Shaping Genetic Diversity Research Articles

Divergence and serial colonization shape genetic variation and define conservation units in Asian elephants

Asian elephants (Elephas maximus) are the largest extant terrestrial megaherbivores native to Asia, with 60% of their wild population found in India. Despite ecological and cultural importance, their population genetic structure and diversity, demographic history, and ensuing implications for management/conservation remain understudied. We analyzed 34 whole genomes (between 11× and 32×) from most known elephant landscapes in India and identified five management/conservation units corresponding to elephants in Northern (Northwestern/Northeastern), Central, and three in Southern India. Our data reveal signatures of divergence and serial colonization and a potential dilution of genetic diversity from north to south of India. The northern populations diverged from others more than 70,000 years ago, have higher genetic diversity, and have low inbreeding (pi= 0.0016± 0.0001; FROH>1 MB= 0.09± 0.03). Two of three populations in Southern India have low diversity and are inbred, with very low effective population sizes compared with census sizes (pi= 0.0014± 0.00009 and 0.0015± 0.0001; FROH>1 MB= 0.25± 0.09 and 0.17± 0.02). Analyses of genetic load reveal the purging of potentially high-effect insertion/deletion (indel) deleterious alleles in the southern populations and a decreasing number of deleterious alleles from north to south in India. However, despite dilution and purging for the damaging mutation load in Southern India, the load that remains is homozygous. High homozygosity of deleterious alleles, coupled with low neutral genetic diversity, make southernmost populations high priority for conservation attention. Most surprisingly, our study suggests that patterns of genetic diversity and genetic load can correspond to genomic signatures of serial founding events, even in large, highly mobile, endangered mammals.

Unveiling population structure and selection signatures of riverine and genetically improved rohu, Labeo rohita using genome wide SNPs.

Captive breeding, along with artificial selection can significantly impact population structure by influencing allele frequencies and driving populations towards specific adaptation. Selective sweeps are powerful forces in shaping genetic variation within populations and can drive rapid spread of beneficial alleles while simultaneously reducing genetic diversity in localized regions of the genome. The present work was undertaken to assess the genetic structure and consequences of artificial selection in 10th generation of genetically improved rohu by comparing with wild populations. The present study used 11,022 high-quality genome wide SNPs to compare the population genetic structure and signatures of selection between Jayanti rohu population and its wild counterpart. Outlier analysis revealed presence of 14 adaptive SNPs, out of which 5 were classified to be under decisive selection pressure. Notably, Jayanti rohu (JR) displayed 297 private alleles exclusive to its population. Chromosomes 7 and 16 emerged as potential hotspots containing a majority of the identified SNPs. Structure and principal component analysis revealed two distinct clusters, effectively distinguishing the JR and wild rohu populations. Phylogenetic analysis indicated a separate cluster of JR population distant from wild groups. The results of present study shall help in elucidating patterns of genetic variation and characterizing selection signatures associated with captive bred and natural populations of rohu. The genomic resources generated through this work shall be helpful in improving the traceability of selectively bred germplasm for developing future strategies of genetic management.

Analysis of Endangered Andalusian Black Cattle (Negra Andaluza) Reveals Genetic Reservoir for Bovine Black Trunk.

This comprehensive study on the Andalusian Black cattle breed reveals a substantial population decline, with the average herd size decreasing significantly from 305.54 to 88.28 animals per herd. This decline is primarily attributed to agricultural changes and the introduction of foreign meat-focused breeds. The male-to-female ratio shift is noteworthy, with more cows than bulls, impacting selection intensity for both genders. Inbreeding levels, though relatively low historically (5.94%) and currently (7.23%), raise concerns as 37.08% historically and 48.82% currently of the animals exhibit inbreeding. Positive assortative mating is evident, reflected by the increasing non-random mating coefficient (α). Key ancestors play a crucial role in shaping genetic diversity, with one ancestor significantly influencing the current genetic pool and the top 10 ancestors contributing substantially. Breed maintains a conservation index of 2.75, indicating relatively high genetic diversity. Recent conservation efforts have led to an increase in registered animals. The Cañadas Reales, historical transhumance routes, may have contributed to genetic connections among provinces. Challenges include the historical bottleneck, demographic changes, and potential impacts from reproductive practices. The Andalusian Black breed's conservation necessitates ongoing efforts in genealogical registration, targeted breeding programs, and collaborative initiatives to address the observed demographic shifts and ensure sustainable genetic diversity.

Investigating the Influence of ANTXR2 Gene Mutations on Protective Antigen Binding for Heightened Anthrax Resistance.

Bacillus anthracis is the bacterium responsible for causing the zoonotic disease called anthrax. The disease presents itself in different forms like gastrointestinal, inhalation, and cutaneous. Bacterial spores are tremendously adaptable, can persist for extended periods and occasionally endanger human health. The Anthrax Toxin Receptor-2 (ANTXR2) gene acts as membrane receptor and facilitates the entry of the anthrax toxin into host cells. Additionally, mutations in the ANTXR2 gene have been linked to various autoimmune diseases, including Hyaline Fibromatosis Syndrome (HFS), Ankylosing Spondylitis (AS), Juvenile Hyaline Fibromatosis (JHF), and Infantile Systemic Hyalinosis (ISH). This study delves into the genetic landscape of ANTXR2, aiming to comprehend its associations with diverse disorders, elucidate the impacts of its mutations, and pinpoint minimal non-pathogenic mutations capable of reducing the binding affinity of the ANTXR2 gene with the protective antigen. Recognizing the pivotal role of single-nucleotide polymorphisms (SNPs) in shaping genetic diversity, we conducted computational analyses to discern highly deleterious and tolerated non-synonymous SNPs (nsSNPs) in the ANTXR2 gene. The Mutpred2 server determined that the Arg465Trp alteration in the ANTXR2 gene leads to altered DNA binding (p = 0.22) with a probability of a deleterious mutation of 0.808; notably, among the identified deleterious SNPs, rs368288611 (Arg465Trp) stands out due to its significant impact on altering the DNA-binding ability of ANTXR2. We propose these SNPs as potential candidates for hypertension linked to the ANTXR2 gene, which is implicated in blood pressure regulation. Noteworthy among the tolerated substitutions is rs200536829 (Ala33Ser), recognized as less pathogenic; this highlights its potential as a valuable biomarker, potentially reducing side effects on the host while also reducing binding with the protective antigen protein. Investigating these SNPs holds the potential to correlate with several autoimmune disorders and mitigate the impact of anthrax disease in humans.

Digest: A model for speciation in island systems.

Ecological pulses, marked by rapid environmental shifts, shape species dynamics such as speciation. Princepe et al. 2024 explore how intermittent migration, seabed depth, and sea-level changes influence species richness in islands. Their model, revealing nuanced richness patterns and migration impacts, contributes to understanding island evolution and offers insights into real-world cases. Examining the Philippines Archipelago, known for rich biodiversity, parallels emerge, showcasing the complex interplay of isolation, land bridges, and sea-level shifts in shaping genetic diversity. Overall, the findings enhance our understanding of population evolution in dynamic island environments.

Gene Flow and Isolation in the Arid Nearctic Revealed by Genomic Analyses of Desert Spiny Lizards.

The opposing forces of gene flow and isolation are two major processes shaping genetic diversity. Understanding how these vary across space and time is necessary to identify the environmental features that promote diversification. The detection of considerable geographic structure in taxa from the arid Nearctic has prompted research into the drivers of isolation in the region. Several geographic features have been proposed as barriers to gene flow, including the Colorado River, Western Continental Divide (WCD), and a hypothetical Mid-Peninsular Seaway in Baja California. However, recent studies suggest that the role of barriers in genetic differentiation may have been overestimated when compared to other mechanisms of divergence. In this study, we infer historical and spatial patterns of connectivity and isolation in Desert Spiny Lizards (Sceloporus magister) and Baja Spiny Lizards (Sceloporus zosteromus), which together form a species complex composed of parapatric lineages with wide distributions in arid western North America. Our analyses incorporate mitochondrial sequences, genomic-scale data, and past and present climatic data to evaluate the nature and strength of barriers to gene flow in the region. Our approach relies on estimates of migration under the multispecies coalescent to understand the history of lineage divergence in the face of gene flow. Results show that the S. magister complex is geographically structured, but we also detect instances of gene flow. The WCD is a strong barrier to gene flow, while the Colorado River is more permeable. Analyses yield conflicting results for the catalyst of differentiation of peninsular lineages in S. zosteromus. Our study shows how large-scale genomic data for thoroughly sampled species can shed new light on biogeography. Furthermore, our approach highlights the need for the combined analysis of multiple sources of evidence to adequately characterize the drivers of divergence.

Assessing population structure and migration patterns of wild boar (Sus scrofa) in Japan

Geographical wildlife patterns reflect historical range expansion and connectivity and provide insights into wildlife population management. In our large-scale phylogeographic population analysis of wild boars (Sus scrofa leucomystax) in Japan, we identified 15 clusters using 29 microsatellite markers, each structured within a range of approximately 200 km. This suggests that evolution was essentially driven by isolation by distance, and that the range of gene flow was limited. One cluster contained subpopulations located approximately 900 km apart, indicating the occurrence of past anthropogenic introductions. Moreover, we estimated effective migration to visualize the geographic genetic population diversity. This analysis identified six potential barriers, one of which involved large plains and mountainous areas in the Kanto region of eastern Japan. This barrier likely persisted in the two eastern clusters for an extended period, restricting migration to the neighboring areas. Overall, our study sheds light on the demographic history of wild boar in Japan, provides evidence of past anthropogenic introductions from distant areas, and highlights the importance of geographic barriers in shaping genetic diversity and population dynamics. This knowledge will be beneficial for forming informed wildlife management strategies toward the conservation of genetic integrity and ecological balance of wild boar populations in Japan.

Phylogeographical patterns are governed by geography in endemic polymorphic snail Indrella ampulla (Gastropoda: Ariophantidae)

Abstract Genetic diversity within a species can be shaped by abiotic factors, such as climate and geography. We aimed to ascertain the relative importance of these two abiotic factors to Indrella ampulla, a monotypic snail species from the Western Ghats, India, that has three colour morphs with some overlapping distributions. We also wanted to investigate whether these colour morphs represent divergent lineages or incipient species. We sequenced one nuclear and two mitochondrial genes from 32 individuals of I. ampulla. We used phylogenetic, population genetic, and niche modelling tools to address these questions. The results suggested that the colour morphs were not reciprocally monophyletic and exhibited considerable niche overlap, suggesting that they cannot be considered as incipient species. Furthermore, the results showed that the impact of palaeoclimatic oscillations in shaping the genetic diversity of this species cannot be determined conclusively. The Palghat Gap seems to have shaped the genetic diversity in this group to a certain degree. The colour morph distributed south of the Palghat Gap did not show admixture and exhibited the least amount of niche overlap with the other morphs. The geography of the landscape seems to have played a prominent role in shaping genetic diversity in this species.

Genomic insights into the phage-defense systems of Stenotrophomonas maltophilia clinical isolates

Stenotrophomonas maltophilia is a rapidly evolving multidrug-resistant opportunistic pathogen that can cause serious infections in immunocompromised patients. Although phage therapy is one of promising strategies for dealing with MDR bacteria, the main challenges of phage therapeutics include accumulation of phage resistant mutations and acquisition of the phage defense systems. To systematically evaluate the impact of (pro)phages in shaping genetic and evolutionary diversity of S. maltophilia, we collected 166 S. maltophilia isolates from three hospitals in southern China to analyze its pangenome, virulence factors, prophage regions, and anit-viral immune systems. Pangenome analysis indicated that there are 1328 saturated core genes and 26961 unsaturated accessory genes in the pangenome, suggesting existence of highly variable parts of S. maltophilia genome. The presence of genes in relation to T3SS and T6SS mechanisms suggests the great potential to secrete toxins by the S. maltophilia population, which is contrary to the conventional notion of low-virulence of S. maltophilia. Additionally, we characterized the pan-immune system maps of these clinical isolates against phage infections and revealed the co-harboring of CBASS and anti-CBASS in some strains, suggesting a never-ending arms race and the co-evolutionary dynamic between bacteria and phages. Furthermore, our study predicted 310 prophage regions in S. maltophilia with high genetic diversity. Six viral defense systems were found to be located at specific position of the S. maltophilia prophage genomes, indicating potential evolution of certain site/region similar to bacterial ‘defense islands’ in prophage. Our study provides novel insights into the S. maltophilia pangenome in relation to phage-defense mechanisms, which extends our understanding of bacterial-phage interactions and might guide the application of phage therapy in combating S. maltophilia infections.

Genomic analyses indicate the North American Ap-ha variant of the tick-vectored bacterium Anaplasma phagocytophilum was introduced from Europe

BackgroundAnaplasma phagocytophilum is a tick-vectored, obligately intracellular bacterium that infects a diversity of vertebrate hosts. In North America, the Ap-ha variant of A. phagocytophilum can cause dangerous infections in humans, whereas symptomatic human infections in Europe are rare. Conversely, the European host-generalist ecotype of A. phagocytophilum frequently causes illness in domestic ruminants while no comparable infections have been recorded from North America. Despite these differences in pathogenicity, the Ap-ha variant is closely aligned phylogenetically with the European host-generalist ecotype. Furthermore, North American populations of A. phagocytophilum are less genetically diverse than those in Europe. Taken together, these observations suggest that the North American Ap-ha variant may represent an introduced population of this bacterium.Methods Data from publicly available whole genomes of A. phagocytophilum were used to compare phylogeographic patterns and the extent of genetic divergence between the North American Ap-ha variant and the European host-generalist ecotype.ResultsThe results confirm that North American Ap-ha samples are phylogenetically nested within the diversity of the European host-generalist ecotype, and that Ap-ha likely radiated within the last 100 years. As expected, the Ap-ha variant also exhibited relatively low genetic diversity levels compared to the European host-generalist ecotype. Finally, North American Ap-ha harbored significantly more derived alleles than the European host-generalist A. phagocytophilum population.ConclusionsCollectively, these results support the hypothesis that the Ap-ha variant was recently introduced to North America from Europe and underwent a strong genetic bottleneck during this process (i.e. a ‘founder event’). Adaptation to novel vectors may have also played a role in shaping genetic diversity and divergence patterns in these pathogenic bacteria. These findings have implications for future studies aimed at understanding evolutionary patterns and pathogenicity variation within A. phagocytophilum.Graphical

Landscape genomics reveals signals of climate adaptation and a cryptic lineage in Arthropodium fimbriatum

Habitat loss and fragmentation are critical threats to biodiversity. Consequent decreases in population size and connectivity can impact genetic diversity and, thus, future adaptability and resilience to environmental change. Understanding landscape patterns of genetic diversity, including patterns of adaptive variation, can assist in developing conservation strategies that maximise population persistence and adaptability in the face of environmental change. Using a reduced-representation genomic approach, we investigated genetic diversity, structure, and adaptive variation across an aridity gradient in the woodland forb Arthropodium fimbriatum. Moderate levels of genetic diversity (HS = 0.14–0.23) were found in all 13 sampled provenances. Inbreeding varied among provenances (FIS = 0.08–0.42) but was not associated with estimated population size. Four genetic clusters were identified, including one highly differentiated cluster. Higher pairwise FST (0.23–0.42) between the three provenances of this cluster and the remaining 10 provenances (pairwise FST between 10 provenances 0.02–0.32) suggested two highly divergent lineages or potentially a cryptic species. After excluding the three highly differentiated populations, outlier and genotype-environment association analysis identified 275 putatively adaptive loci suggesting genomic signatures of climate adaptation in A. fimbriatum is primarily associated with changes in aridity. Combined, these results suggest that all provenances have conservation value, contributing to the maintenance of genetic diversity and adaptive variation in this species. The uncovering of a potential cryptic taxon highlights the power of genomics approaches in conservation genetics and the importance of understanding the role of landscape variation shaping genetic variation to effectively define conservation management units in an era of rapid biodiversity decline.

Fine‐scale spatial genetic structure in a locally abundant native bunchgrass (Achnatherum thurberianum) including distinct lineages revealed within seed transfer zones

AbstractAnalyses of the factors shaping genetic variation in widespread plant species are important for understanding the evolutionary history and local adaptation and have applied significance for guiding conservation and restoration decisions. Thurber's needlegrass (Achnatherum thurberianum) is a widespread, locally abundant grass that inhabits heterogeneous arid environments of western North America and is of restoration significance. It is a common component of shrubland steppe communities in the Great Basin Desert, where drought, fire, and invasive grasses have degraded natural communities. Using a reduced representation sequencing approach, we generated SNP data at 5677 loci across 246 individuals from 17 A. thurberianum populations spanning five previously delineated seed zones from the western Great Basin. Analyses revealed a pronounced population genetic structure, with individuals forming consistent geographical clusters across a variety of population genetic analyses and spatial scales. Low levels of genetic diversity within populations, as well as high population estimates of linkage disequilibrium and relatedness, were consistent with self‐fertilization as a contributor to population differentiation. Variance partitioning and partial redundancy analysis (pRDA) indicated local adaptation to environment as additionally influencing the spatial distribution of genetic variation. The environmental variables driving these results were similar to those implicated in recent genecological work which inferred local adaptation for seed zone delineation. Our analyses also revealed a complex evolutionary history of A. thurberianum in the Great Basin, where previously delineated seed zones contain distantly related populations. Our results indicate evolutionary history, mating system, and differentiation across distinct geographic and environmental scales have shaped genetic variation in A. thurberianum and illustrate how numerous aspects of population genetic variation might require consideration for restoration planning.

Genetic Diversity of Florida Scrub Lizards (Sceloporus woodi) Varies with Wildfire History

Fire shapes habitats and therefore influences the genetic characteristics of populations. Florida scrub is a fire-dependent habitat with several precinctive species, including Florida Scrub Lizards (Sceloporus woodi). Fire history of scrub patches could affect the movement patterns of Florida Scrub Lizards, thereby altering the genetic characteristics of local populations. We characterized the effect of time since fire (TSF) on genetic diversity and differentiation at 6 microsatellite loci in the Florida Scrub Lizard (n = 413) collected from 17 sites in Highlands County, Florida. Private allelic richness was positively correlated with TSF (r = 0.56, P = 0.009). In sites with a TSF of 3–17 yr, TSF was negatively correlated with expected heterozygosity (r = -0.90, P = 0.009), inbreeding (r = -0.77, P = 0.04), allelic richness (r = -0.79, P = 0.03), and private allelic richness (r = -0.80, P = 0.03); TSF was positively correlated with mean pairwise relatedness (r = 0.85, P = 0.02). Therefore, a consequence of TSF is short-term change to local population genetics that is likely precipitated by responses of Florida Scrub Lizards to habitat modification. At a TSF of >20 yr, TSF and genetic diversity were not correlated, indicating that factors other than fire shape genetic diversity in long-unburned locations. We detected genetic differentiation using Bayesian clustering and estimates of F-statistics. Our results highlight the importance of consistent fire regimes in the Florida scrub on the genetic diversity of Florida Scrub Lizards. The presence of Florida Scrub Lizard populations in long-unburned sites, however, warrants further investigation.

Molecular and quantitative genetic variation within and between populations of the declining grassland species Saxifraga granulata.

Formerly common plant species are expected to be particularly susceptible to recent habitat fragmentation. We studied the population genetics of 19 recently fragmented Saxifraga granulata populations (max. distance 61 km) in Luxembourg and neighboring Germany using RAPD markers and a common garden experiment. We assessed (1) the relationships between plant fitness, quantitative genetic variation, molecular genetic variation, and population size; and (2) the relative importance of genetic drift and selection in shaping genetic variation. Molecular genetic diversity was high but did not correlate with population size, habitat conditions, or plant performance. Genetic differentiation was low (F ST=0.079 ± 0.135), and there was no isolation by distance. Longevity, clonality, and the long-lived seed bank of S.granulata may have prevented strong genetic erosion and genetic differentiation among populations. However, genetic distinctness increased with decreasing genetic diversity indicating that random genetic drift occurred in the studied populations. Quantitative and molecular genetic variations were correlated, and their differentiation (Q ST vs. F ST) among S.granulata populations was similar, suggesting that mainly random processes have shaped the quantitative genetic differentiation among populations. However, pairwise quantitative genetic distances increased with geographic and climatic distances, even when adjusted for molecular genetic distances, indicating diversifying selection. Our results indicate that long-lived clonal species may be buffered at least temporarily against the negative effects of fragmentation. The relationship between quantitative genetic and geographic distance may be a more sensitive indicator of selection than Q ST-F ST differences.

Environmental response in gene expression and DNA methylation reveals factors influencing the adaptive potential of Arabidopsis lyrata.

Understanding what factors influence plastic and genetic variation is valuable for predicting how organisms respond to changes in the selective environment. Here, using gene expression and DNA methylation as molecular phenotypes, we study environmentally induced variation among Arabidopsis lyrata plants grown at lowland and alpine field sites. Our results show that gene expression is highly plastic, as many more genes are differentially expressed between the field sites than between populations. These environmentally responsive genes evolve under strong selective constraint - the strength of purifying selection on the coding sequence is high, while the rate of adaptive evolution is low. We find, however, that positive selection on cis-regulatory variants has likely contributed to the maintenance of genetically variable environmental responses, but such variants segregate only between distantly related populations. In contrast to gene expression, DNA methylation at genic regions is largely insensitive to the environment, and plastic methylation changes are not associated with differential gene expression. Besides genes, we detect environmental effects at transposable elements (TEs): TEs at the high-altitude field site have higher expression and methylation levels, suggestive of a broad-scale TE activation. Compared to the lowland population, plants native to the alpine environment harbor an excess of recent TE insertions, and we observe that specific TE families are enriched within environmentally responsive genes. Our findings provide insight into selective forces shaping plastic and genetic variation. We also highlight how plastic responses at TEs can rapidly create novel heritable variation in stressful conditions.

Breeding system and geospatial variation shape the population genetics of Triodanis perfoliata.

Both intrinsic and extrinsic forces work together to shape connectivity and genetic variation in populations across the landscape. Here we explored how geography, breeding system traits, and environmental factors influence the population genetic patterns of Triodanis perfoliata, a widespread mix‐mating annual plant in the contiguous US. By integrating population genomic data with spatial analyses and modeling the relationship between a breeding system and genetic diversity, we illustrate the complex ways in which these forces shape genetic variation. Specifically, we used 4705 single nucleotide polymorphisms to assess genetic diversity, structure, and evolutionary history among 18 populations. Populations with more obligately selfing flowers harbored less genetic diversity (π: R 2 = .63, p = .01, n = 9 populations), and we found significant population structuring (F ST = 0.48). Both geographic isolation and environmental factors played significant roles in predicting the observed genetic diversity: we found that corridors of suitable environments appear to facilitate gene flow between populations, and that environmental resistance is correlated with increased genetic distance between populations. Last, we integrated our genetic results with species distribution modeling to assess likely patterns of connectivity among our study populations. Our landscape and evolutionary genetic results suggest that T. perfoliata experienced a complex demographic and evolutionary history, particularly in the center of its distribution. As such, there is no singular mechanism driving this species' evolution. Together, our analyses support the hypothesis that the breeding system, geography, and environmental variables shape the patterns of diversity and connectivity of T. perfoliata in the US.

Plio-Pleistocene climatic change drives allopatric speciation and population divergence within the Scrophularia incisa complex (Scrophulariaceae) of desert and steppe subshrubs in Northwest China.

Numerous temperate plants and animals on the Qinghai-Tibet Plateau (QTP) are hypothesized to have differentiated due to vicariant allopatric speciation associated with the geologic uplifts. However, this hypothesis has rarely been tested through a phylogeographic study of relative species in a broader geographic context, including the QTP, Tianshan Mountains, Mongolian Plateau, and surrounding regions. To understand the speciation and diversification process of plants across this wide area, phylogeographic analysis were examined from Scrophularia incisa and two other closely relative species comprising S. kiriloviana and S. dentata. Thirty-two populations of the three close relatives were genotyped using chloroplast DNA fragments and nuclear microsatellite loci to assess population structure and diversity, supplemented by phylogenetic dating, ancestral area reconstructions and species distribution modelings, as well as niche identity tests. Our chloroplast DNA (cpDNA) phylogeny showed that this monophyletic group of desert and steppe semi-shrub is derived from a Middle Pliocene ancestor of the Central Asia. Lineages in Central Asia vs. China diverged through climate/tectonic-induced vicariance during Middle Pliocene. Genetic and ENM data in conjunction with niche differentiation analyses support that the divergence of S. incisa, S. dentata and S. kiriloviana in China lineage proceeded through allopatric speciation, might triggered by early Pleistocene climate change of increase of aridification and enlargement of deserts, while subsequent climate-induced cycles of range contractions/expansions enhanced the geographical isolation and habit fragmentation of these taxa. These findings highlight the importance of the Plio-Pleistocene climate change in shaping genetic diversity and driving speciation in temperate steppes and deserts of Northwestern China.

Genetic structure correlates with ethnolinguistic diversity in eastern and southern Africa

SummaryAfrican populations are the most diverse in the world yet are sorely underrepresented in medical genetics research. Here, we examine the structure of African populations using genetic and comprehensive multi-generational ethnolinguistic data from the Neuropsychiatric Genetics of African Populations-Psychosis study (NeuroGAP-Psychosis) consisting of 900 individuals from Ethiopia, Kenya, South Africa, and Uganda. We find that self-reported language classifications meaningfully tag underlying genetic variation that would be missed with consideration of geography alone, highlighting the importance of culture in shaping genetic diversity. Leveraging our uniquely rich multi-generational ethnolinguistic metadata, we track language transmission through the pedigree, observing the disappearance of several languages in our cohort as well as notable shifts in frequency over three generations. We find suggestive evidence for the rate of language transmission in matrilineal groups having been higher than that for patrilineal ones. We highlight both the diversity of variation within Africa as well as how within-Africa variation can be informative for broader variant interpretation; many variants that are rare elsewhere are common in parts of Africa. The work presented here improves the understanding of the spectrum of genetic variation in African populations and highlights the enormous and complex genetic and ethnolinguistic diversity across Africa.

Growth instabilities shape morphology and genetic diversity of microbial colonies

Cellular populations assume an incredible variety of shapes ranging from circular molds to irregular tumors. While we understand many of the mechanisms responsible for these spatial patterns, little is known about how the shape of a population influences its ecology and evolution. Here, we investigate this relationship in the context of microbial colonies grown on hard agar plates. This a well-studied system that exhibits a transition from smooth circular disks to more irregular and rugged shapes as either the nutrient concentration or cellular motility is decreased. Starting from a mechanistic model of colony growth, we identify two dimensionless quantities that determine how morphology and genetic diversity of the population depend on the model parameters. Our simulations further reveal that population dynamics cannot be accurately described by the commonly-used surface growth models. Instead, one has to explicitly account for the emergent growth instabilities and demographic fluctuations. Overall, our work links together environmental conditions, colony morphology, and evolution. This link is essential for a rational design of concrete, biophysical perturbations to steer evolution in the desired direction.

Sex-biased admixture and assortative mating shape genetic variation and influence demographic inference in admixed Cabo Verdeans.

Genetic data can provide insights into population history, but first, we must understand the patterns that complex histories leave in genomes. Here, we consider the admixed human population of Cabo Verde to understand the patterns of genetic variation left by social and demographic processes. First settled in the late 1400s, Cabo Verdeans are admixed descendants of Portuguese colonizers and enslaved West African people. We consider Cabo Verde’s well-studied historical record alongside genome-wide SNP data from 563 individuals from 4 regions within the archipelago. We use genetic ancestry to test for patterns of nonrandom mating and sex-specific gene flow, and we examine the consequences of these processes for common demographic inference methods and genetic patterns. Notably, multiple population genetic tools that assume random mating underestimate the timing of admixture, but incorporating nonrandom mating produces estimates more consistent with historical records. We consider how admixture interrupts common summaries of genomic variation such as runs of homozygosity. While summaries of runs of homozygosity may be difficult to interpret in admixed populations, differentiating runs of homozygosity by length class shows that runs of homozygosity reflect historical differences between the islands in their contributions from the source populations and postadmixture population dynamics. Finally, we find higher African ancestry on the X chromosome than on the autosomes, consistent with an excess of European males and African females contributing to the gene pool. Considering these genomic insights into population history in the context of Cabo Verde’s historical record, we can identify how assumptions in genetic models impact inference of population history more broadly.