scholarly journals Towards a conceptual and operational union of bacterial systematics, ecology, and evolution

2006 ◽  
Vol 361 (1475) ◽  
pp. 1985-1996 ◽  
Author(s):  
Frederick M Cohan
Keyword(s):  
Evolutionary Dynamics ◽  
Sequence Data ◽  
Sequence Divergence ◽  
Molecular Approaches ◽  
Bacterial Speciation ◽  
Bacterial Systematics ◽  
History Of ◽  
Operational Criteria ◽  
Fundamental Units ◽  
Ecological Differences

To completely understand the ecology of a bacterial community, we need to identify its ecologically distinct populations (ecotypes). The greatest promise for enumerating a community's constituent ecotypes is held by molecular approaches that identify bacterial ecotypes as DNA sequence clusters. These approaches succeed when ecotypes correspond with sequence clusters, but some models of bacterial speciation predict a one-to-many and others a many-to-one relationship between ecotypes and sequence clusters. A further challenge is that sequence-based phylogenies often contain a hierarchy of clusters and subclusters within clusters, and there is no widely accepted theory to guide systematists and ecologists to the size of cluster most likely to correspond to ecotypes. While present systematics attempts to use universal thresholds of sequence divergence to help demarcate species, the recently developed ‘community phylogeny’ approach assumes no universal thresholds, but demarcates ecotypes based on the analysis of a lineage's evolutionary dynamics. Theory-based approaches like this one can give a conceptual framework as well as operational criteria for hypothesizing the identity and membership of ecotypes from sequence data; ecology-based approaches can then confirm that the putative ecotypes are actually ecologically distinct. Bacterial ecotypes that are demonstrated to have a history of coexistence as ecologically distinct lineages (based on sequence analysis) and as a prognosis of future coexistence (based on ecological differences), are the fundamental units of bacterial ecology and evolution, and should be recognized by bacterial systematics.

scholarly journals Ecotype Simulation 2: An improved algorithm for efficiently demarcating microbial species from large sequence datasets

2020 ◽  
Author(s):  
Jason M. Wood ◽  
Eric D. Becraft ◽  
Daniel Krizanc ◽  
Frederick M. Cohan ◽  
David M. Ward
Keyword(s):  
Evolutionary Dynamics ◽  
Microbial Mats ◽  
Hot Springs ◽  
Sequence Data ◽  
Ecological Theory ◽  
Single Species ◽  
Population Based ◽  
Natural Microbial Community ◽  
High Throughput Dna Sequencing ◽  
Fundamental Units

AbstractBackgroundMicrobial systematists have used molecular cutoffs to classify the vast diversity present within a natural microbial community without invoking ecological theory. The use of ecological theory is needed to identify whether or not demarcated groups are the ecologically distinct, fundamental units (ecotypes), necessary for understanding the system. Ecotype Simulation, a Monte-Carlo approach to modeling the evolutionary dynamics of a microbial population based on the Stable Ecotype Model of microbial speciation, has proven useful for finding these fundamental units. For instance, predicted ecotypes of Synechococcus forming microbial mats in Yellowstone National Park hot springs, which were previously considered to be a single species based on phenotype, have been shown to be ecologically distinct, with specialization to different temperature and light levels. Unfortunately, development of high-throughput DNA sequencing methods has outpaced the ability of the program to analyze all of the sequence data produced.ResultsWe developed an improved version of the program called Ecotype Simulation 2, which can rapidly analyze alignments of very large sequence datasets. For instance, while the older version takes days to analyze 200 sequences, the new version can analyze 1.92 × 105 sequences in about six hours. The faster simulation identified similar ecotypes as found with the slower version, but from larger amounts of sequence data.ConclusionsBased on ecological theory, Ecotype Simulation 2 provides a much-needed approach that will help guide microbial ecologists and systematists to the natural, fundamental units of bacterial diversity.

scholarly journals Inversions shape the divergence of Drosophila pseudoobscura and D. persimilis on multiple timescales

2019 ◽  
Author(s):  
Katharine L Korunes ◽  
Carlos A Machado ◽  
Mohamed AF Noor
Keyword(s):  
Gene Flow ◽  
Evolutionary History ◽  
Sequence Data ◽  
Sequence Divergence ◽  
Whole Genome Sequence ◽  
Drosophila Pseudoobscura ◽  
Ancestral Polymorphism ◽  
Chromosomal Inversions ◽  
History Of ◽  
Ancient Gene

AbstractBy shaping meiotic recombination, chromosomal inversions can influence genetic exchange between hybridizing species. Despite the recognized importance of inversions in evolutionary processes such as divergence and speciation, teasing apart the effects of inversions over time remains challenging. For example, are their effects on sequence divergence primarily generated through creating blocks of linkage-disequilibrium pre-speciation or through preventing gene flux after speciation? We provide a comprehensive look into the influence of chromosomal inversions on gene flow throughout the evolutionary history of a classic system: Drosophila pseudoobscura and D. persimilis. We use extensive whole-genome sequence data to report patterns of introgression and divergence with respect to chromosomal arrangements. Overall, we find evidence that inversions have contributed to divergence patterns between Drosophila pseudoobscura and D. persimilis over three distinct timescales: 1) pre-speciation segregation of ancestral polymorphism, 2) post-speciation ancient gene flow, and 3) recent gene flow. We discuss these results in terms of our understanding of evolution in this classic system and provide cautions for interpreting divergence measures in similar datasets in other systems.

scholarly journals Evolutionary Dynamics of wAu-Like Wolbachia Variants in Neotropical Drosophila spp

2006 ◽  
Vol 72 (1) ◽  
pp. 826-835 ◽  
Author(s):  
Wolfgang J. Miller ◽  
Markus Riegler
Keyword(s):  
Evolutionary Dynamics ◽  
Germ Line ◽  
Sequence Data ◽  
World Species ◽  
Time Points ◽  
Potential Source ◽  
Somatic Tissues ◽  
History Of ◽  
Saltans Group ◽  
Group Species

ABSTRACT Wolbachia bacteria are common intracellular symbionts of arthropods and have been extensively studied in Drosophila. Most research focuses on two Old Word hosts, Drosophila melanogaster and Drosophila simulans, and does not take into account that some of the Wolbachia associations in these species may have evolved only after their fast global expansion and after the exposure to Wolbachia of previously isolated habitats. Here we looked at Wolbachia of Neotropical Drosophila species. Seventy-one lines of 16 Neotropical Drosophila species sampled in different regions and at different time points were analyzed. Wolbachia is absent in lines of Drosophila willistoni collected before the 1970s, but more recent samples are infected with a strain designated wWil. Wolbachia is absent in all other species of the willistoni group. Polymorphic wWil-related strains were detected in some saltans group species, with D. septentriosaltans being coinfected with at least four variants. Based on wsp and ftsZ sequence data, wWil of D. willistoni is identical to wAu, a strain isolated from D. simulans, but can be discriminated when using a polymorphic minisatellite marker. In contrast to wAu, which infects both germ line and somatic tissues of D. simulans, wWil is found exclusively in the primordial germ line cells of D. willistoni embryos. We report on a pool of closely related Wolbachia strains in Neotropical Drosophila species as a potential source for the wAu strain in D. simulans. Possible evolutionary scenarios reconstructing the infection history of wAu-like Wolbachia in Neotropical Drosophila species and the Old World species D. simulans are discussed.

Identifying the Fundamental Units of Diversity Among Bacillus Isolates From "Evolution Canyon" III

2006 ◽  
Vol 52 (3-4) ◽  
pp. 543-552 ◽  
Author(s):  
Elizabeth B. Perry ◽  
Alexander Koeppel ◽  
Danny Krizanc ◽  
Alejandro P. Rooney ◽  
Johannes Sikorski ◽  
...  
Keyword(s):  
Sequence Data ◽  
Bacterial Species ◽  
Sequence Diversity ◽  
Sequence Evolution ◽  
Rates Of Evolution ◽  
Evolution Canyon ◽  
Bacterial Systematics ◽  
Actual Sequence ◽  
Evolutionary Simulations ◽  
Fundamental Units

Bacterial systematics currently lacks a theory-based approach to identify the fundamental units of ecology and evolution. Consequently, a single bacterial species typically contains multiple phylogenetically and ecologically distinct lineages. Thus, the species of bacterial systematics are too broadly conceived to help the microbial ecologist who seeks to behold the full ecological diversity within a community, and to determine the interactions and functions of its ecologically distinct populations. Here, we review some of our recent work aiming to discover the ecologically distinct populations of a clade through analysis of DNA sequence diversity. We have developed an algorithm to compare simulations of bacterial sequence evolution with observed sequence diversity patterns within a clade. By finding the set of parameters that give a maximum likelihood fit between evolutionary simulations and actual sequence data, we are able to estimate lineage-specific rates of evolution and to make predictions about sequence clusters that correspond to ecologically distinct populations (ecotypes). We applied this approach to bacterial isolates of "Evolution Canyon" III in the southern Negev Desert. Within theBacillus subtilis-B. licheniformisclade, our simulation identified numerous putative ecotypes, some of which were shown to be strongly associated with different microhabitats, confirming their ecological distinctness. Also, several confirmed ecotypes were found to be grouped within a single named species, demonstrating the power of the algorithm to discern ecologically significant variation that is beyond the current focus of bacterial systematics. These findings highlight the promise of a theory-driven approach to identify fundamental units of bacterial diversity.

Morphological and molecular evidence for a new species of longnose skate (Rajiformes: Rajidae: Dipturus) from Argentinean waters based on DNA barcoding

Zootaxa ◽  
2008 ◽  
Vol 1921 (1) ◽  
pp. 35-46 ◽  
Author(s):  
JUAN MARTIN DÍAZ DE ASTARLOA ◽  
EZEQUIEL MABRAGAÑA ◽  
ROBERT HANNER ◽  
DANIEL E. FIGUEROA
Keyword(s):  
New Species ◽  
Sequence Data ◽  
Sequence Divergence ◽  
Color Pattern ◽  
Molecular Evidence ◽  
Dna Barcodes ◽  
Southwestern Atlantic ◽  
Cytochrome C Oxidase I ◽  
Molecular Approaches ◽  
A New Species

A new species of Dipturus is described from ten specimens collected off Patagonia, Argentina. Morphological and molecular approaches were used to compare among specimens of recognized Dipturus species. By comparing morphometric, meristic and mitochondrial cytochrome c oxidase I (COI) sequence data, specimens referred to as longnose skate and originally regarded as D. chilensis were shown to be a discrete species as distinguished from both the Yellownose skate, D. chilensis and the Roughskin skate, D. trachyderma. Dipturus argentinensis n. sp. can be distinguished from all other southwestern Atlantic longnose skate species by its color pattern, lack of squamation on both upper and lower surfaces of the disc, and a long, thin tail that is approximately half the total length. The new species has one median row of 10 to 24 small caudal thorns, one or two interdorsal thorns and 35 to 40, and 34 to 43 tooth rows on upper and lower jaws, respectively. The 648 base pair COI mitochondrial DNA “barcodes” derived from specimens of D. argentinensis are identical to each other and exhibit greater than 3% sequence divergence from all other Dipturus species similarly characterized to date. Taken together, these independent morphological and molecular observations serve to corroborate one another and thus provide strong evidence for the recognition of D. argentinensis as a new species.

scholarly journals Different Within-Host Viral Evolution Dynamics in Severely Immunosuppressed Cases with Persistent SARS-CoV-2

Biomedicines ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 808
Author(s):  
Laura Pérez-Lago ◽  
Teresa Aldámiz-Echevarría ◽  
Rita García-Martínez ◽  
Leire Pérez-Latorre ◽  
Marta Herranz ◽  
...  
Keyword(s):  
Single Nucleotide Polymorphisms ◽  
Evolutionary Dynamics ◽  
Viral Evolution ◽  
Special Focus ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
New Variant ◽  
History Of ◽  
Evolution Dynamics ◽  
The Uk

A successful Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) variant, B.1.1.7, has recently been reported in the UK, causing global alarm. Most likely, the new variant emerged in a persistently infected patient, justifying a special focus on these cases. Our aim in this study was to explore certain clinical profiles involving severe immunosuppression that may help explain the prolonged persistence of viable viruses. We present three severely immunosuppressed cases (A, B, and C) with a history of lymphoma and prolonged SARS-CoV-2 shedding (2, 4, and 6 months), two of whom finally died. Whole-genome sequencing of 9 and 10 specimens from Cases A and B revealed extensive within-patient acquisition of diversity, 12 and 28 new single nucleotide polymorphisms, respectively, which suggests ongoing SARS-CoV-2 replication. This diversity was not observed for Case C after analysing 5 sequential nasopharyngeal specimens and one plasma specimen, and was only observed in one bronchoaspirate specimen, although viral viability was still considered based on constant low Ct values throughout the disease and recovery of the virus in cell cultures. The acquired viral diversity in Cases A and B followed different dynamics. For Case A, new single nucleotide polymorphisms were quickly fixed (13–15 days) after emerging as minority variants, while for Case B, higher diversity was observed at a slower emergence: fixation pace (1–2 months). Slower SARS-CoV-2 evolutionary pace was observed for Case A following the administration of hyperimmune plasma. This work adds knowledge on SARS-CoV-2 prolonged shedding in severely immunocompromised patients and demonstrates viral viability, noteworthy acquired intra-patient diversity, and different SARS-CoV-2 evolutionary dynamics in persistent cases.

Sequence variation and evolution of nuclear DNA in man and the primates

1981 ◽  
Vol 292 (1057) ◽  
pp. 133-142 ◽  
Keyword(s):  
Dna Sequence ◽  
Sequence Variation ◽  
Nuclear Dna ◽  
Sequence Divergence ◽  
Gene Arrangement ◽  
Human Populations ◽  
Genetic Changes ◽  
Detailed Structural Analysis ◽  
Dna Sequence Variation ◽  
History Of

Recent advances in nucleic acid technology have facilitated the detection and detailed structural analysis of a wide variety of genes in higher organisms, including those in man. This in turn has opened the way to an examination of the evolution of structural genes and their surrounding and intervening sequences. In a study of the evolution of haemoglobin genes and neighbouring sequences in man and the primates, we have investigated gene arrangement and DNA sequence divergence both within and between species ranging from Old World monkeys to man. This analysis is beginning to reveal the evolutionary constraints that have acted on this region of the genome during primate evolution. Furthermore, DNA sequence variation, both within and between species, provides, in principle, a novel and powerful method for determining inter-specific phylogenetic distances and also for analysing the structure of present-day human populations. Application of this new branch of molecular biology to other areas of the human genome should prove important in unravelling the history of genetic changes that have occurred during the evolution of man.

Molecular Systematics of Tribe Physarieae (Brassicaceae) Based on Nuclear ITS, LUMINIDEPENDENS, and Chloroplast ndhF

2021 ◽  
Author(s):  
Sara Fuentes-Soriano ◽  
Elizabeth A. Kellogg
Keyword(s):  
Sequence Data ◽  
Plastid Dna ◽  
Sister Relationship ◽  
Data Set ◽  
Woody Perennial ◽  
History Of ◽  
Nuclear Its ◽  
Phylogenetic Framework ◽  
Phylogenetic Hypotheses ◽  
Relationship Of

Physarieae is a small tribe of herbaceous annual and woody perennial mustards that are mostly endemic to North America, with its members including a large amount of variation in floral, fruit, and chromosomal variation. Building on a previous study of Physarieae based on morphology and ndhF plastid DNA, we reconstructed the evolutionary history of the tribe using new sequence data from two nuclear markers, and compared the new topologies against previously published cpDNA-based phylogenetic hypotheses. The novel analyses included ca. 420 new sequences of ITS and LUMINIDEPENDENS (LD) markers for 39 and 47 species, respectively, with sampling accounting for all seven genera of Physarieae, including nomenclatural type species, and 11 outgroup taxa. Maximum parsimony, maximum likelihood, and Bayesian analyses showed that these additional markers were largely consistent with the previous ndhF data that supported the monophyly of Physarieae and resolved two major clades within the tribe, i.e., DDNLS (Dithyrea, Dimorphocarpa, Nerisyrenia, Lyrocarpa, and Synthlipsis)and PP (Paysonia and Physaria). New analyses also increased internal resolution for some closely related species and lineages within both clades. The monophyly of Dithyrea and the sister relationship of Paysonia to Physaria was consistent in all trees, with the sister relationship of Nerisyrenia to Lyrocarpa supported by ndhF and ITS, and the positions of Dimorphocarpa and Synthlipsis shifted within the DDNLS Clade depending on the employed data set. Finally, using the strong, new phylogenetic framework of combined cpDNA + nDNA data, we discussed standing hypotheses of trichome evolution in the tribe suggested by ndhF.

scholarly journals Reverse transcriptase sequences from mulberry LTR retrotransposons: characterization analysis

2017 ◽  
Vol 12 (1) ◽  
pp. 266-276
Author(s):  
Bi Ma ◽  
Lulu Kuang ◽  
Youchao Xin ◽  
Fei Hou ◽  
Ningjia He
Keyword(s):  
Reverse Transcriptase ◽  
Evolutionary Dynamics ◽  
Selective Pressure ◽  
Sequence Divergence ◽  
Degenerate Primers ◽  
Random Mutation ◽  
Functional Studies ◽  
Study Support ◽  
Element Transfer

AbstractCopia and Gypsy play important roles in structural, functional and evolutionary dynamics of plant genomes. In this study, a total of 106 and 101, Copia and Gypsy reverse transcriptase (rt) were amplified respectively in the Morus notabilis genome using degenerate primers. All sequences exhibited high levels of heterogeneity, were rich in AT and possessed higher sequence divergence of Copia rt in comparison to Gypsy rt. Two reasons are likely to account for this phenomenon: a) these elements often experience deletions or fragmentation by illegitimate or unequal homologous recombination in the transposition process; b) strong purifying selective pressure drives the evolution of these elements through “selective silencing” with random mutation and eventual deletion from the host genome. Interestingly, mulberry rt clustered with other rt from distantly related taxa according to the phylogenetic analysis. This phenomenon did not result from horizontal transposable element transfer. Results obtained from fluorescence in situ hybridization revealed that most of the hybridization signals were preferentially concentrated in pericentromeric and distal regions of chromosomes, and these elements may play important roles in the regions in which they are found. Results of this study support the continued pursuit of further functional studies of Copia and Gypsy in the mulberry genome.

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