated males determines the breeding success of the pair through its effect on nestling provisioning efficiency. The model predicts that intersexual selection plays a major role in most ecological conditions, by either reinforcing or acting against the effect of natural selection. The latter case occurs under harsh environmental conditions, where intersexual selection contributes to maintaining cognitive diversity. Our findings thus demonstrate the importance of considering the interaction between both selective forces and highlight the need to build a conceptual framework to target relevant cognitive traits.</span></p>
Following Darwin's footsteps: Evaluating the impact of an activity designed for elementary school students to link historically important evolution key concepts on their understanding of natural selection
<p>While several researchers have suggested that evolution should be explored from the initial years of schooling, little information is available on effective resources to enhance elementary school students' level of understanding of evolution by natural selection (LUENS). For the present study, we designed, implemented and evaluated an educational activity planned for fourth graders to explore concepts and conceptual fields that were historically important for the discovery of natural selection. Observation field notes and students' productions were used to analyse how the students explored the proposed activity. Additionally, an evaluation framework consisting of a test, the evaluation criteria and the scoring process was applied in two fourth-grade classes to estimate elementary school students' LUENS before and after engaging in the activity. Our results suggest that our activity allowed students to effectively link all of the key concepts in the classroom and produced a significant increase in their LUENS. These results indicate that our activity had a positive impact on students' understanding of natural selection. They also reveal that additional activities and minor fine-tuning of the present activity are required to further support students' learning about the concept of differential reproduction. We also observed a low level of teleological predictions for both pre- and post-tests. --</p>
Ecology and evolution of competitive trait variation in natural phytoplankton communities under selection
<p>Competition for limiting resources is a major force structuring ecological communities. Species minimum resource requirements (<em>R*</em>s) can predict competitive outcomes and evolve under selection in simple communities under controlled conditions. However, whether <em>R*</em>s predict competitive outcomes or demonstrate adaptive evolution in naturally complex communities is unknown. We subjected natural phytoplankton communities to three types of resource limitation (nitrogen, phosphorus, light) in outdoor mesocosms over ten weeks. We examined the community composition weekly and isolated 21 phytoplankton strains from seven species to quantify responses to selection of R* for these resources. We investigated evolutionary change in R*s in the dominant species, <em>Desmodesmus armatus</em>. <em>R*</em>s were good predictors of species changes in relative abundance, though this was largely driven by the success of <em>D. armatus </em>across several treatments. This species also demonstrated evolutionary change in <em>R*</em>s under resource limitation, supporting the potential for adaptive trait change to modify competitive outcomes in natural communities.</p>
The evolution of sexually dimorphic traits in ecological gradients: An interplay between natural and sexual selection in hummingbirds
<p><span>Traits that exhibit differences between the sexes have been of special interest in the study of phenotypic evolution. Classic hypotheses explain sexually dimorphic traits via intrasexual competition and mate selection, yet natural selection may also act differentially on the sexes to produce dimorphism. Natural selection can act either through physiological and ecological constraints on one of the sexes or by modulating the strength of sexual/social selection. This predicts an association between the degree of dimorphism and variation in ecological environments. Here, we characterise the variation in hummingbird dimorphism across ecological gradients using rich databases of morphology, colouration, and song. We show that morphological dimorphism decreases with elevation in the understorey and increases with elevation in mixed habitats, that dichromatism increases at high altitudes in open and mixed habitats, and that song is less complex in mixed habitats. Our results are consistent with flight constraints, lower predation pressure at high elevations, and with habitat effects on song transmission. We also show that dichromatism and song complexity are positively associated, while tail dimorphism and song complexity are negatively associated. Our results demonstrate that key ecological factors shape sexually dimorphic traits and that different communication modalities do not always evolve in tandem.</span></p>
Data from: Population genomics of rapid evolution in natural populations: polygenic selection in response to power station thermal effluents
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Data from: Nutritional geometry provides insight into the dual roles of natural and sexual selection in insect cuticular hydrocarbon evolution
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The evolution of sexually dimorphic traits in ecological gradients: An interplay between natural and sexual selection in hummingbirds
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Exploring the interplay between natural and intersexual selection on the evolution of a cognitive trait
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Ecology and evolution of competitive trait variation in natural phytoplankton communities under selection
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Natural selection drives genome-wide evolution via chance genetic associations
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Data from: Rapid evolution of prehistoric dogs from wolves by natural and sexual selection emerges from an agent-based model
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Following Darwin’s footsteps: Evaluating the impact of an activity designed for elementary school students to link historically important evolution key concepts on their understanding of natural selection
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Data from: Hybridization, natural selection and evolution of reproductive isolation: a 25-years survey of an artificial sympatric area between two mosquito sibling species of the Aedes mariae complex
Natural selection can act against maladaptive hybridization between co-occurring divergent populations leading to evolution of reproductive isolation among them. A critical unanswered question about this process that provides a basis for the theory of speciation by reinforcement, is whether natural selection can cause hybridization rates to evolve to zero. Here we investigated this issue in two sibling mosquitoes species, Aedes mariae and Ae. zammitii, that show post-mating reproductive isolation (F1 males sterile) and partial pre-mating isolation (different height of mating swarms) that could be reinforced by natural selection against hybridization. In 1986, we created an artificial sympatric area between the two species and sampled about 20,000 individuals over the following 25 years. Between 1986 to 2011, the composition of mating swarms and the hybridization rate between the two species were investigated across time in the sympatric area. Our results showed that Ae. mariae and Ae. zammitii have not completed reproductive isolation since their first contact in the artificial sympatric area. We have discussed the relative role of factors such as time of contact, gene flow, strength of natural selection, and biological mechanisms causing prezygotic isolation to explain the observed results.
Data from: Contemporary evolution during invasion: evidence for differentiation, natural selection, and local adaptation
Biological invasions are 'natural' experiments that can improve our understanding of contemporary evolution. We evaluate evidence for population differentiation, natural selection and adaptive evolution of invading plants and animals at two nested spatial scales: (i) among introduced populations (ii) between native and introduced genotypes. Evolution during invasion is frequently inferred, but rarely confirmed as adaptive. In common garden studies, quantitative trait differentiation is only marginally lower (~3.5%) among introduced relative to native populations, despite genetic bottlenecks and shorter timescales (i.e. millennia vs. decades). However, differentiation between genotypes from the native vs. introduced range is less clear and confounded by nonrandom geographic sampling; simulations suggest this causes a high false-positive discovery rate (>50%) in geographically structured populations. Selection differentials (¦s¦) are stronger in introduced than in native species, although selection gradients (¦β¦) are not, consistent with introduced species experiencing weaker genetic constraints. This could facilitate rapid adaptation, but evidence is limited. For example, rapid phenotypic evolution often manifests as geographical clines, but simulations demonstrate that nonadaptive trait clines can evolve frequently during colonization (~two-thirds of simulations). Additionally, QST-FST studies may often misrepresent the strength and form of natural selection acting during invasion. Instead, classic approaches in evolutionary ecology (e.g. selection analysis, reciprocal transplant, artificial selection) are necessary to determine the frequency of adaptive evolution during invasion and its influence on establishment, spread and impact of invasive species. These studies are rare but crucial for managing biological invasions in the context of global change.
Data from: Recent natural selection causes adaptive evolution of an avian polygenic trait
We used extensive data from a long-term study of great tits (Parus major) in the United Kingdom and Netherlands to better understand how genetic signatures of selection translate into variation in fitness and phenotypes. We found that genomic regions under differential selection contained candidate genes for bill morphology and used genetic architecture analyses to confirm that these genes, especially the collagen gene COL4A5, explained variation in bill length. COL4A5 variation was associated with reproductive success, which, combined with spatiotemporal patterns of bill length, suggested ongoing selection for longer bills in the United Kingdom. Last, bill length and COL4A5 variation were associated with usage of feeders, suggesting that longer bills may have evolved in the United Kingdom as a response to supplementary feeding.
Phenotypic variability can promote the evolution of adaptive plasticity by reducing the stringency of natural selection
Adaptive phenotypic plasticity is a potent but not ubiquitous solution to environmental heterogeneity, driving interest in what factors promote and limit its evolution. Here a novel computational model representing stochastic information flow in development is used to explore evolution from a constitutive phenotype to an adaptively plastic response. Results show that populations tend to evolve robustness to developmental stochasticity, but this evolved robustness limits evolvability; specifically, robust genotypes have less ability to evolve adaptive plasticity when presented with a mix of both the ancestral environment and a new environment. Analytic calculations and computational experiments confirm that this constraint occurs when the initial mutational steps toward plasticity are pleiotropic, such that mutant fitnesses decline in the environment to which their parents are well-adapted. Greater phenotypic variability improves evolvability in the model by lessening this decline as well as improving the fitness of partial adaptations to the new environment. By making initial plastic mutations more palatable to natural selection, phenotypic variability can increase the evolvability of an innovative, plastic response without improving evolvability to simpler challenges such as a shifted optimum in a single environment. Populations that evolved robustness by negative feedback between the trait and its rate of change show a particularly strong constraining effect on the evolvability of plasticity, revealing another mechanism by which evolutionary history can limit later innovation. These results document a novel mechanism by which weakening selection could actually stimulate the evolution of a major innovation.
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Allen Brain Atlas
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DANDI Archive for NWB datasets
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International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.