Evidence of recent population expansion in the field cricket Teleogryllus commodus

2010 ◽  
Vol 58 (1) ◽  
pp. 33 ◽  
Author(s):  
Kylie M. Cairns ◽  
Jonci N. Wolff ◽  
Robert C. Brooks ◽  
J. William O. Ballard
Keyword(s):  
Genetic Variation ◽  
Large Scale ◽  
Elongation Factor ◽  
Population Expansion ◽  
Field Cricket ◽  
Molecular Variation ◽  
Effective Population ◽  
Recent Population Expansion ◽  
Teleogryllus Commodus ◽  
European Farming

The patterns of intraspecific genetic variation can be driven by large-scale environmental events or smaller-scale phenomena such as land clearing. In Australia, European farming techniques have altered the landscape by increasing the amount of arable farmland. We hypothesised that this increase in farmland would result in a concomitant increase in the effective population size of the black field cricket (Teleogryllus commodus). To test our hypothesis, we investigated genetic variation in 1350 bp of mitochondrial mtDNA and in two nuclear encoded loci, hexokinase and elongation factor 1-α, from 20 crickets collected at Smiths Lake, New South Wales. Molecular variation in T. commodus was characterised by an over-representation of singleton mutations (negative Tajima’s D and Fu and Li’s D) in all loci studied. Further, HKA tests do not suggest that selection is acting on any one gene. Combined, these data support the hypothesis that population expansion is the force driving molecular variation in T. commodus. If an increase in agricultural habitats is the cause of population expansion in T. commodus we hypothesise greater genetic subdivision in natural than farmland habitats. An alternative possibility is that the effective geographical range of the species has increased but the density at a given site remains unchanged.

scholarly journals Refining the Y chromosome phylogeny with southern African sequences

2015 ◽  
Author(s):  
Chiara Barbieri ◽  
Alexander Hübner ◽  
Enrico Macholdt ◽  
Shengyu Ni ◽  
Sebastian Lippold ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Large Scale ◽  
Sequence Data ◽  
Population Expansion ◽  
Branch Length ◽  
Paternal Age ◽  
Effective Population ◽  
Chromosome Sequence ◽  
Human Y Chromosome ◽  
Major Haplogroups

The recent availability of large-scale sequence data for the human Y chromosome has revolutionized analyses of and insights gained from this non-recombining, paternally inherited chromosome. However, the studies to date focus on Eurasian variation, and hence the diversity of early-diverging branches found in Africa has not been adequately documented. Here we analyze over 900 kb of Y chromosome sequence obtained from 547 individuals from southern African Khoisan and Bantu-speaking populations, identifying 232 new sequences from basal haplogroups A and B. We find new branches within haplogroups A2 and A3b1 and suggest that the prehistory of haplogroup B2a is more complex than previously suspected; this haplogroup is likely to have existed in Khoisan groups before the arrival of Bantu-speakers, who brought additional B2a lineages to southern Africa. Furthermore, we estimate older dates than obtained previously for both the A2-T node within the human Y chromosome phylogeny and for some individual haplogroups. Finally, there is pronounced variation in branch length between major haplogroups; haplogroups associated with Bantu-speakers have significantly longer branches. This likely reflects a combination of biases in the SNP calling process and demographic factors, such as an older average paternal age (hence a higher mutation rate), a higher effective population size, and/or a stronger effect of population expansion for Bantu-speakers than for Khoisan groups.

scholarly journals Assessing the origin, genetic structure and demographic history of the common pheasant (Phasianus colchicus) in the introduced European range

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohammad Reza Ashrafzadeh ◽  
Rasoul Khosravi ◽  
Carlos Fernandes ◽  
Cecilia Aguayo ◽  
Zoltán Bagi ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Demographic History ◽  
Population Expansion ◽  
Game Species ◽  
Recent Population Expansion ◽  
Biogeographic Patterns ◽  
Clustering Model ◽  
History Of ◽  
Common Pheasant ◽  
The Common

AbstractThe common pheasant, a game species widely introduced throughout the world, can be considered as an ideal model to study the effects of introduction events on local adaptations, biogeographic patterns, and genetic divergence processes. We aimed to assess the origin, spatial patterns of genetic variation, and demographic history of the introduced populations in the contact zone of Central and Southeast Europe, using mitochondrial DNA control region sequences and microsatellite loci. Both types of molecular markers indicated relatively low to moderate levels of genetic variation. The mtDNA analyses revealed that common pheasants across the study area are divided into two distinct clades: B (mongolicus group) and F (colchicus group). Analyses of the microsatellite data consistently suggested a differentiation between Hungary and Serbia, with the pheasant population in Hungary being much more genetically homogeneous, while that of Serbia has much more genetic mixture and admixture. This cryptic differentiation was not detected using a non-spatial Bayesian clustering model. The analyses also provided strong evidence for a recent population expansion. This fundamental information is essential for adequate and effective conservation management of populations of a game species of great economic and ecological importance in the studied geographical region.

scholarly journals De novo genome assembly of the marine teleost, Bluefin Trevally (Caranx melampygus)

2021 ◽  
Author(s):  
Brandon D Pickett ◽  
Jessica R Glass ◽  
Perry G Ridge ◽  
John S K Kauwe
Keyword(s):  
Genome Assembly ◽  
Large Scale ◽  
De Novo ◽  
Demographic History ◽  
Population Expansion ◽  
Marine Teleost ◽  
Population Demography ◽  
Population Declines ◽  
Effective Population ◽  
De Novo Genome Assembly

Abstract The bluefin trevally, Caranx melampygus, also known as the bluefin kingfish or bluefin jack, is known for its remarkable, bright-blue fins. This marine teleost is a widely-prized sportfish, but few resources have been devoted to the genomics and conservation of this species because it is not targeted by large-scale commercial fisheries. Population declines from recreational and artisanal overfishing have been observed in Hawai‘i, USA, resulting in both an interest in aquaculture and concerns about the long-term conservation of this species. Most research to-date has been performed in Hawai‘i, raising questions about the status of bluefin trevally populations across its Indo-Pacific range. Genomic resources allow for expanded research on stock status, genetic diversity, and population demography. We present a high-quality, 711Mbp nuclear genome assembly of a Hawaiian bluefin trevally from noisy long-reads with a contig NG50 of 1.2Mbp and longest contig length of 8.9Mbp. As measured by single-copy orthologs, the assembly was 95% complete, and the genome is comprised of 16.9% repetitive elements. The assembly was annotated with 33.1K protein-coding genes, 71.4% of which were assigned putative functions, using RNA-seq data from eight tissues from the same individual. This is the first whole-genome assembly published for the carangoid genus Caranx. Using this assembled genome, a multiple sequentially Markovian coalescent model was implemented to assess population demography. Estimates of effective population size suggest population expansion has occurred since the Late Pleistocene. This genome will be a valuable resource for comparative phylogenomic studies of carangoid fishes and will help elucidate demographic history and delineate stock structure for bluefin trevally populations throughout the Indo-Pacific.

scholarly journals A Survey of Chromosomal and Nucleotide Sequence Variation inDrosophila miranda

Genetics ◽  
2003 ◽  
Vol 164 (4) ◽  
pp. 1369-1381 ◽  
Author(s):  
Soojin Yi ◽  
Doris Bachtrog ◽  
Brian Charlesworth
Keyword(s):  
Nucleotide Sequence ◽  
Sequence Variation ◽  
General Pattern ◽  
Population Expansion ◽  
Convincing Evidence ◽  
Population Subdivision ◽  
Effective Population ◽  
Recent Population Expansion ◽  
Local Selection ◽  
Nucleotide Sequence Variation

AbstractThere have recently been several studies of the evolution of Y chromosome degeneration and dosage compensation using the neo-sex chromosomes of Drosophila miranda as a model system. To understand these evolutionary processes more fully, it is necessary to document the general pattern of genetic variation in this species. Here we report a survey of chromosomal variation, as well as polymorphism and divergence data, for 12 nuclear genes of D. miranda. These genes exhibit varying levels of DNA sequence polymorphism. Compared to its well-studied sibling species D. pseudoobscura, D. miranda has much less nucleotide sequence variation, and the effective population size of this species is inferred to be several-fold lower. Nevertheless, it harbors a few inversion polymorphisms, one of which involves the neo-X chromosome. There is no convincing evidence for a recent population expansion in D. miranda, in contrast to D. pseudoobscura. The pattern of population subdivision previously observed for the X-linked gene period is not seen for the other loci, suggesting that there is no general population subdivision in D. miranda. However, data on an additional region of period confirm population subdivision for this gene, suggesting that local selection is operating at or near period to promote differentiation between populations.

scholarly journals Genetic models reveal historical patterns of sea lamprey population fluctuations within Lake Champlain

PeerJ ◽  
2015 ◽  
Vol 3 ◽  
pp. e1369 ◽  
Author(s):  
Cassidy C. D’Aloia ◽  
Christina B. Azodi ◽  
Sallie P. Sheldon ◽  
Stephen C. Trombulak ◽  
William R. Ardren
Keyword(s):  
Population Size ◽  
Population Decline ◽  
Population Expansion ◽  
Sea Lamprey ◽  
Genetic Models ◽  
Parameter Estimates ◽  
Population Fluctuations ◽  
Lake Champlain ◽  
Effective Population ◽  
Recent Population Expansion

The origin of sea lamprey (Petromyzon marinus) in Lake Champlain has been heavily debated over the past decade. Given the lack of historical documentation, two competing hypotheses have emerged in the literature. First, it has been argued that the relatively recent population size increase and concomitant rise in wounding rates on prey populations are indicative of an invasive population that entered the lake through the Champlain Canal. Second, recent genetic evidence suggests a post-glacial colonization at the end of the Pleistocene, approximately 11,000 years ago. One limitation to resolving the origin of sea lamprey in Lake Champlain is a lack of historical and current measures of population size. In this study, the issue of population size was explicitly addressed using nuclear (nDNA) and mitochondrial DNA (mtDNA) markers to estimate historical demography with genetic models. Haplotype network analysis, mismatch analysis, and summary statistics based on mtDNA noncoding sequences for NCI (479 bp) and NCII (173 bp) all indicate a recent population expansion. Coalescent models based on mtDNA and nDNA identified two potential demographic events: a population decline followed by a very recent population expansion. The decline in effective population size may correlate with land-use and fishing pressure changes post-European settlement, while the recent expansion may be associated with the implementation of the salmonid stocking program in the 1970s. These results are most consistent with the hypothesis that sea lamprey are native to Lake Champlain; however, the credibility intervals around parameter estimates demonstrate that there is uncertainty regarding the magnitude and timing of past demographic events.

scholarly journals Population genetics of Aedes albopictus (Diptera: Culicidae) in its native range in Lao People’s Democratic Republic

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Maysa Tiemi Motoki ◽  
Dina Madera Fonseca ◽  
Elliott Frederic Miot ◽  
Bruna Demari-Silva ◽  
Phoutmany Thammavong ◽  
...  
Keyword(s):  
Population Structure ◽  
Gene Flow ◽  
Aedes Albopictus ◽  
Isolation By Distance ◽  
Genetic Locus ◽  
Lao Pdr ◽  
Phylogenetic Network ◽  
Population Expansion ◽  
Recent Population Expansion ◽  
The Usa

Abstract Background The Asian tiger mosquito, Aedes (Stegomyia) albopictus (Skuse) is an important worldwide invasive species and can be a locally important vector of chikungunya, dengue and, potentially, Zika. This species is native to Southeast Asia where populations thrive in both temperate and tropical climates. A better understanding of the population structure of Ae. albopictus in Lao PDR is very important in order to support the implementation of strategies for diseases prevention and vector control. In the present study, we investigated the genetic variability of Ae. albopictus across a north-south transect in Lao PDR. Methods We used variability in a 1337-bp fragment of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1), to assess the population structure of Ae. albopictus in Lao PDR. For context, we also examined variability at the same genetic locus in samples of Ae. albopictus from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA. Results We observed very high levels of genetic polymorphism with 46 novel haplotypes in Ae. albopictus from 9 localities in Lao PDR and Thailand populations. Significant differences were observed between the Luangnamtha population and other locations in Lao PDR. However, we found no evidence of isolation by distance. There was overall little genetic structure indicating ongoing and frequent gene flow among populations or a recent population expansion. Indeed, the neutrality test supported population expansion in Laotian Ae. albopictus and mismatch distribution analyses showed a lack of low frequency alleles, a pattern often seen in bottlenecked populations. When samples from Lao PDR were analyzed together with samples from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA, phylogenetic network and Bayesian cluster analysis showed that most populations from tropical/subtropical regions are more genetically related to each other, than populations from temperate regions. Similarly, most populations from temperate regions are more genetically related to each other, than those from tropical/subtropical regions. Conclusions Aedes albopictus in Lao PDR are genetically related to populations from tropical/subtropical regions (i.e. Thailand, Singapore, and California and Texas in the USA). The extensive gene flow among locations in Lao PDR indicates that local control is undermined by repeated introductions from untreated sites.

Population Genetics ofCaenorhabditis elegans: The Paradox of Low Polymorphism in a Widespread Species

Genetics ◽  
2003 ◽  
Vol 163 (1) ◽  
pp. 147-157 ◽  
Author(s):  
Arjun Sivasundar ◽  
Jody Hey
Keyword(s):  
Genetic Variation ◽  
Microsatellite Loci ◽  
Population Expansion ◽  
Widespread Species ◽  
C Elegans ◽  
Model Research ◽  
The World ◽  
Natural Isolates ◽  
History Of ◽  
Low Levels

AbstractCaenorhabditis elegans has become one of the most widely used model research organisms, yet we have little information on evolutionary processes and recent evolutionary history of this widespread species. We examined patterns of variation at 20 microsatellite loci in a sample of 23 natural isolates of C. elegans from various parts of the world. One-half of the loci were monomorphic among all strains, and overall genetic variation at microsatellite loci was low, relative to most other species. Some population structure was detected, but there was no association between the genetic and geographic distances among different natural isolates. Thus, despite the nearly worldwide occurrence of C. elegans, little evidence was found for local adaptation in strains derived from different parts of the world. The low levels of genetic variation within and among populations suggest that recent colonization and population expansion might have occurred. However, the patterns of variation are not consistent with population expansion. A possible explanation for the observed patterns is the action of background selection to reduce polymorphism, coupled with ongoing gene flow among populations worldwide.

scholarly journals DNA Sequence Variation and the Recombinational Landscape in Drosophila pseudoobscura: A Study of the Second Chromosome

Genetics ◽  
1999 ◽  
Vol 153 (2) ◽  
pp. 859-869 ◽  
Author(s):  
Martha T Hamblin ◽  
Charles F Aquadro
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Dna Sequence ◽  
Sequence Variation ◽  
Population Expansion ◽  
Drosophila Pseudoobscura ◽  
Effective Population ◽  
Standing Variation ◽  
Dna Sequence Polymorphism ◽  
Slightly Deleterious Mutations

Abstract The relationship between rates of recombination and DNA sequence polymorphism was analyzed for the second chromosome of Drosophila pseudoobscura. We constructed integrated genetic and physical maps of this chromosome using molecular markers at 10 loci spanning most of its physical length. The total length of the map was 128.2 cM, almost twice that of the homologous chromosome arm (3R) in D. melanogaster. There appears to be very little centromeric suppression of recombination, and rates of recombination are quite uniform across most of the chromosome. Levels of sequence variation (θW, based on the number of segregating sites) at seven loci (tropomyosin 1, Rhodopsin 3, Rhodopsin 1, bicoid, Xanthine dehydrogenase, Myosin light chain 1, and ribosomal protein 49) varied from 0.0036 to 0.0167. Generally consistent with earlier studies, the average estimate of θW at total sites is 1.5-fold higher than that in D. melanogaster, while average θW at silent sites is almost 3-fold higher. These estimates of variation were analyzed in the context of a background selection model under the same parameters of mutation rate and selection as have been proposed for D. melanogaster. It is likely that a significant fraction of the higher level of sequence variation in D. pseudoobscura can be explained by differences in regional rates of recombination rather than a larger species-level effective population size. However, the distribution of variation among synonymous, nonsynonymous, and noncoding sites appears to be quite different between the species, making direct comparisons of neutral variation, and hence inferences about effective population size, difficult. Tajima’s D statistics for 6 out of the 7 loci surveyed are negative, suggesting that D. pseudoobscura may have experienced a rapid population expansion in the recent past or, alternatively, that slightly deleterious mutations constitute an important component of standing variation in this species.

scholarly journals Phylogeography of Prunus armeniaca L. revealed by chloroplast DNA and nuclear ribosomal sequences

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wen-Wen Li ◽  
Li-Qiang Liu ◽  
Qiu-Ping Zhang ◽  
Wei-Quan Zhou ◽  
Guo-Quan Fan ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Chloroplast Dna ◽  
Population Expansion ◽  
Prunus Armeniaca ◽  
River Valley ◽  
Nuclear Ribosomal Dna ◽  
Glacial Refugium ◽  
Ili River Valley ◽  
Wild Apricot

AbstractTo clarify the phytogeography of Prunus armeniaca L., two chloroplast DNA fragments (trnL-trnF and ycf1) and the nuclear ribosomal DNA internal transcribed spacer (ITS) were employed to assess genetic variation across 12 P. armeniaca populations. The results of cpDNA and ITS sequence data analysis showed a high the level of genetic diversity (cpDNA: HT = 0.499; ITS: HT = 0.876) and a low level of genetic differentiation (cpDNA: FST = 0.1628; ITS: FST = 0.0297) in P. armeniaca. Analysis of molecular variance (AMOVA) revealed that most of the genetic variation in P. armeniaca occurred among individuals within populations. The value of interpopulation differentiation (NST) was significantly higher than the number of substitution types (GST), indicating genealogical structure in P. armeniaca. P. armeniaca shared genotypes with related species and may be associated with them through continuous and extensive gene flow. The haplotypes/genotypes of cultivated apricot populations in Xinjiang, North China, and foreign apricot populations were mixed with large numbers of haplotypes/genotypes of wild apricot populations from the Ili River Valley. The wild apricot populations in the Ili River Valley contained the ancestral haplotypes/genotypes with the highest genetic diversity and were located in an area considered a potential glacial refugium for P. armeniaca. Since population expansion occurred 16.53 kyr ago, the area has provided a suitable climate for the population and protected the genetic diversity of P. armeniaca.

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