Browsing by Subject "DIVERGENCE"

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  • Kess, Tony; Bentzen, Paul; Lehnert, Sarah J.; Sylvester, Emma V.A.; Lien, Sigbjorn; Kent, Matthew P.; Sinclair-Waters, Marion; Morris, Corey J.; Regular, Paul; Fairweather, Robert; Bradbury, Ian R. (2019)
    Chromosome structural variation may underpin ecologically important intraspecific diversity by reducing recombination within supergenes containing linked, coadapted alleles. Here, we confirm that an ancient chromosomal rearrangement is strongly associated with migratory phenotype and individual genetic structure in Atlantic cod (Gadus morhua) across the Northwest Atlantic. We reconstruct trends in effective population size over the last century and reveal declines in effective population size matching onset of industrialized harvest (after 1950). We find different demographic trajectories between individuals homozygous for the chromosomal rearrangement relative to heterozygous or homozygous individuals for the noninverted haplotype, suggesting different selective histories across the past 150 years. These results illustrate how chromosomal structural diversity can mediate fine-scale genetic, phenotypic, and demographic variation in a highly connected marine species and show how overfishing may have led to loss of biocomplexity within Northern cod stock.
  • Howlader, Mohammad Sajid Ali; Nair, Abhilash; Gopalan, Sujith V.; Merilä, Juha (2015)
  • Kivikoski, Mikko; Rastas, Pasi; Löytynoja, Ari; Merila, Juha (2021)
    We describe an integrative approach to improve contiguity and haploidy of a reference genome assembly and demonstrate its impact with practical examples. With two novel features of Lep-Anchor software and a combination of dense linkage maps, overlap detection and bridging long reads, we generated an improved assembly of the nine-spined stickleback (Pungitius pungitius) reference genome. We were able to remove a significant number of haplotypic contigs, detect more genetic variation and improve the contiguity of the genome, especially that of X chromosome. However, improved scaffolding cannot correct for mosaicism of erroneously assembled contigs, demonstrated by a de novo assembly of a 1.6-Mbp inversion. Qualitatively similar gains were obtained with the genome of three-spined stickleback (Gasterosteus aculeatus). Since the utility of genome-wide sequencing data in biological research depends heavily on the quality of the reference genome, the improved and fully automated approach described here should be helpful in refining reference genome assemblies.
  • Holm, Liisa (2020)
    DALI is a popular resource for comparing protein structures. The software is based on distance-matrix alignment. The associated web server provides tools to navigate, integrate and organize some data pushed out by genomics and structural genomics. The server has been running continuously for the past 25 years. Structural biologists routinely use DALI to compare a new structure against previously known protein structures. If significant similarities are discovered, it may indicate a distant homology, that is, that the structures are of shared origin. This may be significant in determining the molecular mechanisms, as these may remain very similar from a distant predecessor to the present day, for example, from the last common ancestor of humans and bacteria. Meta-analysis of independent reference-based evaluations of alignment accuracy and fold discrimination shows DALI at top rank in six out of 12 studies. The web server and standalone software are available from .
  • Acanski, Jelena; Vujic, Ante; Djan, Mihajla; Obreht Vidakovic, Dragana; Ståhls, Gunilla; Radenkovic, Snezana (2016)
    Several recent studies have detected and described complexes of cryptic and sibling species in the genus Merodon (Diptera, Syrphidae). One representative of these complexes is the Merodon avidus complex that contains four sibling species, which have proven difficult to distinguish using traditional morphological characters. In the present study, we use two geometric morphometric approaches, as well as molecular characters of the 5' -end of the mtDNA COI gene, to delimit sibling taxa. Analyses based on these data were used to strengthen species boundaries within the complex, and to validate the status of a previously-recognized cryptic taxon from Lesvos Island (Greece), here described as Merodon megavidus Vujic & Radenkovic sp. nov. Geometric morphometric results of both wing and surstylus shape confirm the present classification for three sibling species-M. avidus (Rossi, 1790), M. moenium Wiedemann in Meigen, 1822 and M. ibericus Vujic, 2015-and, importantly, clearly discriminate the newly-described taxon Merodon megavidus sp. nov. In addition to our geometric morphometric results, supporting characters were obtained from molecular analyses of mtDNA COI sequences, which clearly differentiated M. megavidus sp. nov. from the other members of the M. avidus complex. Molecular analyses revealed that the earliest divergence of M. ibericus occurred around 800 ky BP, while the most recent separation happened between M. avidus and M. moenium around 87 ky BP.
  • Feng, Shaohong; Stiller, Josefin; Deng, Yuan; Armstrong, Joel; Fang, Qi; Reeve, Andrew Hart; Xie, Duo; Chen, Guangji; Guo, Chunxue; Faircloth, Brant C.; Petersen, Bent; Wang, Zongji; Zhou, Qi; Diekhans, Mark; Chen, Wanjun; Andreu-Sanchez, Sergio; Margaryan, Ashot; Howard, Jason Travis; Parent, Carole; Pacheco, George; Sinding, Mikkel-Holger S.; Puetz, Lara; Cavill, Emily; Ribeiro, Angela M.; Eckhart, Leopold; Fjeldsa, Jon; Hosner, Peter A.; Brumfield, Robb T.; Christidis, Les; Bertelsen, Mads F.; Sicheritz-Ponten, Thomas; Tietze, Dieter Thomas; Robertson, Bruce C.; Song, Gang; Borgia, Gerald; Claramunt, Santiago; Lovette, Irby J.; Cowen, Saul J.; Njoroge, Peter; Dumbacher, John Philip; Ryder, Oliver A.; Fuchs, Jerome; Bunce, Michael; Burt, David W.; Cracraft, Joel; Meng, Guanliang; Hackett, Shannon J.; Ryan, Peter G.; Jønsson, Knud Andreas; Jamieson, Ian G.; da Fonseca, Rute R.; Braun, Edward L.; Houde, Peter; Mirarab, Siavash; Suh, Alexander; Hansson, Bengt; Ponnikas, Suvi; Sigeman, Hanna; Stervander, Martin; Frandsen, Paul B.; van der Zwan, Henriette; van der Sluis, Rencia; Visser, Carina; Balakrishnan, Christopher N.; Clark, Andrew G.; Fitzpatrick, John W.; Bowman, Reed; Chen, Nancy; Cloutier, Alison; Sackton, Timothy B.; Edwards, Scott V.; Foote, Dustin J.; Shakya, Subir B.; Sheldon, Frederick H.; Vignal, Alain; Soares, Andre E. R.; Shapiro, Beth; Gonzalez-Solis, Jacob; Ferrer-Obiol, Joan; Rozas, Julio; Riutort, Marta; Tigano, Anna; Friesen, Vicki; Dalen, Love; Urrutia, Araxi O.; Szekely, Tamas; Liu, Yang; Campana, Michael G.; Corvelo, Andre; Fleischer, Robert C.; Rutherford, Kim M.; Gemmell, Neil J.; Dussex, Nicolas; Mouritsen, Henrik; Thiele, Nadine; Delmore, Kira; Liedvogel, Miriam; Franke, Andre; Hoeppner, Marc P.; Krone, Oliver; Fudickar, Adam M.; Mila, Borja; Ketterson, Ellen D.; Fidler, Andrew Eric; Friis, Guillermo; Parody-Merino, Angela M.; Battley, Phil F.; Cox, Murray P.; Lima, Nicholas Costa Barroso; Prosdocimi, Francisco; Parchman, Thomas Lee; Schlinger, Barney A.; Loiselle, Bette A.; Blake, John G.; Lim, Haw Chuan; Day, Lainy B.; Fuxjager, Matthew J.; Baldwin, Maude W.; Braun, Michael J.; Wirthlin, Morgan; Dikow, Rebecca B.; Ryder, T. Brandt; Camenisch, Glauco; Keller, Lukas F.; DaCosta, Jeffrey M.; Hauber, Mark E.; Louder, Matthew I. M.; Witt, Christopher C.; McGuire, Jimmy A.; Mudge, Joann; Megna, Libby C.; Carling, Matthew D.; Wang, Biao; Taylor, Scott A.; Del-Rio, Glaucia; Aleixo, Alexandre; Vasconcelos, Ana Tereza Ribeiro; Mello, Claudio V.; Weir, Jason T.; Haussler, David; Li, Qiye; Yang, Huanming; Wang, Jian; Lei, Fumin; Rahbek, Carsten; Gilbert, M. Thomas P.; Graves, Gary R.; Jarvis, Erich D.; Paten, Benedict; Zhang, Guojie (2020)
    Whole-genome sequencing projects are increasingly populating the tree of life and characterizing biodiversity(1-4). Sparse taxon sampling has previously been proposed to confound phylogenetic inference(5), and captures only a fraction of the genomic diversity. Here we report a substantial step towards the dense representation of avian phylogenetic and molecular diversity, by analysing 363 genomes from 92.4% of bird families-including 267 newly sequenced genomes produced for phase II of the Bird 10,000 Genomes (B10K) Project. We use this comparative genome dataset in combination with a pipeline that leverages a reference-free whole-genome alignment to identify orthologous regions in greater numbers than has previously been possible and to recognize genomic novelties in particular bird lineages. The densely sampled alignment provides a single-base-pair map of selection, has more than doubled the fraction of bases that are confidently predicted to be under conservation and reveals extensive patterns of weak selection in predominantly non-coding DNA. Our results demonstrate that increasing the diversity of genomes used in comparative studies can reveal more shared and lineage-specific variation, and improve the investigation of genomic characteristics. We anticipate that this genomic resource will offer new perspectives on evolutionary processes in cross-species comparative analyses and assist in efforts to conserve species. A dataset of the genomes of 363 species from the Bird 10,000 Genomes Project shows increased power to detect shared and lineage-specific variation, demonstrating the importance of phylogenetically diverse taxon sampling in whole-genome sequencing.
  • Bolotovskiy, Aleksey A.; Levina, Marina A.; DeFaveri, Jacquelin; Merila, Juha; Levin, Boris A. (2018)
    The three-spined stickleback Gasterosteus aculeatus is an important model for studying microevolution and parallel adaptation to freshwater environments. Marine and freshwater forms differ markedly in their phenotype, especially in the number of lateral plates, which are serially repeated elements of the exoskeleton. In fishes, thyroid hormones are involved in adaptation to salinity, as well as the developmental regulation of serially repeated elements. To study how thyroid hormones influence lateral plate development, we manipulated levels of triiodothyronine and thiourea during early ontogeny in a marine and freshwater population with complete and low plate phenotypes, respectively. The development of lateral plates along the body and keel was heterochronic among experimental groups. Fish with a low dosage of exogenous triiodothyronine and those treated with thiourea exhibited retarded development of bony plates compared to both control fish and those treated with higher a triiodothyronine dosage. Several triiodothyronine-treated individuals of the marine form expressed the partial lateral plate phenotype. Some individuals with delayed development of lateral plates manifested 1-2 extra bony plates located above the main row of lateral plates.
  • Toivonen, Jaakko; Fromhage, Lutz (2020)
    We investigate competition between separate periodical cicada populations each possessing different life-cycle lengths. We build an individual-based model to simulate the cicada life cycle and allow random migrations to occur between patches inhabited by the different populations. We show that if hybridization between different cycle lengths produces offspring that have an intermediate life-cycle length, then predation acts disproportionately to select against the hybrid offspring. This happens because they emerge in low densities without the safety-in-numbers provided by either parent population. Thus, prime-numbered life cycles that can better avoid hybridization are favored. However, we find that this advantage of prime-numbered cycles occurs only if there is some mechanism that can occasionally synchronize emergence between local populations in sufficiently many patches.
  • Ronnegard, Lars; McFarlane, S. Eryn; Husby, Arild; Kawakami, Takeshi; Ellegren, Hans; Qvarnstrom, Anna (2016)
    1. Genomewide association studies (GWAS) enable detailed dissections of the genetic basis for organisms' ability to adapt to a changing environment. In long-term studies of natural populations, individuals are often marked at one point in their life and then repeatedly recaptured. It is therefore essential that a method for GWAS includes the process of repeated sampling. In a GWAS, the effects of thousands of single-nucleotide polymorphisms (SNPs) need to be fitted and any model development is constrained by the computational requirements. A method is therefore required that can fit a highly hierarchical model and at the same time is computationally fast enough to be useful. 2. Our method fits fixed SNP effects in a linear mixed model that can include both random polygenic effects and permanent environmental effects. In this way, the model can correct for population structure and model repeated measures. The covariance structure of the linear mixed model is first estimated and subsequently used in a generalized least squares setting to fit the SNP effects. The method was evaluated in a simulation study based on observed genotypes from a long-term study of collared flycatchers in Sweden. 3. The method we present here was successful in estimating permanent environmental effects from simulated repeated measures data. Additionally, we found that especially for variable phenotypes having large variation between years, the repeated measurements model has a substantial increase in power compared to a model using average phenotypes as a response. 4. The method is available in the R package RepeatABEL. It increases the power in GWAS having repeated measures, especially for long-term studies of natural populations, and the R implementation is expected to facilitate modelling of longitudinal data for studies of both animal and human populations.
  • Kess, Tony; Bentzen, Paul; Lehnert, Sarah J.; Sylvester, Emma V.A.; Lien, Sigbjørn; Kent, Matthew P.; Sinclair-Waters, Marion; Morris, Corey J.; Wringe, Brendan; Fairweather, Robert; Bradbury, Ian R. (2020)
    Genomic architecture and standing variation can play a key role in ecological adaptation and contribute to the predictability of evolution. In Atlantic cod (Gadus morhua), four large chromosomal rearrangements have been associated with ecological gradients and migratory behavior in regional analyses. However, the degree of parallelism, the extent of independent inheritance, and functional distinctiveness of these rearrangements remain poorly understood. Here, we use a 12K single nucleotide polymorphism (SNP) array to demonstrate extensive individual variation in rearrangement genotype within populations across the species range, suggesting that local adaptation to fine-scale ecological variation is enabled by rearrangements with independent inheritance. Our results demonstrate significant association of rearrangements with migration phenotype and environmental gradients across the species range. Individual rearrangements exhibit functional modularity, but also contain loci showing multiple environmental associations. Clustering in genetic distance trees and reduced differentiation within rearrangements across the species range are consistent with shared variation as a source of contemporary adaptive diversity in Atlantic cod. Conversely, we also find that haplotypes in the LG12 and LG1 rearranged region have diverged across the Atlantic, despite consistent environmental associations. Exchange of these structurally variable genomic regions, as well as local selective pressures, has likely facilitated individual diversity within Atlantic cod stocks. Our results highlight the importance of genomic architecture and standing variation in enabling fine-scale adaptation in marine species.
  • Sasic, Ljiljana; Acanski, Jelena; Vujic, Ante; Ståhls, Gunilla; Radenkovic, Snezana; Milic, Dubravka; Vidakovic, Dragana Obreht; Dan, Mihajla (2016)
    The Merodon aureus species group (Diptera: Syrphidae: Eristalinae) comprises a number of different sub-groups and species complexes. In this study we focus on resolving the taxonomic status of the entity previously identified as M. cinereus B, here identified as M. atratus species complex. We used an integrative approach based on morphological descriptions, combined with supporting characters that were obtained from molecular analyses of the mitochondrial cytochrome c oxidase I gene as well as from geometric morphometry of wing and surstylus shapes and environmental niche comparisons. All applied data and methods distinguished and supported three morphologically cryptic species: M. atratus stat. nov., M. virgatus sp. nov. and M. balkanicus sp. nov., which constitute the M. atratus species complex. We present an identification key for the sub-groups and species complexes of the M. aureus species group occurring in Europe, describe the taxa and discuss the utility of the applied methods for species delimitation. The estimated divergence times for the species splits of these taxa coincide with the Pleistocene Gunz-Mindel interglaciation and the Great interglaciation (between the Ris and Mindel glacial periods).
  • Gerwin, Jan; Urban, Sabine; Meyer, Axel; Kratochwil, Claudius F. (2021)
    Abstract Understanding the origins of phenotypic diversity among closely related species remains an important largely unsolved question in evolutionary biology. With over 800 species, Lake Malawi haplochromine cichlid fishes are a prominent example of extremely fast evolution of diversity including variation in coloration. Previously, a single major effect gene, agrp2 (asip2b), has been linked to evolutionary losses and gains of horizontal stripe patterns in cichlids, but it remains unknown what causes more fine-scale variation in the number and continuity of the stripes. Also, the genetic basis of the most common color pattern in African cichlids, vertical bars, and potential interactions between the two color patterns remain unknown. Based on a hybrid cross of the horizontally striped Lake Malawi cichlid Pseudotropheus cyaneorhabdos and the vertically barred species Chindongo demasoni we investigated the genetic basis of both color patterns. The distribution of phenotypes in the F2 generation of the cross indicates that horizontal stripes and vertical bars are independently inherited patterns that are caused by two sets of genetic modules. While horizontal stripes are largely controlled by few major effect loci, vertical bars are a highly polygenic trait. Horizontal stripes show substantial variation in the F2 generation that, interestingly, resemble naturally occurring phenotypes found in other Lake Malawi cichlid species. Quantitative trait loci (QTL) mapping of this cross reveals known (agrp2) and unknown loci underlying horizontal stripe patterns. These findings provide novel insights into the incremental fine-tuning of an adaptive trait that diversified through the evolution of additional modifier loci.
  • Koblmüller, Stephan; Zangl, Lukas; Börger, Christine; Daill, Daniel; Vanhove, Maarten P. M.; Sturmbauer, Christian; Sefc, Kristina M. (2019)
    In the absence of dispersal barriers, species with great dispersal ability are expected to show little, if at all, phylogeographic structure. The East African Great Lakes and their diverse fish faunas provide opportunities to test this hypothesis in pelagic fishes, which are presumed to be highly mobile and unrestricted in their movement by physical barriers. Here, we address the link between panmixis and pelagic habitat use by comparing the phylogeographic structure among four deepwater cichlid species of the tribe Bathybatini from Lake Tanganyika. We show that the mitochondrial genealogies (based on the most variable part or the control region) of the four species are very shallow (0.8–4% intraspecific divergence across entire distribution ranges) and that all species experienced recent population growth. A lack of phylogeographic structure in the two eupelagic species, Bathybates fasciatus and B. leo, was consistent with expectations and with findings in other pelagic cichlid species. Contrary to expectations, a clear phylogeographic structure was detected in the two benthopelagic species, B. graueri and Hemibates stenosoma. Differences in genetic diversity between eupelagic and benthopelagic species may be due to differences in their dispersal propensity, mediated by their respective predatory niches, rather than precipitated by external barriers to dispersal.
  • Cronemberger, Aurea A.; Aleixo, Alexandre; Mikkelsen, Else K.; Weir, Jason T. (2020)
    How species evolve reproductive isolation in the species-rich Amazon basin is poorly understood in vertebrates. Here, we sequenced a reference genome and used a genome-wide sample of SNPs to analyze a hybrid zone between two highly cryptic species ofHypocnemiswarbling-antbirds-the Rondonia warbling-antbird (H. ochrogyna) and Spix's warbling-antbird (H. striata)-in a headwater region of southern Amazonia. We found that both species commonly hybridize, producing F(1)s and a variety of backcrosses with each species but we detected only one F-2-like hybrid. Patterns of heterozygosity, hybrid index, and interchromosomal linkage disequilibrium in hybrid populations closely match expectations under strong postzygotic isolation. Hybrid zone width (15.4 km) was much narrower than expected (211 km) indicating strong selection against hybrids. A remarkably high degree of concordance in cline centers and widths across loci, and a lack of reduced interspecificF(st)between populations close to versus far from the contact zone, suggest that genetic incompatibilities have rendered most of the genome immune to introgression. These results support intrinsic postzygotic isolation as a driver of speciation in a moderately young cryptic species pair from the Amazon and suggest that species richness of the Amazon may be grossly underestimated.
  • Schmidt, Alexander R.; Regalado, Ledis; Weststrand, Stina; Korall, Petra; Sadowski, Eva-Maria; Schneider, Harald; Jansen, Eva; Bechteler, Julia; Krings, Michael; Müller, Patrick; Wang, Bo; Wang, Xin; Rikkinen, Jouko; Seyfullah, Leyla J. (2020)
  • Kulmuni, Jonna; Butlin, Roger K.; Lucek, Kay; Savolainen, Vincent; Westram, Anja Marie (2020)
    y Speciation, that is, the evolution of reproductive barriers eventually leading to complete isolation, is a crucial process generating biodiversity. Recent work has contributed much to our understanding of how reproductive barriers begin to evolve, and how they are maintained in the face of gene flow. However, little is known about the transition from partial to strong reproductive isolation (RI) and the completion of speciation. We argue that the evolution of strong RI is likely to involve different processes, or new interactions among processes, compared with the evolution of the first reproductive barriers. Transition to strong RI may be brought about by changing external conditions, for example, following secondary contact. However, the increasing levels of RI themselves create opportunities for new barriers to evolve and, and interaction or coupling among barriers. These changing processes may depend on genomic architecture and leave detectable signals in the genome. We outline outstanding questions and suggest more theoretical and empirical work, considering both patterns and processes associated with strong RI, is needed to understand how speciation is completed. This article is part of the theme issue 'Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers'.