scholarly journals Oscillations of laboratory populations of the polychaete Capitella capitata (Type I): their cause and implications for natural populations

1985 ◽  
Vol 20 ◽  
pp. 289-296 ◽  
Author(s):  
EJ Chesney ◽  
KR Tenore
Keyword(s):  
Natural Populations ◽  
Type I ◽  
Laboratory Populations ◽  
Capitella Capitata

Fecundity and energy partitioning in Capitella capitata type I (Annelida: Polychaeta)

1989 ◽  
Vol 100 (3) ◽  
pp. 365-371 ◽  
Author(s):  
A. Gr�mare ◽  
A. G. Marsh ◽  
K. R. Tenore
Keyword(s):  
Energy Partitioning ◽  
Type I ◽  
Capitella Capitata

Virulence and transmission modes of two microsporidia in Daphnia magna

Parasitology ◽  
1995 ◽  
Vol 111 (2) ◽  
pp. 133-142 ◽  
Author(s):  
K. L. Mangin ◽  
M. Lipsitch ◽  
D. Ebert
Keyword(s):  
Daphnia Magna ◽  
High Efficiency ◽  
Horizontal Transmission ◽  
Natural Populations ◽  
Life Time ◽  
Female Offspring ◽  
Alternate Host ◽  
Additional Degree ◽  
Large Populations ◽  
Laboratory Populations

SUMMARYTo understand the relationship between mode of transmission and virulence, we investigated 2 microsporidian parasites in Daphnia magna laboratory populations. Pleistophora intestinalis is only transmitted horizontally, while Tuzetia sp. is transmitted vertically with high efficiency from mothers to parthenogenetic male and female offspring. We were not able to transmit Tuzetia horizontally in the laboratory. Tuzetia reduces host life-time reproductive success and host survival to a much greater extent than does P. intestinalis. Tuzetia-infected hosts were rapidly outcompeted by uninfected hosts. We suspect that Tuzetia infections may persist in natural populations by an as yet undiscovered horizontal transmission. It is possible that an alternate host species may be involved. We present a mathematical model to analyse the conditions for the persistence of a parasite with perfect vertical and an additional degree of horizontal transmission. We show that horizontal and vertical transmission contribute additively to a parasite's ability to invade and persist. Since the fitness contribution of horizontal transmission increases with population size, only very low transmission probabilities per host-to-host contact are necessary for the persistence of parasites occurring in large populations such as those commonly found for Daphnia. The detection of such low rates of horizontal transmission appears unlikely under laboratory conditions since the necessary number of host-to-host (or host-to-spore) contacts is not feasible. We review mechanisms that can maintain vertically transmitted parasites in nature.

The action of evolutionary forces on metric traits

2011 ◽  
Vol 1 (3) ◽  
pp. 532-537
Author(s):  
C. López-Fanjul
Keyword(s):  
Genetic Variance ◽  
Natural Populations ◽  
Substantial Contribution ◽  
Additive Variance ◽  
Evolutionary Forces ◽  
Bristle Number ◽  
Laboratory Populations ◽  
Component Traits ◽  
Mean Fitness ◽  
Metric Traits

Fisher's theorem of natural selection implies that the population genetic variance of quasi-neutral traits should be mostly additive. In the case of fitness component traits, however, that variance would be characterised by a substantial contribution from non-additive loci. In parallel, Robertson's theorem states that selection will change the population mean of a trait proportionally to the magnitude of the genetic correlation between that trait and fitness, which should be weak for quasi-neutral traits or strong for the mean fitness components. Drosophila data from inbreeding and artificial selection experiments are discussed within that theoretical framework. In addition, the process of regeneration by mutation of the genetic variance of a quasi-neutral trait (abdominal bristle number) in a Drosophila population initially homozygous at all loci has been analysed. After 485 generations of mutation accumulation, the levels of additive variance found in this population closely approached those commonly observed in laboratory populations. Furthermore, these values, together with previously reported estimates for natural populations, could be jointly explained by a model assuming weak causal stabilising selection.

scholarly journals Evolution of Resistance Against CRISPR/Cas9 Gene Drive

2016 ◽  
Author(s):  
Robert L. Unckless ◽  
Andrew G. Clark ◽  
Philipp W. Messer
Keyword(s):  
De Novo ◽  
Natural Populations ◽  
Resistance Mechanisms ◽  
Target Site ◽  
Pest Species ◽  
Gene Drive ◽  
Guide Rna ◽  
Deleterious Alleles ◽  
Laboratory Populations ◽  
Potential Applications

AbstractThe idea of driving genetically modified alleles to fixation in a population has fascinated scientists for over 40 years1,2. Potential applications are broad and ambitious, including the eradication of disease vectors, the control of pest species, and the preservation of endangered species from extinction3. Until recently, these possibilities have remained largely abstract due to the lack of an effective drive mechanism. CRISPR/Cas9 gene drive (CGD) now promise a highly adaptable approach for driving even deleterious alleles to high population frequency, and this approach was recently shown to be effective in small laboratory populations of insects4–7. However, it remains unclear whether CGD will also work in large natural populations in the face of potential resistance mechanisms. Here we show that resistance against CGD will inevitably evolve unless populations are small and repair of CGD-induced cleavage via nonhomologous end joining (NHEJ) can be effectively suppressed, or resistance costs are on par with those of the driver. We specifically calculate the probability that resistance evolves from variants at the target site that are not recognized by the driver's guide RNA, either because they are already present when the driver allele is introduced, arise byde novomutation, or are created by the driver itself when NHEJ introduces mutations at the target site. Our results shed light on strategies that could facilitate the engineering of a successful drive by lowering resistance potential, as well as strategies that could promote resistance as a possible mechanism for controlling a drive. This study highlights the need for careful modeling of CGD prior to the actual release of a driver construct into the wild.

scholarly journals ADVANTAGES AND DISADVANTAGES OF PERFORMING ECOTOXICOLOGICAL BIOASSAYS WITH LARVAE OF POLYCHAETES BELONGING TO THE Capitella capitata SPECIES-COMPLEX

2006 ◽  
Vol 21 (1-2) ◽  
pp. 145
Author(s):  
N. Méndez-Ubach ◽  
C. Green-Ruíz
Keyword(s):  
Species Complex ◽  
Small Body ◽  
Natural Populations ◽  
Individual Variability ◽  
Life Cycles ◽  
Juvenile Stage ◽  
Toxic Substances ◽  
Advantages And Disadvantages ◽  
Experimental Protocols ◽  
Capitella Capitata

The deposit feeder polychaete Capitella capitata contributes to the elimination of toxic substances from sediments. The taxon comprises a sibling species-complex that differs in their reproductive modes. It is known that larvae from this species-complex can delay or inhibit metamorphosis to the juvenile stage in the presence of toxic substances in the environment. The incorporation of these substances can delay the recruitment of individuals into natural populations. The advantages of performing bioassays to test effects on metamorphosis of C. capitata larvae are that these organisms are cosmopolitan, and are easy to collect, transport and culture without feeding. In addition, each brood can produce a high number of known-aged larvae, which are sensitive to different toxicants, especially when in solution. Nevertheless, the lack of knowledge about their life cycles and experimental protocols, the requirement of daily observations, the intraspecific individual variability, and their small body size and motility can difficult the experimental work. The use of C. capitata larvae to perform ecotoxicological studies in laboratory is recommended. Ventajas y desventajas de realizar bioensayos ecotoxicológicos con larvas de poliquetos pertenecientes al complejo de especies Capitella capitata El poliqueto detritívoro Capitella capitata contribuye a la eliminación de tóxicos del sedimento. Este taxón constituye un complejo de especies crípticas que difieren en sus estrategias reproductivas. Las larvas de este complejo de especies son sensibles a la presencia de tóxicos en el ambiente, al grado de retrasar o inhibir la metamorfosis al estado juvenil. La incorporación de estos tóxicos al medio ambiente puede afectar el reclutamiento de los individuos a las poblaciones naturales. Las ventajas de realizar bioensayos para evaluar los efectos sobre la metamorfosis de larvas de C. capitata son que dichas larvas son cosmopolitas, y son fáciles de recolectar, transportar y cultivar sin alimento. Además, en cada desove se pro duce un número elevado de individuos de edad conocida, los cuales son sensibles a diferentes tóxicos, especialmente en solución. Sin em bargo, el trabajo ex per i men tal puede dificultarse debido al desconocimiento de los ciclos reproductivos y de los protocolos experimentales, al requerimiento de observaciones diarias, a la variabilidad in di vid ual intraespecífica, y a su pequeña talla y movilidad. Se recomienda el uso de larvas de C. capitata para realizar estudios ecotoxicológicos en laboratorio.

scholarly journals Population genetics of Drosophila ananassae: Chromosomal association studies in Indian populations

Genetika ◽  
2010 ◽  
Vol 42 (2) ◽  
pp. 209-222 ◽  
Author(s):  
Pranveer Singh ◽  
B.N. Singh
Keyword(s):  
Association Studies ◽  
Natural Populations ◽  
Drosophila Ananassae ◽  
Previous Suggestion ◽  
Linked Gene ◽  
Chromosome Inversions ◽  
Tight Linkage ◽  
Laboratory Populations ◽  
Chromosomal Association

Forty-five natural populations of Drosophila ananassae and laboratory stocks made from these flies were analyzed for chromosome inversions. Quantitative data on the frequencies of these inversions were utilized to test intra- and interchromosomal interactions in D. ananassae. In most of the natural as well as laboratory populations no significant deviation from randomness of intra- and interchromosomal associations (2L-3L, 2L-3R, 3L-3R) was found hence, providing evidence for random associations. However, in some instances, significant deviation from randomness was found in both natural and laboratory populations, which could be due to excess of certain combinations, deficiency of others and complete absence of some combinations. Possible role of genetic drift could be implicated due to tight-linkage between linked gene arrangements. This strengthens the previous suggestion that there is lack of genetic coadaptation in D. ananassae.

scholarly journals Population genetics of Drosophila ananassae

2008 ◽  
Vol 90 (5) ◽  
pp. 409-419 ◽  
Author(s):  
PRANVEER SINGH ◽  
BASHISTH N. SINGH
Keyword(s):  
Genetic Drift ◽  
Natural Populations ◽  
Chromosomal Polymorphism ◽  
Drosophila Ananassae ◽  
Isolated Populations ◽  
Domestic Species ◽  
Laboratory Populations ◽  
Varying Environments ◽  
High Level ◽  
High Degree

SummaryDrosophila ananassae Doleschall is a cosmopolitan and domestic species. It occupies a unique status among Drosophila species due to certain peculiarities in its genetic behaviour and is of common occurrence in India. Quantitative genetics of sexual and non-sexual traits provided evidence for genetic control of these traits. D. ananassae exhibits high level of chromosomal polymorphism in its natural populations. Indian natural populations of D. ananassae show geographic differentiation of inversion polymorphism due to their adaptation to varying environments and natural selection operates to maintain three cosmopolitan inversions. Populations do not show divergence on temporal scale, an evidence for rigid polymorphism. D. ananassae populations show substantial degree of sub-structuring and exist as semi-isolated populations. Gene flow is low despite co-transportation with human goods. There is persistence of cosmopolitan inversions when populations are transferred to laboratory conditions, which suggests that heterotic buffering is associated with these inversions in D. ananassae. Populations collected from similar environmental conditions that initially show high degree of genetic similarity have diverged to different degrees in laboratory environment. This randomness could be due to genetic drift. Interracial hybridization does not lead to breakdown of heterosis associated with cosmopolitan inversions, which shows that there is lack of genetic co-adaptation in D. ananassae. Linkage disequilibrium between independent inversions in laboratory populations has often been observed, which is likely to be due to suppression of crossing-over and random genetic drift. No evidence for chromosomal interactions has been found in natural and laboratory populations of D. ananassae. This strengthens the previous suggestion that there is lack of genetic co-adaptation in D. ananassae.

scholarly journals Avoidance of Trinucleotide Corresponding to Consensus Protospacer Adjacent Motif Controls the Efficiency of Prespacer Selection during Primed Adaptation

mBio ◽  
2018 ◽  
Vol 9 (6) ◽  
Author(s):  
Olga Musharova ◽  
Danylo Vyhovskyi ◽  
Sofia Medvedeva ◽  
Jelena Guzina ◽  
Yulia Zhitnyuk ◽  
...  
Keyword(s):  
Selection Process ◽  
Natural Populations ◽  
Type I ◽  
Dna Fragments ◽  
Dna Arrays ◽  
Content Type ◽  
Factors Affecting ◽  
Crispr Array ◽  
Protospacer Adjacent Motif ◽  
Foreign Dna

ABSTRACT CRISPR DNA arrays of unique spacers separated by identical repeats ensure prokaryotic immunity through specific targeting of foreign nucleic acids complementary to spacers. New spacers are acquired into a CRISPR array in a process of CRISPR adaptation. Selection of foreign DNA fragments to be integrated into CRISPR arrays relies on PAM (protospacer adjacent motif) recognition, as only those spacers will be functional against invaders. However, acquisition of different PAM-associated spacers proceeds with markedly different efficiency from the same DNA. Here, we used a combination of bioinformatics and experimental approaches to understand factors affecting the efficiency of acquisition of spacers by the Escherichia coli type I-E CRISPR-Cas system, for which two modes of CRISPR adaptation have been described: naive and primed. We found that during primed adaptation, efficiency of spacer acquisition is strongly negatively affected by the presence of an AAG trinucleotide—a consensus PAM—within the sequence being selected. No such trend is observed during naive adaptation. The results are consistent with a unidirectional spacer selection process during primed adaptation and provide a specific signature for identification of spacers acquired through primed adaptation in natural populations. IMPORTANCE Adaptive immunity of prokaryotes depends on acquisition of foreign DNA fragments into CRISPR arrays as spacers followed by destruction of foreign DNA by CRISPR interference machinery. Different fragments are acquired into CRISPR arrays with widely different efficiencies, but the factors responsible are not known. We analyzed the frequency of spacers acquired during primed adaptation in an E. coli CRISPR array and found that AAG motif was depleted from highly acquired spacers. AAG is also a consensus protospacer adjacent motif (PAM) that must be present upstream from the target of the CRISPR spacer for its efficient destruction by the interference machinery. These results are important because they provide new information on the mechanism of primed spacer acquisition. They add to other previous evidence in the field that pointed out to a “directionality” in the capture of new spacers. Our data strongly suggest that the recognition of an AAG PAM by the interference machinery components prior to spacer capture occludes downstream AAG sequences, thus preventing their recognition by the adaptation machinery.

scholarly journals Creating outbred and inbred populations of haplodiploid mites to measure adaptive responses in the lab

2020 ◽  
Author(s):  
Diogo P. Godinho ◽  
Miguel A. Cruz ◽  
Maud Charlery de la Masselière ◽  
Jéssica Teodoro-Paulo ◽  
Cátia Eira ◽  
...  
Keyword(s):  
Experimental Evolution ◽  
Natural Populations ◽  
Model Organism ◽  
Spider Mites ◽  
Ecological Interactions ◽  
Adaptive Responses ◽  
Biological Resources ◽  
Laboratory Populations ◽  
Outbred Populations ◽  
Inbred Populations

AbstractLaboratory studies are often criticized for not being representative of processes occurring in natural populations. This can be partially mitigated by using lab populations that capture large amounts of variation. Additionally, many studies addressing adaptation of organisms to their environment are done with laboratory populations, using quantitative genetics or experimental evolution methodologies. Such studies rely on populations that are either highly outbred or inbred. However, the methodology underlying the generation of such biological resources are usually not explicitly documented.Given their small size, short generation time, amenability to laboratory experimentation and knowledge of their ecological interactions, haplodiploid spider mites are becoming a widely used model organism. Here, we describe the creation of outbred populations of two species of spider mites, Tetranychus urticae and T. evansi, obtained by performing controlled crosses between individuals from field-collected populations. Subsequently, from the outbred population of T. evansi, we derived inbred lines, by performing several generations of sib-mating. These can be used to measure broad-sense heritability as well as correlations among traits. Finally, we outline an experimental evolution protocol that can be widely used in other systems. Sharing these biological resources with other laboratories and combining them with the available powerful genetic tools for T. urticae (and other species) will allow consistent and comparable studies that greatly contribute to our understanding of ecological and evolutionary processes.

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