Natural selection and ribosomal DNA in Drosophila

Genome ◽  
1989 ◽  
Vol 31 (1) ◽  
pp. 296-303 ◽  
Author(s):  
Alan R. Templeton ◽  
Hope Hollocher ◽  
Susan Lawler ◽  
J. Spencer Johnston
Keyword(s):  
Life History ◽  
Natural Selection ◽  
Ribosomal Dna ◽  
Allelic Variation ◽  
Natural Populations ◽  
Population Level ◽  
Developmental Time ◽  
Adult Age ◽  
Drosophila Hydei ◽  
Drosophila Mercatorum

Natural populations of Drosophila mercatorum are variable for the number of X-linked 28S ribosomal genes bearing a 5-kilobase insert. A separate polymorphic X-linked gene controls whether 28S repeats bearing the insert are preferentially underreplicated during the formation of polytene tissue. Female flies having at least a third of their 28S genes bearing the insert and lacking the ability to preferentially underreplicate inserted repeats display the abnormal abdomen syndrome. The syndrome is characterized by retention of juvenile abdominal cuticle into the adult, a slowdown in larval developmental time, and an increase in early female fecundity. The life history traits are expressed in nature and provide a basis for strong natural selection. The abnormal abdomen syndrome should be favored whenever the adult age structure is skewed towards young individuals, and field studies confirm this prediction. The closely related species, Drosophila hydei, also bears these inserts and appears to be subject to similar selection. However, D. mercatorum responds to this selection primarily through the allelic variation that controls preferential underreplication, whereas D. hydei responds primarily through adjustment of the proportion of inserted 28S genes. This is interpreted to mean that the evolution of a multigene family arises from the interaction of population-level and DNA-level processes.Key words: ribosomal DNA, natural selection, concerted evolution, life history, multigene families, Drosophila mercatorum, Drosophila hydei.

scholarly journals The molecular through ecological genetics of abnormal abdomen. IV. Components of genetic variation in a natural population of Drosophila mercatorum.

Genetics ◽  
1992 ◽  
Vol 130 (2) ◽  
pp. 355-366
Author(s):  
H Hollocher ◽  
A R Templeton ◽  
R DeSalle ◽  
J S Johnston
Keyword(s):  
Genetic Variation ◽  
Natural Population ◽  
Allelic Variation ◽  
Natural Populations ◽  
Developmental Time ◽  
Ecological Genetics ◽  
Adult Longevity ◽  
Genetic Determinants ◽  
Drosophila Mercatorum ◽  
Y Chromosomes

Abstract Natural populations of Drosophila mercatorum are polymorphic for a phenotypic syndrome known as abnormal abdomen (aa). This syndrome is characterized by a slow-down in egg-to-adult developmental time, retention of juvenile abdominal cuticle in the adult, increased early female fecundity, and decreased adult longevity. Previous studies revealed that the expression of this syndrome in females is controlled by two closely linked X chromosomal elements: the occurrence of an R1 insert in a third or more of the X-linked 28S ribosomal genes (rDNA), and the failure of replicative selection favoring uninserted 28S genes in larval polytene tissues. The expression of this syndrome in males in a laboratory stock was associated with the deletion of the rDNA normally found on the Y chromosome. In this paper we quantify the levels of genetic variation for these three components in a natural population of Drosophila mercatorum found near Kamuela, Hawaii. Extensive variation is found in the natural population for both of the X-linked components. Moreover, there is a significant association between variation in the proportion of R1 inserted 28S genes with allelic variation at the underreplication (ur) locus such that both of the necessary components for aa expression in females tend to cosegregate in the natural population. Accordingly, these two closely linked X chromosomal elements are behaving as a supergene in the natural population. Because of this association, we do not believe the R1 insert to be actively transposing to an appreciable extent. The Y chromosomes extracted from nature are also polymorphic, with 16% of the Ys lacking the Y-specific rDNA marker. The absence of this marker is significantly associated with the expression of aa in males. Hence, all three of the major genetic determinants of the abnormal abdomen syndrome are polymorphic in this natural population.

Chromosomal and allelic variation in Drosophila americana: selective maintenance of a chromosomal cline

Genome ◽  
2002 ◽  
Vol 45 (1) ◽  
pp. 13-21 ◽  
Author(s):  
Bryant F McAllister
Keyword(s):  
Natural Selection ◽  
Hybrid Zone ◽  
Allelic Variation ◽  
Natural Populations ◽  
Chromosomal Evolution ◽  
Geographic Region ◽  
Hybrid Zones ◽  
Geographic Structure ◽  
Latitudinal Transect ◽  
Selective Maintenance

Geographically structured genetic variation, as represented by clines and hybrid zones, offers unique opportunities to study adaptation and speciation in natural populations. A hybrid zone has been reported between Drosophila americana americana and Drosophila americana texana, two taxa that are distinguished solely by the arrangement of their X and 4th chromosomes. In this study, samples of D. americana were collected along a latitudinal transect across the inferred hybrid zone, and the frequency of the alternative chromosomal arrangements is reported. These data illustrate that the alternative chromosomal arrangements are distributed along a shallow cline over a broad geographic region, and that the frequency of the arrangements is tightly correlated with latitude. Allelic variants at 13 RFLP loci in three genes on chromosome 4 exhibit no evidence of association with the cline. Presence of a cline for the chromosomal arrangements, as well as a general absence of geographic structure for variation at these genes, is interpreted as evidence that natural selection is responsible for the maintenance of this chromosomal cline. Furthermore, these results demonstrate that taxonomic subdivision of D. americana is unwarranted, because it exists as a cohesive species that is segregating a chromosomal fusion.Key words: chromosomal evolution, Robertsonian fusion, hybrid zone, cline, geographic variation, natural selection.

GENETIC ANALYSIS OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER IN JAPAN. IV. NATURAL SELECTION ON THE INDUCIBILITY, BUT NOT ON THE STRUCTURAL GENES, OF AMYLASE LOCI

Genetics ◽  
1984 ◽  
Vol 108 (4) ◽  
pp. 879-896
Author(s):  
Yoshinori Matsuo ◽  
Tsuneyuki Yamazaki
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Specific Activity ◽  
Natural Populations ◽  
Fold Increase ◽  
Developmental Time ◽  
Frequency Change ◽  
Inducing Factors ◽  
Highly Correlated ◽  
The One

ABSTRACT To test the validity of previous results the inducibility of amylase as well as other biochemical parameters was measured using 45 homozygous strains of Drosophila melanogaster from Akayu, Japan. Only the inducibility (but not protein contents or specific activity of the enzyme) was highly correlated with productivity measured using a starch food regime (rp = 0.41, P < 0.005, rg = 0.73 ± 0.21). Inducibility was also negatively correlated with developmental time using starch food; namely, the one with high inducibility developed the fastest. Population cage experiments using 1600 genomes from the same natural population showed that the inducibility responded positively to natural selection (1.6-fold increase in inducibility in cages using starch food relative to those using normal food), but little frequency change of allozymes was observed. All of these results were consistent and indicated that polymorphisms of inducing factors or regulatory genes were major determinants of fitness differences in a particular environment and may be the genetic materials responsible for the adaptive evolution of organisms, at least in amylase loci.

scholarly journals The molecular through ecological genetics of abnormal abdomen in Drosophila mercatorum. V. Female phenotypic expression on natural genetic backgrounds and in natural environments.

Genetics ◽  
1993 ◽  
Vol 134 (2) ◽  
pp. 475-485 ◽  
Author(s):  
A R Templeton ◽  
H Hollocher ◽  
J S Johnston
Keyword(s):  
Life History ◽  
Phenotypic Expression ◽  
Developmental Time ◽  
Ecological Genetics ◽  
Adult Longevity ◽  
Natural Environments ◽  
X Chromosomes ◽  
Rdna Genes ◽  
Drosophila Mercatorum ◽  
Female Life History

Abstract The abnormal abdomen (aa) syndrome in Drosophila mercatorum depends on the presence of R1 inserts in a third or more of the X-linked 28S rDNA genes and the absence of selective underreplication of inserted repeats in polytene tissues that is controlled by an X-linked locus (ur) half a map unit from the rDNA complex. This syndrome affects both life history and morphology in the laboratory. Because abnormal morphologies are rarely encountered in nature, the purpose of this study is to see if the female life history traits are still affected under more natural genetic backgrounds and environmental conditions. Two outbred stocks were extracted from the natural population living near Kamuela, Hawaii: KaaX that has only X chromosomes with uraa alleles, and K+X that has only ur+ alleles. These two stocks have nonoverlapping distributions of insert proportions, indicating strong disequilibrium between the ur locus and the rDNA complex. The KaaX stock had almost no morphological penetrance of uraa, indicating that genetic background is important. KaaX expressed longer female egg-to-adult developmental times, increased early adult female fecundity, and decreased female adult longevity compared with K+X. By bagging natural rots of the cactus Opuntia megacantha near Kamuela, Hawaii, it was shown that egg-to-adult developmental time is slowed down by 0.92 days in females bearing uraa alleles in nature, with no detectable slowdown in uraa males. The bagged rot data also indicate that females bearing uraa alleles have a strong fecundity advantage in nature under some ecological conditions but not others.

Selection

2016 ◽  
Author(s):  
Andrew P. Hendry
Keyword(s):  
Sexual Selection ◽  
Life History ◽  
Gene Flow ◽  
Natural Selection ◽  
Mating Success ◽  
Natural Populations ◽  
Meta Analyses

This chapter begins with a description of how natural selection works and how it is studied in natural populations. It draws on recent meta-analyses to answer fundamental questions about selection in nature, such as how strong and consistent it is, how often it is stabilizing (disfavoring extreme individuals) or disruptive (favoring extreme individuals), what types of traits (e.g., life history or morphology) are under the strongest selection, and how selection differs when fitness is indexed as mating success (sexual selection) or survival/fecundity (natural selection). The chapter also examines selection within “populations,” which are considered to be conspecific groups of individuals within which interbreeding is common (close to panmixia) but among which interbreeding (and therefore gene flow) is restricted.

scholarly journals Age is not just a number – senescence affects how fish populations respond to different fishing regimes

2021 ◽  
Author(s):  
Pauliina Anna Ahti ◽  
Silva Uusi-Heikkilä ◽  
Timo J Marjomäki ◽  
Anna Kuparinen
Keyword(s):  
Life History ◽  
Natural Populations ◽  
Evolutionary Model ◽  
Population Level ◽  
Fish Population ◽  
Reproductive Capacity ◽  
Natural Mortality ◽  
Empirical Estimates ◽  
Trade Offs ◽  
Age Dependent

Abstract The presence of senescence in natural populations remains an unsolved problem in biology. Described as an age-dependent increase in natural mortality (known as actuarial senescence) and an age-dependent decrease in fecundity (known as reproductive senescence), the role of senescence in nature is still poorly understood. Based on empirical estimates of reproductive and actuarial senescence, we explored how senescence affects the population dynamics of Coregonus albula, a small, schooling salmonid fish. Using an empirically-based eco-evolutionary model, we investigated how the presence or absence of senescence affects how the fish population responds to pristine, intensive harvest, and recovery phases. Our results showed that at an individual level, the presence of senescence was accompanied by life-history trade-offs, i.e. lower asymptotic length and smaller size and younger age at maturity, both in the presence and absence of fishing. At the population level, the response to different fisheries selection patterns depended on the presence or absence of senescence. Importantly, the results indicate that through the lifehistory trade-offs between early reproduction and late life survival, the young and small individuals can have an important role in population recovery, especially when senescence is present. Since most life-history and fisheries models ignore senescence, they may be over-estimating reproductive capacity and under-estimating natural mortality. Our results highlight the need for increasing biological realism in these models to ensure the successful management of our natural resources.

Senescence

2001 ◽  
Author(s):  
Marc Tatar
Keyword(s):  
Natural Selection ◽  
Life Expectancy ◽  
Life Histories ◽  
Natural Populations ◽  
Mortality Rates ◽  
Progressive Increase ◽  
Underlying Assumption ◽  
Continuous Increase ◽  
Adult Age ◽  
Trade Offs

At all taxonomic levels, there exists tremendous variation in life expectancy. A field mouse Peromyscus may live 1.2 years, while the African elephant may persist for 60 years, and even a mousesized bat such as Corynorhinus rafinesquei lives a healthy 20 years (Promislow 1991). Part of this variance is caused by differences in ecological risks, rodents being perhaps the most susceptible to predation, and to vagaries of climate and resources. Another portion is caused by differences in senescence, the intrinsic degeneration of function that produces progressive decrement in age-specific survival and fecundity. Senescence occurs in natural populations, where it affects life expectancy and reproduction as can be seen, for instance, from the progressive change in age-specific mortality and maternity of lion and baboon in East Africa. The occurrence of senescence and of the widespread variation in longevity presents a paradox: How does the age-dependent deterioration of fitness components evolve under natural selection? The conceptual and empirical resolutions to this problem will be explored in this chapter. We shall see that the force of natural selection does not weigh equally on all ages and that there is therefore an increased chance for genes with late-age-deleterious effects to be expressed. Life histories are expected to be optimized to regulate intrinsic deterioration, and in this way, longevity evolves despite the maladaptive nature of senescence. From this framework, we will then consider how the model is tested, both through studies of laboratory evolution and of natural variation, and through the physiological and molecular dissection of constraints underlying trade-offs between reproduction and longevity. As humans are well aware from personal experience, performance and physical condition progressively deteriorate with adult age. And in us, as well as in many other species, mortality rates progressively increase with cohort age. Medawar (1955), followed by Williams (1957), stated the underlying assumption connecting these events: Senescent decline in function causes a progressive increase in mortality rate. Although mortality may increase episodically across some age classes, such as with increases in reproductive effort, we assume that the continuous increase of mortality across the range of adult ages represents our best estimate of senescence.

scholarly journals Allelic polymorphism at foxo contributes to local adaptation in Drosophila melanogaster

2018 ◽  
Author(s):  
Nicolas J. Betancourt ◽  
Subhash Rajpurohit ◽  
Esra Durmaz ◽  
Daniel K. Fabian ◽  
Martin Kapun ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Life History ◽  
Body Size ◽  
Local Adaptation ◽  
Development Time ◽  
Genetic Variance ◽  
Allelic Variation ◽  
Natural Populations ◽  
Life History Variation ◽  
Starvation Tolerance

AbstractThe insulin insulin-like growth factor signaling pathway has been hypothesized as a major determinant of life history profiles that vary adaptively in natural populations. In Drosophila melanogaster, multiple components of this pathway vary predictably with latitude; this includes foxo, a conserved gene that regulates insulin signaling and has pleiotropic effects on a variety of fitness-associated traits. We hypothesized that allelic variation at foxo underlies genetic variance for traits that vary with latitude and reflect local adaptation. To evaluate this, we generated recombinant outbred populations in which the focal foxo allele was homozygous and fixed for either the allele common at high latitude or low latitude and the genomic background was randomized across 20 inbred lines. After eight generations of recombination, experimental populations were phenotyped for a series of traits related to gene function. Our results demonstrate that natural allelic variation at foxo has major and predictable effects on body size and starvation tolerance, but not on development time. These patterns mirror those observed in natural populations collected across the latitudinal gradient in the eastern U.S.: clines were observed for starvation tolerance and body size, but development time exhibited no association with latitude. Furthermore, differences in size between foxo genotypes were equivalent to those observed between populations sampled from the latitudinal extremes, although contribution to the genetic variance for starvation tolerance was less pronounced. These results suggest that allelic variation at foxo is a major contributor to adaptive patterns of life history variation in natural populations of this genetic model.

scholarly journals Temperature and Rainfall Are Separate Agents of Selection Shaping Population Differentiation in a Forest Tree

Forests ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 1145
Author(s):  
João Costa e Silva ◽  
Brad Potts ◽  
Peter A. Harrison ◽  
Tanya Bailey
Keyword(s):  
Natural Selection ◽  
Population Differentiation ◽  
Natural Populations ◽  
Population Level ◽  
Direct Consequence ◽  
Arid Environment ◽  
Forest Tree ◽  
Machine Learning Algorithms ◽  
Multiple Sources ◽  
Genetic Constraints

Research highlights: We present evidence indicating that covariation of functional traits among populations of a forest tree is not due to genetic constraints, but rather selective covariance arising from local adaptation to different facets of the climate, namely rainfall and temperature. Background and Aims: Traits frequently covary among natural populations. Such covariation can be caused by pleiotropy and/or linkage disequilibrium, but also may arise when the traits are genetically independent as a direct consequence of natural selection, drift, mutation and/or gene flow. Of particular interest are cases of selective covariance, where natural selection directly generates among-population covariance in a set of genetically independent traits. We here studied the causes of population-level covariation in two key traits in the Australian tree Eucalyptus pauciflora. Materials and Methods: We studied covariation in seedling lignotuber size and vegetative juvenility using 37 populations sampled from throughout the geographic and ecological ranges of E. pauciflora on the island of Tasmania. We integrated evidence from multiple sources: (i) comparison of patterns of trait covariation within and among populations; (ii) climate-trait modelling using machine-learning algorithms; and (iii) selection analysis linking trait variation to field growth in an arid environment. Results: We showed strong covariation among populations compared with the weak genetic correlation within populations for the focal traits. Population differentiation in these genetically independent traits was correlated with different home-site climate variables (lignotuber size with temperature; vegetative juvenility with rainfall), which spatially covaried. The role of selection in shaping the population differentiation in lignotuber size was supported by its relationship with fitness measured in the field. Conclusions: Our study highlights the multi-trait nature of adaptation likely to occur as tree species respond to spatial and temporal changes in climate.

scholarly journals Compensatory evolution via cryptic genetic variation: Distinct trajectories to phenotypic and fitness recovery

2017 ◽  
Author(s):  
Sudarshan Chari ◽  
Christian Marier ◽  
Cody Porter ◽  
Emmalee Northrop ◽  
Alexandra Belinky ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Natural Selection ◽  
Allelic Variation ◽  
Courtship Behavior ◽  
Natural Populations ◽  
Wing Morphology ◽  
Cryptic Genetic Variation ◽  
Compensatory Evolution ◽  
Compensatory Adaptation ◽  
Deleterious Alleles

AbstractPopulations are constantly exposed to deleterious alleles, most of which are purged via natural selection. However, deleterious fitness effects of alleles can also be suppressed by compensatory adaptation. Compensatory mutations can act directly to reduce deleterious effects of an allele. Alternatively, compensation may also occur by altering other aspects of an organisms’ phenotype or performance, without suppressing the phenotypic effects of the deleterious allele. Moreover, the origin of allelic variation contributing to compensatory adaptation remains poorly understood. Compensatory evolution driven by mutations that arise during the selective process are well studied. However less is known about the role standing (cryptic) genetic variation plays in compensatory adaptation. To address these questions, we examined evolutionary trajectories of natural populations of Drosophila melanogaster fixed for mutations that disrupt wing morphology, resulting in deleterious effects on several components of fitness. Lineages subjected only to natural selection, evolved modifications to courtship behavior and several life history traits without compensation in wing morphology. Yet, we observed rapid phenotypic compensation of wing morphology under artificial selection, consistent with segregating variation for compensatory alleles. We show that alleles contributing to compensation of wing morphology have deleterious effects on other fitness components. These results demonstrate the potential for multiple independent avenues for rapid compensatory adaptation from standing genetic variation, which ultimately may reveal novel adaptive trajectories.

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