Heterosis for Viability, Fecundity, and Male Fertility in Drosophila melanogaster: Comparison of Mutational and Standing Variation

Genetics ◽  
1998 ◽  
Vol 148 (3) ◽  
pp. 1171-1188 ◽  
Author(s):  
James D Fry ◽  
Stefanie L Heinsohn ◽  
Trudy F C Mackay
Keyword(s):  
Male Fertility ◽  
Natural Populations ◽  
Inbred Lines ◽  
Hybrid Vigor ◽  
High Rate ◽  
Female Fecundity ◽  
Standing Variation ◽  
Fitness Traits ◽  
Fertility Variation ◽  
Dominance Properties

Abstract If genetic variation for fitness traits in natural populations (“standing” variation) is maintained by recurrent mutation, then quantitative-genetic properties of standing variation should resemble those of newly arisen mutations. One well-known property of standing variation for fitness traits is inbreeding depression, with its converse of heterosis or hybrid vigor. We measured heterosis for three fitness traits, pre-adult viability, female fecundity, and male fertility, among a set of inbred Drosophilia melanogaster lines recently derived from the wild, and also among a set of lines that had been allowed to accumulate spontaneous mutations for over 200 generations. The inbred lines but not the mutation-accumulation (MA) lines showed heterosis for pre-adult viability. Both sets of lines showed heterosis for female fecundity, but heterosis for male fertility was weak or absent. Crosses among a subset of the MA lines showed that they were strongly differentiated for male fertility, with the differences inherited in autosomal fashion; the absence of heterosis for male fertility among the MA lines was therefore not caused by an absence of mutations affecting this trait. Crosses among the inbred lines also gave some, albeit equivocal, evidence for male fertility variation. The contrast between the results for female fecundity and those for male fertility suggests that mutations affecting different fitness traits may differ in their average dominance properties, and that such differences may be reflected in properties of standing variation. The strong differentiation among the MA lines in male fertility further suggests that mutations affecting this trait occur at a high rate.

scholarly journals On the Rate and Linearity of Viability Declines in Drosophila Mutation-Accumulation Experiments: Genomic Mutation Rates and Synergistic Epistasis Revisited

Genetics ◽  
2004 ◽  
Vol 166 (2) ◽  
pp. 797-806 ◽  
Author(s):  
James D Fry
Keyword(s):  
Mutation Rate ◽  
Average Rate ◽  
Natural Populations ◽  
Mutation Accumulation ◽  
High Rate ◽  
Deleterious Mutations ◽  
Order Of Magnitude ◽  
Contamination Event ◽  
Genomic Mutation ◽  
The 1960S

Abstract High rates of deleterious mutations could severely reduce the fitness of populations, even endangering their persistence; these effects would be mitigated if mutations synergize each others’ effects. An experiment by Mukai in the 1960s gave evidence that in Drosophila melanogaster, viability-depressing mutations occur at the surprisingly high rate of around one per zygote and that the mutations interact synergistically. A later experiment by Ohnishi seemed to support the high mutation rate, but gave no evidence for synergistic epistasis. Both of these studies, however, were flawed by the lack of suitable controls for assessing viability declines of the mutation-accumulation (MA) lines. By comparing homozygous viability of the MA lines to simultaneously estimated heterozygous viability and using estimates of the dominance of mutations in the experiments, I estimate the viability declines relative to an appropriate control. This approach yields two unexpected conclusions. First, in Ohnishi’s experiment as well as in Mukai’s, MA lines showed faster-than-linear declines in viability, indicative of synergistic epistasis. Second, while Mukai’s estimate of the genomic mutation rate is supported, that from Ohnishi’s experiment is an order of magnitude lower. The different results of the experiments most likely resulted from differences in the starting genotypes; even within Mukai’s experiment, a subset of MA lines, which I argue probably resulted from a contamination event, showed much slower viability declines than did the majority of lines. Because different genotypes may show very different mutational behavior, only studies using many founding genotypes can determine the average rate and distribution of effects of mutations relevant to natural populations.

scholarly journals Fertility Variation and its Impact on Effective Population Size in Seed Stands of Tamarindus indica and Azadirachta indica

2015 ◽  
Vol 64 (1-6) ◽  
pp. 91-99 ◽  
Author(s):  
R. Kamalakannan ◽  
M. Varghese ◽  
J.-M. Park ◽  
S.-H. Kwon ◽  
J.-H. Song ◽  
...  
Keyword(s):  
Azadirachta Indica ◽  
Male Fertility ◽  
Reproductive Traits ◽  
Fruit Production ◽  
Female Fertility ◽  
Tamarindus Indica ◽  
Individual Tree ◽  
Male And Female ◽  
Fertility Variation ◽  
Status Number

Abstract Growth and reproductive traits were assessed in seed stands of two native Indian tree species Tamarindus indica and Azadirachta indica. Positive correlation between growth (height and GBH) and reproductive traits (male and female contribution) were found in both species. Fertility was estimated from the flower and fruit production of individuals. Based on the fertility variation among individuals, parental balance, femaleness index and status number (Ns) were determined. The option of equal seed collection among individuals was also considered for estimating Ns. The percentage of fertile trees was higher in the high flowering year in both species. The best male contributing individuals also showed high female contribution (fruit production). The parental contribution in seed stands showed high deviation from expectation; 20% individuals contributed about 70% of male and female gametes in both species. Femaleness index showed that female and male contribution of individual tree was more balanced in the good flowering year, compared to the poor year. Coefficient of variation in male and female fertility was higher in the low flowering year resulting in high fertility variation among individuals and low status number. In T. indica, the female contribution was less variable compared to that of male fertility whereas in A. indica the female fertility variation was higher than that of male fertility. The relative status number (Nr = Ns/N) of the stands was lower for male and female fertility compared to the combined (male and female) fertility of individual trees.

scholarly journals Intraspecific variation in symbiont density in an insect-microbe symbiosis

2020 ◽  
Author(s):  
Benjamin J. Parker ◽  
Jan Hrček ◽  
Ailsa H.C. McLean ◽  
Jennifer A. Brisson ◽  
H. Charles J. Godfray
Keyword(s):  
Intraspecific Variation ◽  
Fungal Pathogens ◽  
Acyrthosiphon Pisum ◽  
Natural Populations ◽  
Pea Aphid ◽  
Optimal Density ◽  
Evolutionary Forces ◽  
Standing Variation ◽  
Dramatic Decline

AbstractMany insects host vertically-transmitted microbes, which can confer benefits to their hosts but are costly to maintain and regulate. A key feature of these symbioses is variation: for example, symbiont density can vary among host and symbiont genotypes. However, the evolutionary forces maintaining this variation remain unclear. We studied variation in symbiont density using the pea aphid (Acyrthosiphon pisum) and the bacterium Regiella insecticola, a symbiont that can protect its host against fungal pathogens. We found that relative symbiont density varies both between two Regiella phylogenetic clades and among aphid ‘biotypes’. Higher-density symbiont infections are correlated with stronger survival costs, but variation in density has little effect on the protection Regiella provides against fungus. Instead, we found that in some aphid genotypes, a dramatic decline in symbiont density precedes the loss of a symbiont infection. Together, our data suggest that the optimal density of a symbiont infection is likely different from the perspective of aphid and microbial fitness. Regiella might prevent loss by maintaining high within-host densities, but hosts do not appear to benefit from higher symbiont numbers and may be advantaged by losing costly symbionts in certain environments. The standing variation in symbiont density observed in natural populations could therefore be maintained by antagonistic coevolutionary interactions between hosts and their symbiotic microbes.

scholarly journals Male Fertility in Natural Populations of Red Deer Is Determined by Sperm Velocity and the Proportion of Normal Spermatozoa1

2005 ◽  
Vol 72 (4) ◽  
pp. 822-829 ◽  
Author(s):  
Aurelio F. Malo ◽  
J. Julián Garde ◽  
Ana J. Soler ◽  
Andrés J. García ◽  
Montserrat Gomendio ◽  
...  
Keyword(s):  
Male Fertility ◽  
Red Deer ◽  
Natural Populations ◽  
Sperm Velocity

scholarly journals Locating the Sex Determining Region of Linkage Group 12 of Guppy (Poecilia reticulata)

2020 ◽  
Vol 10 (10) ◽  
pp. 3639-3649
Author(s):  
Deborah Charlesworth ◽  
Roberta Bergero ◽  
Chay Graham ◽  
Jim Gardner ◽  
Lengxob Yong
Keyword(s):  
Poecilia Reticulata ◽  
Population Genomics ◽  
False Positive Rate ◽  
Natural Populations ◽  
Proximal Region ◽  
High Rate ◽  
Chromosome 12 ◽  
Small Samples ◽  
Autosomal Region ◽  
Y Chromosomes

Despite over 100 years of study, the location of the fully sex-linked region of the guppy (Poecilia reticulata) carrying the male-determining locus, and the regions where the XY pair recombine, remain unclear. Previous population genomics studies to determine these regions used small samples from recently bottlenecked captive populations, which increase the false positive rate of associations between individuals’ sexes and SNPs. Using new data from multiple natural populations, we show that a recently proposed candidate for this species’ male-determining gene is probably not completely sex-linked, leaving the maleness factor still unidentified. Variants in the chromosome 12 region carrying the candidate gene sometimes show linkage disequilibrium with the sex-determining factor, but no consistently male-specific variant has yet been found. Our genetic mapping with molecular markers spread across chromosome 12 confirms that this is the guppy XY pair. We describe two families with recombinants between the X and Y chromosomes, which confirm that the male-determining locus is in the region identified by all previous studies, near the terminal pseudo-autosomal region (PAR), which crosses over at a very high rate in males. We correct the PAR marker order, and assign two unplaced scaffolds to the PAR. We also detect a duplication, with one copy in the male-determining region, explaining signals of sex linkage in a more proximal region.

scholarly journals Colour plasticity in response to social context and parasitic infection in a self-fertilizing fish

2019 ◽  
Vol 6 (7) ◽  
pp. 181418
Author(s):  
Rebecca Jane Pawluk ◽  
Carlos Garcia de Leaniz ◽  
Joanne Cable ◽  
Bernard Tiddeman ◽  
Sofia Consuegra
Keyword(s):  
Social Context ◽  
Individual Variation ◽  
Genetic Background ◽  
Social Dynamics ◽  
Parasitic Infection ◽  
Natural Populations ◽  
Data Interpretation ◽  
Inbred Lines ◽  
Body Coloration ◽  
Pathogen Avoidance

Many animal species rely on changes in body coloration to signal social dominance, mating readiness and health status to conspecifics, which can in turn influence reproductive success, social dynamics and pathogen avoidance in natural populations. Such colour changes are thought to be controlled by genetic and environmental conditions, but their relative importance is difficult to measure in natural populations, where individual genetic variability complicates data interpretation. Here, we studied shifts in melanin-related body coloration in response to social context and parasitic infection in two naturally inbred lines of a self-fertilizing fish to disentangle the relative roles of genetic background and individual variation. We found that social context and parasitic infection had a significant effect on body coloration that varied between genetic lines, suggesting the existence of genotype by environment interactions. In addition, individual variation was also important for some of the colour attributes. We suggest that the genetic background drives colour plasticity and that this can maintain phenotypic variation in inbred lines, an adaptive mechanism that may be particularly important when genetic diversity is low.

scholarly journals Properties of spontaneous mutations affecting quantitative traits

1999 ◽  
Vol 74 (3) ◽  
pp. 341-350 ◽  
Author(s):  
A. GARCÍA-DORADO ◽  
C. LÓPEZ-FANJUL ◽  
A. CABALLERO
Keyword(s):  
Deleterious Mutation ◽  
Natural Populations ◽  
Detectable Effect ◽  
Environment Interaction ◽  
Fitness Component ◽  
Standing Variation ◽  
Genotype Environment Interaction ◽  
Component Traits ◽  
Mutational Variance ◽  
New Mutations

Recent mutation accumulation results from invertebrate species suggest that mild deleterious mutation is far less frequent than previously thought, implying smaller expressed mutational loads. Although the rate (λ) and effect (s) of very slight deleterious mutation remain unknown, most mutational fitness decline would come from moderately deleterious mutation (s ≈ 0·2, λ ≈ 0·03), and this situation would not qualitatively change in harsh environments. Estimates of the average coefficient of dominance (h¯) of non-severe deleterious mutations are controversial. The typical value of h¯ = 0·4 can be questioned, and a lower estimate (about 0·1) is suggested. Estimated mutational parameters are remarkably alike for morphological and fitness component traits (excluding lethals), indicating low mutation rates and moderate mutational effects, with a distribution generally showing strong negative asymmetry and little leptokurtosis. New mutations showed considerable genotype–environment interaction. However, the mutational variance of fitness-component traits due to non-severe detrimental mutations did not increase with environmental harshness. For morphological traits, a class of predominantly additive mutations with no detectable effect on fitness and relatively small effect on the trait was identified. This should be close to that responsible for standing variation in natural populations.

scholarly journals Limited potential for adaptation to climate change in a broadly distributed marine crustacean

2011 ◽  
Vol 279 (1727) ◽  
pp. 349-356 ◽  
Author(s):  
Morgan W. Kelly ◽  
Eric Sanford ◽  
Richard K. Grosberg
Keyword(s):  
Climate Change ◽  
Local Adaptation ◽  
Thermal Tolerance ◽  
Extinction Risk ◽  
Empirical Studies ◽  
Natural Populations ◽  
Adaptation To Climate Change ◽  
Isolated Populations ◽  
Tigriopus Californicus ◽  
Standing Variation

The extent to which acclimation and genetic adaptation might buffer natural populations against climate change is largely unknown. Most models predicting biological responses to environmental change assume that species' climatic envelopes are homogeneous both in space and time. Although recent discussions have questioned this assumption, few empirical studies have characterized intraspecific patterns of genetic variation in traits directly related to environmental tolerance limits. We test the extent of such variation in the broadly distributed tidepool copepod Tigriopus californicus using laboratory rearing and selection experiments to quantify thermal tolerance and scope for adaptation in eight populations spanning more than 17° of latitude. Tigriopus californicus exhibit striking local adaptation to temperature, with less than 1 per cent of the total quantitative variance for thermal tolerance partitioned within populations. Moreover, heat-tolerant phenotypes observed in low-latitude populations cannot be achieved in high-latitude populations, either through acclimation or 10 generations of strong selection. Finally, in four populations there was no increase in thermal tolerance between generations 5 and 10 of selection, suggesting that standing variation had already been depleted. Thus, plasticity and adaptation appear to have limited capacity to buffer these isolated populations against further increases in temperature. Our results suggest that models assuming a uniform climatic envelope may greatly underestimate extinction risk in species with strong local adaptation.

Mating patterns in self-compatible distylous populations of Amsinckia (Boraginaceae)

1975 ◽  
Vol 53 (8) ◽  
pp. 773-779 ◽  
Author(s):  
Fred R. Ganders
Keyword(s):  
Random Mating ◽  
Marker Gene ◽  
Natural Populations ◽  
Breeding Systems ◽  
High Rate ◽  
Structure Population ◽  
Disassortative Mating ◽  
Progeny Tests ◽  
Flower Form ◽  
Two Populations

Progeny tests of naturally pollinated pin- and thrum-form plants of two species of Amsinckia were conducted to determine whether net selfing, random mating, or net disassortative mating occurred in natural populations. The locus determining flower form was used as a marker gene. Amsinckia spectabilis experienced close to random mating in a dense population, but in a small, diffuse population a high rate of selfing was indicated. Pin plants of Amsinckia vernicosa var. furcata experienced 44.3% net disassortative mating, and thrum plants in this species experienced complete (100%) disassortative mating.Compared with A. spectabilis, stigmas and anthers are about twice as far apart in A. vernicosa var. furcata; yet the pollinators are essentially similar, suggesting that greater separation of stigmas and anthers greatly improves the efficiency of distyly at promoting disassortative pollination. The two populations of A. spectabilis studied indicate that autogamy and (or) geitonogamy is much higher in diffuse populations. The results support previous studies that disassortative pollination is greater in thrum-form flowers than in pin flowers. Distyly without self-incompatibility can be an effective outbreeding system but is much more sensitive to variations in floral structure, population density, and pollinator behavior than are self-incompatible breeding systems.

scholarly journals The transposable elements of the Drosophila serrata reference panel

2020 ◽  
Author(s):  
Zachary Tiedeman ◽  
Sarah Signor
Keyword(s):  
Transposable Elements ◽  
Transposable Element ◽  
Copy Number ◽  
Genetic Background ◽  
Natural Populations ◽  
Inbred Lines ◽  
Transposable Element Insertion ◽  
Defense Systems ◽  
Drosophila Serrata ◽  
Transposable Element Copy

AbstractTransposable elements are an important element of the complex genomic ecosystem, proving to be both adaptive and deleterious - repressed by the piRNA system and fixed by selection. Transposable element insertion also appears to be bursty – either due to invasion of new transposable elements that are not yet repressed, de-repression due to instability of organismal defense systems, stress, or genetic variation in hosts. Here, we characterize the transposable element landscape in an important model Drosophila, D. serrata, and investigate variation in transposable element copy number between genotypes and in the population at large. We find that a subset of transposable elements are clearly related to elements annotated in D. melanogaster and D. simulans, suggesting they spread between species more recently than other transposable elements. We also find that transposable elements do proliferate in particular genotypes, and that often if an individual is host to a proliferating transposable element, it is host to more than one proliferating transposable element. In addition, if a transposable element is active in a genotype, it is often active in more than one genotype. This suggests that there is an interaction between the host and the transposable element, such as a permissive genetic background and the presence of potentially active transposable element copies. In natural populations an active transposable element and a permissive background would not be held in association as in inbred lines, suggesting the magnitude of the burst would be much lower. Yet many of the inbred lines have actively proliferating transposable elements suggesting this is an important mechanism by which transposable elements maintain themselves in populations.

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