共查询到20条相似文献,搜索用时 31 毫秒
1.
Stephen M. Shuster William R. Briggs Patricia A. Dennis 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2013,368(1613)
Multiple mating by females is widely thought to encourage post-mating sexual selection and enhance female fitness. We show that whether polyandrous mating has these effects depends on two conditions. Condition 1 is the pattern of sperm utilization by females; specifically, whether, among females, male mating number, m (i.e. the number of times a male mates with one or more females) covaries with male offspring number, o. Polyandrous mating enhances sexual selection only when males who are successful at multiple mating also sire most or all of each of their mates'' offspring, i.e. only when Cov♂(m,o), is positive. Condition 2 is the pattern of female reproductive life-history; specifically, whether female mating number, m, covaries with female offspring number, o. Only semelparity does not erode sexual selection, whereas iteroparity (i.e. when Cov♀(m,o), is positive) always increases the variance in offspring numbers among females, which always decreases the intensity of sexual selection on males. To document the covariance between mating number and offspring number for each sex, it is necessary to assign progeny to all parents, as well as identify mating and non-mating individuals. To document significant fitness gains by females through iteroparity, it is necessary to determine the relative magnitudes of male as well as female contributions to the total variance in relative fitness. We show how such data can be collected, how often they are collected, and we explain the circumstances in which selection favouring multiple mating by females can be strong or weak. 相似文献
2.
Peter B. Bright 《Bulletin of mathematical biology》1973,35(1-2):69-79
If the concentrationc
1(t)=∑
i=1
n
A
i
exp (−α
i
t) for one compartment, one presumes a linear catenaryn-compartment system without sinks and loss only from the same compartment, then the volumesV
i
, rate constantsk
ij
, and concentrationsc
i
(t) in each compartment can be determined in terms of theA
i
's,A
i
′s, α
i
′s, the dose injectedD
o
and the partition coefficientsr
ij
=k
ij
/k
ji
. If the concentration would become uniform at equilibrium, then the total volume of distribution may be determined without
knowledge ofr
ij
or restriction to catenary configuration. 相似文献
3.
R.C. Griffiths 《Theoretical population biology》1980,17(1):51-70
The diffusion form of a multiple-allele Wright-Fisher model of allele frequencies of types A1,…,AK at a neutral locus where there are general symmetric mutation rates of Mij (=Mji) from Ai → Aj is studied. A convenient recurrence relationship for the moments of linear forms in the allele frequencies is found. A formula is derived for the expected homozygosity in the transient and stationary models, which is applied to general stepwise mutation models where mutation over more than one step is possible. The probability that two randomly chosen genes are j steps apart at time t in the stepwise mutation model is found to have a reasonably simple form if conditioning is on the initial allele frequencies arranged in order of magnitude. Of interest is a new geometric charge state model, mutation over several steps roughly corresponding to independent charge changes. The expected homozygosity and expected distance between two randomly chosen genes is tabulated in this model. 相似文献
4.
Pollak E 《Journal of mathematical biology》2004,48(5):500-514
A population, reproducing wholly by selfing, is assumed to be observed at times
. Individuals between x–1 and x units of age at time t are said to be in age class x at that time. The rate of increase in the long run of individuals of type AiAj is denoted by mij+1=mji+1. For each genotype there is also a set of reproductive values, corresponding to all age classes and genotypes of individuals having descendants of that genotype. Then, if the number of individuals of each sort of ancestor is multiplied by its reproductive value and the products are summed, the result is the total value, which is Vij(t) for genotype AiAj. Then Vij(t+1)–Vij(t) is equal to mijVij(t), where mij is the Malthusian parameter for AiAj. Furthermore, if the mean and variance at time t of the mijs, weighted by their corresponding reproductive values, are respectively (t) and m2(t), then m¯(t+1)–m¯(t)=m2(t)/(1+m¯(t)). 相似文献
5.
Masae Shiyomi 《Population Ecology》1967,9(2):167-176
- The logistic function has been generally used to describe the reproductive process of a “population” of animal. However, this model can not give us any information about the reproductive process of “individuals” in the population. In this study a statistical model on the basis of the reproduction of individuals of barley aphid is presented to find the proportion of the mature individuals, the heterogeneity in reproductive ability of the aphids, etc.
- The model is constructed as follows:
- The probability that j insects are found on a plant at time t0 is represented as Q(j).
- The probability that h individuals of j have reproductive ability, say, mature individuals, in the period t0 to t1 is represented as B(h/j)=jChwh(1−w)j−h, where w is the proportion of mature individuals.
- In a population with a homogeneous reproductive ability, the probability that each parent lays i offspring in the period t0 to t1 is represented as P(i/m)=e−mmi/i!, where m is mean. And, in a population, m changes according to the gamma distribution. Hence the probability that a parent lays i offspring between t0 and t1 is represented as , where p and k are parameters of negative binomial distribution. The probability that h parents on a plant lays s offspring is represented as .
- From the assumptions mentioned above, the probability that s offspring are to be found at time t1 on a plant with the original j individuals at time t0 is represented by
- The experimental populations were demonstrated to fit well to the model.
6.
Charles J. Mode 《Bulletin of mathematical biology》1972,34(1):13-31
A bisexual multiple branching process is studied. Consider a population with respect to three genotypes in both the female and male populations and let $$X(n) = \left\langle {X_1 (n), X_2 (n), X_3 (n)} \right\rangle and Y(n) = \left\langle {Y_1 (n), Y_2 (n), Y_3 (n)} \right\rangle$$ be random vectors giving the number of females and males (respectively) of each genotype in generationn. The mating of females and males is accommodated in the model withZ ij (n) representing the number of females of theith genotype mated with a male of thejth genotype in generationn. The mating system is such that a female may be mated to only one male but a male may be mated with more than one female. By arranging the nine random variablesZ ij (n),i, j=1, 2, 3, in a 1×9, vectorZ(n) it is shown that under certain conditions there is a positive constant ? such that when ?>1 the vectorsZ n /ρn,X n /ρn andY n /ρn converge almost surely asn→∞ to random vectors with fixed directions. The paper is divided into four sections. In section 1 the model is described in detail and its potential applications to population genetics are discussed. In section 2, the generating function of the transition probabilities of theZ-process are derived. Section3 is devoted to the study of the limiting behavior of the first and second moments of theZ-process, and in section4 the results of section3 are utilized to study the behavior of the random vectorsZ(n),X(n) andY(n) asn→∞. 相似文献
7.
蝇蛹金小蜂的交配行为及雄蜂交配次数对雌蜂繁殖的影响 总被引:1,自引:0,他引:1
多数昆虫能够进行多次交配,随寄生蜂雄蜂交配次数的增加,雄蜂体内精子减少,雌蜂获得的精子数量减少,产下更多的单倍体卵,发育为雄性后代;一些单寄生性的寄生蜂雌蜂一生仅能够交配1次。描述了蝇蛹金小蜂雌雄蜂的交配行为,探讨了雄蜂交配次数对雌蜂后代产量等的影响以及雌蜂的可交配次数。结果表明,交配过程包括求偶、交尾前期、交尾和交尾后期;雄蜂已交配的次数并不能够显著影响其配偶的寿命、产卵期和后代总数量,但显著影响到其配偶的雌、雄后代数量和性比。随雄蜂交配次数的增加,与之交配的雌蜂的后代雄性百分比显著增大,雌蜂在产卵期内更早地出现较多雄性后代,体内精子不足的现象更加明显。无论已交配的蝇蛹金小蜂雌蜂在产卵期中是否出现精子不足,均不能再次完成交配。 相似文献
8.
9.
Masae Shiyomi 《Population Ecology》1967,9(1):53-61
The plant-to-plant movement of insects in one of the factors determining the distribution of individuals in insect populations. In this report the movement of barley aphids was analyzed by a statistical model. The model is represented as the convolution of three probability functions:
- The probability that s individuals are found on a plant at time t0:Q(s);
- The probability that i individuals leave the plant and remain on the ground from time t0 to t1:sCipiqs−i and p+q=1, where p and q are the proportions of individuals which do not leave a plant and which leave it once or more, respectively;
- The probability that j individuals climb a plant between time t0 to t1 and stay there at time t1:e−λλj/λ!, where λ is the mean of the individuals.
10.
W. J. V. Osterhout 《The Journal of general physiology》1929,13(2):261-294
When the only solute present is a weak acid, HA, which penetrates as molecules only into a living cell according to a curve of the first order and eventually reaches a true equilibrium we may regard the rate of increase of molecules inside as See PDF for Equation where PM is the permeability of the protoplasm to molecules, Mo, denotes the external and Mi the internal concentration of molecules, Ai denotes the internal concentration of the anion A- and See PDF for Equation (It is assumed that the activity coefficients equal 1.) Putting PMFM = VM, the apparent velocity constant of the process, we have See PDF for Equation where e denotes the concentration at equilibrium. Then See PDF for Equation where t is time. The corresponding equation when ions alone enter is See PDF for Equation. where K is the dissociation constant of HA, PA is the permeability of the protoplasm to the ion pair H+ + A-, and Aie denotes the internal concentration of Ai at equilibrium. Putting PAKFM = VA, the apparent velocity constant of the process, we have See PDF for Equation and See PDF for Equation When both ions and molecules of HA enter together we have See PDF for Equation where Si = Mi + Ai and Sie is the value of Si at equilibrium. Then See PDF for Equation VM, VA, and VMA depend on FM and hence on the internal pH value but are independent of the external pH value except as it affects the internal pH value. When the ion pair Na+ + A- penetrates and Nai = BAi, we have See PDF for Equation and See PDF for Equation where P
NaA is the permeability of the protoplasm to the ion pair Na+ + A-, Nao and Nai are the external and internal concentrations of Na+, See PDF for Equation, and V
Na is the apparent velocity constant of the process. Equations are also given for the penetration of: (1) molecules of HA and the ion pair Na+ + A-, (2) the ion pairs H+ + A- and Na+ + A-, (3) molecules of HA and the ion pairs Na+ + A- and H+ + A-. (4) The penetration of molecules of HA together with those of a weak base ZOH. (5) Exchange of ions of the same sign. When a weak electrolyte HA is the only solute present we cannot decide whether molecules alone or molecules and ions enter by comparing the velocity constants at different pH values, since in both cases they will behave alike, remaining constant if FM is constant and falling off with increase of external pH value if FM falls off. But if a salt (e.g., NaA) is the only substance penetrating the velocity constant will increase with increase of external pH value: if molecules of HA and the ions of a salt NaA. penetrate together the velocity constant may increase or decrease while the internal pH value rises. The initial rate See PDF for Equation (i.e., the rate when Mi = 0 and Ai = 0) falls off with increase of external pH value if HA alone is present and penetrates as molecules or as ions (or in both forms). But if a salt (e.g., NaA) penetrates the initial rate may in some cases decrease and then increase as the external pH value increases. At equilibrium the value of Mi equals that of Mo (no matter whether molecules alone penetrate, or ions alone, or both together). If the total external concentration (So = Mo + Ao) be kept constant a decrease in the external pH value will increase the value of Mo and make a corresponding increase in the rate of entrance and in the value at equilibrium no matter whether molecules alone penetrate, or ions alone, or both together. What is here said of weak acids holds with suitable modifications for weak bases and for amphoteric electrolytes and may also be applied to strong electrolytes. 相似文献
11.
- 1 In double mating experiments with Drosophila melanogaster in which one male had been irradiated, it was confirmed that sperm displacement is extensive, i.e. the second male to mate displaces most of the previously-stored sperm.
- 2 The predominance of the second ejaculate over the first increases with the interval between the two matings, from about P2= 0.83 (second mating on the first day after the first mating) to about P2= 0.99 (interval between mating = 14 days) where P2 is the proportion of offspring fathered by the second male.
- 3 A more accurate method for calculating P2 values is developed for experiments in which sperm are ‘labelled’ by irradiation treatment (equation 1).
- 4 Observations of the reducing egg production of the female throughout life were also obtained. A model is examined which incorporates both the sperm competition and egg production data to predict the reproductive value to a male of a mating with a given type of female, varying in age and mating status. The relative value (in terms of probable numbers of progeny gained) of a mating with a virgin or 4 day post-mating female is about twice that of a 14 day post-mating female, mainly because of the fecundity difference.
- 5 Some evolutionary aspects of sperm competition and multiple mating in insects are reviewed and discussed.
12.
Marc Artzrouni 《Journal of mathematical biology》1986,24(4):405-422
In an age-structured population that grows exponentially, each age groupP
i(t) at periodt is asymptotically equivalent tox
0
t
for some positive number x0. In this paper we show that the speed at which the ith age group reaches its exponential state of equilibrium can be measured by the rate at which the ratio vi(t)=Pi(t)/pi(t–1) converges tox
0. The age specific rate of convergence is determined by considering a quantityr satisfyingv
i(t)-x
0
¦ r
t
whent is large;R
i=Infr (over all initial populations,r satisfying the above inequality) is the R-factor used in numerical analysis to measure the rate at which the sequencev
i
(t) converges tox
0;S
i
=- In Ri is then defined as the rate of convergence to stability of the ith age group. The case of constant net maternity rates is studied in detail; in this contextS
0 is compared to the population entropyH, which was proposed by Tuljapurkar (1982) as a measure of the rate of convergence to stability. 相似文献
13.
Mohamed Hussein George A. Milliken 《Biometrical journal. Biometrische Zeitschrift》1978,20(4):329-338
Consider the model Yijk=μ + ai + bij + eijk (i=1, 2,…, t; j=1,2,…, Bi; k=1,2…,nij), where μ is a constant and a1,bij and eijk are distributed independently and normally with zero means and variances σ2adij and σ2, respectively, where it is assumed that the di's and dij's are known. In this paper procedures for estimating the variance components (σ2, σ2a and σ2b) and for testing the hypothesis σ2b = 0 and σ2a = 0 are presented. In the last section the mixed model yijk, where xijkkm are known constants and βm's are unknown fixed effects (m = 1, 2,…,p), is transformed to a fixed effect model with equal variances so that least squares theory can be used to draw inferences about the βm's. 相似文献
14.
Maydianne C.B. AndradeErin M. Banta 《Animal behaviour》2002,63(5):857-870
In the Australian redback spider, Latrodectus hasselti, males typically use their paired copulatory organs (palps) to copulate twice with a single female then sacrifice themselves to their cannibalistic mates in a strategy that increases their paternity in that one mating, but leads to death. This type of terminal investment in one mating is predicted only if the expected value of future matings is low for males relative to the value of repeated mating with the same female. In this laboratory study, we quantified the reproductive value of mating more than once with the same female (repeated mating) and mating with more than one female (multiple mating) for male redback spiders. We tested two natural selection hypotheses for repeated mating, sperm limitation and reproductive insurance, but found no support for either hypothesis. We show that, in the absence of sperm competition or cannibalism, male lifetime reproductive output is the same whether a male copulates once, twice, or several times with a given female. Repeated mating does not increase the probability of successful fertilization, nor does it increase the number of offspring produced in successful matings. Although male repeated mating is not favoured because of increased fertility of mates, other studies suggest it may be important in sperm competition. Here we show that the relative reproductive value of the first two copulations is very high for redback males because they are functionally sterile after each palp has been used once; nonvirgin males are unable to father offspring. Functional sterility and repeated mating by male redbacks may be favoured by the same factors that lead to male sacrifice behaviour: ecological constraints on multiple mating combined with competitive benefits of maximal investment in the first mating. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved. 相似文献
15.
Described are the syntheses and structures of a phosphonium salt of the anionic ligand O-t-butyl-1,1-dithiooxalate, [PPh3Bz][i-dtotBu] ([PPh3Bz][1]), and of two Cu(I) complexes of this anion, Cu(PPh3)2(η2-i-dtotBu) (2) and Cu(dmp)(PPh3)(η1-i-dtotBu) (3, dmp = 2,9-dimethyl-1,10-phenanthroline). In addition, it was found that the reaction of CuBr2 with i-dtotBu− gives a O-t-butyl-1-perthio-1-thiooxalato complex of copper(I), [BzPh3P][Cu(Br)(S-i-dtotBu)] ([BzPh3P][4]), where [S-i-dtotBu]− is a disulfide-containing anionic ligand. The electronic structure and absorption spectrum of this species were investigated by time dependent DFT methods. 相似文献
16.
Diego Rojas-Benitez Patrick C. Thiaville Valérie de Crécy-Lagard Alvaro Glavic 《The Journal of biological chemistry》2015,290(30):18699-18707
N6-Threonylcarbamoyl-adenosine (t6A) is a universal modification occurring at position 37 in nearly all tRNAs that decode A-starting codons, including the eukaryotic initiator tRNA (tRNAiMet). Yeast lacking central components of the t6A synthesis machinery, such as Tcs3p (Kae1p) or Tcs5p (Bud32p), show slow-growth phenotypes. In the present work, we show that loss of the Drosophila tcs3 homolog also leads to a severe reduction in size and demonstrate, for the first time in a non-microbe, that Tcs3 is required for t6A synthesis. In Drosophila and in mammals, tRNAiMet is a limiting factor for cell and animal growth. We report that the t6A-modified form of tRNAiMet is the actual limiting factor. We show that changing the proportion of t6A-modified tRNAiMet, by expression of an un-modifiable tRNAiMet or changing the levels of Tcs3, regulate target of rapamycin (TOR) kinase activity and influences cell and animal growth in vivo. These findings reveal an unprecedented relationship between the translation machinery and TOR, where translation efficiency, limited by the availability of t6A-modified tRNA, determines growth potential in eukaryotic cells. 相似文献
17.
Consider the model yijk=u ± ai ± bi ± cij ± eijk i=1, 2,…, t; j=1, 2,…b; k=1, 2,…,nij where μ is a constant and ai, bi, cij are distributed independently and normally with zero means and variances Δ2 Δ2/bdij and δ2 respectively. It is assumed that di's, and dij's are known (positive) constants (for all i and j). In this paper procedures for estimating the variance components (Δ2, Δ2b and Δ2a) and for testing the hypothesis Hoc:Δ2c/Δ2 = y3 and Hoa:Δ2b/Δ2 = y4 (where y2, y3, and y4, are specified constants) are presented. A generalization for the mixed model case is discussed in the last section. 相似文献
18.
Courtship behaviour in spiders in the form of premating vibrations by males may function (1) as a male identity signal used for species recognition, (2) in suppression of female aggressiveness, (3) to stimulate female mating behaviour, or (4) as a quality signal used in female choice. We investigated the function of web vibration by male Stegodyphus lineatus in a series of experiments. Regardless of vibratory performance, all males mated successfully with virgin females but only 56.4% of males mated with nonvirgin females. Vibratory performance did not influence male mating success, but heavier males had a higher probability of mating with mated females. Males vibrated less often and produced fewer vibrations when introduced on the web of a mated female. Males that vibrated webs of virgin females mated faster than nonvibrating males, but there was no effect of vibration rate or body mass. There was no effect of male vibratory effort or vibration rate on female reproductive success measured as time to egg laying, clutch size, number of hatched young, number of dispersed young and offspring body mass after a single mating. Males vibrated on abandoned virgin female webs but the response decreased with increasing duration of female absence, suggesting that females produce a web-borne pheromone, which elicits male vibrating behaviour. Mated females were less receptive and not stimulated by male vibrating behaviour. We conclude that male premating vibrations in S. lineatus do not function as a male quality signal selected via female choice. Rather, the primary function of this behaviour may be to stimulate a receptive female to mate. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. 相似文献
19.
Michiko Tashiro 《Biophysical journal》2009,96(12):4941-4950
We measured intracellular Mg2+ concentration ([Mg2+]i) in rat ventricular myocytes using the fluorescent indicator furaptra (25°C). In normally energized cells loaded with Mg2+, the introduction of extracellular Na+ induced a rapid decrease in [Mg2+]i: the initial rate of decrease in [Mg2+]i (initial Δ[Mg2+]i/Δt) is thought to represent the rate of Na+-dependent Mg2+ efflux (putative Na+/Mg2+ exchange). To determine whether Mg2+ efflux depends directly on energy derived from cellular metabolism, in addition to the transmembrane Na+ gradient, we estimated the initial Δ[Mg2+]i/Δt after metabolic inhibition. In the absence of extracellular Na+ and Ca2+, treatment of the cells with 1 μM carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone, an uncoupler of mitochondria, caused a large increase in [Mg2+]i from ∼0.9 mM to ∼2.5 mM in a period of 5-8 min (probably because of breakdown of MgATP and release of Mg2+) and cell shortening to ∼50% of the initial length (probably because of formation of rigor cross-bridges). Similar increases in [Mg2+]i and cell shortening were observed after application of 5 mM potassium cyanide (KCN) (an inhibitor of respiration) for ≥90 min. The initial Δ[Mg2+]i/Δt was diminished, on average, by 90% in carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone-treated cells and 92% in KCN-treated cells. When the cells were treated with 5 mM KCN for shorter times (59-85 min), a significant decrease in the initial Δ[Mg2+]i/Δt (on average by 59%) was observed with only a slight shortening of the cell length. Intracellular Na+ concentration ([Na+]i) estimated with a Na+ indicator sodium-binding benzofuran isophthalate was, on average, 5.0-10.5 mM during the time required for the initial Δ[Mg2+]i/Δt measurements, which is well below the [Na+]i level for half inhibition of the Mg2+ efflux (∼40 mM). Normalization of intracellular pH using 10 μM nigericin, a H+ ionophore, did not reverse the inhibition of the Mg2+ efflux. From these results, it seems likely that a decrease in ATP below the threshold of rigor cross-bridge formation (∼0.4 mM estimated indirectly in the this study), rather than elevation of [Na+]i or intracellular acidosis, inhibits the Mg2+ efflux, suggesting the absolute necessity of ATP for the Na+/Mg2+ exchange. 相似文献
20.
This study investigated male attractiveness rankings in a small-scale Amazonian society. In the rural community of Conambo, Ecuador, men and women practice self-sufficient horticulture, men hunt, and, traditionally, men have experienced a high rate of mortality due to homicide. We tested whether male attractiveness rankings would be related to male age, warriorship, hunting ability, status, coalitional affiliation, and female age. Twenty-five women aged between 14 and 78 years ranked photographs of 29 local men aged between 16 and 74 years for attractiveness in addition to warriorship, hunting ability, and status. Results revealed that male age was negatively correlated (r=?.683, p=.01) with female rankings of male attractiveness. Warriorship (r=.517, p=.005), status (r=.489, p=.008), and hunting ability (r=.577, p=.001) were found to be positively correlated with attractiveness, after controlling for age. Additionally, females showed a bias for males in their in-group when ranking attractiveness (one-sample t test: T29=16.727, p<.001). Attention is given to male age and coalitional affiliation as factors important in attractiveness rankings; warriorship and hunting ability also serve as ecologically salient features of male social worth. These findings contribute to a broader understanding of human attractiveness research by adding a new case study to the literature that documents previously unreported findings from a cultural context that is significantly different from the standard university-level student sample. 相似文献