Browsing by Subject "EVOLUTIONARY HISTORY"
Now showing items 1-8 of 8
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(2018)An increasing number of mammalian species have been shown to have a history of hybridization and introgression based on genetic analyses. Only relatively few fossils, however, preserve genetic material, and morphology must be used to identify the species and determine whether morphologically intermediate fossils could represent hybrids. Because dental and cranial fossils are typically the key body parts studied in mammalian palaeontology, here we bracket the potential for phenotypically extreme hybridizations by examining uniquely preserved cranio-dental material of a captive hybrid between grey and ringed seals. We analysed how distinct these species are genetically and morphologically, how easy it is to identify the hybrids using morphology and whether comparable hybridizations happen in the wild. We show that the genetic distance between these species is more than twice the modern human–Neanderthal distance, but still within that of morphologically similar species pairs known to hybridize. By contrast, morphological and developmental analyses show grey and ringed seals to be highly disparate, and that the hybrid is a predictable intermediate. Genetic analyses of the parent populations reveal introgression in the wild, suggesting that grey–ringed seal hybridization is not limited to captivity. Taken together, we postulate that there is considerable potential for mammalian hybridization between phenotypically disparate taxa.
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(2021)Intra-tumor heterogeneity (ITH) is a mechanism of therapeutic resistance and therefore an important clinical challenge. However, the extent, origin, and drivers of ITH across cancer types are poorly understood. To address this, we extensively characterize ITH across whole-genome sequences of 2,658 cancer samples spanning 38 cancer types. Nearly all informative samples (95.1 %) contain evidence of distinct subclonal expansions with frequent branching relationships between subclones, We observe positive selection of subclonal driver mutations across most cancer types and identify cancer type-specific subclonal patterns of driver gene mutations, fusions, structural variants, and copy number alterations as well as dynamic changes in mutational processes between subclonal expansions. Our results underline the importance of ITH and its drivers in tumor evolution and provide a pan-cancer resource of comprehensively annotated subclonal events from whole-genome sequencing data.
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(2019)This is the first study to describe the mitochondrial genome of the Himalayan Griffon, Gyps himalayensis, which is an Old World vulture belonging to the family Accipitridae and occurring along the Himalayas and the adjoining Tibetan Plateau. Its mitogenome is a closed circular molecule 17,381 bp in size containing 13 protein-coding genes, 22 tRNA coding genes, two rRNA-coding genes, a control region (CR), and an extra pseudo-control region (CCR) that are conserved in most Accipitridae mitogenomes. The overall base composition of the G. himalayensis mitogenome is 24.55% A, 29.49% T, 31.59% C, and 14.37% G, which is typical for bird mitochondrial genomes. The alignment of the Accipitridae species control regions showed high levels of genetic variation and abundant AT content. At the 5 ' end of the domain I region, a long continuous poly-C sequence was found. Two tandem repeats were found in the pseudo-control regions. Phylogenetic analysis with Bayesian inference and maximum likelihood based on 13 protein-coding genes indicated that the relationships at the family level were (Falconidae + (Cathartidae + (Sagittariidae + (Accipitridae + Pandionidae))). In the Accipitridae clade, G. himalayensis is more closely related to Aegypius monachus than to Spilornis cheela. The complete mitogenome of G. himalayensis provides a potentially useful resource for further exploration of the taxonomic status and phylogenetic history of Gyps species.
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(2022)The grey wolf (Canis lupus) was the first species to give rise to a domestic population, and they remained widespread throughout the last Ice Age when many other large mammal species went extinct. Little is known, however, about the history and possible extinction of past wolf populations or when and where the wolf progenitors of the present-day dog lineage (Canisfamiliaris) lived(1-8). Here we analysed 72 ancient wolf genomes spanning the last 100,000 years from Europe, Siberia and North America. We found that wolf populations were highly connected throughout the Late Pleistocene, with levels of differentiation an order of magnitude lower than they are today. This population connectivity allowed us to detect natural selection across the time series, including rapid fixation of mutations in the gene IFT8840,000-30,000 years ago. We show that dogs are overall more closely related to ancient wolves from eastern Eurasia than to those from western Eurasia, suggesting a domestication process in the east. However, we also found that dogs in the Near East and Africa derive up to half of their ancestry from a distinct population related to modern southwest Eurasian wolves, reflecting either an independent domestication process or admixture from local wolves. None of the analysed ancient wolf genomes is a direct match for either of these dog ancestries, meaning that the exact progenitor populations remain to be located.
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(2019)The diversity of archaeal viruses is severely undersampled compared with that of viruses infecting bacteria and eukaryotes, limiting our understanding on their evolution and environmental impacts. Here, we describe the isolation and characterization of four new viruses infecting halophilic archaea from the saline Lake Retba, located close to Dakar on the coast of Senegal. Three of the viruses, HRPV10, HRPV11 and HRPV12, have enveloped pleomorphic virions and should belong to the family Pleolipoviridae, whereas the forth virus, HFTV1, has an icosahedral capsid and a long non-contractile tail, typical of bacterial and archaeal members of the order Caudovirales. Comparative genomic and phylogenomic analyses place HRPV10, HRPV11 and HRPV12 into the genus Betapleolipovirus, whereas HFTV1 appears to be most closely related to the unclassified Halorubrum virus HRTV-4. Differently from HRTV-4, HFTV1 encodes host-derived minichromosome maintenance helicase and PCNA homologues, which are likely to orchestrate its genome replication. HFTV1, the first archaeal virus isolated on a Haloferax strain, could also infect Halorubrum sp., albeit with an eightfold lower efficiency, whereas pleolipoviruses nearly exclusively infected autochthonous Halorubrum strains. Mapping of the metagenomic sequences from this environment to the genomes of isolated haloarchaeal viruses showed that these known viruses are underrepresented in the available viromes.
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(2019)Classification of tribe Cardueae in natural subtribes has always been a challenge due to the lack of support of some critical branches in previous phylogenies based on traditional Sanger markers. With the aim to propose a new subtribal delimitation, we applied a Hyb-Seq approach to a set of 76 Cardueae species representing all subtribes and informal groups defined in the tribe, targeting 1061 nuclear conserved orthology loci (COS) designed for Compositae and obtaining chloroplast coding regions as by-product of off-target reads. For the extraction of the target nuclear data, we used two strategies, PHYLUCE and HybPiper, and 776 and 1055 COS loci were recovered with each of them, respectively. Additionally, 87 chloroplast genes were assembled and annotated. With three datasets, phylogenetic relationships were reconstructed using both concatenation and coalescent approaches. Phylogenetic analyses of the nuclear datasets fully resolved virtually all nodes with very high support. Nuclear and plastid tree topologies are mostly congruent with a very limited number of incongruent nodes. Based on the well-solved phylogenies obtained, we propose a new taxonomic scheme of 12 monophyletic and morphologically consistent subtribes: Carlininae, Cardopatiinae, Echinopsinae, Dipterocominae (new), Xerantheminae (new), Berardiinae (new), Staehelininae (new), Onopordinae (new), Carduinae (redelimited), Arctiinae (new), Saussureinae (new), and Centaureinae. In addition, we further updated the temporal framework for origin and diversification of these subtribes. Our results highlight the power of Hyb-Seq over Sanger sequencing of a few DNA markers in solving phylogenetic relationships of traditionally difficult groups.
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(2017)Pleistocene glaciations have strongly affected the biogeography of many species residing in periglacial and previously glaciated regions. Smoothtail nine-spined sticklebacks (Pungitius laevis) have three highly divergent mitochondrial lineages in France, one of which shares the same mitochondrial cluster with a congener P. pungitius. To understand if interspecific introgression has happened between the two species, we carried out phylogeographic and population genetic analyses using mitochondrial and nuclear gene sequences. Our results indicated asymmetric mitochondrial introgression from P. pungitius to P. laevis and genetic admixture of these species in one of the P. laevis lineages, suggesting historical hybridization. Deep intraspecific mitochondrial divergence within P. laevis in central and southern France mostly coinciding with major drainages suggests that these areas were important glacial refugia for the species explaining the observed intraspecific divergence. The historical hybridization between P. laevis and P. pungitius likely occurred in a refugium at central France, and the newly formed P. laevis lineage spread northward during postglacial recolonization. The study adds to the long list of species showing complete mitogenome capture owing to historical hybridizations, and highlights the reticulate nature of population differentiation in taxa subject to postglacial range-expansions.
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(2019)BackgroundPopulation demography and gene flow among African groups, as well as the putative archaic introgression of ancient hominins, have been poorly explored at the genome level.ResultsHere, we examine 15 African populations covering all major continental linguistic groups, ecosystems, and lifestyles within Africa through analysis of whole-genome sequence data of 21 individuals sequenced at deep coverage. We observe a remarkable correlation among genetic diversity and geographic distance, with the hunter-gatherer groups being more genetically differentiated and having larger effective population sizes throughout most modern-human history. Admixture signals are found between neighbor populations from both hunter-gatherer and agriculturalists groups, whereas North African individuals are closely related to Eurasian populations. Regarding archaic gene flow, we test six complex demographic models that consider recent admixture as well as archaic introgression. We identify the fingerprint of an archaic introgression event in the sub-Saharan populations included in the models (similar to 4.0% in Khoisan, similar to 4.3% in Mbuti Pygmies, and similar to 5.8% in Mandenka) from an early divergent and currently extinct ghost modern human lineage.ConclusionThe present study represents an in-depth genomic analysis of a Pan African set of individuals, which emphasizes their complex relationships and demographic history at population level.
