Placentation and maternal investment in mammals

The mammalian placenta exhibits striking interspecific morphological variation, yet the implications of such diversity for reproductive strategies and fetal development remain obscure. More invasive hemochorial placentas, in which fetal tissues directly contact the maternal blood supply, are believed to facilitate nutrient transfer, resulting in higher fetal growth rates, and to be a state of relative fetal advantage in the evolution of maternal-offspring conflict. The extent of interdigitation between maternal and fetal tissues has received less attention than invasiveness but is also potentially important because it influences the surface area for exchange. We show that although increased placental invasiveness and interdigitation are both associated with shorter gestations, interdigitation is the key variable. Gestation times associated with highly interdigitated labyrinthine placentas are 44% of those associated with less interdigitated villous and trabecular placentas. There is, however, no relationship between placental traits and neonatal body and brain size. Hence, species with more interdigitated placentas produce neonates of similar body and brain size but in less than half the time. We suggest that the effects of placental interdigitation on growth rates and the way that these are traded off against gestation length may be promising avenues for understanding the evolutionary dynamics of parent-offspring conflict.     

Variable modes of inheritance of morphometrical traits in hybrids between Drosophila melanogaster and Drosophila simulans.

We investigated body-size inheritance in interspecific sterile hybrids by crossing a Drosophila simulans strain with 13 strains of Drosophila melanogaster, which were of various origins and chosen for their broad range of genetic variation. A highly significant parent-offspring correlation was observed, showing that the D. melanogaster genes for size are still expressed in a hybrid background. Superimposed on to this additive inheritance, the size of hybrids was always less than the mid-parent value. This phenomenon, which at first sight might be described as dominance or overdominance, is more precisely interpreted as a consequence of a hybrid breakdown, that is, a dysfunction of the parental genes for size when put to work together. This interpretation is enforced by the fact that phenotypic variability was much more prevalent in hybrids than in parents. We also analysed body pigmentation inheritance in the same crosses and got a very different picture. There was no increase in the phenotypic variance of F(1) hybrids and only a low parent-offspring correlation. Apparent overdominance could be observed but in opposite directions, with no evidence of hybrid breakdown. Our data point to the possibility of analysing a diversity of quantitative traits in interspecific hybrids, and indicate that breakdown might be restricted to some traits only.     

中华鳖GHRL基因SNPs的筛选及生长性状的关联分析

为探究GHRL基因多态性对中华鳖(Pelodiscus sinensis)生长性状的影响, 采用直接测序法在GHRL基因上检测到14个单核苷酸多态性位点C289T、G501T、T738C、G776T、A841G、T885C、T2960C、A2987T、G3390A、A3857C、G4718A、T4820C、A4850C、T4979C。随机选取同批繁殖的120只中华鳖用飞行时间质谱法进行SNPs位点的分型, 并分析与生长性状的相关性。检测结果显示, 所有SNP位点均符合Hardy-Weinberg平衡状态(P>0.05)。方差分析结果显示, C289T位点CT、CC基因型的5项生长数据均显著高于TT基因型(P<0.05)。S2位点AB基因型的体重、背甲长、背甲宽和裙边宽4项数据均显著高于AA基因型(P<0.05)。G3390A位点AG基因型的背甲长、背甲宽2项数据显著高于AA基因型(P<0.05)。G4718A位点AG基因型的背甲长、背甲宽、裙边宽3项数据显著高于AA基因型(P<0.05)。在GHRL基因上获得的SNP位点可能影响着中华鳖的生长性状或与之紧密连锁, 可为中华鳖分子辅助育种提供助力与参考。     

Estimating heritabilities and genetic correlations: comparing the 'animal model' with parent-offspring regression using data from a natural population

Quantitative genetic parameters are nowadays more frequently estimated with restricted maximum likelihood using the 'animal model' than with traditional methods such as parent-offspring regressions. These methods have however rarely been evaluated using equivalent data sets. We compare heritabilities and genetic correlations from animal model and parent-offspring analyses, respectively, using data on eight morphological traits in the great reed warbler (Acrocephalus arundinaceus). Animal models were run using either mean trait values or individual repeated measurements to be able to separate between effects of including more extended pedigree information and effects of replicated sampling from the same individuals. We show that the inclusion of more pedigree information by the use of mean traits animal models had limited effect on the standard error and magnitude of heritabilities. In contrast, the use of repeated measures animal model generally had a positive effect on the sampling accuracy and resulted in lower heritabilities; the latter due to lower additive variance and higher phenotypic variance. For most trait combinations, both animal model methods gave genetic correlations that were lower than the parent-offspring estimates, whereas the standard errors were lower only for the mean traits animal model. We conclude that differences in heritabilities between the animal model and parent-offspring regressions were mostly due to the inclusion of individual replicates to the animal model rather than the inclusion of more extended pedigree information. Genetic correlations were, on the other hand, primarily affected by the inclusion of more pedigree information. This study is to our knowledge the most comprehensive empirical evaluation of the performance of the animal model in relation to parent-offspring regressions in a wild population. Our conclusions should be valuable for reconciliation of data obtained in earlier studies as well as for future meta-analyses utilizing estimates from both traditional methods and the animal model.     

THE EFFECTS OF THE MATING SYSTEM ON PROGENY PERFORMANCE IN HYLA CRUCIFER (ANURA: HYLIDAE)

We performed a controlled mating experiment to determine whether genetic variation in larval traits in Hyla crucifer was predictable on the basis of mating status or body size of male parent. Larval growth rate was predictably related to body size of the sire. Males from the upper half of the body-size distribution sired offspring with 6% higher growth rates than those of offspring sired by males from the lower half of the body-size distribution. Offspring sired by males that obtained mates in nature had 3% higher growth rates than their half-siblings sired by males that did not mate in nature. Genetic variation for larval-period duration and size at metamorphosis was detected; however, neither mating status nor body size of sire could be used to predict values of these traits in the progeny. Although all three larval traits can affect fitness, there was no evidence that the offspring of some sires would always outperform the offspring of others in all three traits. The predictable association between adult male size and larval growth rate means that the H. crucifer mating system would have a directional effect on larval growth rate if male body size influences the outcome of male-male competition or female choice.     

Quantitative genetics and fitness effects of basal metabolism

The physiological requirements of reproduction are predicted to generate a link between energy, physiology and life history traits. Simultaneously, low maintenance costs, measured by energy consumption, are expected to be advantageous. Here we investigated fitness relatedness of traits by estimating genetic correlations between, and inbreeding depression for, body mass, basal metabolic rate (BMR) and other life history characters in a wild rodent, Myodes glareolus. The narrow-sense heritability of absolute and mass corrected BMRs were high for females (h² = 0.48 and 0.42) but low and non-significant for males (0.32 and 0.09). A significant positive genetic correlation between BMR and litter size suggests that traits connected to female fecundity might favour higher metabolism (i.e. support increased intake hypothesis). However, the estimates of inbreeding depression indicate that, while higher values of body mass and female litter size could be positively associated with overall fitness, the association between BMR and overall fitness in bank voles would be negative (i.e. support compensation hypothesis). This result suggests that the advantages of larger litters and larger body mass might be evolutionary constrained by high costs of maintenance of those traits, as reflected by the level of basal metabolism.     

GENETIC AND MATERNAL INFLUENCES ON BRAIN AND BODY SIZE IN RANDOMBRED HOUSE MICE

Genetic and environmental (chiefly maternal) variance and covariance components were estimated for brain and body size in randombred house mice of three different ages (one, three, and five months). Heritabilities estimated from regressions of offspring on their five-month-old male parents were fairly low over all three ages, averaging about 0.2 for brain size and about 0.3 for body size. Heritability estimates from female parents were higher, however, presumably because of the influence of maternal-environmental components of variance. The total maternal impact was estimated from full-sib analyses and, for the more reliable three- and five-month ages, averaged 23% for brain size and 20% for body size. Phenotypic, genetic, and environmental correlations and regressions of brain and body size also were calculated by parent-offspring and sib-correlation techniques, the phenotypic correlations generally decreasing from about 0.4 at one month to 0.2 at three and five months. Genetic correlations of brain and body size estimated from covariances of offspring on male parents were negative whereas those from female parents were positive in sign, and this as well as positive maternal correlations was taken as evidence of the influence of maternal sources of covariance for these traits. It was concluded that, in addition to direct genetic effects, indirect genetic sources of variance and covariance mediated through the prenatal maternal environment are quite important in the determination of brain size and its association with body size.     

Sex-specific growth rates in zebra finch nestlings: a possible mechanism for sex ratio adjustment

Wild and captive zebra finches (Taenopygia guttata), like severalother species, produce a male-biased sex ratio at fledging whenfood is scarce. This is due to primary sex-ratio adjustmentand female-biased nestling mortality. Given that young femalesfledging at low body masses have been shown to have low fecundityas adults, lower returns to parents from producing female offspringin conditions of restricted food has been raised as a functionalexplanation (Trivers and Willard's hypothesis of adaptive sexualinvestment; 1973). However, an alternative, mechanistic hypothesisis that under restricted conditions female chicks are more costlyto produce. In consequence, lower returns to parents under theseconditions would happen earlier in the life of female offspringrather than later. To test this hypothesis, I hand-reared chickson a food gradient. In the absence of parent-offspring and sib-sibinteractions, final body mass and growth rates for females werelower in conditions of restricted food. For males, final bodymass and growth rates did not differ with food condition. Lowfemale growth rates in food-restricted conditions might be onepotential mechanism causing female-biased mortality in birds.More importantly, this result is the strongest evidence yetof female offspring experiencing higher marginal fitness benefitsfrom additional food than males and it has implications forprimary and secondary sex-ratio adjustment. Also, as this mechanismhas been shown in the absence of parent-offspring interactions,significant questions can now be raised as to how parental andoffspring behavior interact in their effects on secondary sex-ratioadjustment.     

湖羊、东湖杂种羊POMC基因外显子3单核苷酸多态性及其与生长性状的关联分析

阿黑皮素原(Pro-opiomelanocortin, POMC)在动物采食和能量平衡调控中发挥重要作用, 文章对绵羊POMC基因外显子3进行扩增和测序, 筛选多态性位点, 并分析多态位点与湖羊和东弗里生×湖羊杂种羊生长性状的相关性。测序后发现湖羊POMC基因外显子3有2个单碱基突变(g.273 T/C和g.456 G/A), 根据273位点处发生的T/C突变, 建立PCR-RFLP分析方法, 并对162只湖羊和130只东湖杂种羊进行检测分析。结果发现, 在湖羊群体中检测到TT(0.469)、TC(0.438)和CC(0.093)3种基因型, 而在东湖杂种羊群体中仅检测到TT(0.754)和TC(0.246)两种基因型。POMC基因外显子3的273位点多态性与生长性状的相关性研究结果显示：湖羊群体中CC基因型个体的2月龄断奶重、4月龄尻高及TC基因型个体4月龄体长和管围均显著高于TT型个体(P<0.05); CC基因型个体的4月龄重、6月龄重极显著高于TT和TC基因型个体(P<0.01); CC基因型个体的4月龄体高和体长极显著高于TT型个体(P<0.01), 且显著高于TC基因型个体(P<0.05)。此外, CC型个体的管围极显著高于TT基因型个体(P<0.01)。东湖杂种羊群体中TC基因型个体的2月龄断奶重、4月龄重及4月龄体高、体长、胸深和管围都显著高于TT型个体(P<0.05), TC型个体的6月龄重极显著高于TT型个体(P<0.01)。研究结果表明, POMC基因外显子3与绵羊生长性状相关, C等位基因对体重及体尺性状的增加更有利。该结果为进一步探讨POMC基因作为绵羊生长性状的辅助选育标记奠定了基础。     

中华鳖GHSR基因SNPs的筛选及生长性状的关联分析

为探究GHSR基因多态性对中华鳖(Pelodiscus sinensis)生长相关性状的影响,采用直接测序法在GHSR基因5'侧翼和3'侧翼上筛选SNPs位点,共检测到5个单核苷酸多态性位点:A335T、G397T、A527G、A13482C和T13526A。随机选取同批繁殖的1冬龄200只中华鳖用直接测序法进行SNPs位点的分型,并分析与生长性状的相关性。检测结果显示,所有SNP位点均符合Hardy-Weinberg平衡状态(p>0.05)。方差分析显示,A336T位点的AT、TT基因型的体重、背甲长、背甲宽和裙边宽4项生长数据均显著高于AA基因型。A13482C位点的AC基因型的体重、背甲长、背甲宽和裙边宽4项数据均显著高于AA基因型(p<0.05)。研究表明,本实验在GHSR基因上获得的这些SNP位点可能影响着中华鳖的生长性状或与之紧密连锁,可为中华鳖分子辅助育种提供助力与参考。     

Sexual size dimorphism and timing of spring migration in birds

Sexually selected traits are limited by selection against those traits in other fitness components, such as survival. Thus, sexual selection favouring large size in males should be balanced by higher mortality of larger males. However, evidence from red-winged blackbirds (Agelaius phoeniceus) indicates that large males survive better than small males. A survival advantage to large size could result from males migrating north in early spring, when harsh weather favours large size for energetic reasons. From this hypothesis we predicted that, among species, sex differences in body size should be correlated with sex differences in timing of spring migration. The earlier males migrate relative to females, the larger they should be relative to females. We tested this prediction using a comparative analysis of data collected from 30 species of passerine birds captured on migration. After controlling for social mating system, we found that sexual size dimorphism and difference in arrival dates of males and females were significantly positively correlated. This result is consistent with the hypothesis that selection for survival ability promotes sexual size dimorphism (SSD), rather than opposes SSD as is the conventional view. If both natural selection and sexual selection favour large adult males, then limits to male size must be imposed before males become adults.     

Matriline effects on metamorphic traits in a natural system in the European common frog (Rana temporaria)

Successful reproduction is an important determinant of the fitness of an individual and of the dynamics of populations. Offspring of the European common frog (Rana temporaria) exhibit a high degree of variability in metamorphic traits. However, environmental factors alone cannot explain this phenotypic variability, and the influence of genetic factors remains to be determined. Here, we tested whether the maternal genotype influences developmental time, body size, and body condition of offspring in a forest pond in Germany. We collected fertilized eggs from all 57 clutches deposited in the pond. We used multilocus genotypes based on seven microsatellite loci to assign metamorphosed offspring to mothers and to determine the number of fathers for a single matriline. We tested the influence of genetic effects in the same environment by comparing variability of metamorphic traits within and between full‐sib offspring grouped to matrilines and tested whether multiple paternity increases the variability of metamorphic traits in a single matriline. The variability in size and body condition was higher within matrilines than between them, which indicates that these traits are more strongly influenced by environmental effects, which are counteracting underlying genetic effects. The developmental time varied considerably between matrilines and variability increased with the effective number of fathers, suggesting an additive genetic effect of multiple paternity. Our results show that metamorphic traits are shaped by environmental as well as genetic effects.     

尼罗罗非鱼ghrelin基因的多态性及其与生长性状相关SNP位点的筛选

为了研究尼罗罗非鱼(Oreochromis niloticus)生长激素促分泌素基因(ghrelin)的多态性及其与生长的相关性, 研究以两个尼罗罗非鱼群体(快长群体和基础群体)的DNA样本各40份为模板, 通过PCR扩增和测序获得ghrelin基因序列。通过Dnasp v5和MEGA 5.0分析序列多态性、筛选有效SNP 位点; 采用Snapshot法对两个群体子代ghrelin基因中SNP位点进行基因分型, 然后分析SNP位点基因型与生长性状的相关性。结果表明, 快长群体ghrelin基因中的单核苷酸变异位点数(S)比基础群体要少, 而核苷酸多态性(Pi)和平均核苷酸差异数(K)要略高于基础群体。共筛得3个有效SNP 位点(S1、S2和S3), 均分布于第1个内含子中。遗传结构分析表明, 3个SNP 位点在两个群体的子代中均为低度多态性位点(PIC0.25), 但处于Hardy-Weinberg平衡(P0.05);快长群体子代中3个SNP 位点的观测杂合度、期望杂合度和多态信息含量等遗传多样性参数均小于基础群体子代的相应值, 3个SNP 位点的遗传多样性参数、基因型和基因频率在同一群体中高度一致, SNP 位点之间完全连锁。两个群体子代中3个SNP 位点处的优势基因型相同, 但快长群体子代中优势基因型频率要明显大于基础群体子代中相应基因型频率。对两个群体子代的生长性状与SNP基因型进行关联性分析的结果表明,尼罗罗非鱼个体的多项生长指标(体重、体长、体高、头长和尾柄高等)在不同基因型中存在显著差异(S1:GG AG, S2:TT AT, S3:AA AT)(P0.05)。D1双倍型(S1:GG, S2:TT, S3:AA)所对应的尼罗罗非鱼个体的多项生长指标(体重、体长、体高、头长和尾柄高等)显著高于D2双倍型(S1:AG, S2:AT, S3:AT)。以上结果表明, 尼罗罗非鱼ghrelin基因3个SNP 位点完全连锁, D1双倍型与快长性状密切相关, 可作为尼罗罗非鱼分子标记辅助育种的候选标记。     

Variation in human mate choice: simultaneously investigating heritability, parental influence, sexual imprinting, and assortative mating

Human mate choice is central to individuals' lives and to the evolution of the species, but the basis of variation in mate choice is not well understood. Here we looked at a large community-based sample of twins and their partners and parents ([Formula: see text] individuals) to test for genetic and family environmental influences on mate choice, while controlling for and not controlling for the effects of assortative mating. Key traits were analyzed, including height, body mass index, age, education, income, personality, social attitudes, and religiosity. This revealed near-zero genetic influences on male and female mate choice over all traits and no significant genetic influences on mate choice for any specific trait. A significant family environmental influence was found for the age and income of females' mate choices, possibly reflecting parental influence over mating decisions. We also tested for evidence of sexual imprinting, where individuals acquire mate-choice criteria during development by using their opposite-sex parent as the template of a desirable mate; there was no such effect for any trait. The main discernible pattern of mate choice was assortative mating; we found that partner similarity was due to initial choice rather than convergence and also at least in part to phenotypic matching.     

Leptin基因的PCR-SSCP与牛体重、体尺指标的相关性

利用PCR—SSCP技术研究了南阳牛、秦川牛、郏县红牛、西镇牛、鲁西牛和荷斯坦奶牛6个牛品种539个个体leptin基因的遗传多态性。结果表明,PCR扩增产物大小为330bp,PCR—SSCP分析表现出多态。南阳牛、秦川牛、郏县红牛、西镇牛、鲁西牛和荷斯坦奶牛的A等位基因频率分别为0．558,0．492,0．571,0．658,0．591,0．615;B等位基因频率分别为0．442,0．508,0．429,0．342,0．409,0．385。不同基因型与体重、体尺等生长性状指标相关性分析的结果表明：南阳牛群体内除12月龄的体高和日增重、18月龄的坐骨端宽和日增重外,BB型个体的六月龄、十二月龄、十八月龄、二十四月龄体斜长、胸围、体重、坐骨端宽、体高和日增重均显著的大于AB和AA型个体（P〈0．05）;秦川牛群体内BB基因型个体十字部高上显著高于群体AA、AB型个体（P〈0．05）,即BB〉AA、AB,可作为秦川牛体尺指标（十字部高）候选基因之一,但在体重、胸围、体长指标上均无显著差异（P〉0．05）,所以不宜作为体重、胸围、体长指标候选基因;郏县红牛群体内AB与BB基因型个体在十字部高和坐骨端宽上显著高于群体AA型个体（P〈0．05）,而群体内不同基因型在体重和体尺指标（体高、体斜长、胸围）上无显著差异（P〉0．05）。序列分析表明,leptin基因多态是第66位发生G→T、第67位发生A→C及299位发生新的单核苷酸突变C→T所造成。     

Sex- and age-dependent effects of population density on life history traits of red deer Cervus elaphus in a temperate forest

We studied both the short‐ and long‐term effects of density on three life history traits of a red deer population inhabiting a temperate forest. Both male and female body mass increased when population density decreased, but male mass changed to a greater extent than female mass. Density did not influence female survival irrespective of age, however, survival of males was lower at high density for all age classes except the prime‐age class. Pregnancy rates of primiparous females increased markedly with decreasing density, whereas those of adult hinds were fairly constant and unrelated to density. For both sexes, of the studied life history traits we detected a long‐term effect of density at birth (cohort effect) only on body mass. These results suggest that density influences life history traits in the same way as factors of environmental variation such as climate. In this population we did not find any evidence for an influence of climatic conditions on life history traits of red deer. Both mild winters and the absence of summer droughts during the study period could account for such an absence of climatic effects. We interpreted our results to show that 1) as expected for a highly dimorphic and polygynous species such as red deer, male traits showed consistently higher sensitivity to variation in density than female traits, illustrating possible costs caused by sexual selection in males, 2) the female‐based Eberhardt's model according to which increasing density should sequentially affect juvenile survival, reproductive rates of primiparous females, reproductive rates of adults and lastly adult survival was only partly supported because we found that pregnancy rate of primiparous females rather than juvenile survival was the most sensitive trait to variation in density. We propose that including variation in male traits would improve the accuracy of models of population dynamics of large mammals, at least for highly dimorphic species. Because the population we studied was not fenced, we only measured apparent survival. We discuss how dispersal, in relation to the phenotypic quality of young deer, might be a potential regulating factor under such conditions.     

Quantitative Genetics of Sex Ratio Traits in the Parasitic Wasp, Nasonia Vitripennis

We detected significant parent-offspring regressions for the first sex ratio (the sex ratio produced by a female in a fresh host) and the second sex ratio (the sex ratio produced by a female in a previously parasitized host) in the parasitic wasp, Nasonia vitripennis. For both traits, estimates of the narrow-sense heritability range from &0.05 to &0.15 (depending on how the data are analyzed). The study population was derived from isofemale strains created from wasps captured in a single bird nest. The same population exhibited no significant parent-offspring regression for the brood sizes associated with the first and second sex ratios. There may be a significant negative parent-offspring regression for diapause proportion in the first sex ratio broods. The estimates of the genetic correlations between first and second sex ratios are positive although almost all are not significantly different from 0.0. To our knowledge, this study is the first ``fine-scale' analysis of genetic variation for sex ratio traits in any species of insect. Such studies are an essential part of the assessment of the validity of claims that sex ratio traits are locally optimal.     

Heritability of flight distance for Cydia pomonella

Cydia pomonella L. (Lepidoptera: Tortricidae) is considered to be rather sedentary, but some individuals undertake flights of several kilometres in the field. This paper investigates the genetic influence on this variability. The flight capacity was measured in the laboratory by a flight mill and its heritability was estimated for two different strains. The laboratory strain was kept for more than 45 generations and the field strain from Embrach (northern Switzerland) was recently collected in the field.The multiple-trait-restricted-maximum-likelihood method was used for the estimation of genetic variances and covariances. A mixed full-sib/half-sib design was applied for the field strain and a full-sib design for the laboratory strain. The heritability of total distance was 0.57 for the field strain and 0.37 for the laboratory strain (both sexes). In addition, a heritability of 0.38 for total distance was estimated by parent-offspring regression for the laboratory strain. All three values were significantly different from zero P<0.05 and show that there is a significant additive genetic influence on flight capacity.The genetic correlations between total distance and other flight traits (total duration, flight velocity, longest flight) were between 0.84 and 1.00 for both strains and suggest that these traits actually belong to a single one. High genetic correlations were also found between total distance and the morphological traits body weight and wing length for the field strain, whereas a negative correlation was found between total flight distance and body weight for the laboratory strain. This difference between the two strains was interpreted as a possible trade-off between flight capacity and fecundity.     

GENETIC AND SOCIAL INHERITANCE OF BODY AND EGG SIZE IN THE BARNACLE GOOSE (BRANTA LEUCOPSIS)

We present heritability estimates for final size of body traits and egg size as well as phenotypic and genetic correlations between body and egg traits in a recently established population of the barnacle goose (Branta leucopsis) in the Baltic area. Body traits as well as egg size were heritable and, hence, could respond evolutionarily to phenotypic selection. Genetic correlations between body size traits were significantly positive and of similar magnitude or higher than the corresponding phenotypic correlations. Heritability estimates for tarsus length obtained from full-sib analyses were higher than those obtained from midoffspring-midparent regressions, and this indicates common environment effects on siblings. Heritabilities for tarsus length obtained from midoffspring-mother regressions were significantly higher than estimates from midoffspring-father regressions. The results suggest that this discrepancy is not caused by maternal effects through egg size, nor by extra-pair fertilizations, but by a socially inherited foraging site fidelity in females.