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1.
We modify a simple mathematical model for natural selection originally formulated by Robert M. May in 1983 by permitting
one homozygote to have a larger selective advantage when rare than the other, and show that the new model exhibits dynamical
chaos. We determine an open region of parameter space associated with homoclinic points, and prove that there are infinite
sequences of period-doubling bifurcations along selected paths through parameter space. We also discuss the possibility of
chaos arising from imbalance in the homozygote fitnesses in more realistic biological situations, beyond the constraints of
the model.
Received 3 February 1995; received in revised form 1 November 1995 相似文献
2.
Comparison of quantitative genetic parameters between two natural populations of a selfing plant species, Medicago truncatula Gaertn. 总被引:2,自引:0,他引:2
I. Bonnin J. M. Prosperi I. Olivieri 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(5):641-651
In this paper we compare mean values, heritability estimates, coefficient of genetic variation, and genetic correlations
among several fitness components of two natural populations of a selfing plant species, Medicago truncatula L. It is shown that the population that had been found most polymorphic for molecular markers in a previous study was also
the most variable for quantitative characters. Depending on the traits, the larger heritabilities in this population were
due to either larger coefficients of genetic variances or smaller coefficients of environmental variances. Whereas genetic
and phenotypic correlation matrices were very similar within each population, they were quite different between populations.
In particular, although a positive correlation between age and size at maturity was found in both populations, the correlation
between age at maturity and reproductive success was negative in the more variable population (late flowering plant, with
a larger size at flowering, produced fewer pods), whereas no correlation was observed in the less variable population. We
suggest that while in the less variable population all individuals have a high reproductive effort, several strategies coexist
in the more variable population, with some early-flowering genotypes showing a high reproductive effort and other late-flowering
genotypes showing a larger competitive ability through increased vegetative growth.
Received: 25 June 1996 / Accepted: 11 October 1996 相似文献
3.
Herbivory and natural selection on flowering phenology in wild sunflower, Helianthus annuus 总被引:2,自引:0,他引:2
D. Pilson 《Oecologia》2000,122(1):72-82
Plant fitness is strongly affected by flowering phenology, and there are several ecological factors that are thought to shape
the distribution of flowering times. One relatively underexamined factor is the timing and intensity of attack by herbivores
that feed on flowers or developing seeds. This study tests the hypothesis that herbivores that feed on developing seeds of
wild sunflower, Helianthus annuus (Asteraceae), impose selection on flowering phenology. First, the study population was found to contain genetic variation
for mean date of flowering, so this trait could evolve if natural selection were operating. Next, the phenological pattern
of abundance of five seed-feeding herbivores was documented. Damage by three herbivores, Haplorhynchites aeneus (Cucurlionidae), the head-clipping weevil, Homoeosoma electellum (Lepidoptera: Pyralidae), the sunflower moth, and Suleima helianthana (Lepidoptera: Tortricidae), the sunflower bud moth, was highest early in the flowering season, and declined as the season
progressed. Damage by one herbivore, the seed fly Gymnocarena diffusa (Diptera: Tephrididae), was lowest early in the flowering season and increased as the season progressed. Finally, damage
by two seed weevils, Smicronyx fulvus and S. sordidus (Curculionidae), whose damage was not distinguished, was constant through the flowering period. Third, damage by Haplorhynchites, Homoeosoma, and Suleima was found to be detrimental to plant fitness, suggesting that plants that flower when these herbivores are not abundant should
have higher fitness. Finally, two phenotypic selection analyses were performed. The first included damage by Homoeosoma and Suleima, as well as flowering date, leaf area, and inflorescence diameter, as characters predicting plant fitness. In this analysis
directional selection was found to act to decrease damage by the two herbivores, but did not act on flowering date. The second
selection analysis was identical except that damage by the two herbivores was not included. In this analysis significant directional
selection was found to favor later-flowering plants. Comparison of these two analyses suggests that all selection on flowering
phenology is attributable to damage by Homoeosoma and Suleima: plants that flower later avoid damage by these two herbivores. While other influences on flowering phenology, such as pollination,
mate availability, and seasonality, have been well documented, this study is one of few to demonstrate natural selection on
flowering phenology that is a direct consequence of insect attack.
Received: 17 November 1998 / Accepted: 18 July 1999 相似文献
4.
T. Fahima G. L. Sun A. Beharav T. Krugman A. Beiles E. Nevo 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(3-4):434-447
Genetic diversity in random amplified polymorphic DNAs (RAPDs) was studied in 110 genotypes of the tetraploid wild progenitor
of wheat, Triticum dicoccoides, from 11 populations sampled in Israel and Turkey. Our results show high level of diversity of RAPD markers in wild wheat
populations in Israel. The ten primers used in this study amplified 59 scorable RAPD loci of which 48 (81.4%) were polymorphic
and 11 monomorphic. RAPD analysis was found to be highly effective in distinguishing genotypes of T. dicoccoides originating from diverse ecogeographical sites in Israel and Turkey, with 95.5% of the 100 genotypes correctly classified
into sites of origin by discriminant analysis based on RAPD genotyping. However, interpopulation genetic distances showed
no association with geographic distance between the population sites of origin, negating a simple isolation by distance model.
Spatial autocorrelation of RAPD frequencies suggests that migration is not influential. Our present RAPD results are non-random
and in agreement with the previously obtained allozyme patterns, although the genetic diversity values obtained with RAPDs
are much higher than the allozyme values. Significant correlates of RAPD markers with various climatic and soil factors suggest
that, as in the case of allozymes, natural selection causes adaptive RAPD ecogeographical differentiation. The results obtained
suggest that RAPD markers are useful for the estimation of genetic diversity in wild material of T. dicoccoides and the identification of suitable parents for the development of mapping populations for the tagging of agronomically important
traits derived from T. dicoccoides.
Received: 13 July 1998 / Accepted: 13 August 1998 相似文献
5.
R. van Berloo Piet Stam 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(1):147-154
Molecular markers may enable plant breeders to select indirectly for genes affecting quantitative traits by selecting for
molecular markers closely linked to these genes (marker-assisted selection, MAS). We have assessed the effectiveness of MAS
compared to phenotypic selection. Key variables in this assessment were: trait heritability, selection intensity, genetic
architecture and uncertainty in QTL mapping. Simulation studies showed that the application of MAS in autogamous crops, with
the objective of obtaining transgressive genotypes, can improve selection results when compared to conventional selection
procedures. Marker-assisted selection appears particularly promising when dominant alleles at quantitative trait loci are
present and linked in coupling phase. Uncertainty in estimated QTL map positions reduces the benefits of marker-assisted selection,
but this reduction remains limited in most cases.
Received: 5 September 1997 / Accepted: 6 October 1997 相似文献
6.
Microsatellite polymorphism in natural populations of wild emmer wheat,Triticum dicoccoides,in Israel 总被引:5,自引:0,他引:5
Fahima T Röder MS Wendehake K Kirzhner VM Nevo E 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2002,104(1):17-29
Diversity in 20 microsatellite loci of wild emmer wheat, Triticum dicoccoides, was examined in 15 populations (135 genotypes) representing a wide range of ecological conditions of soil, temperature, and
water availability, in Israel and Turkey. An extensive amount of diversity at microsatellite loci was observed despite the
predominantly selfing nature of this plant species. The 20 Gatersleben wheat microsatellites (GWM), representing 13 chromosomes
of genomes A and B of wheat, revealed a total of 364 alleles, with an average of 18 alleles per GWM marker (range: 5–26).
The proportion of polymorphic loci per population averaged 0.90 (range: 0.45– 1.00); genic diversity, He, averaged 0.50 (range 0.094– 0.736); and Shannon’s information index averaged 0.84 (range 0.166–1.307). The coefficients
of genetic distance between populations were high and averaged D=1.862 (range 0.876–3.320), an indication of sharp genetic divergence over short distances. Interpopulation genetic distances
showed no association with geographic distance between the population sites of origin, which ruled out a simple isolation
by distance model. Genetic dissimilarity values between genotypes were used to produce a dendrogram of the relationships among
wild wheat populations by the unweighted pair-group method with arithmetic averages (UPGMA). The results showed that all the
wild emmer wheat populations could be distinguished. Microsatellite analysis was found to be highly effective in distinguishing
genotypes of T. dicoccoides, originating from diverse ecogeographical sites in Israel and Turkey, with 88% of the 135 genotypes correctly classified into
sites of origin by discriminant analysis. Our present microsatellite results are non-random and in agreement with the previously
obtained allozyme and RAPD patterns, although the genetic-diversity values obtained with microsatellites are much higher.
Significant correlates of microsatellite markers with various climatic and soil factors suggest that, as in allozymes and
RAPDs, natural selection causes adaptive microsatellite ecogeographical differentiation, not only in coding, but most importantly
in non-coding genomic regions. Hence, the concept of ”junk DNA” needs to be replaced by at least partly regulatory DNA. The
obtained results suggest that microsatellite markers are useful for the estimation of genetic diversity in natural populations
of T. dicoccoides and for the tagging of agronomically important traits derived from wild emmer wheat.
Received: 27 February 2001 / Accepted: 22 March 2001 相似文献
7.
A. Gimelfarb 《Journal of mathematical biology》1996,35(1):88-96
The existence of two stable, symmetric (allelic frequency 0.5 in each locus) polymorphic states is demonstrated for a two-locus
model of an additive quantitative trait under strong Gaussian selection. Linkage disequilibrium at one of the states is negative
whereas it is positive at the other state. For a three-locus model, it is shown that in order to maintain a stable polymorphism
in all three loci, selection must be sufficiently but not exces- sively strong relative to recombination. Also, positive linkage disequilibrium can be maintained in a three-locus model under stabilizing
selection that is not very strong.
Received 15 July 1995 相似文献
8.
A. W. Campbell P. J. Campbell W. B. Griffin D. J. Burritt A. J. Conner 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(6-7):1028-1036
Marker selection (MS) and doubled-haploid (DH) technologies have the potential to reduce the time taken to breed new cereal
cultivars. However, a limiting factor is the potential increased genetic drift. The aim of this study was to design and test
a genetic model for predicting the sample sizes needed to maintain genetic variation among DH plants following marker selection.
The model estimates the amount of the genome that is fixed during the production of DH populations of a given size using a
given number of markers. To test the model, doubled-haploids were produced from wheat plants selected for three PCR-based
markers. When the genetic variation of the DH population (108 plants), produced from 15 selected F2 plants homozygous at three loci, was compared to the genetic variation of an unselected F3 population (200 plants), five of the six measured quantitative traits were identical and normally distributed. This model
should prove to be a valid breeding tool, allowing a breeder to apply MS to a breeding programme and estimate the minimum
DH population sizes required for minimal loss of genetic variation through genetic drift.
Received: 16 October 2000 / Accepted: 20 March 2001 相似文献
9.
10.
Al. V. Konarev I. N. Anisimova V. A. Gavrilova V. T. Rozhkova R. Fido A. S. Tatham P. R. Shewry 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,100(1):82-88
A highly sensitive gelatin overlay procedure was used to identify inhibitors of serine proteinases and of the cysteine proteinase
ficin in seeds and leaves of sunflower. One major and two minor groups of trypsin inhibitors were identified in seeds, the
former having a high pI (@10) and also inhibiting chymotrypsin. Three groups of trypsin/subtilisin inhibitors were also present
in seeds, together with three inhibitors of ficin. All groups showed polymorphism between lines of Helianthus annuus, while the trypsin and trypsin/subtilisin inhibitors also varied between wild species of Helianthus, with no apparent relationship to growth type (annual or perennial), genome constitution or ploidy level. Genetic analysis
showed that the major trypsin inhibitor and three groups of trypsin/subtilisin inhibitors are each controlled by single Mendelian
loci, with the three loci for trypsin/subtilisin inhibitors showing recombination values of 0.23–0.40. Purification by RP-HPLC
allowed the M
r
of two trypsin inhibitors to be determined by SDS-PAGE to be about 1,500 and 2,500, while the three trypsin/subtilisin inhibitors
varied in M
r
from about 1,500 to 6,000.
Received: 7 March 1999 / Accepted: 18 March 1999 相似文献
11.
Assessing the genetic divergence of Pinus leucodermis Ant. endangered populations: use of molecular markers for conservation purposes 总被引:2,自引:0,他引:2
G. Bucci G. G. Vendramin L. Lelli F. Vicario 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(7):1138-1146
In this study, 23 previously identified Mendelian RAPD markers and 16 polymorphic allozymic markers were used to assess divergence
among two Greek populations and five Italian populations of Pinus leucodermis. Confidence intervals of observed genetic divergence were obtained using bootstrap analysis. Divergence among Italian populations
was found to be about as large as that between Italian and Greek populations. Since it is likely that the split of two nuclei
took place more than 10,000 years ago, a larger differentiation between, rather than within, the above nuclei was expected.
If genetic drift was responsible for the larger divergence of Italian populations, large randomly generated disequilibrium
between alleles at neutral, unlinked loci was expected. Indeed, the proportion of pairs of loci showing a non-random association
of alleles within each of the Italian populations was larger than what was expected by pure chance (7.95–10.88%). Effective
population size based on randomly generated disequilibrium was quite small for three out of the five populations considered
(N
e
=17.31±1.88, 16.57± 1.73, and 31.41±7.26, respectively). The implications of the results with respect to the conservation
of endangered species of trees are discussed.
Received: 27 April 1997 / Accepted: 14 June 1997 相似文献
12.
Progeny selection for agronomic characters in early generations of a potato breeding programme 总被引:8,自引:0,他引:8
J. Gopal 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(1-2):307-311
Repeatabilities of progeny means, and the univariate cross prediction method were used to study the effectiveness of progeny
selection for agronomically important characters in early generations of potato (Solanum tuberosum L.) breeding. The study was based on 90 progenies (72 crosses+18 selfs) evaluated for three successive generations, i.e.
seedling, first clonal and second clonal generations. Repeatabilities of progeny means were measured as correlation coefficients
between generations. In the univariate cross prediction method, progeny means and within-progeny standard deviations were
used to calculate the proportions of clones exceeding the target values, and correlation coefficients between generations
for predicted and observed proportions of clones, were calculated. Population means varied from generation to generation.
Correlation coefficients between generations for progeny means for most of the characters were significant, but moderate.
These were higher than the correlation coefficients between predicted and observed proportions of clones exceeding the target
values. The possibility of using progeny means as a selection parameter to reduce the number of genotypes to be examined in
later stages by rejecting the poor crosses in seedling generation is discussed.
Received: 8 January 1997/Accepted: 28 February 1997 相似文献
13.
14.
Summary. The effect of human recombinant growth hormone (hrGH) on intestinal adaptation in rats subjected to massive small bowel resection
has been followed by monitoring changes in the tissue polyamine system and in red blood cell (RBC) polyamine levels. In parallel,
the activities of monoamine oxidase A and B and diamine oxidase, the enzymes that catalyse one of the major routes of biogenic
amine metabolism, oxidative deamination, were also examined.
The results suggest that whilst hrGH treatment accelerates adaptive intestinal hyperplasia evoked by the resection, it has
no significant effect on RBC polyamine level or gut mucosal DNA concentration as measured 3 weeks post surgery. hrGH treated
operated rats exhibited significantly lower amine oxidase activities which implies that GH may alter biogenic amine systems.
Received February 13, 2002 Accepted June 27, 2002 Published online November 14, 2002
Acknowledgement We thank Ms Krystyna Adach, Zofia Grzelinska, Ing. M.Sc, and Ms Halina Kuchciak for skillful technical assistance.
Authors' address: Prof. W. Agnieszka Fogel, Institute of Biogenic Amines, Polish Academy of Sciences, 90364 Lodz, Poland, Fax: +48 42 6815283,
E-mail: wafogel@mazurek.man.lodz.pl 相似文献
15.
Kana Konishi Kentarou Matsumura Wataru Sakuno Takahisa Miyatake 《Journal of evolutionary biology》2020,33(8):1120-1128
Death feigning is considered to be an adaptive antipredator behaviour. Previous studies on Tribolium castaneum have shown that prey which death feign have a fitness advantage over those that do not when using a jumping spider as the predator. Whether these effects are repeatable across species or whether they can be seen in nature is, however, unknown. Therefore, the present study involved two experiments: (a) divergent artificial selection for the duration of death feigning using a related species T. freemani as prey and a predatory bug as predator, demonstrating that previous results are repeatable across both prey and predator species, and (b) comparison of the death‐feigning duration of T. castaneum populations collected from field sites with and without predatory bugs. In the first experiment, T. freemani adults from established selection regimes with longer durations of death feigning had higher survival rates and longer latency to being preyed on when they were placed with predatory bugs than the adults from regimes selected for shorter durations of death feigning. As a result, the adaptive significance of death‐feigning behaviour was demonstrated in another prey–predator system. In the second experiment, wild T. castaneum beetles from populations with predators feigned death longer than wild beetles from predator‐free populations. Combining the results from these two experiments with those from previous studies provided strong evidence that predators drive the evolution of longer death feigning. 相似文献
16.
Objective In order to examine whether chronic exposure to natural sour gas containing sulfur compounds act as natural selection force
on genetic polymorphisms of glutathione S-transferase M1 (GSTM1) and T1 (GSTT1), the present study was done. Methods The study was performed on two groups of healthy individuals of Masjid-i-Sulaiman (Khozestan province, southwest of Iran)
citizens with the mean ages of 47.5 ± 12.4 (36 male and 58 female) and 16.3 ± 2.4 (47 male and 140 female) that were considered
as first and second generation, respectively. The GSTT1 and GSTM1 genotypes were determined using a PCR-based method. Results The genotypic frequencies of GSTM1 did not change significantly (χ2 = 0.085, df = 1, P = 0.770). The frequency of the GSTT1 null genotype was 52.1% in the first generation and reached to 36.4% in the second generation. There was significant difference
between two generations for the GSTT1 polymorphism (χ2 = 6.397, df = 1, P = 0.011). Conclusion It was suggested that the GSTT1 polymorphism may be under natural selection because of probably favored ability of GSTT1-active genotype to survival and reproduction. 相似文献
17.
J. Hill R. Ortiz W. W. Wagoire O. Stølen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(2):305-309
Effectiveness of indirect selection for grain yield was investigated among eight bread wheat lines, selected in a stress
environment in the East African Highlands, where they showed a wide response to yellow rust, the biotic factor causing the
stress. The lines were intercrossed to give an 8×8F1 diallel, which was grown in this same environment for three consecutive growing seasons during 1994 and 1995. Half of the
last trial was sprayed with fungicide. From the estimates of narrow-sense heritabilities for yield and yellow rust severity,
and the genetic correlation between them, indirect selection for yield in the unsprayed plots, obtained by choosing the most
resistant 5% of this material was, on average, 12% higher than selecting for yield itself. In the fungicide-treated plots,
indirect selection was only 73% as efficient as direct selection. The implications of these results for selecting for yield
in stress environments are discussed.
Received: 10 April 1998 / Accepted: 5 August 1998 相似文献
18.
Conservation in wheat high-molecular-weight glutenin gene promoter sequences: comparisons among loci and among alleles of the GLU-B1-1 locus 总被引:2,自引:0,他引:2
O. D. Anderson F. A. Abraham-Pierce A. Tam 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(5):568-576
The high-molecular-weight glutenin (HMW) genes and encoded subunits are known to be critical for wheat quality characteristics
and are among the best-studied cereal research subjects. Two lines of experiments were undertaken to further understand the
structure and high expression levels of the HMW-glutenin gene promoters. Cross hybridizations of clones of the paralogous
x-type and y-type HMW-glutenin genes to a complete set of six genes from a single cultivar showed that each type hybridizes
best within that type. The extent of hybridization was relatively restricted to the coding and immediate flanking DNA sequences.
Additional DNA sequences were determined for four published members of the HMW-glutenin gene family (encoding subunits Ax2*, Bx7, Dx5, and Dy10) and showed that the flanking DNA of the examined genes diverge at approximately −1200 bp 5′ to the start
codon and 200–400 bp 3′ to the stop codon. These divergence sites may indicate the boundaries of sequences important in gene
expression. In addition, promoter sequences were determined for alleles of the Bx gene (Glu-B1-1), a gene reported to show higher levels of expression than other HMW-glutenin genes and with variation among cultivars. The
sequences of Bx promoters from three cultivars and one wild tetraploid wheat indicated that all Bx alleles had few differences
and contained a duplicated portion of the promoter sequence “cereal-box” previously suspected as a factor in higher levels
of expression. Thus, the “cereal-box” duplication preceeded the origin of hexaploid wheat, and provides no evidence to explain
the variations in Bx subunit synthesis levels. One active Bx allele contained a 185-bp insertion that evidently resulted from
a transposition event.
Received: 5 August 1997 / Accepted: 6 November 1997 相似文献
19.
David L. Boose 《Oecologia》1997,110(4):493-500
Sources of variation in floral nectar production were investigated in a natural population of Epilobium canum (Onagraceae), a hummingbird-pollinated herbaceous shrub. Field measurements showed significant phenotypic variation among
plants in floral nectar production rates. Average variance among flowers within plants was approximately one-third to one-half
as great as variance among plants, with coefficients of variation among flowers ranging from 6.5% to 116.7%. A greenhouse
experiment using clonally propagated ramets from field plants showed significant genetic variation for nectar production rates;
broad sense heritability was estimated to have a maximum value of 0.64. In the greenhouse, plants grown under low water or
low light conditions produced approximately 25% less nectar on average than those grown under control conditions. However,
significant genotype-environment interactions indicated that genets differed in their responses to the changes in conditions.
Rank correlations for genet mean nectar production rates across environmental conditions were low, and in two out of three
comparisons were not different from zero. It is concluded that although the opportunity for natural selection on nectar production
rates exits in this population, the response to selection will likely be slow, and the opportunity for selection of a narrow-optimum
nectar production phenotype may be limited.
Received: 9 January 1996 / Accepted: 18 December 1996 相似文献
20.
This study examined the effects of increased leaf N in natural food plants on oviposition, preimaginal survival, growth, and
adult size of the butterfly Lycaena tityrus. Female butterflies did not discriminate between leaves of high and low N content. In accordance with previous studies, we
found higher growth rates and concomitantly decreased development times at a high N level. However, because of high pupal
(and larval) mortality (overall 73.0%) as well as a reduction in adult size (by ca. 8%) this was, overall, not beneficial
to the butterflies. Thus, our results were not consistent with the broad interspecific trend that insect herbivore performance
is positively correlated with leaf N. These findings undermine the general applicability of the N limitation hypothesis. As
the detrimental effects were largely confined to the pupal and adult stages, results obtained from the larval phase only may
not yield reliable results and must therefore be interpreted with caution. If negative effects of N enrichment are found more
frequently in declining species inhabiting nutrient poor grassland, this will have major implications for the conservation
of these species.
Received: 30 November 1999 / Accepted: 14 February 2000 相似文献