Selection component analysis of natural polymorphisms using population samples including mother-offspring combinations, II

Population samples including mother-offspring combinations provide information on the selection components: zygotic selection, sexual selection, gametic seletion and fecundity selection, on the mating pattern, and on the deviation from linkage equilibrium among the loci studied. The theory for the analysis of a sample consisting of adult individuals including combinations of a mother and one randomly chosen offspring in the case of n polymorphic autosomal loci with m_a alleles at the ath locus, a = 1, 2,…, n, is developed for an organism with discrete non-overlapping generations. In this general analysis complete determination of the genotypes is assumed. The modifications in the analysis for the case n = 2 and m₁ = m₂ = 2 when the two double heterozygotes cannot be separated are discussed, and the analysis is illustrated by data from a population of Zoarces viviparus (a marine teleost).     

Effects of maternal diet on offspring fitness in the bird cherry‐oat aphid

1. Maternal and offspring diet effects on life‐history traits of the bird cherry‐oat aphid Rhopalosiphum padi were tested on three wheat varieties. Using nine reciprocal combinations of wheat varieties, the effects of previous experience (maternal diet effect) on the aphid's response to resistant and susceptible varieties (offspring diet effect) were tested. Batis was susceptible, and Xiaoyan22 and Ww2730 were both resistant, but with different mechanisms. 2. Aphids produced the most alatae in the treatments with the most resistant maternal diet variety Xiaoyan22. The fecundity (F) and intrinsic rate of increase (r_m) of these alatae were at their greatest in the most resistant offspring diet variety, but these traits were not influenced in the apterae. 3. There were significant interactions in the alatae production and apterae life‐history traits, such as r_m, development time, weight gain, and mean relative growth rate, between the maternal and offspring diet varieties. The interactions in apterae responses between varieties, some of which were reciprocal, indicated phenotypic plasticity in these parthenogenetic aphids. 4. Rhopalosiphum padi produced more alatae on the most resistant variety; the alatae would disperse and were more fecund. The growth responses of the apterae showed phenotypic plasticity to the different combinations of maternal and offspring diet varieties. The phenotypic plasticity would allow R. padi to better utilise the variable environments represented by the small wheat plots of different varieties in China.     

Developmental analysis of fs(1)gastrulation defective,a dorsal-group gene of Drosophila melanogaster

Summary The gastrulation defective (gd) locus is a maternally expressed gene in Drosophila required for normal differentiation of structures along the embryonic dorso-ventral axis. Cuticular defects of the offspring from females with different combinations of gd alleles comprised a phenotypic continuum. Complementation among several alleles produced normal offspring while progressively more severe mutations produced a graded loss of structures from ventral, and then lateral, blastoderm cells. The most severely affected embryos consisted entirely of structures derived from dorsal blastoderm cells. Histological examination of staged siblings from selected allelic combinations showed that internal tissues were similarly affected. The tissues observed in amorphic embryos support new, more dorsal, assignments of fate map positions for blastoderm precursors of the cephalopharyngeal apparatus, hindgut and ventral nerve cord. The loss of ventral and lateral structures did not occur through cell death and appeared to involve a change in blastoderm cell fate. A direct effect of the mutations on blastoderm cell determination, however, was insufficient to explain the development of the dorsalized embryos. Intermediate phenotypes suggested that cell interactions or movements associated with morphogenesis are required for the determination of some cell fates in the dorsoventral axis. Thus, the developmental fate of all blastoderm cells may not be fixed at the time of blastoderm formation.     

Dispersal of a nearshore marine fish connects marine reserves and adjacent fished areas along an open coast

Marine species with pelagic larvae typically exhibit little population structure, suggesting long‐distance dispersal and high gene flow. Directly quantifying dispersal of marine fishes is challenging but important, particularly for the design of marine protected areas (MPAs). Here, we studied kelp rockfish (Sebastes atrovirens) sampled along ~25 km of coastline in a boundary current‐dominated ecosystem and used genetic parentage analysis to identify dispersal events and characterize them, because the distance between sedentary parents and their settled offspring is the lifetime dispersal distance. Large sample sizes and intensive sampling are critical for increasing the likelihood of detecting parent–offspring matches in such systems and we sampled more than 6,000 kelp rockfish and analysed them with a powerful set of 96 microhaplotype markers. We identified eight parent–offspring pairs with high confidence, including two juvenile fish that were born inside MPAs and dispersed to areas outside MPAs, and four fish born in MPAs that dispersed to nearby MPAs. Additionally, we identified 25 full‐sibling pairs, which occurred throughout the sampling area and included all possible combinations of inferred dispersal trajectories. Intriguingly, these included two pairs of young‐of‐the‐year siblings with one member each sampled in consecutive years. These sibling pairs suggest monogamy, either intentional or accidental, which has not been previously demonstrated in rockfishes. This study provides the first direct observation of larval dispersal events in a current‐dominated ecosystem and direct evidence that larvae produced within MPAs are exported both to neighbouring MPAs and to proximate areas where harvest is allowed.     

Maternal Effects of Photoperiod and Food Level on Life History Characteristics of the Cladoceran Daphnia Pulicaria Forbes

The response of various life-history characteristics of Daphnia pulicaria to photoperiod and food concentration was measured in 16 combinations of maternal and offspring environments (long vs. short day, high vs. low food) in flow-through experiments. Response variables in offspring were time and survival to release of first offspring, clutch size and neonate mass in the first brood, mass of adult females after 30days and somatic growth rate during the course of the experiment. Most of these parameters were directly controlled by food concentration in the offspring environment, but maternal effects frequently modified the response. A long day length in the maternal environment resulted in a prolongation of the time to first clutch release in offspring similar to the direct effect of low food. Likewise, survival to maturation and female mass were affected by maternal photoperiod. Somatic growth rate and clutch size responded to combined effects of maternal food conditions and photoperiod. The laboratory results were used to predict the seasonal change of fecundity of Daphnia in the field. When data on clutch size are ordered in a sequence as the different combinations of maternal and offspring environment occur during the seasonal succession in a temperate lake, they show a bimodal distribution with a high peak in spring and a lower peak in fall. This pattern is consistent with field observations. We conclude that photoperiod and maternal effects are important factors influencing life history and population dynamics of Daphnia.     

Paternity in Sooty Mangabeys

We determined paternity for 78 sooty mangabeys [(Cercocebus torquatus atys (Groves, 1978) equivalent to C. atys (Napier and Napier, 1967)], born between 1986 and 1993, using DNA profile analysis. The analysis is based on two independent assays of the genome of each individual via multilocus DNA probes. The mangabeys were members of either a large (n = 98) or a small (n = 18) group. Overall, during two periods of analysis in the large group, higher-ranking males sired more offspring than their lower-ranking counterparts did, though during one period the correlation between dominance rank and reproductive success is not significant. Of the two males in the small group, the alpha male sired all of the offspring during one period. There is a significant correlation between mounts and the number of surviving offspring each male sired in one birth year. Moreover, the same male did not always sire the offspring of a given female from year to year. Behavioral data focusing on male–offspring interactions show that offspring (n = 15) did not preferentially affiliate with their sire and that males affiliated with infants too infrequently for analysis. Thus, in a large sooty mangabey colony: (1) dominance rank generally predicts reproductive success; (2) adult males are not preferentially attracted to their offspring, or infants to their sires; and (3) the same male generally does not sire the offspring of a given female from year to year.     

Demographic consequences of nestbox use for Red‐footed Falcons Falco vespertinus in Central Asia

Nestbox programmes are frequently implemented for the conservation of cavity‐nesting birds, but their effectiveness is rarely evaluated in comparison with birds not using nestboxes. In the European Palaearctic, Red‐footed Falcon Falco vespertinus populations are both of high conservation concern and are strongly associated with nestbox programmes in heavily managed landscapes. We used a 21‐year monitoring dataset collected on 753 nesting attempts by Red‐footed Falcons in unmanaged natural or semi‐natural habitats to provide basic information on this poorly known species; to evaluate long‐term demographic trends within this population; and to evaluate response of demographic parameters of Red‐footed Falcons to environmental factors including use of nestboxes. We observed significant differences among years in laying date, offspring loss and numbers of fledglings produced, but not in egg production. Of these four parameters, offspring loss and, to a lesser extent, number of fledglings exhibited directional trends over time. Variation in laying date and in numbers of eggs were not well explained by any one model of environmental factors, but instead by combinations of models, each with informative terms for nest type. Nevertheless, laying in nestboxes occurred 2.10 ± 0.70 days earlier than in natural nests. In contrast, variation in both offspring loss and numbers of fledglings produced were fairly well explained by a single model including terms for nest type, nest location and an interaction between the two parameters (65 and 81% model weights, respectively), with highest offspring loss in nestboxes on forest edges. Because, for other species, earlier laying dates are associated with more fit individuals, this interaction highlighted a possible ecological trap, whereby birds using nestboxes on forest edges lay eggs earlier but suffer greater offspring loss and produce lower numbers of fledglings than do those in other nesting settings. If nestboxes increase offspring loss for Red‐footed Falcons in heavily managed landscapes where populations are at greater risk, or for the many other species of rare or endangered birds supported by nestbox programmes, these processes could have important demographic and conservation consequences.     

板栗与锥栗杂交F1代叶片表型变异及杂种优势研究

为探索栗属杂交F₁代幼林期叶片性状遗传变异规律及杂种优势,以板栗、锥栗种内和种间9个杂交组合235个杂交单株及其亲本为研究材料,利用巢式方差分析、Pearson相关性分析及主成分分析等统计学方法对其14个叶表型及光合生理性状进行分析。结果表明:①栗属杂交F₁代叶表型及光合生理性状存在丰富的遗传多样性,14个性状平均变异系数范围为4.40%~27.76%;②性状组合间表型分化系数VST均值为32.32%,组合内变异是主要的变异来源;③性状中亲优势率为-27.16%~90.53%,且不同组合性状杂种优势存在差异;④Pearson相关性分析结果显示14个性状中分别有46对和13对相关性达到极显著(P<0.01)和显著水平(P<0.05),其中叶长、叶宽等5个叶表型性状及叶绿素a、叶绿素b等4个光合生理指标相互间影响较大;⑤利用主成分分析法筛选出“魁栗×YLZ 15号”和“魁栗×YLZ 1号”两个优良杂交组合,其子代叶片具有叶面积大、干物质含量及光合有关色素含量高的特点,可为进一步筛选优良杂交子代提供主要素材。     

Artificial diet for the parasitic mitePyemotes tritici (Acari:Pyemotidae)

In previous work,Pyemotes tritici, an ectoparasite of stored-product insects, was induced to probe and pierce a synthetic membrane and feed on a homogenate of cigarette-beetle pupae. Later work with commercially prepared semi-synthetic insect diets, or combinations thereof, were judged to be completely unsatisfactory as few offspring were produced. Subsequently, 150 semi-synthetic diets were formulated and tested, of which one repeatedly produced near-normal numbers of offspring or about 150/female. The improved diet is of an appropriate consistency for feeding and contains comparatively high levels of lipo-proteins thought to be essential for development.     

The colour of paternity: extra‐pair paternity in the wild Gouldian finch does not appear to be driven by genetic incompatibility between morphs

In socially monogamous species, individuals can use extra‐pair paternity and offspring sex allocation as adaptive strategies to ameliorate costs of genetic incompatibility with their partner. Previous studies on domesticated Gouldian finches (Erythrura gouldiae) demonstrated a genetic incompatibility between head colour morphs, the effects of which are more severe in female offspring. Domesticated females use differential sex allocation, and extra‐pair paternity with males of compatible head colour, to reduce fitness costs associated with incompatibility in mixed‐morph pairings. However, laboratory studies are an oversimplification of the complex ecological factors experienced in the wild and may only reflect the biology of a domesticated species. This study aimed to examine the patterns of parentage and sex ratio bias with respect to colour pairing combinations in a wild population of the Gouldian finch. We utilized a novel PCR assay that allowed us to genotype the morph of offspring before the morph phenotype develops and to explore bias in morph paternity and selection at the nest. Contrary to previous findings in the laboratory, we found no effect of pairing combinations on patterns of extra‐pair paternity, offspring sex ratio or selection on morphs in nestlings. In the wild, the effect of morph incompatibility is likely much smaller, or absent, than was observed in the domesticated birds. Furthermore, the previously studied domesticated population is genetically differentiated from the wild population, consistent with the effects of domestication. It is possible that the domestication process fostered the emergence (or enhancement) of incompatibility between colour morphs previously demonstrated in the laboratory.     

Developmental changes in mother-offspring grooming in Japanese macaques

A cross-sectional analysis was made of developmental changes in mother-offspring grooming in Japanese macaques, Macaca,. fuscata. When offspring were immature, time spent grooming by their mothers decreased with offspring age. Soliciting by offspring increased steadily with age, in contrast to their successful soliciting, which decreased gradually until early adolescence. This is in accord with the hypothesis that grooming is one form of post-weaning maternal investment, which may entail behavioral conflict between mothers and immature offspring. On the other hand, mothers spent much more time for grooming of their adult female offspring than for their adolescent male and female offspring. It is argued that grooming by mothers may shift from a form of maternal investment in their offspring to a benefit to be exchanged reciprocally with them. © 1995 Wiley-Liss, Inc.     

CPDNA INHERITANCE IN INTERSPECIFIC CROSSES AND EVOLUTIONARY INFERENCE IN LOUISIANA IRISES

Inheritance of chloroplast DNA haplotypes was determined for progeny from interspecific crosses involving Iris fulva and Iris hexagona. Polymerase chain reaction amplification of chloroplast DNA followed by restriction fragment length analysis of the amplification products was used to identify the haplotypes of 213 experimental hybrids. This analysis allowed a test for maternal, paternal, and biparental inheritance in the hybrid offspring. Two of the hybrid progeny possessed haplotypes that were combinations of those present in the pollen and seed parents. One of the offspring possessed only the paternal haplotype. The remaining 210 plants had the haplotypes characteristic of the maternal plant. Chloroplast DNA variation in iris populations has previously been used to infer not only introgressive hybridization between I. fulva and I. hexagona, but also the greater role of direct pollen transfer relative to seed dispersal as the avenue for interspecific gene flow. We reexamined the previous conclusions concerning the mode of introgressive hybridization between I. fulva and I. hexagona in light of the results from the chloroplast DNA inheritance analysis. The low level of paternal and biparental inheritance detected in this analysis suggests that previous analyses using the chloroplast DNA as a seed-specific marker were robust. Furthermore, data concerning barriers to hybridization between I. fulva and I. hexagona suggest that the probability of chloroplast DNA introgression via pollen is low.     

Morphological variation and preadult viability at one-generation inbreeding in Drosophila melanogaster: A family selection hypothesis

Wing length, thorax length, sterno-pleural and sternal chaetae numbers were determined in offspring of sib crosses in a Drosophila melanogaster population, in relation to egg-to-adult viability. It appears that high between- and within-family variabilities for wing and thorax length together with lack of developmental homeostasis are associated with a high rate of embryonic and larvo-pupal mortality. Effects on chaetae numbers are more controversial. Results suggest that families which are homozygous for particular gene combinations may be eliminated by natural selection. Maintenance of high levels of heterozygosity might result in populations where circumstances foster substantial inbreeding.     

Maternal effects across life stages: larvae experiencing predation risk increase offspring provisioning

1. Maternal provisioning can reduce offspring vulnerability to predators by promoting offspring growth and eliciting of antipredator behaviours. Mothers perceiving predation risk may improve offspring survival if producing larger, higher‐quality offspring. However, empirical evidence suggests that offspring quality is often reduced, probably reflecting predator‐induced physiological costs, or a selfish maternal strategy aimed at producing more offspring by sacrificing their quality. While perception and impact of predators can vary across the prey's life stage, a majority of studies have focused on understanding how reproductive allocation decisions are influenced by the risk of predation during adulthood. 2. In this study, Leptinotarsa decemlineata beetles were used to examine if the risk of predation during the larval stage: (i) impacts the mother's physiological condition, including body mass and metabolic rate; and (ii) alters maternal allocation of reproductive resources to offspring quantity versus quality. 3. Results revealed that L. decemlineata mothers responded to perceived predation risk by producing clutches with fewer but larger eggs, thus increasing offspring provisioning. Surprisingly, while females that had faced predation risk as larva emerged with a similar body mass to control females, they exhibited lower metabolic rates. 4. Although predation risk in L. decemlineata larvae is known to impair their ability to acquire and maintain energy resources, adult females appeared to ameliorate such costs by improving their metabolic efficiency and by allocating more of their limited reproductive resources to produce fewer but better‐quality offspring.     

No reversion to single mating in a socially parasitic ant

Social Hymenoptera are ideal biological models for the study of the selective forces affecting the evolution of multiple mating (polyandry), because sister species can evolve different lifestyles and mating strategies. Single mating is predicted in workerless social parasites, because the key benefit of multiple mating in social insects, that is, the increase in genetic diversity among worker offspring, does not hold for workerless species. We compared the queen mating frequency between the ant Plagiolepis pygmaea and its derived social parasite P. xene. Previous studies showed that queens of the host P. pygmaea are obligately polyandrous. Here, pedigree analyses of mother–offspring combinations indicate that queens of the parasite P. xene did not revert to single mating; more than 50% of queens mated multiply, with 2–4 males. This result shows that reversal from multiple to single mating may be not selected in polyandrous social insect workerless parasites. We propose that such reversion does not occur when multiple mating is virtually cost free.     

BOTH MALE AND FEMALE SEXUAL ORNAMENTS REFLECT OFFSPRING PERFORMANCE IN A FISH

Secondary sexual characters are often expressed in both sexes (mutual ornamentation), but are less often studied simultaneously. We studied the adaptive signaling function of male and female ornamentation in a mutually ornamented fish, the whitefish Coregonus lavaretus. In an experimental design in which nongenetic environmental effects were minimized, we found that highly ornamented females, males, and their parental combinations had offspring with better swimming performance and predator‐avoidance ability than less ornamented individuals or combinations. Furthermore, highly ornamented females had larger offspring that also had higher yolk volume than less ornamented individuals. Offspring swimming performance was not dependent on offspring size and was only weakly affected by yolk volume, which suggest that swimming performance and measured morphological traits are independent fitness measures. In conclusion, mutual ornamentation of whitefish may signal the quality of individuals in both sexes, which may indicate ongoing directional selection for these ornamental traits. However, offspring fitness traits were also dependent on parental combination, which suggests that genetic compatibility effects may weaken the directional selection and the indicator value of the ornamentation.     

Reproductive investiment in the scorpion Centruroides vittatus

Among invertebrates, scorpions possess a relatively unique set of reproductive traits. The interrelationships of these traits may have important implications for life history theory, yet there have been few studies of these traits in scorpions. Our data indicate that larger female Centruroides vittatus produce more offspring and have a higher total litter mass than smaller females. There was, however, no significant relationship between offspring size and female or litter size. Mean offspring mass increased with increases in total litter mass and within litter variation in offspring size (coefficients of variation) decreased with increasing total litter mass. These results suggest that large female scorpions with a larger investment in reproduction produced more offspring that were more uniform in size, but not significantly larger, than small females with less investment. The fractional clutch principle and physiological and functional constraints on size and number of offspring are suggested as possible explanations for the relationships we found among offspring size, variation in offspring size and total investment in offspring in C. vittatus.     

Heritable variation and mechanisms of inheritance of spore shape within a population of Scutellospora pellucida,an arbuscular mycorrhizal fungus

Substantial variation was found among single-spore cultures established from a single population of the arbuscular mycorrhizal fungus Scutellospora pellucida. A common environment experiment demonstrated that five single-spore cultures differed in their average spore shape (as measured by length:width ratios) and size (volume) with interisolate heritabilities of offspring mean values of 0.96 and 0.87, respectively (0.66 and 0.43 for the shape and size of individual spores). The distribution of offspring spore shapes also differed in levels of variance, skewness, and kurtosis. In fact, these aspects of the distributions shifted with mean spore shape as predicted by the binomial distribution—the distribution expected due to the segregation of genetically diverse nuclei through dividing hyphae. Thus, the original parental spores generating these cultures appear to have contained genetically variable nuclei, which then segregate into the offspring spores to generate consistent differences in the mean, variance, skewness, and kurtosis of the distribution of offspring spore shapes. This nuclear segregation may be followed by the assemblage of novel combinations of nuclei through hyphal fusion. Together these processes are rarely considered mechanisms for the creation of novel genetic combinations and may contribute to the maintenance of the high level of heritable variation observed in this study.     

Linkage analysis by genotyping of sibling populations: a genetic map for the potato cyst nematode constructed using a “pseudo-F2” mapping strategy

A mapping strategy is described for the construction of a linkage map of a non-inbred species in which individual offspring genotypes are not amenable to marker analysis. After one extra generation of random mating, the segregating progeny was propagated, and bulked populations of offspring were analyzed. Although the resulting population structure is different from that of commonly used mapping populations, we show that the maximum likelihood formula for a normal F2 is applicable for the estimation of recombination. This “pseudo-F2” mapping strategy, in combination with the development of an AFLP assay for single cysts, facilitated the construction of a linkage map for the potato cyst nematode Globodera rostochiensis. Using 12 pre-selected AFLP primer combinations, a total of 66 segregating markers were identified, 62 of which were mapped to nine linkage groups. These 62 AFLP markers are randomly distributed and cover about 65% of the genome. An estimate of the physical size of the Globodera genome was obtained from comparisons of the number of AFLP fragments obtained with the values for Caenorhabditis elegans. The methodology presented here resulted in the first genomic map for a cyst nematode. The low value of the kilobase/centimorgan (kb/cM) ratio for the Globodera genome will facilitate map-based cloning of genes that mediate the interaction between the nematode and its host plant. Received: 7 January 1999 / Accepted: 16 April 1999