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Results for “evolutionary biology”

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 Read source abstracts and check manuscript versions; preprints are not peer reviewed.

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bioRxiv2018

Two levels of host-specificity in a fig-associated Caenorhabditis

BackgroundBiotic interactions are ubiquitous and require information from ecology, evolutionary biology, and functional genetics in order to be completely understood. However, study systems that are amenable to investigations across such disparate fields are rare. Figs and fig wasps are a classic system for ecology and evolutionary biology with poor functional genetics; C. elegans is a classic system for functional genetics with poor ecology. In order to help bridge these disciplines, here we describe the natural history of a close relative of C. elegans, C. sp. 34, that is associated with the fig Ficus septica and its pollinating Ceratosolen wasps.\n\nResultsTo understand the natural context of fig-associated Caenorhabditis, fresh F. septica figs from four Okinawan islands were sampled, dissected, and observed under microscopy. C. sp. 34 was found in all islands where F. septica figs were found. C. sp. 34 was routinely found in the fig interior and almost never observed on the outside surface. Caenorhabditis was only found in pollinated figs, and C. sp. 34 was more likely to be observed in figs with more foundress pollinating wasps. Actively reproducing C. sp. 34 dominated younger figs, whereas older figs with emerging wasp progeny harbored C. sp. 34 dispersal larvae. Additionally, C. sp. 34 was observed dismounting from plated Ceratosolen pollinating wasps. C. sp. 34 was never found on non-pollinating, parasitic Philotrypesis wasps. Finally, C. sp. 34 was only observed in F. septica figs among five Okinawan Ficus species sampled.\n\nConclusionThese observations suggest a natural history where C. sp. 34 proliferates in young F. septica figs and disperses from old figs on Ceratosolen pollinating fig wasps. The fig and wasp host specificity of this Caenorhabditis is highly divergent from its close relatives and frames hypotheses for future investigations. This natural co-occurrence of the fig/fig wasp and Caenorhabditis study systems sets the stage for an integrated research program that can help to explain the evolution of interspecific interactions.

ecology↗
bioRxiv2026

Genomic signatures of selection and putative adaptive introgression during the African expansion of the house mouse

How species adapt to novel environments following biological invasion remains a central question in evolutionary biology. The recent human-mediated expansion of the western house mouse (Mus musculus domesticus) across Africa provides an opportunity to investigate the genomic basis of these rapid evolutionary responses. Using whole-genome data from 218 wild mice sampled across Europe and Africa, we combined complementary genome-wide differentiation, genotype-environment association, haplotype-based selection, and localized introgression analyses to investigate genomic signatures of selection and assess the contribution of interspecific gene flow from the native congener Mus spretus to these patterns. Genome-wide differentiation analyses identified candidate regions enriched for immune and epithelial-barrier functions, chemosensory perception, and neural or developmental pathways. Genotype-environment association analyses recovered fewer candidates linked mainly to precipitation, whereas haplotype-based scans highlighted recent selective signals involving sensory, immune, and neural functions. Across analyses, candidate regions were dominated by non-coding variation, supporting a predominantly regulatory and likely polygenic genomic architecture. Although excess allele sharing with M. spretus varied among populations, overlap between introgression and selection candidates was limited but greater than expected by chance. Several overlapping regions were also present in European populations, indicating that introgressed variants likely predated African colonization. Overall, our results suggest that the genomic signatures accompanying the African expansion of house mice were driven mainly by selection on M. m. domesticus variation, whereas introgressed M. spretus alleles contributed to a smaller subset of candidate loci and may have played a role in adaptation in African populations.

evolutionary biology↗
bioRxiv2025

Tree Explorer (T-REX): Bridging Phylogenetic and Phenotypic Data for Enhanced Analysis and Interpretation

BackgroundThe Tree Explorer (T-REX) project is an open-source initiative designed to enhance the visualization and integration of phylogenetic and phenotypic data. Utilizing the ete3 toolkit, T-REX offers a user-friendly interface and a suite of tools written in Python. This project addresses the longstanding need to easily label phylogenetic trees with phenotypic data stored in other files and efficiently query this data to find entities of interest. ResultsT-REX includes various tools to help users prepare their input files and refine the output to create publication-worthy figures. It aims to facilitate the rapid identification of strains of interest for research projects, making large phylogenetic trees more interpretable and useful for evolutionary biology studies. ConclusionsT-REX provides an easy-to-use tool that allows users to effectively link their phylogenetic and phenotypic datasets in order to answer diverse biological questions. Available as a pre-compiled binary or rapid install, users can label trees, perform complex queries to identify individuals of interest, link large-scale quantitative datasets, and produce publication-ready figures. This tool, along with its future developments, is expected to assist in evolutionary biological studies and in the identification and selection of biological entities exhibiting traits of interest.

bioinformatics↗
bioRxiv2025

Museum genomics links MC1R alleles to adaptive winter coat color polymorphism in the long-tailed weasel

Understanding the architecture of biological adaptations is a major endeavor of evolutionary biology. Using Natural History collections, we study the genetic basis and evolution of white/brown winter coat color variation in the long-tailed weasel (Neogale frenata), a crucial phenological adaptation for camouflage in habitats with seasonal snow. We produced whole-genome sequencing data for museum specimens, along two winter color morph transition areas in North America, at the West and East coasts. Genome-wide association scans identified a single genomic region linked to color variation polymorphism with approximately 300kb and 200kb in the West and East regions, respectively, which included the pigmentation gene MC1R. We identified three MC1R alleles, two of which with deletions of nine or eight amino acids, alternatively associated with the winter brown morphs in the West and East, respectively. These deletions affect the second transmembrane domain, and in one case also the first extracellular loop, which in silico analyses predicted to impact the proteins function. Our findings show alternative intraspecific evolutionary solutions for environmental adaptation in long-tailed weasels, building on the evidence that major genes of the melanin production pathway are hotspots for recurrent and independent evolution of winter camouflage adaptation.

evolutionary biology↗
bioRxiv2016

Tradeoffs between microbial growth phases lead to frequency-dependent and non-transitive selection

Mutations in a microbial population can increase the frequency of a genotype not only by increasing its exponential growth rate, but also by decreasing its lag time or adjusting the yield (resource efficiency). The contribution of multiple life-history traits to selection is a critical question for evolutionary biology as we seek to predict the evolutionary fates of mutations. Here we use a model of microbial growth to show there are two distinct components of selection corresponding to the growth and lag phases, while the yield modulates their relative importance. The model predicts rich population dynamics when there are tradeo[ff]s between phases: multiple strains can coexist or exhibit bistability due to frequency-dependent selection, and strains can engage in rock-paper-scissors interactions due to non-transitive selection. We characterize the environmental conditions and patterns of traits necessary to realize these phenomena, which we show to be readily accessible to experiments. Our results provide a theoretical framework for analyzing high-throughput measurements of microbial growth traits, especially interpreting the pleiotropy and correlations between traits across mutants. This work also highlights the need for more comprehensive measurements of selection in simple microbial systems, where the concept of an ordinary fitness landscape breaks down.

evolutionary biology↗
bioRxiv2018

Untangling the role of selection and drift in population divergence via transcriptional network simulations: Extended analysis of Ghalambor et al. (2015)

Introduction Introduction Literature Cited A long-standing question in evolutionary biology is whether phenotypic plasticity influences adaptive evolutionary change (e.g. Waddington 1961; Price et al. 2003; Ghalambor et al. 2007; Lande 2009; Wund 2012). The same genotype can produce different phenotypes in response to different environments, but whether such plasticity constrains or facilitates evolutionary change remains an unresolved and controversial problem (Ghalambor et al. 2007). Theoretical models to date have made diverse predictions on the role of plasticity in evolutionary divergence (e.g. Ancel 2000; Paenke et al. 2007; Thibert-Plante and Hendry 2011), and empirical studies have largely been limited to retrospective approaches that infer the role of plasticity long-after popu ...

evolutionary biology↗
bioRxiv2024

A hypercubic Mk model framework for capturing reversibility in disease, cancer, and evolutionary accumulation modelling

Accumulation models, where a system progressively acquires binary features over time, are common in the study of cancer progression, evolutionary biology, and other fields. Many approaches have been developed to infer the accumulation pathways by which features (for example, mutations) are acquired over time. However, most of these approaches do not support reversibility: the loss of a feature once it has been acquired (for example, the clearing of a mutation from a tumour or population). Here, we demonstrate how the well-established Mk model from evolutionary biology, embedded on a hypercubic transition graph, can be used to infer the dynamics of accumulation processes, including the possibility of reversible transitions, from data which may be uncertain and cross-sectional, longitudinal, or phylogenetically / phylogenomically embedded. Positive and negative interactions between arbitrary sets of features (not limited to pairwise interactions) are supported. We demonstrate this approach with synthetic datasets and real data on bacterial drug resistance and cancer progression. While this implementation is limited in the number of features that can be considered, we discuss how this limitation may be relaxed to deal with larger systems.

bioinformatics↗
bioRxiv2026

Evolutionary and biological insights into the paternally expressed Snord116-Ipw-Snord115 gene array at the imprinted Prader-Willi syndrome domain

Placental mammal-specific box C/D small nucleolar RNA (SNORD) genes within the imprinted human 15q11q13 domain have garnered increasing attention because their poorly understood roles in the brain and their potential involvement in Prader-Willi syndrome (PWS). Using two novel knockout (KO) mouse models, we demonstrate that combined deletion of Snord116 and Snord115 genes, but not the intervening Ipw ncRNA gene, leads to partially penetrant perinatal lethality (40-50%). Snord116/115-deficient neonates display postnatal growth impairment, hypoglycemia and endocrine dysregulation, including failure of the postnatal leptin surge. Despite showing no overt alterations in feeding behavior, adult Snord116/115-KO mice recapitulate most phenotypes previously reported in Snord116-KO models. RNA-seq analyses of the hypothalamus, prefrontal cortex and cerebellum reveal limited global changes. However, we observed upregulation of two of the most compelling putative RNA targets of Snord116 and Snord115 (Dgkk and Htr2c, respectively) in the postnatal hypothalamus. Nevertheless, no evidence was found to support efficient Snord115-guided ribose methylation of Htr2c mRNA. Finally, comparative analyses across 64 representative placental mammal species reveal that many PWS-associated SNORD genes, including SNORD115, display greater evolutionary changes than previously appreciated, raising questions about the functional relevance and evolutionary selective pressures that have shaped the diversification of certain family members across species. Overall, our study provides an unbiased re-assessment of the evolutionary, molecular and physiological significance of the paternally expressed Snord116-Ipw-Snord115 genomic interval and highlights the early postnatal period as a critical, yet largely underexplored, developmental window during which recently evolved SNORDs likely function as dispensable fine-tuners of gene expression.

genetics↗
bioRxiv2018

Sequence variation of rare outer membrane protein β-barrel domains in clinical strains provides insights into the evolution of Treponema pallidum subsp. pallidum, the syphilis spirochete.

In recent years, considerable progress has been made in topologically and functionally characterizing integral outer membrane proteins (OMPs) of Treponema pallidum subspecies pallidum (TPA), the syphilis spirochete, and identifying its surface-exposed {beta}-barrel domains. Extracellular loops in OMPs of Gram-negative bacteria are known to be highly variable. We examined the sequence diversity of {beta}-barrel-encoding regions of tprC, tprD, and bamA, in 31 specimens from Cali, Colombia; San Francisco, California; and the Czech Republic and compared them to allelic variants in the 41 reference genomes in the NCBI database. To establish a phylogenetic framework, we used tp0548 genotyping and tp0558 sequences to assign strains to the Nichols or SS14 clades. We found that (i) {beta}-barrels in clinical strains could be grouped according to allelic variants in TPA reference genomes; (ii) for all three OMP loci, clinical strains within the Nichols or SS14 clades often harbored {beta}-barrel variants that differed from the Nichols and SS14 reference strains; and (iii) OMP variable regions often reside in predicted extracellular loops containing B-cell epitopes. Based upon structural models, non-conservative amino acid substitutions in predicted transmembrane {beta}-strands of TprC and TprD2 could give rise to functional differences in their porin channels. OMP profiles of some clinical strains were mosaics of different reference strains and did not correlate with results from enhanced molecular typing. Our observations suggest that human host selection pressures drive TPA OMP diversity and that genetic exchange contributes to the evolutionary biology of TPA. They also set the stage for topology-based analysis of antibody responses against OMPs and help frame strategies for syphilis vaccine development.\n\nIMPORTANCEDespite recent progress characterizing outer membrane proteins (OMPs) of Treponema pallidum (TPA), little is known about how their surface-exposed, {beta}-barrel-forming domains vary among strains circulating within high-risk populations. In this study, sequences for the {beta}-barrel-encoding regions of three OMP loci, tprC, tprD, and bamA, in TPA from a large number of patient specimens from geographically disparate sites were examined. Structural models predict that sequence variation within {beta}-barrel domains occurred predominantly within predicted extracellular loops. Amino acid substitutions in predicted transmembrane strands that could potentially affect porin channel function also were noted. Our findings suggest that selection pressures exerted by human populations drive TPA OMP diversity and that recombination at OMP loci contributes to the evolutionary biology of syphilis spirochetes. These results also set the stage for topology-based analysis of antibody responses that promote clearance of TPA and frame strategies for vaccine development based upon conserved OMP extracellular loops.

microbiology↗
bioRxiv2023

A standard protocol to report discrete stage-structured demographic information

O_LIStage-based demographic methods, such as matrix population models (MPMs), are powerful tools used to address a broad range of fundamental questions in ecology, evolutionary biology, and conservation science. Accordingly, MPMs now exist for over 3,000 species worldwide. These data are being digitised as an ongoing process and periodically released into two large open-access online repositories: the COMPADRE Plant Matrix Database and the COMADRE Animal Matrix Database. During the last decade, data archiving and curation of COMPADRE and COMADRE, and subsequent comparative research, have revealed pronounced variation in how MPMs are parameterized and reported. C_LIO_LIHere, we summarise current issues related to the parameterisation and reporting of MPMs that arise most frequently and outline how they affect MPM construction, analysis, and interpretation. To quantify variation in how MPMs are reported, we present results from a survey identifying key aspects of MPMs that are frequently unreported in manuscripts. We then screen COMPADRE and COMADRE to quantify how often key pieces of information are omitted from manuscripts using MPMs. C_LIO_LIOver 80% of surveyed researchers (n=60) state a clear benefit to adopting more standardised methodologies for reporting MPMs. Furthermore, over 85% of the 300 MPMs assessed from COMPADRE and COMADRE omitted one or more elements that are key to their accurate interpretation. Based on these insights, we identify fundamental issues that can arise from MPM construction and communication and provide suggestions to improve clarity, reproducibility, and future research utilising MPMs and their required metadata. To fortify reproducibility and empower researchers to take full advantage of their demographic data, we introduce a standardized protocol to present MPMs in publications. This standard is linked to www.compadre-db.org, so that authors wishing to archive their MPMs can do so prior to submission of publications, following examples from other open-access repositories such as DRYAD, Figshare, and Zenodo. C_LIO_LICombining and standardising MPMs parameterized from populations around the globe and across the tree of life opens up powerful research opportunities in evolutionary biology, ecology, and conservation research. However, this potential can only be fully realised by adopting standardised methods to ensure reproducibility. C_LI

ecology↗
bioRxiv2015

Extensive de novo mutation rate variation between individuals and across the genome of Chlamydomonas reinhardtii

Describing the process of spontaneous mutation is fundamental for understanding the genetic basis of disease, the threat posed by declining population size in conservation biology, and in much evolutionary biology. However, directly studying spontaneous mutation is difficult because of the rarity of de novo mutations. Mutation accumulation (MA) experiments overcome this by allowing mutations to build up over many generations in the near absence of natural selection. In this study, we sequenced the genomes of 85 MA lines derived from six genetically diverse wild strains of the green alga Chlamydomonas reinhardtii. We identified 6,843 spontaneous mutations, more than any other study of spontaneous mutation. We observed seven-fold variation in the mutation rate among strains and that mutator genotypes arose, increasing the mutation rate dramatically in some replicates. We also found evidence for fine-scale heterogeneity in the mutation rate, driven largely by the sequence flanking mutated sites, and by clusters of multiple mutations at closely linked sites. There was little evidence, however, for mutation rate heterogeneity between chromosomes or over large genomic regions of 200Kbp. Using logistic regression, we generated a predictive model of the mutability of sites based on their genomic properties, including local GC content, gene expression level and local sequence context. Our model accurately predicted the average mutation rate and natural levels of genetic diversity of sites across the genome. Notably, trinucleotides vary 17-fold in rate between the most mutable and least mutable sites. Our results uncover a rich heterogeneity in the process of spontaneous mutation both among individuals and across the genome.

Genomics↗
bioRxiv2020

Quantifying Evolutionary Importance of Protein Sites: A Tale of Two Measures

A key challenge in evolutionary biology is the accurate quantification of selective pressure on proteins and other biological macromolecules at single-site resolution. The evolutionary importance of a protein site under purifying selection is typically measured by the degree of conservation of the protein site itself. A possible alternative measure is the strength of the site-induced conservation gradient in the rest of the protein structure. However, the quantitative relationship between these two measures remains unknown. Here, we show that despite major differences, there is a strong linear relationship between the two measures such that more conserved protein sites also induce stronger conservation gradient in the rest of the protein. This linear relationship is universal as it holds for different types of proteins and functional sites in proteins. Our results show that the strong selective pressure acting on the functional site in general percolates through the rest of the protein via residue-residue contacts. Surprisingly however, catalytic sites in enzymes are the principal exception to this rule. Catalytic sites induce significantly stronger conservation gradients in the rest of the protein than expected from the degree of conservation of the site alone. The unique requirement for the active site to selectively stabilize the transition state of the catalyzed chemical reaction imposes additional selective constraints on the rest of the enzyme.

evolutionary biology↗
bioRxiv2020

Generative probabilistic biological sequence models that account for mutational variability

Generative probabilistic modeling of biological sequences has widespread existing and potential application across biology and biomedicine, from evolutionary biology to epidemiology to protein design. Many standard sequence analysis methods preprocess data using a multiple sequence alignment (MSA) algorithm, one of the most widely used computational methods in all of science. However, as we show in this article, training generative probabilistic models with MSA preprocessing leads to statistical pathologies in the context of sequence prediction and forecasting. To address these problems, we propose a principled drop-in alternative to MSA preprocessing in the form of a structured observation distribution (the ``MuE" distribution). The MuE is a latent alignment model in which not only the alignment variable but also the regressor sequence can be latent. We prove theoretically that the MuE distribution comprehensively generalizes popular methods for inferring biological sequence alignments, and provide a precise characterization of how such biological models have differed from natural language latent alignment models. We show empirically that models that use the MuE as an observation distribution outperform comparable methods across a variety of datasets, and apply MuE models to a novel problem for generative probabilistic sequence models: forecasting pathogen evolution.

genomics↗
bioRxiv2024

Evolutionary Systems Biology Identifies Genetic Trade-offs In Rice Defense Against Above- and Belowground Attackers

Like other plants, wild and domesticated rice species (Oryza nivara, O. rufipogon, and O. sativa) evolve in environments with various biotic and abiotic stresses that fluctuate in intensity through space and time. Microbial pathogens and invertebrate herbivores such as plant-parasitic nematodes and caterpillars show geographical and temporal variation in activity patterns and may respond differently to certain plant defensive mechanisms. As such, plant interactions with multiple community members may result in conflicting selection pressures on genetic polymorphisms. Here, through assays with different above- and belowground herbivores, the fall armyworm (Spodoptera frugiperda) and the southern root-knot nematode (Meloidogyne incognita), respectively, and comparison with rice responses to microbial pathogens, we identify potential genetic trade-offs at the KSL8 and MG1 loci on chromosome 11. KSL8 encodes the first committed step towards biosynthesis of either stemarane- or stemodane-type diterpenoids through the japonica (KSL8-jap) or indica (KSL8-ind) allele. Knocking out KSL8-jap and CPS4, encoding an enzyme that acts upstream in diterpenoid synthesis, in japonica rice cultivars increased resistance to S. frugiperda and decreased resistance to M. incognita. Furthermore, MG1 resides in a haplotype that provided resistance to M. incognita, while alternative haplotypes are involved in mediating resistance to the rice blast fungus Magnaporthe oryzae and other pests and pathogens. Finally, KSL8 and MG1 alleles are located within trans-species haplotypes and may be evolving under long-term balancing selection. Our data are consistent with a hypothesis that polymorphisms at KSL8 and MG1 may be maintained through complex and diffuse community interactions.

systems biology↗
bioRxiv2019

bioRxiv: the preprint server for biology

The traditional publication process delays dissemination of new research, often by months, sometimes by years. Preprint servers decouple dissemination of research papers from their evaluation and certification by journals, allowing researchers to share work immediately, receive feedback from a much larger audience, and provide evidence of productivity long before formal publication. Launched in 2013 as a non-profit community service, the bioRxiv server brought preprinting to the life sciences and recently posted its 310,000th manuscript. The server now receives around ten million views per month and hosts papers spanning all areas of biology. Initially dominated by evolutionary biology, genetics/genomics and computational biology, bioRxiv has been increasingly populated by papers in neuroscience, cell and developmental biology, and many other fields. bioRxiv and its sister server, medRxiv, also played a critical role during the pandemic, rapidly disseminating new discoveries in immunology, virology and epidemiology related to the SARS-CoV-2 virus and its effects. Changes in journal and funder policies that encourage preprint posting helped drive adoption, as did the development of bioRxiv technologies that allow authors to transfer papers easily between bioRxiv and journals. A recent user survey found that 30% of authors post their preprints weeks to months before submitting to a journal whereas 55% post around the time of journal submission. Authors are motivated by a desire to share work early; they value the feedback they receive and very rarely experience any negative consequences of preprint posting. Rapid dissemination via bioRxiv is also encouraging new initiatives that experiment with the peer review process and the development of novel approaches to literature filtering and assessment.

scientific communication and education↗
bioRxiv2026

Haplotype-level metabarcoding revealed the relationship between species occurrence and population genetic structure at the catchment scale in aquatic insects

A longstanding question in ecology and evolutionary biology is understanding the evolutionary mechanisms whereby some species appear frequently while others do not. Current research examined this phenomenon through computer simulations and empirical studies involving a few species, while community-wide investigations of this relationship in natural settings remain largely unexplored. To address this, we employed haplotype-level bulk DNA metabarcoding to infer haplotypes from many aquatic insect species with varying occurrence in a catchment. We identified 891 haplotypes belonging to 200 taxonomically identified Operational Taxonomic Units (OTUs). Results showed that species with higher occurrence in the catchment had greater {gamma}-genetic diversity, a wider range of environmental conditions, and an increased probability of {beta}-species-genetic diversity correlations (SGDC). We found negative -SGDC in species with lower occurrence in the catchment. Dispersal abilities and environmental factors may influence the relationship among species occurrence, population genetic structure, and SGDC. Our findings present a novel approach to address the association of species occurrence and population genetic structure, as well as SGDC, from a community-level perspective. This has important implications for addressing biodiversity loss driven by rapid environmental changes from human activities and climate change.

ecology↗
bioRxiv2026

Are theoretical advances in distance-based tree learning practical for phylogenetic inference?

The phylogenetic tree of relatedness for species, viral samples, or other biological taxa is essential information for all fields of evolutionary biology. Many different statistical and computational tools for phylogeny inference are used by practicing biologists, but none take advantage of a body of theoretical work on fast-converging algorithms that guarantee correctness with high probability under particular conditions. Here, we assess the utility of one of the most advanced of these algorithms when applied in reasonable biological situations. Our simulation study shows that realistic datasets will often not meet the assumptions of the algorithm, but also that the results are relatively robust to this problem. We additionally provide guidance on how the algorithm can be deployed when the true tree is not known, which is essential for any real-world application. Overall, our intention is to bring a class of methods to the attention of the phylogenetics community, and to make the algorithmic community aware of the needs of practicing biologists.

evolutionary biology↗
bioRxiv2024

The importance of mistakes: Variation in spores reveals trade-offs for range expansion in the xeric-adapted Australasian species Cheilanthes distans (Pteridaceae)

Biological trade-offs present a central issue for evolutionary biology: it has been a fundamental understanding within the field that limits exist on the phenotypic traits a species is able to exhibit in part due to trade-offs. Reproduction--with its myriad forms--has been studied extensively in the context of these dynamics. And while considerable literature has explored trade-offs between seed size and number and their associated environmental conditions, none has looked at spore size trade-offs in ferns. We can hypothesise potential trade-offs in spore size: smaller spores should be able to disperse farther, but may not have sufficient provisions to survive in environments that require them to remain at the gametophyte stage for longer periods if their germination cues are mismatched. Reproductive mode (sexual vs. asexual) and ploidy may also be playing a role. In order to study trade-offs related to spore size, I focus on the Australasian fern species Cheilanthes distans (Pteridaceae), which is most often found in xeric environments, growing in crevices or on top of rocks which are haphazardly scattered across their range. Apomictic diplospores in this species are formed through first division restitution, a meiotic pathway particularly prone to mistakes in chromosome pairing and cell division (as compared to premeiotic endomitosis). Rather than being problematic, these mistakes ultimately lead to considerable additional variation in spore size, spore products (through a range of aneuploid spores), and spore ploidy. In this study, I explore trade-offs between spore size, dispersal, and germination, taking into account effects from reproductive mode and ploidy. I carried out an extensive survey of C. distans specimens to establish the prevalence of sexual vs. apomictic (asexual) specimens, and to describe in greater depth the variation in ploidy across the species. I also collected data on spore size and sporogenesis forms. With these data I then asked: is spore size correlated with range area or with germination? And does spore form correlate with either spore size or germination? Ultimately, I find that variations in sporogenesis may be leading to large variation in spore sizes--especially since spores traditionally considered abortive are in fact viable--and that this variation may provide abundant fodder for evolution to act through trade-offs between dispersal into large ranges and germination leading to establishment. Especially in light of the fact that many spores that were historically considered abortive are fully viable and likely shaping evolution in important ways, it is worth remarking on what these results illustrate more broadly: the way in which we have constructed disability ultimately affects how we perceive so-called genetic errors--both in humans and in other species--and thus limits what we allow ourselves to imagine disabled beings are capable of.

evolutionary biology↗