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opencc-zeroOct 2021View details →

Data from: Axes of multivariate sexual signal divergence among incipient species: concordance with selection, genetic variation, and phenotypic plasticity

Sexual signaling traits are often observed to diverge rapidly among populations, thereby playing a potentially key early role in the evolution of reproductive isolation. While often assumed to reflect divergent sexual selection among populations, patterns of sexual trait diversification might sometimes be biased along axes of standing additive genetic variation and covariation among trait components. Additionally, theory predicts that environmentally-induced phenotypic variation might facilitate rapid trait evolution, suggesting that patterns of divergence between populations should mirror phenotypic plasticity within populations. Here we evaluate the concordance between observed axes of multivariate sexual trait divergence and predicted divergence based on (1) interpopulation variation in sexual selection, (2) additive genetic variances, and (3) temperature-related phenotypic plasticity in male courtship song among geographically isolated populations of the Hawaiian swordtail cricket, Laupala cerasina, which exhibit sexual isolation due sexual signaling traits. The major axis of multivariate divergence, dmax, accounted for 76% of variation among population male song trait means, and was moderately correlated with interpopulation differences in directional sexual selection based on female preferences. However, the majority of additive genetic variance was largely oriented away from the direction of divergence, suggesting that standing genetic variation may not play a dominant role in the patterning of signal divergence. In contrast, the axis of phenotypic plasticity strongly mirrored patterns of interpopulation phenotypic divergence, which is consistent with a role for temperature-related plasticity in facilitating instead of inhibiting male song evolution and sexual isolation in these incipient species. We propose potential mechanisms by which sexual selection might interact with phenotypic plasticity to facilitate the rapid acoustic diversification observed in this species and clade.

opencc-zeroOct 2021View details →

Natural selection drives genome-wide evolution via chance genetic associations

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.

opencc-zeroOct 2021View details →

Selection against individuals from genetic introgression of escaped farmed salmon in a natural population of Atlantic salmon

The viability of wild Atlantic salmon populations is threatened by genetic introgression from escaped farmed salmon. Farmed Atlantic salmon are genetically improved for important commercial traits and a life in captivity but are poorly adapted to the natural environment. The rate of geneflow from escaped farmed to wild salmon depends on their spawning success and on offspring survival at various life-stages. We here investigate relative survival of introgressed juvenile Atlantic salmon (parr) in a river in northern Norway. The studied population has experienced genetic introgression from farmed salmon for about four generations (20 years). We followed two cohorts of parr from the year of hatching (0+) to the age of two years (2+). Farmed genetic introgression was quantified at the individual level and on a continuous scale using diagnostic SNPs. Population-level genetic introgression decreased from 0+ to 2+ by 64% (2011 cohort) and 37% (2013 cohort) . This change was driven by a 70% (2011 cohort) and 49% (2013 cohort) lower survival from age 0+ to 2+ in introgressed parr compared to parr of wild origin. Our observations show that there is natural selection against genetic introgression with a potential cost of lower productivity.The viability of wild Atlantic salmon populations is threatened by genetic introgression from escaped farmed salmon. Farmed Atlantic salmon are genetically improved for important commercial traits and a life in captivity but are poorly adapted to the natural environment. The rate of geneflow from escaped farmed to wild salmon depends on their spawning success and on offspring survival at various life-stages. We here investigate relative survival of introgressed juvenile Atlantic salmon (parr) in a river in northern Norway. The studied population has experienced genetic introgression from farmed salmon for about four generations (20 years). We followed two cohorts of parr from the year of hatching (0+) to the age of two years (2+). Farmed genetic introgression was quantified at the individual level and on a continuous scale using diagnostic SNPs. Population-level genetic introgression decreased from 0+ to 2+ by 64% (2011 cohort) and 37% (2013 cohort) . This change was driven by a 70% (2011 cohort) and 49% (2013 cohort) lower survival from age 0+ to 2+ in introgressed parr compared to parr of wild origin. Our observations show that there is natural selection against genetic introgression with a potential cost of lower productivity.

Comparative transcriptomics reveals the molecular genetic basis of pigmentation loss in Sinocyclocheilus cavefishes

Cave-dwelling animals evolve distinct troglomorphic traits, such as loss of eyes, skin pigmentation, and augmentation of senses following long-term adaptation to the perpetual darkness. However, the molecular genetic mechanisms underlying these phenotypic variations remain unclear. In this study, we conducted comparative histology and comparative transcriptomics study of the skin of eight Sinocyclocheilus species (Cypriniformes: Cyprinidae) that included surface and cave-dwelling species. We analyzed four surface and four cavefish species by using next-generation sequencing, and a total of 802,798,907 clean reads were generated and assembled into 505,495,009 transcripts, which contributed to 1,037,334 unigenes. Bioinformatics comparisons of four different surface-cave fish groups revealed between 10,629 and 6442 significantly differentially expressed unigenes. Further, tens of differentially expressed genes (DEGs) potentially related to skin pigmentation were identified. Most of these DEGs (including GNAQ, PKA, NRAS, and p38) are downregulated in cavefish species. They are involved in key signaling pathways of pigment synthesis, such as the melanogenesis, Wnt, and MAPK pathways. This trend of downregulation was confirmed through qPCR experiments. This study will deepen our understanding of the formation of troglomorphic traits in cavefishes.

Populations restored using regional seed are genetically diverse and similar to natural populations in the region

Ecological restoration and plant re-introductions aim to create plant populations that are genetically similar to natural populations to preserve the regional gene pool, yet genetically diverse to allow adaptation to a changing environment. For this purpose, seeds for restoration are increasingly sourced from multiple populations in the target region. However, it has only rarely been tested whether using regional seed indeed leads to genetically diverse restored populations which are genetically similar to natural populations. We used single nucleotide polymorphism (SNP) markers to investigate genetic diversity within and differentiation among populations of Centaurea jacea and Betonica officinalis on restored and natural meadows in the White Carpathians, Czech Republic. The restoration took place 20 years ago using regional seeds propagated from a mix of multiple regional source populations. We included original regional seeds in our analysis to compare the restored populations with their origin (only in C. jacea). Additionally, we analysed conventional seeds without certified origin because these would have constituted a common alternative for restoration seeding in the absence of regional seeds. The differentiation between restored and natural populations (mean pairwise FST = 0.018 in Centaurea and 0.021 in Betonica) was similar to the differentiation among natural populations (FST = 0.023 and 0.021), and the restored populations were slightly more genetically diverse than the natural populations. In addition, restored populations were relatively similar to their origin, the regional seeds (FST = 0.015). In contrast, conventional seeds were strongly differentiated from all regional populations (FST = 0.100 and 0.059, in Centaurea and Betonica, respectively) and harboured substantially lower genetic diversity. We also found signs of gene flow via pollen or seed dispersal from natural to restored populations but not vice versa. Policy implications. Regionally sourced seeds can produce genetically diverse populations at natural levels of genetic differentiation.

Probabilistic inference of the genetic architecture of functional enrichment of complex traits

We develop a Bayesian model (BayesRR-RC) that provides robust SNP-heritability estimation, an alternative to marker discovery, and accurate genomic prediction, taking 22 seconds per iteration to estimate 8.4 million SNP-effects and 78 SNP-heritability parameters in the UK Biobank. We find that only $\leq$ 10\% of the genetic variation captured for height, body mass index, cardiovascular disease, and type 2 diabetes is attributable to proximal regulatory regions within 10kb upstream of genes, while 12-25% is attributed to coding regions, 32-44% to introns, and 22-28% to distal 10-500kb upstream regions. Up to 24% of all cis and coding regions of each chromosome are associated with each trait, with over 3,100 independent exonic and intronic regions and over 5,400 independent regulatory regions having >95% probability of contributing >0.001% to the genetic variance of these four traits. Our open-source software (GMRM) provides a scalable alternative to current approaches for biobank data.

Landscape genetics Afromontane forest birds - microsatellite data

<a name="_Hlk61564128"></a>Species confined to naturally fragmented habitats may exhibit intrinsic population complexity which may challenge interpretations of species response to anthropogenic landscape transformation. In South Africa, where native forests are naturally fragmented, forest‐dependent birds have undergone range declines since 1992, most notably among insectivores. These insectivores appear sensitive to the quality of natural matrix habitats, and it is unknown whether transformation of the landscape matrix has disrupted gene flow in these species. We undertook a landscape genetics study of four forest‐dependent insectivorous songbirds across southeast South Africa. Microsatellite data were used to conduct a priori optimization of landscape resistance surfaces (land cover, rivers and dams, and elevation) using cost‐distances along least‐cost pathway (LCP), and resistance distances (IBR). We detected pronounced declines in effective population sizes over the past two centuries for the endemic forest specialist Cossypha dichroa and Batis capensis, alongside recent gene flow disruption in B. capensis, C. dichroa and Pogonocichla stellata. Landscape resistance modelling showed both native forest and dense thicket configuration facilitates gene flow in P. stellata, B. capensis and C. dichroa. Facultative dispersal of P. stellata through dense thicket likely aided resilience against historic landscape transformation, whereas combined forest‐thicket degradation adversely affected the forest generalist B. capensis. By contrast, Phylloscopus ruficapilla appears least reliant upon landscape features to maintain gene flow and was least impacted by anthropogenic landscape transformation. Collectively, gene flow in all four species is improved at lower elevations, along river valleys, and riparian corridors— where native forest and dense thicket better persist. Consistent outperformance of LCP over IBR land‐cover models for P. stellata, B. capensis and C. dichroa demonstrates the benefits of wildlife corridors for South African forest‐dependent bird conservation, to ameliorate the extinction debts from past and present anthropogenic forest exploitation.

Population genetics as a tool to elucidate pathogen reservoirs: Lessons from Pseudogymnoascus destructans, the causative agent of White-Nose disease in bats

Emerging infectious diseases pose a major threat to human, animal, and plant health. The risk of species-extinctions increases when pathogens can survive in the absence of the host. Environmental reservoirs can facilitate this. However, identifying such reservoirs and modes of infection is often highly challenging. In this study, we investigated the presence and nature of an environmental reservoir for the ascomycete fungus Pseudogymnoascus destructans, the causative agent of White-Nose disease. Using 18 microsatellite markers, we determined the genotypic differentiation between 1,497 P. destructans isolates collected from nine closely situated underground sites where bats hibernate (i.e., hibernacula) in Northeastern Germany. This approach was unique in that it ensured that every isolate and resulting multi-locus genotype was not only present, but also viable and therefore theoretically capable of infecting a bat. The distinct distribution of multi-locus genotypes across hibernacula demonstrates that each hibernaculum has an essentially unique fungal population. This would be expected if bats become infected in their hibernaculum (i.e., the site they spend winter in to hibernate) rather than in other sites visited before they start hibernating. In one hibernaculum where both the walls and the hibernating bats were sampled at regular intervals over five consecutive winter seasons (1,062 isolates), higher genotypic richness was found on walls compared to bats and multi-locus genotypes showed a stable frequency over multiple winters. This clearly implicates hibernacula walls as the main environmental reservoir of the pathogen, from which bats become re-infected annually during hibernation.

Genetic divergence and local adaptation of Liriodendron driven by heterogeneous environments

Ecological adaptive differentiation alters both the species diversity and intraspecific genetic diversity in forests, thus affecting the stability of forest ecosystems. Therefore, knowledge of the genetic underpinnings of the ecological adaptive differentiation of forest species is critical for effective species conservation. In this study, single-nucleotide polymorphisms (SNPs) from population transcriptomes were used to investigate the spatial distribution of genetic variation in Liriodendron to assess whether environmental variables can explain genetic divergence. We examined the contributions of environmental variables to population divergence and explored the genetic underpinnings of local adaptation using a landscape genomic approach. Niche models and statistical analyses showed significant niche divergence between L. chinense and L. tulipifera, suggesting that ecological adaptation may play a crucial role in driving interspecific divergence. We detected a new fine-scale genetic structure in L. chinense, and divergence of the six groups occurred during the late Pliocene to early Pleistocene. Redundancy analysis (RDA) revealed significant associations between genetic variation and multiple environmental variables. Environmental association analyses identified 67 environmental association loci (EALs; nonsynonymous SNPs) that underwent interspecific or intraspecific differentiation, 28 of which were associated with adaptive genes. These 28 candidate adaptive loci provide substantial evidence for local adaptation in Liriodendron. Our findings reveal ecological adaptive divergence pattern between Liriodendron species and provide novel insight into the role of heterogeneous environments in shaping genetic structure and driving local adaptation among populations, informing future L. chinense conservation efforts.

A roadmap to durable BCTV resistance using long-read genome assembly of genetic stock KDH13

PacBio Sequence data associated with genetic stock KDH13.Datasets include genome resources and annotated files associated with the manuscript "Long-read genome assembly of Double Haploid Sugar Beet KDH13 provides roadmap for durable genetic resistance to Beet Curly Top Virus". This includes genome assembly, ordered genome assembly, protein predictions, variant call format files for an F1 hybrid (KDH13xKDH19-17).

Phenotype and QTL mapping data from: Genetic trade-offs underlie divergent life history strategies for local adaptation in white clover

Local adaptation is common in plants, yet characterization of its underlying genetic basis is rare in herbaceous perennials. Moreover, while many plant species exhibit intraspecific chemical defense polymorphisms, their importance for local adaptation remains poorly understood. We examined the genetic architecture of local adaptation in a perennial, obligately-outcrossing herbaceous legume, white clover (Trifolium repens). This widespread species displays a well-studied chemical defense polymorphism for cyanogenesis (HCN release following tissue damage) and has evolved climate-associated cyanogenesis clines throughout its range. Two biparental F2 mapping populations, derived from three parents collected in environments spanning the U.S. latitudinal species range (Duluth, MN, St. Louis, MO and Gainesville, FL), were grown in triplicate for two years in reciprocal common garden experiments in the parental environments (6,012 total plants). Vegetative growth and reproductive fitness traits displayed trade-offs across reciprocal environments, indicating local adaptation. Genetic mapping of fitness traits revealed a genetic architecture characterized by allelic trade-offs between environments, with 100% and 80% of fitness QTL in the two mapping populations showing significant QTL X E interactions, consistent with antagonistic pleiotropy. Across the genome there were three hotspots of QTL co-localization. Unexpectedly, we found little evidence that the cyanogenesis polymorphism contributes to local adaptation. Instead, divergent life history strategies in reciprocal environments were major fitness determinants: selection favored early investment in flowering at the cost of multi-year survival in the southernmost site vs. delayed flowering and multi-year persistence in the northern environments. Our findings demonstrate that multi-locus genetic tradeoffs contribute to contrasting life history characteristics that allow for local adaptation in this outcrossing herbaceous perennial.

Pinpointing genetic breaks in the southeastern Pacific: phylogeography and genetic structure of Pyura chilensis, a commercially important tunicate

Aim: Accurate characterization of evolutionary units (species or populations) underlies all ecological and evolutionary studies and is crucial to conservation planning. Seascapes have long been thought to be highly permeable to gene flow, yet over the last decade building evidence has shown that barriers to gene flow in marine environments are much more common than previously thought. Here, we precisely characterize barriers to gene flow in the tunicate Pyura chilensis across 26° of latitude in the southeastern Pacific, assess the magnitude of said barriers, and explore their congruence with current biogeographic patterns of this region. Location: The southeastern Pacific (SEP), from Ilo, Perú (17ºS) to Chiloe, Chile (43ºS). Taxon: Pyura chilensis Methods: We used a combination of highly polymorphic microsatellite markers and a 540 bp fragment of the Cytochrome Oxidase subunit I (COI) to compare individuals sampled at 26 localities spanning approximately 2500 km of the SEP. Genetic diversity was analyzed using Bayesian clustering, haplotype networks, Isolation by Distance, and cline models. Coalescent simulators were used to estimate migration rates. Results: The results from both the microsatellite and COI markers indicate the presence of two genetic discontinuities: one at 34°S and one at 39°S which coincide with genetic breaks reported for other species. Interestingly, we were able to determine that genetic transitions occur abruptly and within short geographic distances (~ 30 km) compared with previous studies of this tunicate. Coalescent simulations indicate the 34ºS break is less permeable than the 39ºS break, and gene flow appears to be mostly unidirectional from north to south. Main conclusions: Our results support other studies that show that seascapes are complex, and also highlight the importance of accurately sampling distribution ranges when making conclusions about gene flow. Overall, the two main biogeographic barriers to gene flow characterized in the southeastern Pacific are not homogenously permeable and can be narrow (< 30 km). These results are relevant for the management of fisheries in this region and specifically for this commercially important species.

Spatially explicit genetic capture-recapture data from black bears in Ontario, Canada, 2017-2019

The Ontario Ministry of Northern Development, Mines, Natural Resources and Forestry sampled black bear (Ursus americanus) DNA at baited barbed wire hair corrals on 77 independent study areas in Ontario Canada, 2017-2019. Spatially explicit capture-recapture data from these surveys (>12 000 independent, spatially referenced detections of nearly 4000 individual bears) are archived here. This data set will be cited in manuscripts presenting different analyses of the entire data set or subsets thereof.

opencc-by-4.0Dec 2013View details →

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Fig. 3. FCAanalysisoftheallozymedataacrosspopulationsof Daphniaatkinsoni and D in Allozyme-Based Genetic Variability Of The Daphnia Atkinsoni-Bolivari Species Complex (Cladocera: Daphniidae) In The Hungarian Great Plain

Fig. 3. FCAanalysisoftheallozymedataacrosspopulationsof Daphniaatkinsoni and D. bolivari.

Data for genetic characterization and curation of diploid a-genome wheat species

Diploid A-genome relatives of wheat comprises T. urartu, T. monococcum subsp. monococcum (domesticated einkorn) and T. monococcum subsp. aegilopoides (wild einkorn). About 930 accessions of A-genome diploid wheat species preserved in the gene bank of the Wheat Genetics Resource Center (WGRC) at Kansas State University were genotyped using genotyping-by-sequencing (GBS). We constructed four pooled GBS libraries (384- and 288-plex) using restriction enzymes (Pst1-Msp1) combinations and the libraries were sequenced on the Illumina platform. The sequence data was processed using Tassel 5 GBS v2 pipeline and identified thousands of single nucleotide polymorphisms (SNPs) for downstream genetic and genomic dissections of the tested population. We have used T. urartu pseudomolecule (Tu2.0) as a reference genome to detect the genetic markers. Four fastq files with raw sequence reads information can be obtained at the National Center for Biotechnology Information (NCBI) SRA database with the BioProject accession PRJNA744683 (<a href="https://www.ncbi.nlm.nih.gov/sra/PRJNA744683" rel="noopener noreferrer">https://www.ncbi.nlm.nih.gov/sra/PRJNA744683</a>). Provided key file has information for demultiplexing including flowcell, lane number, barcodes and sample names to replicate the analysis. This experiment led us to curate the gene bank through identification of genetically duplicated accessions, miss-classified accessions and miss-classified non-diploid accessions. We were able to observe the unique genetic and evolutionary relationships among the diploid A-genome wheat species along with the unique population structures per species and sub-species.

Even more oak species in Mexico? Genetic structure and morphological differentiation support the presence of at least two specific entities within Quercus laeta

Differentiation among populations, sometimes despite ongoing gene exchange, is a key step in speciation. Therefore, comparison of intra- and interspecific differentiation patterns is of great significance to understanding speciation. The genus Quercus is an interesting system to test speciation models in the presence of gene flow, due to its weak interspecific reproductive barriers. The aim of the present study was to characterize the degree and pattern of morphological and genetic differentiation among different morphotypes in the white oak Quercus laeta, some corresponding to the previously described species Q. centralis, Q. laeta, Q. prinopsis and Q. transmontana, as well as geographically structured variation within Q. transmontana not previously described. Our goal was to evaluate if some of these can be considered distinct specific entities or are rather part of a continuum of variation. Nine microsatellite loci and two intergenic regions of chloroplast DNA were analyzed. Morphological differences were evaluated using geometric morphometrics. Chloroplast DNA showed low differentiation, suggesting introgression or sharing of ancestral haplotypes among the Q. laeta morphotypes. Nuclear microsatellites indicated differentiation into two distinct main genetic groups, which were congruent with morphological differentiation. In conclusion, nuclear markers and morphological variation suggest the existence of at least two different entities within Q. laeta.

Genetic and fitness measurements of Brighamia accessions for APPS

Premise of the study: Living collections maintained for generations are at risk of diversity loss, inbreeding, and adaptation to cultivation. To address these concerns the zoo community uses pedigrees to track individuals and implement crosses that maximize founder contributions and minimize inbreeding. Using a pedigree management approach in an exceptional plant, we demonstrate how conducting such strategic crosses can minimize genetic issues that have arisen under current practices. Methods: We performed crosses between these collections and compared the fitness of progeny, including plant performance and reproductive health. We genotyped the progeny and paternal accessions to measure changes in diversity and relatedness within and between accessions. Results: The mean relatedness among individuals of an accession, suggests they are full siblings. As a result there was high inbreeding and low diversity within an accession, although less so among accessions. Progeny from the wider crosses had increased genetic diversity, while selfed accessions were smaller and less fertile. Discussion: Institutions which hold exceptional species should consider how diversity is maintained within their collections. Implementing a pedigree-based approach to managing reproduction of ex situ plants will slow the inevitable loss of genetic diversity and in turn, result in healthier collections.

opencc-by-4.0Dec 2021View details →

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Combining genotypes and T cell receptor distributions to infer genetic loci determining V(D)J recombination probabilities: validation cohort meta data and parsed TCR repertoire data

Meta data corresponding the the validation cohort for the paper, "Combining genotypes and T cell receptor distributions to infer genetic loci determining V(D)J recombination probabilities" by Magdalena L Russell, Aisha Souquette, David M Levine, Stefan A Schattgen, E Kaitlynn Allen, Guillermina Kuan, Noah Simon, Angel Balmaseda, Aubree Gordon, Paul G Thomas, Frederick A Matsen IV, and Philip Bradley. These meta data include:  (1) SNP genotypes for the two SNPs which overlap with the discovery cohort          - (nicaragua_snp_genotypes_ints.tsv) -- SNP genotypes as integers          - (nicaragua_snp_genotypes_strings.tsv) -- SNP genotypes as allele strings  (2) the ancestry PCs for each individual in the validation cohort (nicaragua_snp_ancestry_PCA.tsv) (3) a file including IMGT genes and sequences used for parsing TCRB repertoire data (human_vj_allele_cdr3_nucseqs.tsv) (4) a file including IMGT genes used for parsing TCRA repertoire data (human_vj_alleles_alpha.tsv) (5) Parsed TCRA repertoire data (nicaragua_parsed_TCRA.tgz) (6) Parsed TCRB repertoire data (nicaragua_parsed_TCRB.tgz)  Corresponding raw validation cohort TCR repertoire data is available here: https://www. ncbi.nlm.nih.gov/bioproject/PRJNA762269 (The BioProject database, accession number: PRJNA762269) Software tools designed to work with these data are available here: https://github.com/phbradley/tcr-gwas

Phenotypic and Genetic data for "Evolution of fruit and seed traits during almond naturalization"

1- Cultivated plant species often naturalize and enter wild communities in a process known as feralization. To successfully feralize, crops must overcome ecological barriers and may undergo selection on certain traits, diverging phenotypically and genetically from their crop ancestors. In spite of the agronomic and ecological relevance of crop feralization, the eco-evolutionary dynamics driving it remain understudied. 2- In this paper, we evaluated phenotypic and genotypic differentiation in fruit and seed traits during the naturalization of the almond tree (Prunus dulcis (Mill.) D.A. Webb) in SE Iberia and evaluated the potential role of natural selection in this process. To do so, we investigated patterns of genetic divergence between cultivated and feral populations using functional (the cyanogenesis Sk gene) and neutral (17 SSR loci) markers and analyzed morphological and biochemical traits in kernels of 342 individuals from 15 cultivated and 24 feral populations. 3- We detected very little genetic differentiation in neutral markers between cultivated and feral populations. The majority of the observed genetic variation was due to differences within each type. Conversely, the recessive allele sk responsible for seed toxicity was significantly more frequent in feral populations. Phenotypic differentiation between cultivated and naturalized almond populations was also significant. Feral almond kernels were smaller and lighter, had denser and more resistant shells (endocarps) and more toxic seeds. Selection analyses indicated that these genetic and phenotypic patterns might be driven by directional selection on fruit and seed traits, potentially linked to defense against predation. 4- Synthesis. Our findings indicate that almond naturalization is consistent with strong directional selection on fruits and seeds, leading to smaller and more toxic seeds encased in harder endocarps. Accordingly, we propose that feralization of this crop is, at least to some degree, driven by adaptive evolution of dispersal and recruitment traits.