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Search indexed bioRxiv preprints in genomics, neuroscience, cell biology and bioinformatics. Read source abstracts and check manuscript versions; preprints are not peer reviewed.

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At least 397 records · Page 22Linked to original sources
bioRxiv2021

Parapatric speciation with recurrent gene flow of two sexual dichromatic pheasants

BackgroundUnderstanding speciation has long been a fundamental goal of evolutionary biology. It is widely accepted that speciation requires an interruption of gene flow to generate strong reproductive isolation between species, in which sexual selection may play an important role by generating and maintaining sexual dimorphism. The mechanism of how sexual selection operated in speciation with gene flow remains an open question and the subject of many research. Two species in genus Chrysolophus, Golden pheasant (C. pictus) and Lady Amhersts pheasant (C. amherstiae), which both exhibit significant plumage dichromatism, are currently parapatric in the southwest China with several hybrid recordings in field. MethodsIn this research, we estimated the pattern of gene flow during the speciation of two pheasants using the Approximate Bayesian Computation (ABC) method based on the multiple genes data. With a new assembled de novo genome of Lady Amhersts pheasant and resequencing of widely distributed individuals, we reconstructed the demographic history of the two pheasants by pairwise sequentially Markovian coalescent (PSMC). ResultsThe results provide clear evidence that the gene flow between the two pheasants were consistent with the prediction of isolation with migration model for allopatric populations, indicating that there was long-term gene flow after the initially divergence (ca. 2.2 million years ago), and further support the secondary contact when included the parapatric populations since around 30 ka ongoing gene flow to now, which might be induced by the population expansion of the Golden pheasant in late Pleistocene. ConclusionsThe results of the study support the scenario of speciation between Golden pheasant (C. pictus) and Lady Amhersts pheasant (C. amherstiae) with cycles of mixing-isolation-mixing due to the dynamics of natural selection and sexual selection in late Pleistocene that provide a good research system as evolutionary model to test reinforcement selection in speciation.

evolutionary biology↗
bioRxiv2023

Scaling the fitness effects of mutations with respect to differentially adapted Arabidopsis thaliana accessions under natural conditions

Mutations are the ultimate source of genetic variation for natural selection to act upon. A major question in evolutionary biology is the extent to which new mutations can generate genetic variation under natural conditions to permit adaptive evolution over ecological time scales. Here we collected fitness data for chemically induced (ethylmethane sulfonate, EMS) mutant lines descended from two Arabidopsis thaliana ecotypes that show differential adaptation to the local environment of our common garden plot. Using a novel nonparametric Bayesian statistical approach, we found that both ecotypes accumulated substantial proportions of beneficial mutations. The poorly adapted ecotype showed higher variance in the fitness effect of mutations than the well-adapted ecotype. Furthermore, we predict that it takes less than 4000 generations for the fitness space of the two ecotypes to overlap through mutation accumulation, and that a single founder, through mutation accumulation, is able to achieve the species-wide genetic variation in less than 10,000 generations. Our results provide evidence for relatively rapid local adaptation of Arabidopsis thaliana in natural conditions through new mutations, as well as the utility of nonparametric Bayesian method for modeling the distribution of fitness effects for field-collected data.

evolutionary biology↗
bioRxiv2026

Sexual conflict, directional sexual selection and phenotypic plasticity jointly drive the evolution of extreme phenotypic variation

How broad phenotypic variation is maintained in natural populations in the face of selection is a central question in evolutionary biology. We address this question in the water strider Microvelia longipes, where males exhibit striking variation in rear leg length used in male-male contests for dominance. Using reaction norm experiments on inbred lines, we demonstrate that phenotypic plasticity contributes to expanding phenotypic variation, but requires high genetic variation to generate the broad range of trait expression observed in natural populations. Experimental evolution favouring trait exaggeration revealed that directional sexual selection not only fails to erode variation of male rear leg length, but rather amplifies it beyond the natural distribution. Additionally, male-limited selection in favour of dominance generated substantial fecundity costs in females, underscoring the role of sexual conflict driven by females in constraining exaggerated secondary sexual traits in males. Our findings show that sexually antagonistic selection and directional sexual selection jointly generate high genetic variation, which phenotypic plasticity inflates into broad phenotypic distribution of male weapon size. This provides an empirical explanation for the high variability of male exaggerated weapons in nature.

evolutionary biology↗
bioRxiv2025

Human-chimpanzee tetraploid system defines mechanisms of species-specific neural gene regulation

A major challenge in human evolutionary biology is to pinpoint genetic differences that underlie human-specific traits, such as increased neuron number and differences in cognitive behaviors. We used human-chimpanzee tetraploid cells to distinguish gene expression changes due to cis-acting sequence variants that change local gene regulation, from trans expression changes due to species differences in the cellular environment. In neural progenitor cells, examination of both cis and trans changes -- combined with CRISPR inhibition and transcription factor motif analyses -- identified cis-acting, species-specific gene regulatory changes, including to TNIK, FOSL2, and MAZ, with widespread trans effects on neurogenesis-related gene programs. In excitatory neurons, we identified POU3F2 as a key cis-regulated gene with trans effects on synaptic gene expression and neuronal firing. This study identifies cis-acting genomic changes that cause cascading trans gene regulatory effects to contribute to human neural specializations, and provides a general framework for discovering genetic differences underlying human traits.

evolutionary biology↗
bioRxiv2024

tbea: tools for pre- and post-processing in Bayesian evolutionary analyses

Estimating phylogenies in which branch lengths are expressed in units of absolute time is crucial for testing hypotheses in evolutionary biology. However, bioinformatic tools to pre- and post-process data from Bayesian divergence time estimation analyses are often not easily interoperable, and documenting methodological choices is not a generalized practice. The R package tbea is a tool-set to integrate biological, geological and palaeontological information to optimize the specification of models, their parameters and prior distributions in divergence times estimation analyses. tbea implements statistical models to (i) better translate time information in dating sources into the specified calibration densities, (ii) improve comparisons between prior and posterior distributions for parameters of interest, (iii) carry out inference on origination times for a set of distributions, (iv) summarise different distributions into a single one, and (v) improve the reproducibility of divergence time estimation analyses allowing users to document methodological choices. We illustrate the package functionalities by carrying out two worked examples. One on the phylogenetic relationships and divergence time estimation of South American Cynodontidae, and another one on the separation time of drainages East and West of the Andes in South America. It is expected that the tools herein available will be key when estimating events in time from sets of point estimates, as well as the combination of different posterior densities from the same parameter are useful to justifying the selection of secondary calibration points, or discussing the timing of biogeographic events when multiple sources are available.

evolutionary biology↗
bioRxiv2018

Efficiently inferring the demographic history of many populations with allele count data

The sample frequency spectrum (SFS), or histogram of allele counts, is an important summary statistic in evolutionary biology, and is often used to infer the history of population size changes, migrations, and other demographic events affecting a set of populations. The expected multipopulation SFS under a given demographic model can be efficiently computed when the populations in the model are related by a tree, scaling to hundreds of populations. Admixture, back-migration, and introgression are common natural processes that violate the assumption of a tree-like population history, however, and until now the expected SFS could be computed for only a handful of populations when the demographic history is not a tree. In this article, we present a new method for efficiently computing the expected SFS and linear functionals of it, for demographies described by general directed acyclic graphs. This method can scale to more populations than previously possible for complex demographic histories including admixture. We apply our method to an 8-population SFS to estimate the timing and strength of a proposed \"basal Eurasian\" admixture event in human history. We implement and release our method in a new open-source software package momi2.

evolutionary biology↗
bioRxiv2018

Drought frequency predicts life history strategies in Heliophila

Explaining variation in life history strategies is a long-standing goal of evolutionary biology. For plants, annual and perennial life histories are thought to reflect adaptation to environments that differ in the frequency of stress events such as drought. Here we test this hypothesis in Heliophila (Brassicaceae), a diverse genus of flowering plants native to Africa, by integrating 34 years of satellite-based drought measurements with 2192 herbaria occurrence records. Consistent with predictions from classic life history theory, we find that perennial Heliophila species occur in environments where droughts are significantly less frequent compared to annuals. These associations are predictive while controlling for phylogeny, lending support to the hypothesis that drought related natural selection has influenced the distributions of these strategies. Additionally, the collection dates of annual and perennial species indicate that annuals escape drought prone seasons during the seed phase of their life cycle. Together, these findings provide empirical support for classic hypotheses about the drivers of life history strategy in plants - that perennials out compete annuals in environments with less frequent drought and that annuals are adapted to environments with more frequent drought by escaping drought prone seasons as seeds.

evolutionary biology↗
bioRxiv2020

The adaptive architecture is shaped by population ancestry and not by selection regime

Understanding the genetic architecture of adaptive phenotypes is a key question in evolutionary biology. One particularly promising approach is Evolve and Resequence (E&R), which combines advantages of experimental evolution such as time series, replicate populations and controlled environmental conditions, with whole genome sequencing. The recent analysis of replicate populations from two different Drosophila simulans founder populations, which were adapting to the same novel hot environment, uncovered very different architectures - either many selection targets with large heterogeneity among replicates or fewer selection targets with a consistent response among replicates. Here, we exposed the founder population from Portugal to a cold temperature regime. Although almost no selection targets were shared between the hot and cold selection regime, the adaptive architecture was similar: we identified a moderate number of loci under strong selection (19 selected alleles, mean selection coefficient = 0.072) and very parallel responses in the cold evolved replicates. This similarity across different environments indicates that the adaptive architecture depends more on the ancestry of the founder population than the specific selection regime. These observations have a pronounced impact on our understanding of adaptation in natural populations.Competing Interest StatementThe authors have declared no competing interest.View Full Text

evolutionary biology↗
bioRxiv2023

Genome size and repeat content contribute to a complex architecture of flowering time in Amaranthus tuberculatus

Genome size variation, largely driven by repeat content, is poorly understood within and among populations, limiting our understanding of its significance for adaptation. Here we characterize intraspecific variation in genome size and repeat content across 186 individuals of Amaranthus tuberculatus, a ubiquitous native weed that shows flowering time adaptation to climate across its range and in response to agriculture. K-mer based genome size estimates vary by up to 20% across individuals, with transposable elements, unknown repeats, and rDNAs being the primary contributors to this variability. The additive effect of this variation has important phenotypic consequences--individuals with more repeats, and thus larger genomes, show slower flowering times and growth rates. Compared to newly-characterized gene copy number and polygenic nucleotide changes underlying variation in flowering time, we show that genome size remains a modest but significant contributor to the genetic basis of flowering time. Differences in flowering time across sexes and habitats are not mirrored by genome size variation, but rather polygenic variation and a gene copy number variant within the ATP synthesis pathway. Repeat content nonetheless shows non-neutral distributions across the genome, and across latitudinal and environmental gradients, reflecting numerous governing processes that in turn influence quantitative genetic variation for phenotypes key to plant adaptation. Author SummaryThe remarkable and seemingly inconsequential variation in genome size across species has long been an enigma in evolutionary biology. Calling this viewpoint into question, correlations between genome size variation and traits linked to fitness are increasingly uncovered. While this suggests that DNA content itself may be a source of adaptive genetic variation, repeat elements that propagate at the cost of the host are known to largely mediate this variation and may thus limit adaptive potential. Here we look to disentangle these multi-level dynamics, characterizing repeat dynamics across the genome and among individuals across diverse collections of a widespread agricultural weed, linking repeat content to genome size variation, and characterizing the relative importance of its phenotypic consequences. In Amaranthus tuberculatus, we find non-neutral repeat distributions across individuals across the range, and while this repeat variation underlies both variation in genome size and flowering time, we show that it makes a relatively minor contribution to variation in a fitness-related trait across the landscape relative to monogenic and polygenic features. Together, this work broadens our perspective on the complex selective dynamics that govern intraspecific variation in genome size and traits key to fitness in plants.

evolutionary biology↗
bioRxiv2019

Metabolic trade-offs hide unforeseen benefits of plasmids carriage

The link between fitness and reproduction rate is a central tenet in microbiology, and indeed evolutionary biology: Mutants reproducing faster than the dominant wild-type are favoured by selection, but otherwise the mutation is lost. This link was given by Ronald Fisher in 1930 under the assumption that fitness can only change through mutations that boost or hinder growth rate, whence the use of logarithms on growth data by experimentalists. Here I show that logarithms are highly sensitive to sampling times, resulting in fitness estimates that are not constant over the growth of bacterial cultures. This variability invalidates typical selection measurements, and unfit mutants can be co-maintained if they reach their equilibrium. And this is what I observed in competition assays between two Escherichia coli constructs, one of which harbours a non-transmissible plasmid that protects against tetracycline (pGW155B), without using the antibiotic. Despite growing 40% slower than its drug-sensitive counterpart, the construct harbouring the plasmid persisted throughout the competition. And, perhaps more importantly, maintained the plasmid. My study suggests that reliance on growth rate masks that selection on plasmid carriage may be stronger than previously thought--explaining the seemingly-paradoxical abundance of plasmids in nature.

evolutionary biology↗
bioRxiv2020

Evolution of bone cortical compactness in slow arboreal mammals

Lifestyle convergences and related phenotypes are a major topic in evolutionary biology. Low bone cortical compactness (CC), shared by the two genera of tree sloths, has been linked to their convergently evolved slow arboreal ecology. The proposed relationship of low CC with tree sloths lifestyle suggests a potential convergent acquisition of this trait in other slow arboreal mammals. Tree sloths, Lorisidae, Palaeopropithecidae, Megaladapis and koalas were included in a phylogenetically informed CC analysis of the humerus and femur, as well as closely related but ecologically distinct taxa. We found that tree sloths are unparalleled by any analysed clade, in featuring an extremely low CC. A tendency for low CC was however found in palaeopropithecids (especially Palaeopropithecus) and Megaladapis. On the other hand, low CC was not found in Lorisidae. Koalas, although deviating from the compact structure generally observed in mammals, are not clearly distinct from their sister taxon (wombats) and show humeral CC that is higher than femoral CC. Multiple factors seem to influence CC, preventing the recognition of a simple relationship between slow arborealism and low CC. Highly compact cortical bone in extinct sloths confirms that low CC in tree sloths likely represents a recent convergence.

evolutionary biology↗
bioRxiv2015

Population genomic scans reveal novel genes underlie convergent flowering time evolution in the introduced range of Arabidopsis thaliana

A long-standing question in evolutionary biology is whether the evolution of convergent phenotypes results from selection on the same heritable genetic components. Using whole genome sequencing and genome scans, we tested whether the evolution of parallel longitudinal flowering time clines in the native and introduced ranges of Arabidopsis thaliana has a similar genetic basis. We found that common variants of large effect on flowering time in the native range do not appear to have been under recent strong selection in the introduced range. Genes in regions of the genome that are under selection for flowering time are also not enriched for functions related to development or environmental sensing. We instead identified a set of 53 new candidate genes putatively linked to the evolution of flowering time in the species introduced range. A high degree of conditional neutrality of flowering time variants between the native and introduced range may preclude parallel evolution at the level of genes. Overall, neither gene pleiotropy nor available standing genetic variation appears to have restricted the evolution of flowering time in the introduced range to high frequency variants from the native range or to known flowering time pathway genes.

Evolutionary Biology↗
bioRxiv2023

Modeling the evolution of segment trees reveals deficiencies in current inferential methods for genomic reassortment

Reassortment is an evolutionary process common in viruses with segmented genomes. These viruses can swap whole genomic segments during cellular co-infection, giving rise to novel progeny formed from the mixture of parental segments. Because large-scale genome rearrangements have the potential to generate new phenotypes, reassortment is important to both evolutionary biology and public health research. However, statistical inference of the pattern of reassortment events from phylogenetic data is exceptionally difficult, potentially involving inference of general graphs in which individual segment trees are embedded. In this paper, we argue that, in general, the number and pattern of reassortment events are not identifiable from segment trees alone, even with theoretically ideal data. We call this fact the fundamental problem of reassortment, which we illustrate using the concept of the first-infection tree, a typically but not always counterfactual genealogy that would have been observed in the segment trees had no reassortment occurred. Further, we illustrate four additional problems that can arise logically in the inference of reassortment events and show, using simulated data, that these problems are not rare and can potentially distort our perception of reassortment even in small data sets. Finally, we discuss how existing methods can be augmented or adapted to account for not only the fundamental problem of reassortment but also the four additional situations that can complicate the inference of reassortment.

evolutionary biology↗
bioRxiv2025

Independent genomic trajectories shape adaptation to life on land across animal lineages

How animals repeatedly adapted to life on land is a central question in evolutionary biology. While terrestrialisation occurred independently across animal phyla, it remains unclear whether shared genomic mechanisms underlie these transitions. Here, we combine large-scale comparative genomics, machine learning, and multi-omics data, including proteomics and transcriptomics from stress experiments relevant to terrestrial environmental challenges in 17 species, to investigate the genomic basis of animal terrestrial adaptation. Gene co-expression networks reveal that genes relevant to stress are largely lineage-specific, yet converge in function through the co-option of gene families pre-dating terrestrialisation events. Phylogenomic and machine learning analyses support a dominant role for early-evolving genes, enriched in stress-related functions, paired with a higher gene loss than gain at terrestrialisation nodes. Our findings support a model of lineage-specific genomic changes involving mostly conserved genes that converged at the functional level during the independent transitions to terrestrial life.

evolutionary biology↗
bioRxiv2017

Diminishing returns of inoculum size on the rate of a plant RNA virus evolution

Understanding how genetic drift, mutation and selection interplay in determining the evolutionary fate of populations is one of the central questions of Evolutionary Biology. Theory predicts that by increasing the number of coexisting beneficial alleles in a population beyond some point does not necessarily translates into an acceleration in the rate of evolution. This diminishing-returns effect of beneficial genetic variability in microbial asexual populations is known as clonal interference. Clonal interference has been shown to operate in experimental populations of animal RNA viruses replicating in cell cultures. Here we carried out experiments to test whether a similar diminishing-returns of population size on the rate of adaptation exists for a plant RNA virus infecting real multicellular hosts. We have performed evolution experiments with tobacco etch potyvirus in two hosts, the natural and a novel one, at different inoculation sizes and estimated the rates of evolution for two phenotypic fitness-related traits. Firstly, we found that evolution proceeds faster in the novel than in the original host. Secondly, we found the predicted diminishing-returns effect of inoculum size on the rate of evolution for one of the fitness traits, but not for the other, which suggests that selection operates differently on each trait.

evolutionary biology↗
bioRxiv2017

Unique genetic variants underlie parallel gene expression within a young adaptive radiation despite specialization on highly divergent resources

Parallel evolution of gene expression commonly underlies convergent niche specialization, but parallel changes in expression could also underlie divergent specialization. We investigated divergence in gene expression and whole-genome genetic variation across three sympatric Cyprinodon pupfishes endemic to San Salvador Island, Bahamas. This recent radiation consists of a generalist and two derived specialists adapted to novel niches - a scale-eater and a snail-eater. We sampled total mRNA from all three species at two early developmental stages and compared gene expression with whole-genome genetic differentiation among all three species in 42 resequenced genomes. 80% of genes that were differentially expressed between snail-eaters and generalists were up or downregulated in the same direction between scale-eaters and generalists; however, there were no fixed variants shared between species underlying these parallel changes in expression. Genes showing parallel evolution of expression were enriched for effects on metabolic processes, whereas genes showing divergent expression were enriched for effects on cranial skeleton development and pigment biosynthesis, reflecting the most divergent phenotypes observed between specialist species. Our findings reveal that even divergent niche specialists may exhibit convergent adaptation to higher trophic levels through shared genetic pathways. This counterintuitive result suggests that parallel evolution in gene expression can accompany divergent ecological speciation during adaptive radiation.\n\nImpact SummaryAdaptations that result in unique forms of ecological specialization are central to research in evolutionary biology, yet little is known about their molecular foundations. We combined transcriptome sequencing with whole-genome divergence scans to study the molecular evolution of two specialist Cyprinodon pupfish species - a scale-eater and a snail-eater - that rapidly diverged from a sympatric generalist ancestor within the last 10,000 years. While parallel evolution of gene expression driving convergent niche specialization seems common, we present, to our knowledge, the first example of significant parallel changes in expression coinciding with divergent niche specialization. 80% of genes that were differentially expressed between snail-eaters and generalists showed the same direction of expression in scale-eaters relative to generalists. Furthermore, parallel evolution in expression seem to be controlled by unique genetic variants in each specialist species. Genes showing parallel changes in expression were enriched for metabolic processes that may facilitate adaptation to a higher trophic level, while genes showing divergent expression likely shape the striking morphological differences between specialists. These findings contribute to a more nuanced understanding of convergent adaptations that arise during speciation, and highlight how species can evolve similar expression profiles adapted to divergent niches.

evolutionary biology↗
bioRxiv2025

Spatially heterogeneous gene flow may hinder linking phylogeographic data to macroevolutionary patterns

How microevolutionary processes translate to macroevolutionary patterns is a central question in evolutionary biology. Macroevolutionary and biogeographic studies often rely on species trees to make inferences about diversification, but gene flow can lead to incorrect phylogenetic inference. Under a range of biogeographic conditions, gene flow may not occur uniformly across space during diversification, which could lead to macroevolutionary misinferences. For example, whenever a "peripheral" population is relatively isolated and inferred as sister to a "core" clade of populations that exchange migrants, it might solely reflect gene flow, as opposed to macroevolutionary processes such as the order of biogeographic dispersal events. We use simulations of the hypothetical case of spatially heterogeneous gene flow described above and found that relatively low levels of gene flow led to monophyly of the adjacent populations, with longer branches for peripheral taxa, regardless of the true divergence history. We highlight an empirical example wherein lowland antbirds (Family: Thamnophilidae)-a clade known for dynamic gene flow in Amazonia-tend to be young in Amazonia, but older at Amazonias periphery. Although it is challenging to know if the simulated bias applies here, our work suggests a distinguishability problem for any nodes stemming from radiations in geographically heterogeneous environments.

evolutionary biology↗
bioRxiv2021

Unraveling patterns of disrupted gene expression across a complex tissue

Whole tissue RNASeq is the standard approach for studying gene expression divergence in evolutionary biology and provides a snapshot of the comprehensive transcriptome for a given tissue. However, whole tissues consist of diverse cell types differing in expression profiles, and the cellular composition of these tissues can evolve across species. Here, we investigate the effects of different cellular composition on whole tissue expression profiles. We compared gene expression from whole testes and enriched spermatogenesis populations in two species of house mice, Mus musculus musculus and M. m. domesticus, and their sterile and fertile F1 hybrids, which differ in both cellular composition and regulatory dynamics. We found that cellular composition differences skewed expression profiles and differential gene expression in whole testes samples. Importantly, both approaches were able to detect large-scale patterns such as disrupted X chromosome expression although whole testes sampling resulted in decreased power to detect differentially expressed genes. We encourage researchers to account for histology in RNASeq and consider methods that reduce sample complexity whenever feasible. Ultimately, we show that differences in cellular composition between tissues can modify expression profiles, potentially altering inferred gene ontological processes, insights into gene network evolution, and processes governing gene expression evolution.

evolutionary biology↗