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opencc-zeroFeb 2022View details →

Genetic structure in the nonbreeding range of rufa Red Knots suggests distinct Arctic breeding populations

An understanding of the migratory connectivity between breeding and nonbreeding areas is fundamental to the management of long-distance migrants under pressure from habitat change along their flyways. Here we describe evidence for genetic structure within the nonbreeding range of the endangered Arctic-Canadian rufa subspecies of Red Knots (Calidris canutus). Using blood and tissue samples from the major nonbreeding regions in Argentina (Tierra del Fuego and Río Negro), northern Brazil (Maranhão), and southeastern USA (Florida), we estimated genetic structure in 514 amplified fragment length polymorphism (AFLP) loci, applying cluster assignment analyses in DAPC, assignPOP, and STRUCTURE. Using a priori location information, individuals could be correctly re-assigned to their nonbreeding regions, which validated that the assignment accuracy of the data was sufficient. Without using a priori location information, we detected 3–5 genotype clusters, and posterior assignment probabilities of samples to these genotype clusters varied among the three regions. Lastly a chi-square test confirmed that allele frequencies varied significantly among nonbreeding regions, rejecting the hypothesis that samples were drawn from a single gene pool. Our findings hint at undescribed structure within the Red Knot rufa breeding range in the Canadian Arctic and indicate that each rufa nonbreeding area in this study hosts a different subsample of these breeding populations. The observation that nonbreeding sites of rufa Red Knots contain different genetic pools argues for separate conservation management of these sites.

Data from: Environment but not geography explains genetic variation in the invasive and largely panmictic European starling in North America

Populations of invasive species that colonize and spread in novel environments may differentiate both through demographic processes and local selection throughout the genome. European starlings (Sturnus vulgaris) were introduced to New York in 1890 and subsequently spread throughout North America, becoming one of the most widespread and numerous bird species on the continent. Genome-wide comparisons across starling individuals and populations can identify demographic and/or selective factors that facilitated this rapid and successful expansion. We investigated patterns of genomic diversity and differentiation using reduced-representation genome sequencing (ddRADseq) of 17 starling populations. Consistent with this species' high dispersal rates and rapid expansion history, we found low genome-wide differentiation and few FST outliers even at a continental scale. Despite starting from a founding population of approximately 180 individuals, North American starlings do not seem to have undergone a detectable genetic bottleneck: they have maintained an extremely large effective population size since introduction. We find more than 200 variants that correlate with temperature and/or precipitation. Genotype-environment associations (but not outlier scans) identify these SNPs against a background of negligible genome- and range-wide divergence. Such variants fall in the coding regions of genes associated with metabolism, stress, and neurological function. This evidence for incipient local adaptation in North American starlings suggests that it can evolve rapidly even in wide-ranging and evolutionarily young populations. This survey of genomic signatures of expansion in North American starlings is the most comprehensive to date and complements ongoing studies of world-wide local adaptation in these highly dispersive and invasive birds.

Challenging a host-pathogen paradigm: Susceptibility to chytridiomycosis is decoupled from genetic erosion

The putatively positive association between host genetic diversity and the ability to defend against pathogens has long attracted the attention of evolutionary biologists. Chytridiomycosis, a disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), has emerged in recent decades as a cause of dramatic declines and extinctions across the amphibian clade. Bd susceptibility can vary widely across populations of the same species, but the relationship between standing genetic diversity and susceptibility has remained notably underexplored so far. Here, we focus on a putatively Bd-naive system of two mainland and two island populations of the common toad (Bufo bufo) at the edge of the species' range, and use controlled infection experiments and dd-RAD sequencing of >10,000 SNPs across 95 individuals to characterise the role of host population identity, genetic variation and individual body mass in mediating host response to the pathogen. We found strong genetic differentiation between populations and marked variation in their susceptibility to Bd. This variation was not, however, governed by isolation-mediated genetic erosion, and individual heterozygosity was even found to be negatively correlated with survival. Individual survival during infection experiments was strongly positively related to body mass, which itself was unrelated to population of origin or heterozygosity. Our findings underscore the general importance of context-dependency when assessing the role of host genetic variation for the ability of defence against pathogens.

Evolution of selfing syndrome and its influence on genetic diversity and inbreeding: A range-wide study in Oenothera primiveris.

Premise of the study: To avoid inbreeding depression plants have evolved diverse breeding systems to favor outcrossing such as self-incompatibility. However, changes in biotic and abiotic conditions can result in selective pressures that lead to a breakdown in self-incompatibility. The shift to increased selfing is commonly associated with reduced floral features, lower attractiveness to pollinators, and increased inbreeding. In this study, we tested the hypothesis that the loss of self-incompatibility, a shift to self-fertilization (autogamy), and concomitant evolution of the selfing syndrome (reduction in floral traits associated with cross-fertilization) will lead to increased inbreeding and population differentiation in Oenothera primiveris. Across its range, this species exhibits a shift in its breeding system and floral traits from a self-incompatible population with large flowers to self-compatible populations with smaller flowers. Methods: We conducted a breeding system assessment, evaluated floral traits in the field and under controlled conditions, and measured population genetic parameters using RADseq data.  Key results: Our results reveal a bimodal transition to the selfing syndrome from the west to the east of the range of O. primiveris. This shift includes variation in the breeding system, mating system, a reduction in floral traits (flower diameter, herkogamy, and scent production), a shift to greater autogamy, reduced genetic diversity, and increased inbreeding. Conclusions: The observed variation highlights the importance of range-wide studies to understand breeding system variation and the evolution of the selfing syndrome within populations and species.

opencc-by-4.0Dec 2021View details →

The population genetics of adaptation through copy-number variation in a fungal plant pathogen

Supplementary Tables S1-S8 for the manuscript "The population genetics of adaptation through copy-number variation in a fungal plant pathogen"

dataset related to article "EXPANDING THE GENETIC SPECTRUM OF PRIMARY FAMILIAL BRAIN CALCIFICATION DUE TO SLC2OA2 MUTATIONS: A CASE SERIES"

Sanger sequences (.abi files) of all patients of our Fondazione Besta Cohort.

Archived data for: Balancing selection, genetic drift, and human mediated-introgression interplay to shape MHC (functional) diversity in Mediterranean brown trout

The extraordinary polymorphism of Major Histocompatibility Complex (MHC) genes is considered a paradigm of pathogen-mediated balancing selection, although empirical evidence is still scarce. Furthermore, the relative contribution of balancing selection to shape MHC population structure and diversity, compared to that of neutral forces, as well as its interaction with other evolutionary processes such as hybridization, remains largely unclear. To investigate these issues, we analysed adaptive (MHC-DAB gene) and neutral (11 microsatellite loci) variation in 156 brown trout (Salmo trutta complex) from six wild populations in central Italy exposed to introgression from domestic hatchery lineages (assessed with the LDH gene). MHC diversity and structuring correlated with those at microsatellites, indicating the substantial role of neutral forces. However, individuals carrying locally rare MHC alleles/supertypes (regardless of the zygosity status and degree of sequence dissimilarity of MHC) were in better body condition (a proxy of individual fitness/parasite load), hence supporting balancing selection under rare allele advantage, but not heterozygote advantage or divergent allele advantage. The association between specific MHC supertypes and body condition confirmed in part this finding. Across populations, MHC allelic richness increased with increasing admixture between native and domestic lineages, indicating introgression as a source of MHC variation. Furthermore, introgression across populations appeared more pronounced for MHC than microsatellites, possibly because initially-rare MHC variants are expected to introgress more readily under rare allele advantage. Providing evidence for the complex interplay among neutral evolutionary forces, balancing selection and human-mediated introgression in shaping the pattern of MHC (functional) variation, our findings contribute to a deeper understanding of the evolution of MHC genes in wild populations exposed to anthropogenic disturbance.

Reduced genetic diversity associated with the northern expansion of an amphibian species with high habitat-specialization, Ascaphus truei, resolved using two types of genetic markers

Reconstruction of historical relationships between geographic regions within a species' range can indicate dispersal patterns and help predict future responses to shifts in climate. Ascaphus truei (coastal tailed frog) is an indicator species of the health of forests and perennial streams in the Coastal and Cascade Mountains of the Pacific Northwest of North America. We used two genetic techniques — microsatellite and genotype-by-sequencing (GBS) — to compare the within region genetic diversity of populations near the northern extent of the species' range (British Columbia, Canada) to two geographic regions in British Columbia and two in Washington, USA, moving towards the core of the range. Allelic richness and heterozygosity declined substantially as latitude increased. The northernmost region had the lowest mean expected heterozygosities for both techniques (microsatellite, M = 0.20, SE = 0.080; GBS, M = 0.025, SE = 0.0010) and the southernmost region had the highest (microsatellite, M = 0.88, SE = 0.054; GBS, M = 0.20, SE = 0.0029). The northernmost regions (NC and MC) clustered together in population structure models for both genetic techniques. Our discovery of reduced diversity may have important conservation and management implications for population connectivity and the response of A. truei to climate change.

Modelling the genetic aetiology of complex disease: human-mouse conservation of noncoding features and disease-associated loci

Understanding the genetic aetiology of loci associated with disease is crucial for developing preventative measures and effective treatments. Mouse models are used extensively to understand human pathobiology and mechanistic functions of disease-associated loci. However, the utility of mouse models is limited by evolutionary divergence in transcription regulation for pathways of interest. Here, we summarise the conservation of genomic (exonic and multi-cell regulatory) features and complex disease associated variant sites between humans and mice. Our results highlight the importance of understanding evolutionary divergence in transcription regulation when interpreting functional studies using mice as models for human disease variants.

Phenotypic but no genetic adaptation in zooplankton 24 years after an abrupt +10°C climate change

Data and scripts for Pais-Costa et al 2022

Demographic, physiological, and genetic factors linked to poleward range expansion along the shoreline of China

Distribution range expansion is one of the most significant consequences of climate change in the Anthropocene. During range expansion, the former biogeographic barrier can be broken and then a new biogeographic pattern might appear. A comprehensive study, including demographic pattern, physiological performance and genetic features, is crucial for understanding how the expanding population occupies and survives in the new habitat, within which it formerly did not occur. In the present study, we investigated the demographic, physiological, and genetic features of the intertidal gastropod Nerita yoldii, which has extended its northern limit by ~200 km into areas that are warming up faster than the historical distribution over the former biogeographic break of the Yangtze River Estuary (YRE) during recent decades. The neutral SNPs data showed that the new marginal populations formed a distinct cluster established by a few founders. Demographic modeling analysis revealed that the new marginal populations experienced strong genetic bottlenecks followed by recent demographic expansion. Successful expansion that overcomes the founder effect (reduced genetic variation) might be attributed to its high capacity of rapid population growth and multiple introductions. According to the non-neutral SNPs under diversifying selection, there were high levels of heterozygosity in the new marginal populations, which might be beneficial for adapting to the novel thermal conditions. The common garden experiment showed that the new marginal populations have evolved divergent transcriptomic and physiological responses to heat stress, allowing them to occupy and survive in the novel environment. Our study also reveals a fast loss of transcriptional plasticity in the new marginal populations, potentially contributing to local adaptation. These results suggest a new biogeographic pattern for the snail N. yoldii has formed with the occurrence of demographic, physiologic and genetic changes, and emphasize the roles of adaptation of marginal populations during distribution range expansion.

Molecular Genetic Analysis of SARS-CoV-2 Lineages in Armenia - additional data

Sequencing of SARS-CoV-2 provides essential information on viral evolution, transmission, and epidemiology. In this study, we performed whole-genome sequencing of SARS-CoV-2 using nanopore and Illumina short-read sequencing to describe the circulation of the virus lineage in Armenia. This dataset contains Nextstrain configuration files, the auspice JSON file, BEAST output logs, and trees files, and resulting log and tree files as well as R scripts and data files used in phylogenetic and functional analyses.

Data from: Ecological genetics of Juglans nigra: differences in early growth patterns of natural populations

Many boreal and temperate forest tree species distributed across large geographic ranges are composed of populations adapted to the climate they inhabit. Forestry provenance studies and common gardens provide evidence of local adaptation to climate when associations between fitness traits and the populations' home climates are observed. Most studies that evaluate tree height as a fitness trait do so at a specific point in time. In this study, we elucidate differences in early growth patterns in black walnut (Juglans nigra L.) populations by modeling height growth from seed up to age 11. The data comprise tree height measurements between ages 2 to 11 for 52 natural populations of black walnut collected through its geographic range and planted in one or more of 3 common gardens. We use the Chapman-Richards growth model in a mixed-effects framework and test whether populations differ in growth patterns by incorporating populations' home climate into the model. In addition, we evaluate differences in populations' absolute growth and relative growth based on the fitted model. Models indicated that populations from warmer climates had the highest cumulative growth through time, with differences in average tree height between populations from home climates with a mean annual temperature (MAT) of 13 °C and of 7 °C estimated to be as high as 80% at age 3. Populations from warmer climates were also estimated to have higher and earlier maximum absolute growth rate than populations from colder climates. In addition, populations from warm climates were predicted to have higher relative growth rates at any given tree size. Results indicate that natural selection may shape early growth patterns of populations within a tree species, suggesting that fast early growth rates are likely selected for in relatively mild environments where competition rather than tolerance to environmental stressors becomes the dominant selection pressure.

opencc-by-4.0Feb 2022View details →

Isolation-by-distance and genetic parentage analysis provide similar larval dispersal estimates

An R studio project that includes original SNP data files used to quantify dispersal in Elacatinus lori via the isolation-by-distance (IBD) method. Associated R-code used to generate IBD regression slopes, calculate sigma, and construct dispersal kernels. Includes output from NeEstimator,  estimating effective population size.  Folders 1-3 contain the code/data needed to obtain the slope of the IBD relationship, effective population size, and the standard deviation (sigma) of the dispersal distribution, respectively. Folder 4 contains the R code needed to construct Laplacian dispersal kernels.

The quantitative genetics of fitness in a wild seabird

Additive genetic variance in fitness is a prerequisite for adaptive evolution, as a trait must be genetically correlated with fitness to evolve. Despite its relevance, additive genetic variance in fitness has not often been estimated in nature. Here, we investigate additive genetic variance in lifetime and annual fitness components in common terns (Sterna hirundo). Using 28 years of data comprising ca. 6000 pedigreed individuals, we find that additive genetic variances in the Zero-inflated and Poisson components of lifetime fitness were effectively zero, but estimated with high uncertainty. Similarly, additive genetic variances in adult annual reproductive success and survival did not differ from zero, but were again associated with high uncertainty. Simulations suggested that we would be able to detect additive genetic variances as low as 0.05 for the Zero-inflated component of fitness, but not for the Poisson component, for which adequate statistical power would require c. two more decades (four tern generations) of data collection. As such, our study suggests heritable variance in common tern fitness to be rather low if not zero, shows how studying the quantitative genetics of fitness in natural populations remains challenging, and highlights the importance of maintaining long-term individual-based studies of natural populations.

Population differentiation and intraspecific genetic admixture in two Eucryptorrhynchus weevils (Coleoptera: Curculionidae) across northern China

Inreasing damage of pests in agriculture and forestry can arise both as a consequence of changes in local species and through the introduction of alien species. In this study, we used population genetics approaches to examine population processes of two pests of the tree-of-heaven trunk weevil (TTW), Eucryptorrhynchus brandti (Harold) and the tree-of-heaven root weevil (TRW), E. scrobiculatus (Motschulsky) on the tree-of-heaven across their native range of China. We analyzed the population genetics of the two weevils based on ten highly polymorphic microsatellite markers. Population genetic diversity analysis showed strong population differentiation among populations of each species, with FST ranges from 0.0197 to 0.6650 and from -0.0724 to 0.6845, respectively. Populations from the same geographical areas can be divided into different genetic clusters, and the same genetic cluster contained populations from different geographical populations, pointing to dispersal of the weevils possibly being human-mediated. Redundancy analysis showed that the independent effects of environment and geography could account for 93.94% and 29.70% of the explained genetic variance in TTW, and 41.90% and 55.73% of the explained genetic variance in TRW, respectively, indicating possible impacts of local climates on population genetic differentiation. Our study helps to uncover population genetic processes of these local pest species with relevance to control methods.

Kernel weight contribution to yield genetic gain of maize: A global dataset of maize yield, kernel number, and kernel weight over the last century

Studies characterizing the effect of a century of plant breeding on physiological traits are highly needed to identify candidate traits for future improvement in maize (Zea mays L.). A global evaluation of kernel weight progress over time requires the assembly of large and reliable data documenting genetic improvements in this trait across commercial breeding programs in different regions. We compiled a global dataset of yield and yield components from 34 published and unpublished studies comparing two or more maize cultivars from different decades of commercial release under field conditions. The dataset includes 750 entries of kernel weight data (requirement to be included in the systematic review), of which 642 and 666 include data entries of grain yield and kernel number, respectively. We also extracted the metadata describing experimental site information, agronomic management practices, and genotypic information. This dataset can be useful to identify trends of yield improvement across management conditions, with proper consideration of the trade-off between kernel number and kernel weight in maize.

opencc-zeroDec 2020View details →

Genetic relationships between sympatric and allopatric Coregonus ciscoes in North and Central Europe

Background Sympatric speciation along ecological gradients has been studied repeatedly, in particular in freshwater fishes. Rapid post-glacial ecological divergence has resulted in numerous endemic species or ecologically distinct populations in lakes of the temperate zones. Here, we focus on the Baltic cisco (Coregonus albula) complex, to study the genetic similarity among two pairs of sympatric autumn- and spring-spawning populations from post-glacial German Lakes Stechlin and Breiter Luzin. For comparison, we included a similar pair of sympatric populations from the Swedish Lake Fegen. We wanted to explore potential genetic similarities between the three sympatric cisco population pairs in the three lakes, to evaluate whether the pairs may have emerged independently in the three lakes, or whether two different species may have colonized all three lakes independently. Furthermore, we considered allopatric C. albula populations from three Polish, three Finnish, and four Swedish locations, and added one Siberian population of the sister species C. sardinella and a Swedish C. maraena (whitefish) population. By genotyping nine microsatellite markers in 655 individuals from these 18 populations, we wanted to elucidate how strongly the cisco populations differ across a larger geographical area within Europe. Finally, we compared the genetic differences between the spring- and autumn-spawning populations of ciscoes in the two German lakes to infer the potentially deteriorating effect of strong anthropogenic pressure on the lakes. Results Dendrogram, Principal Coordinate Analysis and admixture analysis all indicated strong correspondence between population differentiation and geographical location for most cisco populations in Europe, including the Siberian population of C. sardinella. However, populations from some Swedish lakes deviated from this general pattern, by showing a distinct genetic structure. We found evidence for independent evolution of the three sympatric population pairs because the populations co-occurring in the same lake were always most closely related. However, genetic differentiation was weak in the two German population pairs, but strong in the Swedish Lake Fegen, indicating that the weak differentiation in the German pairs reported earlier has eroded further. Conclusions Our results suggest that the genetic differentiation at neutral genetic markers among populations of the Baltic cisco complex has evolved (and is maintained) by random genetic drift in isolated populations. However, earlier studies on the Swedish populations combining mitochondrial DNA and microsatellite data indicate that also post-glacial immigration from separate glacial refugia has shaped the present genetic population structure. The low neutral differentiation of the German sympatric pairs in contrast to the Swedish pair suggests that recent anthropogenic effects on the lakes in Germany may put the endemic spring-spawners at risk to extinction.

opencc-by-4.0Apr 2022View details →

Gene flow between wild trees and cultivated varieties shapes the genetic structure of sweet chestnut (Castanea sativa Mill.) populations

The sweet chestnut orchards (Castanea sativa Mill.) are traditionally planted in the northern Adriatic region. This study investigates their population structure, as well as the genetic background of three toponymous clonal varieties. Six genomic simple sequence repeat (gSSR) and nine EST-derived SSR (EST-SSR) loci were utilized in this study. We have identified five closely related clones, which represent a singular, polyclonal marron variety, found in all three cultivation areas, acompanied by many hybrids, resulting from the breeding between cultivated and wild chestnuts.