scholarly journals The influence of demography, population structure and selection on molecular diversity in the selfing freshwater snail Biomphalaria pfeifferi

2003 ◽  
Vol 81 (3) ◽  
pp. 193-204 ◽  
Author(s):  
BERNARD ANGERS ◽  
NATHALIE CHARBONNEL ◽  
NICOLAS GALTIER ◽  
PHILIPPE JARNE
Keyword(s):  
Population Structure ◽  
Mitochondrial Gene ◽  
Random Mating ◽  
Natural Populations ◽  
Freshwater Snail ◽  
Biomphalaria Pfeifferi ◽  
African Populations ◽  
Size Population ◽  
History Of

Several forces may affect the distribution of genetic diversity in natural populations when compared to what is expected in a random-mating, constant size population of neutral genes. One solution for unravelling their respective influence is to study several genes at once in order to better reflect the true genealogy. Here we reconstruct the evolutionary history of the freshwater snail Biomphalaria pfeifferi over its entire distribution, using eight African populations, and three congeneric species as outgroups. A phylogenetic analysis was conducted using amplified fragment length polymorphism markers, and sequences at eight nuclear non-coding loci and one mitochondrial gene were used to analyse population structure. The geographic distribution of variation suggests greater affinities within than among regions. The pattern of variability at both the nuclear and mitochondrial DNA (mtDNA) loci is consistent with a bottleneck, although population structure may also partly explain our results. Our results are also indicative of the role of selection, whether positive or purifying, in the mtDNA. This highlights the fact that the interfering influences of population structure, demography and selection on molecular variation are not easily distinguished.

scholarly journals Recent evolutionary history of the metallothionein gene Mtn in Drosophila

1991 ◽  
Vol 58 (3) ◽  
pp. 203-210 ◽  
Author(s):  
Laurent Theodore ◽  
Ann-Shu Ho ◽  
Gustavo Maroni
Keyword(s):  
Base Pair ◽  
Restriction Analysis ◽  
Natural Populations ◽  
Fold Increase ◽  
Coding Region ◽  
Tropical Africa ◽  
African Populations ◽  
History Of ◽  
Rna Accumulation ◽  
Abundant Transcript

SummaryA new allele of one of the metallothionein genes of D. melanogaster, Mtn•3, sheds light on the recent evolution of this gene. In comparison to the previously studied Mtnl allele found in Canton S, this new allele, Mtn•3, produces a transcript that is 49 bases longer and 65–70 % less abundant. We detected Mtn•3 in several laboratory strains as well as in isofemale lines derived from natural populations. Sequence comparison showed that Mtn•3 differs from Mtnl in that it has: (a) base-pair substitution and an extra 49 bp-segment in the 3' untranslated region, (b) a substitution in the coding region that replaces the terminal Glu40 in Mtnl with Lys40, and (c) two base-pair substitutions in the promoter region. The Mtn•3-type was detected in six species of the melanogaster group by restriction analysis, and this result was confirmed by sequencing the D. simulans Mtn gene. Thus Mtn•3, which produces a less abundant transcript, appears to be the oldest of the two alleles. We also found that the duplications previously isolated from natural populations all derived from Mtnl, the more recent allele. Thus, two evolutionary steps: Mtn•3 to Mtnl and Mtnl to Dp(Mtnl), are accompanied by an overall 5- to 6-fold increase of RNA accumulation. The two changes seem to have occurred in non-African populations since Mtn•3 but not Mtnl was detected in our sample from tropical Africa, while Mtnl and Dp (Mtnl) are prevalent in European and North American samples.

scholarly journals Population structure and genetic diversity in the invasive freshwater snail Galba schirazensis (Lymnaeidae)

2018 ◽  
Vol 96 (5) ◽  
pp. 425-435 ◽  
Author(s):  
M. Lounnas ◽  
A.C. Correa ◽  
P. Alda ◽  
P. David ◽  
M.-P. Dubois ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Infectious Diseases ◽  
Microsatellite Markers ◽  
New World ◽  
Mitochondrial Gene ◽  
Allelic Diversity ◽  
Freshwater Snail ◽  
Potential Vector ◽  
Old World

We studied the population genetic structure of the freshwater snail Galba schirazensis (Küster, 1862), a potential vector of infectious diseases such as fascioliasis. Galba schirazensis has now a worldwide distribution but a poorly known origin because this species has been distinguished only recently from the morphologically similar and cosmopolitan Galba truncatula (O.F. Müller, 1774). We developed specific microsatellite markers and sequenced a mitochondrial gene (cytochrome oxidase subunit I (CO1)) to study individuals of G. schirazensis from the Old World and the New World. We found very low genetic diversity within populations, no heterozygotes, and marked population structure — a pattern observed in other highly selfing lymnaeid species with recently enlarged distributions as a result of biological invasions. The total lack of observed heterozygosity in the few populations of G. schirazensis that displayed some allelic diversity suggests high selfing rates. We also found that the center of diversity, and by extension the origin area of this species, should be found in the New World, whereas Old World populations should rather result from a recent introduction of a genetically uniform population. The microsatellite markers developed here will help to clarify the history of expansion of G. schirazensis and might help to understand its role as a potential vector of infectious diseases.

scholarly journals Wolbachia affects mitochondrial population structure in two systems of closely related Palaearctic blue butterflies

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Alena Sucháčková Bartoňová ◽  
Martin Konvička ◽  
Jana Marešová ◽  
Martin Wiemers ◽  
Nikolai Ignatev ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Population Structure ◽  
Species Complex ◽  
Mitochondrial Gene ◽  
Mitochondrial Structure ◽  
Distribution Ranges ◽  
Mitochondrial Population ◽  
Two Systems ◽  
History Of ◽  
Mitochondrial Phylogeny

AbstractThe bacterium Wolbachia infects many insect species and spreads by diverse vertical and horizontal means. As co-inherited organisms, these bacteria often cause problems in mitochondrial phylogeny inference. The phylogenetic relationships of many closely related Palaearctic blue butterflies (Lepidoptera: Lycaenidae: Polyommatinae) are ambiguous. We considered the patterns of Wolbachia infection and mitochondrial diversity in two systems: Aricia agestis/Aricia artaxerxes and the Pseudophilotes baton species complex. We sampled butterflies across their distribution ranges and sequenced one butterfly mitochondrial gene and two Wolbachia genes. Both butterfly systems had uninfected and infected populations, and harboured several Wolbachia strains. Wolbachia was highly prevalent in A. artaxerxes and the host’s mitochondrial structure was shallow, in contrast to A. agestis. Similar bacterial alleles infected both Aricia species from nearby sites, pointing to a possible horizontal transfer. Mitochondrial history of the P. baton species complex mirrored its Wolbachia infection and not the taxonomical division. Pseudophilotes baton and P. vicrama formed a hybrid zone in Europe. Wolbachia could obscure mitochondrial history, but knowledge on the infection helps us to understand the observed patterns. Testing for Wolbachia should be routine in mitochondrial DNA studies.

On the dispersion, population structure, and life history of a basommatophoran snail, Helisoma trivolvis, in central Alberta

1982 ◽  
Vol 60 (11) ◽  
pp. 2931-2940 ◽  
Author(s):  
J. R. Morris ◽  
D. A. Boag
Keyword(s):  
Population Structure ◽  
Life History ◽  
Adult Population ◽  
Adaptive Strategy ◽  
Maximum Diameter ◽  
Egg Mass ◽  
Helisoma Trivolvis ◽  
History Of ◽  
Trematode Infections

We studied the dispersion, population structure, and life history of a northern population of Helisoma trivolvis inhabiting an artificial pond in central Alberta in 1968 and 1969. In both years, snails were concentrated from May to October within the first 6 m from shore (150 cm in depth). In spring the number of overwintered snails rose from 21∙m−2 in 1968 to 42∙m−2 in 1969, but juvenile recruitment fell from 160∙m−2 in 1968 to 0∙m−2 in 1969. Based on the number of varices, some individuals survived up to five summers. Varix counts on samples of empty shells suggested that on average about 65% of the adult population was 1 year old with proportionately fewer in each older age category. Maturation among 1-year-old snails appeared to require growth to more than 9.0 mm maximum diameter. Although the diameter attained by young snails in their first summer ranged from 8 to 16 mm, none was recorded spawning before their second summer. Survivors spawned in each succeeding summer unless rendered infertile by trematode infections. Peak spawning occurred in late May. Mean number of eggs per egg mass varied between years from 30 to 37. Juveniles appeared in early July and reached peak numbers by mid-July. Survival of young snails changed dramatically between years. The role of iteroparity as an adaptive strategy of this species is discussed in the context of fluctuating productivity.

scholarly journals Recombination Disequilibrium in Ideal and Natural Populations

2015 ◽  
Author(s):  
Yuan-De Tan
Keyword(s):  
Random Mating ◽  
Natural Populations ◽  
Population History ◽  
Human Populations ◽  
Linkage Maps ◽  
Multiple Loci ◽  
Breeding Populations ◽  
Mating Population ◽  
History Of ◽  
Population Recombination

Following Hardy-Weinberg disequilibrium (HWD) occurring at a single locus and linkage disequilibrium (LD) between two loci in generations, we here proposed the third genetic disequilibrium in population: recombination disequilibrium (RD). RD is a measurement of crossover interference among multiple loci in a random mating population. In natural populations besides recombination interference, RD may also be due to selection, mutation, gene conversion, drift and/or migration. Therefore, similarly to LD, RD will also reflect the history of natural selection and mutation. In breeding populations, RD purely results from recombination interference and hence can be used to build or evaluate and correct a linkage map. Several practical examples from F2, testcross and human populations indeed demonstrate that RD is useful for measuring recombination interference between two short intervals and evaluating linkage maps. As with LD, RD will be important for studying genetic mapping, association of haplotypes with disease, plant breading and population history.

scholarly journals Ancient human genomes reveal a hidden history of strong selection in Eurasia

2020 ◽  
Author(s):  
Yassine Souilmi ◽  
Raymond Tobler ◽  
Angad Johar ◽  
Matthew Williams ◽  
Shane T. Grey ◽  
...  
Keyword(s):  
Bronze Age ◽  
Natural Populations ◽  
Classical Antiquity ◽  
Modern Biology ◽  
Human Genomes ◽  
History Of ◽  
Fitness Benefits ◽  
And Oxidative Stress

AbstractThe role of selection in shaping genetic diversity in natural populations is an area of intense interest in modern biology, especially the characterization of adaptive loci. Within humans, the rapid increase in genomic information has produced surprisingly few well-defined adaptive loci, promoting the view that recent human adaptation involved numerous loci with small fitness benefits. To examine this we searched for signatures of hard sweeps – the selective fixation of a new or initially rare beneficial variant – in 1,162 ancient western Eurasian genomes and identified 57 sweeps with high confidence. This unexpectedly extensive signal was concentrated on proteins acting at the cell surface, and potential selection pressures include cold adaptation in early Eurasian populations, and oxidative stress from carbohydrate-rich diets in farming populations. Critically, these sweep signals have been obscured in modern European genomes by subsequent population admixture, especially during the Bronze Age (5-3kya) and empires of classical antiquity.

Disease and Medicine in African History: A Bibliographical Essay

1974 ◽  
Vol 1 ◽  
pp. 141-148 ◽  
Author(s):  
K. David Patterson
Keyword(s):  
Sub Saharan Africa ◽  
Future Research ◽  
African History ◽  
Colonial Studies ◽  
African Populations ◽  
Trade Politics ◽  
History Of ◽  
Sub Saharan ◽  
The Impact

The medical history of Africa is a vital but neglected field. Disease has been a significant factor throughout African history, and attempts to control endemic and epidemic afflictions have been an important aspect of change in the twentieth century. Unfortunately, historians have rarely paid more than cursory attention to issues involving human health. There is some mention of disease in many pre-colonial studies, especially those of the “trade and politics” variety, but comment is usually directed toward the effects of tropical diseases on Europeans rather than the impact of local and induced diseases on African populations. Similarly, works on the colonial period often mention medical services in passing, but rarely make a serious attempt to assess their reception by local peoples and the results of their activities.It is to be hoped that as the historiography of Africa moves away from its early preoccupation with trade, politics, and the “origins of nationalism,” and as new archival and other sources become available, scholars will take a greater interest in the role of disease and medicine in the history of the continent. In this essay I will discuss some recent writings in this field by historians and by persons in other disciplines whose works are useful to historians, and will suggest possibilities for future research. Coverage will be selective rather than exhaustive, and will be confined to sub-Saharan Africa.

scholarly journals Genetic diversity and relatedness in aquaculture and marina populations of the invasive tunicate Didemnum vexillum in the British Isles

2021 ◽  
Author(s):  
M. B. Prentice ◽  
S. R. Vye ◽  
S. R. Jenkins ◽  
P. W. Shaw ◽  
J. E. Ironside
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Native Species ◽  
Didemnum Vexillum ◽  
Global Spread ◽  
History Of ◽  
Complex Life History ◽  
Source Populations ◽  
Successful Invader

AbstractIntroductions of invasive, non-native species in the marine environment are increasing as human activity within coastal areas rises. Genetic datasets are useful tools to identify source populations, track routes of invasions, and illuminate the role of genetic variation in the establishment and subsequent spread of novel introductions. Here, a microsatellite dataset is used to estimate the genetic diversity and population structure of 7 introduced Didemnum vexillum populations in Britain and Ireland, 4 of which are associated with aquaculture and 3 with marinas. Genetic differentiation observed between these populations indicates human-mediated transport as the main mechanism underlying the population structure of D. vexillum in Britain and Ireland. In addition to elucidating patterns of population structure we found that aquaculture sites showed significantly higher genetic diversity (measured as allelic richness) in comparison to the marina sites. We discuss these findings in relation to the history of each invasion, the complex life history of D. vexillum, and available evidence of the relative invasiveness of these populations. Our results show numerous interesting patterns which highlight further research avenues to elucidate the complex factors underlying the global spread of this successful invader.

Elaborating the role of reflection and individual differences in the study of folk-economic beliefs

2018 ◽  
Vol 41 ◽  
Author(s):  
Kevin Arceneaux
Keyword(s):  
Decision Making ◽  
Individual Differences ◽  
Cognitive Processes ◽  
Evolutionary History ◽  
Behavioral Responses ◽  
History Of ◽  
Economic Beliefs

AbstractIntuitions guide decision-making, and looking to the evolutionary history of humans illuminates why some behavioral responses are more intuitive than others. Yet a place remains for cognitive processes to second-guess intuitive responses – that is, to be reflective – and individual differences abound in automatic, intuitive processing as well.

The role of a family history of adenocarcinomas in patients with Barrett oesophagus

2001 ◽  
Vol 120 (5) ◽  
pp. A442-A442
Author(s):  
P TSIBOURIS ◽  
M HENDRICKSE ◽  
P ISAACS
Keyword(s):  
Family History ◽  
History Of ◽  
Barrett Oesophagus
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