Lifetime Reproductive Success in the Solitary Endoparasitoid, Venturia canescens

Parasitoid wasps have long been considered excellent organisms in studies examining the evolution of reproductive and life-history strategies. In examining the lifetime reproductive success of parasitoids in the laboratory, most investigations have provided the insects with excess hosts and food, where they exist in a relatively constraint-free environment. Importantly, these conditions may not accurately reflect the true heterogeneity of natural systems, where suitable hosts and food sources are likely to be limiting. This study examines the influence of differences in host and food availability on reproductive and life-history parameters in an asexual strain of the solitary endoparasitoid, Venturia canescens (Hymenoptera: Ichneumonidae). Lifetime reproductive success in V. canescens was measured in response to temporal variations in host and food (honey solution) access. Cohorts of parasitoids were provided with 200 fifth-instar larvae of the Indian meal moth, Plodia interpunctella (Lepidoptera: Pyralidae), and food for variable periods daily after eclosion. V. canescens is synovigenic, and host-deprived wasps continued to mature eggs over the first few days after eclosion until the egg storage capacity was reached in the oviducts. When these wasps were subsequently provided with hosts, oogenesis resumed and continued until later in adult life. Constantly fed wasps lived longer and produced more progeny than wasps from cohorts which were alternately fed and starved or were starved from eclosion. Moreover, wasps with constant host and food access produced most progeny early in life and usually experienced prolonged periods of postreproductive survival. In contrast, the reproductive period of wasps with limited host access was more evenly distributed throughout the adult life. Consequently, the cumulative progeny production by V. canescens with constant food access was fairly uniform irrespective of host availability. Longevity and fecundity in V. canescens were positively correlated with adult size. However, variable host access had little effect on the longevity of wasps which were constantly supplied with honey. Over the first 2 days of adult life, variation in food access also had no effect on progeny production by V. canescens. We argue that manipulating temporal host and food access to parasitoids in the laboratory more closely approximates natural conditions, where these resources are likely to be spatially separated. Moreover, our findings suggest that many highly synovigenic parasitoids like V. canescens, which produce microtype (=hydropic) eggs, have a considerably higher reproductive potential than ovary dissections have revealed. Our findings are discussed in relation to life-history evolution in the parasitic Hymenoptera.     

Accurate Alternative Measurements for Female Lifetime Reproductive Success in Drosophila melanogaster

Fitness is an individual’s ability to survive and reproduce, and is an important concept in evolutionary biology. However, accurately measuring fitness is often difficult, and appropriate fitness surrogates need to be identified. Lifetime reproductive success, the total progeny an organism can produce in their lifetime, is thought to be a suitable proxy for fitness, but the measure of an organism’s reproductive output across a lifetime can be difficult or impossible to obtain. Here we demonstrate that the short-term measure of reproductive success across five days provides a reasonable prediction of an individual''s total lifetime reproductive success in Drosophila melanogaster. However, the lifetime reproductive success of a female that has only mated once is not correlated to the lifetime reproductive success of a female that is allowed to mate multiple times, demonstrating that these measures should not serve as surrogates nor be used to make inferences about one another.     

Lifetime Number of Mates Interacts with Female Age to Determine Reproductive Success in Female Guppies

In many species, mating with multiple males confers benefits to females, but these benefits may be offset by the direct and indirect costs associated with elevated mating frequency. Although mating frequency (number of mating events) is often positively associated with the degree of multiple mating (actual number of males mated), most studies have experimentally separated these effects when exploring their implications for female fitness. In this paper I describe an alternative approach using the guppy Poecilia reticulata, a livebearing freshwater fish in which females benefit directly and indirectly from mating with multiple males via consensual matings but incur direct and indirect costs of mating as a consequence of male sexual harassment. In the present study, females were experimentally assigned different numbers of mates throughout their lives in order to explore how elevated mating frequency and multiple mating combine to influence lifetime reproductive success (LRS) and survival (i.e. direct components of female fitness). Under this mating design, survival and LRS were not significantly affected by mating treatment, but there was a significant interaction between brood size and reproductive cycle (a correlate of female age) because females assigned to the high mating treatment produced significantly fewer offspring later in life compared to their low-mating counterparts. This negative effect of mating treatment later in life may be important in these relatively long-lived fishes, and this effect may be further exacerbated by the known cross-generational fitness costs of sexual harassment in guppies.     

小型哺乳动物的繁殖投入与繁殖成功率

动物的繁殖活动关系到整个种群的生存与灭绝, 繁殖投入和繁殖成功率是繁殖生态学研究的重要内容。从繁殖投入的划分入手, 综述了小型哺乳动物的繁殖投入和繁殖成功率之间的关系及其影响因素、分子生物学技术在繁殖生态学中的应用等, 阐述了小型哺乳动物能够根据自身的状态调整每次繁殖活动中的时间投入和能量分配, 采取不同的繁殖对策。这些繁殖对策是长期自然选择的结果, 其目的都是为了最大限度地提高自身的适合度。并且指出分子生物学技术在繁殖生态学中的应用将大大加快这一研究领域的快速发展。     

Endocrine Toxicants and Reproductive Success in Fish

There is compelling evidence on a global scale for compromised growth and reproduction, altered development, and abnormal behaviour in feral fish that can be correlated or in some cases causally linked with exposure to endocrine disrupting chemicals (EDCs). Attributing cause and effect relationships for EDCs is a specific challenge for studies with feral fish as many factors including food availability, disease, competition and loss of habitat also affect reproduction and development. Even in cases where there are physiological responses of fish exposed to EDCs (e.g., changes in reproductive hormone titres, vitellogenin levels), the utility of these measures in extrapolating to whole animal reproductive or developmental outcomes is often limited. Although fish differ from other vertebrates in certain aspects of their endocrinology, there is little evidence that fish are more sensitive to the effects of EDCs. Therefore, to address why endocrine disruption seems so widespread in fish, it is necessary to consider aspects of fish physiology and their environment that may increase their exposure to EDCs. Dependence on aquatic respiration, strategies for iono-osmotic regulation, and maternal transfer of contaminants to eggs creates additional avenues by which fish are exposed to EDCs. This paper provides an overview of responses observed in feral fish populations that have been attributed to EDCs and illustrates many of the factors that need consideration in evaluating the risks posed by these chemicals.     

Male-male Competition and Reproductive Success in Elephant Seals

Male-male competition and reproductive success of northern elephantseals, Mirounga augustirostris, was studied for six consecutivebreeding seasons at Año Nuevo Island, California. Theconclusions were as follows: (i) Less than one third of themales in residence copulate during a breeding season. A fewmales are responsible for the majority of copulations, (ii)The number and age of males copulating varies with: (a) haremlocation and topography, (b) the number of estrous females inthe harem, and (c) the number of males competing for females,(iii) Copulation frequency is related directly to success inmale-male competition, i.e., social rank. (iv) The same individualsmay dominate breeding for three consecutive breeding seasons.(v) Successful males die within a year or two after their reproductivepeak. (vi) The reproductive success of most males is nil orlow because many die before reaching breeding age and some ofthose that reach maturity are prevented from mating by the highestranking males. (vii) Individual strategies have important consequencesfor reproductive success, (viii) Male-male competition is amajor cause of pup mortality prior to weaning. The potential reproductive success of males is much greaterthan that of females. Changes in colony number and compositionaffect the reproductive success of males as well as females.     

The Reproductive Biology and Reproductive Success of Pterocarpus macrocarpus Kurz1

The reproductive biology of Pterocarpus macrocarpus Kurz (pradu) was studied in 37‐year‐old plantation trees in Thailand to determine the causes of seed and fruit loss. Trees flowered at the end of March or early in April at the end of the hot dry season and start of the rainy season. Flowering occurred over about a one‐month period. Fruits developed over the next six months during the rainy season and matured at the start of the cool dry season in October and November. Phenology was similar in the four trees that were studied in detail. Racemes averaged 30 flowers each and each raceme was receptive for several days, although each flower was only receptive for one day. After pollination, floral parts were shed over several days and fruits began to develop. Pradu is entomopholous but its insect pollinators were not identified. The stigma is covered by hairs and a secretion is produced. A high proportion of flowers were pollinated. Then, there was a rapid loss of flowers and young fruits. These observations and earlier genetic studies indicate the probability of a high level of self‐incompatibility in this predominantly outbreeding species. Pradu may have a very late‐acting self‐incompatibility mechanism found in many other hardwoods. The zygote remains quiescent for six weeks as the endosperm develops. During this time most of the ovules and fruits abort, suggesting resource allocation preferentially to cross‐pollinated ovules. Pradu has a high reproductive potential but a low preemergence reproductive success (0.8), which is common for many hardwood species. The major cause of the low reproductive success was fruit loss during early development. Fruit production may be enhanced by increased cross‐pollination among unrelated parent trees. This may be accomplished in seed orchards and seed production areas by the introduction of additional insect pollinators that travel greater distances between trees and by the relatively close spacing of unrelated parent trees.     

Between-Group Competition Impacts Reproductive Success in Wild Chimpanzees

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On Cultural and Reproductive Success: Kipsigis Evidence

Studies testing the evolutionary biological prediction that striving for cultural goals is a proximate means of attaining high reproductive success are reviewed, and some of their problems are examined. Recent data from the Kipsigis of Kenya provide robust demonstration that wealth enhances a man's reproductive success. The evolutionary significance of correlations between cultural and reproductive success, and the additional problem of interpreting studies conducted in the rapidly changing environments of modern man, are discussed.     

杂色山雀的繁殖成功率

2004～2006年的3～7月,在辽宁省白石砬子国家级自然保护区,对杂色山雀(Parus varius)的繁殖及繁殖成功率进行了初步研究。结果显示,杂色山雀主要营巢于海拔400～900m的阔叶杂木林、针叶林及林缘地带;繁殖期在3～7月,其洞巢种类多样,筑巢期约15d;巢为碗状,巢结构的2/3由苔藓构成;窝卵数为6～8枚,平均(6·92±0·92)枚(n=13);雌鸟单独孵卵,孵化期为(14·00±0·00)d(n=10);育雏由雌雄鸟共同承担,育雏期为(17·50±0·58)d(n=4)。杂色山雀繁殖成功率为50·95%,繁殖力为2·22。人为干扰是造成卵和雏鸟损失的主要原因,占总损失的74·19%。     

Reproductive Success and Body Size in the Cricket Gryllus firmus

Male body size influences mate choice and sexual selection in many animal species. Here we investigate the role of male body size in the reproductive success of the field cricket Gryllus firmus. This species hybridizes with a close smaller relative, G. pennsylvanicus, and it is thought that this size difference may affect reproductive isolation between these species. We paired large and small G. firmus males with a single G. firmus female and genotyped the resulting offspring. Overall, larger males sired a greater proportion of offspring and in a majority of the crosses the larger male sired all of the offspring. For crosses in which both males sired offspring, there was no difference in the proportion of offspring sired by small and large males. Intrasexual competition, female choice, and differences in ejaculates between males could all influence the patterns we observe. We discuss the implications of our findings within the context of reproductive isolation between G. firmus and G. pennsylvanicus.     

Heritability of Reproductive Traits in the Medicinal Leech Hirudo medicinalis L.

The phenotype variability and inheritance of reproductive traits were investigated in the medicinal leech. Distribution parameters were determined for the following traits: batch size (X¯ = 4.3 ± 0.2, = 1.7, CV = 40%, As = 0.23 ± 0.25, Ex = 0.19 ± 0.51), number of juveniles in a cocoon ( X¯= 10.9 ± 0.3, = 4.6, CV = 42%, As = 0.31 ± 0.15, Ex = 0.23 ± 0.30), and juvenile weight ( X¯= 32.0 ± 0.3, = 14.9, CV = 47%, As = 1.38 ± 0.05, Ex = 3.32 ± 0.11). A nonlinear negative correlation between the number of juveniles in a cocoon and their weight was found (correlation ratio R= 0.86). It was shown that the environmental variance dominated over the genotypic one in the structure of phenotypic variance of the traits studied. The genetic variability is determined mainly by additive gene interactions and, to a small extent, intralocus dominance. The narrow-sense heritability, h ², for batch size was 0.35–0.40; for the number of juveniles in a cocoon, 0.35; for juvenile weight, 0.42.     

Lek Social Organization and Reproductive Success in the Greater Prairie Chicken

Between 1964 and 1969, studies were made of Prairie Chickenreproductive behavior on a lek with a stable social organization.The social organization of this lek was altered by the removalof dominant males; three in 1970 and two in 1971. Social organizationand reproductive behavior were observed on this lek prior toand following removal of the dominant males. Removal of dominantmales disrupted the stable social organization on the lek. Totalnumber of aggressive interactions between males increased followingremoval of dominant males.No change was noted in the total numberof females visiting the lek in 1970 compared with the previous6-year period. Likewise, no change was noted in the number ofattempted copulations observed in 1970 compared with previousyears. However, the number of successful copulations was drasticallyreduced (90% fewer) during 1970 because of increased male-maleaggressive interactions on the lek. During 1971, fewer territorialmales were on the lek compared to previous years, and fewerfemales visited the lek and fewer successful copulations wererecorded than in previous years.Late nests of Prairie Chickensare less successful and contain fewer eggs compared with nestsbegun earlier. In some instances, the female social hierarchymay serve to delay onset of nesting, therefore reducing totalreproduction for the year.     

Predicting Current Reproductive Success of Goose Pairs Anser indicus from Male and Female Reproductive History

A multiple regression analysis of current reproductive success (goslings fledged) on three male and female life-history traits (age, previous breeding periods, previous successes) was carried out for 31 semicaptive pairs of barheaded geese Anser indicus. Of the female variables, age proved positively and the number of previous nesting periods negatively related to current success. The latter relationship suggests that incubation has costs in terms of future fecundity for the female. Of the male variables, age was negatively and the number of previous fledging successes positively related to current reproductive success. Attempts with additional data to explain these findings in the male either by a positive feedback of success on future success or by differences in male quality gave inconclusive results, as did earlier attempts to demonstrate reproductive costs in geese and swans. In monogamous species with long-term pair bonds, where male and female share most of their life history but specialize in different activities, reproduction may affect the sexes in different ways. If the correlations between life-history traits of mates are not accounted for, individual strategies or constraints may be obscured by opposing effects in the mate.     

Analyses of Sexual Reproductive Success in Transgenic and/or Mutant Plants

The pistil, the female reproductive organ of plants, is a key player in the success of sexual plant reproduction. Ultimately, the production of fruits and seeds depends on the proper pistil development and function. Therefore, the identification and characterization of pistil expressed genes is essential for a better understanding and manipulation of the plant reproduction process. For studying the function of pistil expressed genes, transgenic and/or mutant plants for the genes of interest are used. The present article provides a review of methods already exploited to analyze sexual reproductive success. We intend to supply useful information and to guide future experiments in the study of genes affecting pistil development and function.     

Analyses of Sexual Reproductive Success in Transgenic and/or Mutant Plants

The pistil, the female reproductive organ of plants, is a key player in the success of sexual plant reproduction. Ultimately, the production of fruits and seeds depends on the proper pistil development and function. Therefore, the identification and characterization of pistil expressed genes is essential for a better understanding and manipulation of the plant reproduction process. For studying the function of pistil expressed genes, transgenic and/or mutant plants for the genes of interest are used. The present article provides a review of methods already exploited to analyze sexual reproductive success. We intend to supply useful information and to guide future experiments in the study of genes affecting pistil development and function.     

Stages of Age-Related Reproductive Success in Birds: Simultaneous Effects of Age, Pair-Bond Duration and Reproductive Experience

SYNOPSIS. Most organisms reproduce episodically rather thancontinuously. Forms of discontinuity may include seasonal breedingin annual cycles, and delayed breeding and/or senescence overthe lifespan of individuals. In addition, age can have profoundeffects on the annual reproductive success (RS) of a wide varietyof animals. Explanations of the effects of age on RS can beconfounded, however, by the acquired breeding experience ofindividuals, and the duration of pair-bonds, both of which haveeffects on RS similar to those of age itself. However, moststudies of the effects of age on RS prior to senescence havenot accounted for the effects of pair-bond duration, and manyhave treated age and experience as synonyms. In this paper Isummarize the effects of all three factors, discuss the simultaneousand interrelated nature of their effects, and suggest ways toseparate the relative contributions of each.