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1.
The immunocompetence handicap hypothesis predicts that male sexual trait expression should be positively correlated with immunocompetence. Here we investigate if immune function in the cricket, Teleogryllus commodus, is related to specific individual components of male sexual signals, as well as to certain multivariate combinations of these components that females most strongly prefer. Male T. commodus produce both advertisement and courtship calls prior to mating. We measured fine-scale structural parameters of both call types and also recorded nightly advertisement calling effort. We then measured two standard indices of immune function: lysozyme-like activity of the haemolymph and haemocyte counts. We found a weak, positive relationship between advertisement calling effort and lysozyme-like activity. There was, however, little evidence that individual structural call components or the net multivariate attractiveness of either call type signalled immune function. The relationships between immunity and sexual signaling did not differ between inbred and outbred males. Our data suggest that it is unlikely that females assess overall male immune function using male calls.  相似文献   

2.
The immunocompetence handicap hypothesis suggests that the immune system competes for resources with sexually selected ornaments; variation in ornaments might reflect genetic variation for immunocompetence. We tested this genetic prediction by mating scorpionfly females to males differing in the expression of a condition-dependent ornament trait, saliva secretion, and then comparing offspring immunocompetence. We found several indications of an immunocompetence handicap in our study: females had superior immunocompetence compared with males, the different immune traits were positively correlated, and there were indications of genetic variation in immune traits. However, we found no significant difference in the immunocompetence of offspring derived from males differing in ornament expression, only a tendency for sons of ornamented males to possess slightly better immunocompetence. The estimated effect of fathers on offspring immunocompetence was rather small, but it might be a sufficient benefit of female choice, provided that the costs of choice are small. We conclude that the genetic benefit of female choice is small concerning offspring immunocompetence, but the immunocompetence handicap principle might nevertheless work in scorpionflies.  相似文献   

3.
Parasitoid quality, subject to both genetic and environmental influences, is critical to the success of any biological control program, however, its measurement and improvement is poorly understood. In this study, a classic genetic approach is taken to develop two indices, namely a character index and a fitness index, for the measurement and selection of high quality parasitoids used in inundative release. Six life-history traits and corresponding fitness components in 33 inbred strains of Trichogramma minutum were used to generate both genotypic and phenotypic variance-covariance matrices that then allowed for the construction of the indices. Most traits and their fitness components were positively correlated, both phenotypically and genotypically, with lifetime fecundity and the number of female offspring appearing to have an important influence. Selection of the top three strains showed that parasitoid quality could be improved by 36% using the character index and possibly up to 150% using the fitness index. The two indices were linearly correlated suggesting that either could be used to measure quality. The character index is recommended because it requires information on only three life-history traits (fecundity, number of female offspring, and number of male offspring) and has highly correlated responses of fitness components. Our work demonstrates that the best quality T. minutum will be obtained by using the character index to select for inbred strains which have high fecundity and number of female offspring.  相似文献   

4.
A central paradigm of life-history theory is the existence of resource mediated trade-offs among different traits that contribute to fitness, yet observations inconsistent with this tenet are not uncommon. We previously found a clonal population of the aphid Myzus persicae to exhibit positive genetic correlations among major components of fitness, resulting in strong heritable fitness differences on a common host. This raises the question of how this genetic variation is maintained. One hypothesis states that variation for resource acquisition on different hosts may override variation for allocation, predicting strong fitness differences within hosts as a rule, but changes in fitness hierarchies across hosts due to trade-offs. Therefore, we carried out a life-table experiment with 17 clones of M. persicae, reared on three unrelated host plants: radish, common lambsquarters and black nightshade. We estimated the broad-sense heritabilities of six life-history traits on each host, the genetic correlations among traits within hosts, and the genetic correlations among traits on different hosts (cross-environment genetic correlations). The three plants represented radically different environments with strong effects on performance of M. persicae, yet we detected little evidence for trade-offs. Fitness components were positively correlated within hosts but also between the two more benign hosts (radish and lambsquarters), as well as between those and another host tested earlier. The comparison with the most stressful host, nightshade, was hampered by low survival. Survival on nightshade also exhibited genetic variation but was unrelated to fitness on other hosts. Acknowledging that the number of environments was necessarily limited in a quantitative genetic experiment, we suggest that the rather consistent fitness hierarchies across very different plants provided little evidence to support the idea that the clonal variation for life-history traits and their covariance structure are maintained by strong genotypexenvironment interactions with respect to hosts. Alternative explanations are discussed.  相似文献   

5.
A major challenge in biology is understanding how organisms partition limited resources among physiological processes. For example, offspring production and self-maintenance are important for fitness and survival, yet these critical processes often compete for resources. While physiological trade-offs between reproduction and immune function have been documented, their regulation remains unclear. Most current evidence suggests that physiological changes during specific reproductive states directly suppress various components of the immune system; however, some studies have not found this clear relationship. We performed two experiments in female tree lizards (Urosaurus ornatus) that demonstrate the presence of trade-offs between the reproductive and immune systems under controlled laboratory conditions. These results also support the hypothesis that these trade-offs are a facultative response to resource availability and are not obligatory responses to physiological changes during reproduction. We found that (1) experimentally increasing reproductive investment under limited resources resulted in suppressed immune function and (2) experimentally limiting resources resulted in immunosuppression but only during resource costly reproductive activities. There seems to be a critical balance of resources that is maintained between multiple processes, and changes in the balance between energy intake and output can have major consequences for immune function.  相似文献   

6.
Wild immunology     
In wild populations, individuals are regularly exposed to a wide range of pathogens. In this context, organisms must elicit and regulate effective immune responses to protect their health while avoiding immunopathology. However, most of our knowledge about the function and dynamics of immune responses comes from laboratory studies performed on inbred mice in highly controlled environments with limited exposure to infection. Natural populations, on the other hand, exhibit wide genetic and environmental diversity. We argue that now is the time for immunology to be taken into the wild. The goal of 'wild immunology' is to link immune phenotype with host fitness in natural environments. To achieve this requires relevant measures of immune responsiveness that are both applicable to the host-parasite interaction under study and robustly associated with measures of host and parasite fitness. Bringing immunology to nonmodel organisms and linking that knowledge host fitness, and ultimately population dynamics, will face difficult challenges, both technical (lack of reagents and annotated genomes) and statistical (variation among individuals and populations). However, the affordability of new genomic technologies will help immunologists, ecologists and evolutionary biologists work together to translate and test our current knowledge of immune mechanisms in natural systems. From this approach, ecologists will gain new insight into mechanisms relevant to host health and fitness, while immunologists will be given a measure of the real-world health impacts of the immune factors they study. Thus, wild immunology can be the missing link between laboratory-based immunology and human, wildlife and domesticated animal health.  相似文献   

7.
The sexes often differ in the reproductive trait limiting their fitness, an observation known as Bateman's principle. In many species, females are limited by their ability to produce eggs while males are limited by their ability to compete for and successfully fertilize those eggs. As well as promoting the evolution of sex-specific reproductive strategies, this difference may promote sex differences in other life-history traits due to their correlated effects. Sex differences in disease susceptibility and immune function are common. Two hypotheses based on Bateman's principle have been proposed to explain this pattern: that selection to prolong the period of egg production favors improved immune function in females, or that the expression of secondary sexual characteristics reduces immune function in males. Both hypotheses predict a relatively fixed pattern of reduced male immune function, at least in sexually mature individuals. An alternative hypothesis is that Bateman's principle does not dictate fixed patterns of reproductive investment, but favors phenotypically plastic reproductive strategies with males and females adaptively responding to variation in fitness-limiting resource availability. Under this hypothesis, neither sex is expected to possess intrinsically superior immune function, and immunological sex differences may vary in different environments. We demonstrate that sex-specific responses to experimental manipulation of fitness-limiting resources affects both the magnitude and direction of sex differences in immune function in Drosophila melanogaster. In the absence of sexual interactions and given abundant food, the immune function of adults was maximized in both sexes and there was no sex difference. Manipulation of food availability and sexual activity resulted in female-biased immune suppression when food was limited, and male-biased immune suppression when sexual activity was high and food was abundant. The immunological cost to males of increased sexual activity was found to be due in part to reduced time spent feeding. We suggest that for species similarly limited in their reproduction, phenotypic plasticity will be an important determinant of sex differences in immune function and other life-history traits.  相似文献   

8.
Although crucial for host survival when facing persistent parasite pressure, costly immune functions will inevitably compete for resources with other energetically expensive traits such as reproduction. Optimizing, but not necessarily maximizing, immune function might therefore provide net benefit to overall host fitness. Evidence for associations between fitness and immune function is relatively rare, limiting our potential to understand ultimate fitness costs of immune investment. Here, we assess how measures of constitutive immune function (haptoglobin, natural antibodies, complement activity) relate to subsequent fitness outcomes (survival, reproductive success, dominance acquisition) in a wild passerine (Malurus coronatus). Surprisingly, survival probability was not positively linearly predicted by any immune index. Instead, both low and high values of complement activity (quadratic effect) were associated with higher survival, suggesting that different immune investment strategies might reflect a dynamic disease environment. Positive linear relationships between immune indices and reproductive success suggest that individual heterogeneity overrides potential resource reallocation trade-offs within individuals. Controlling for body condition (size-adjusted body mass) and chronic stress (heterophil-lymphocyte ratio) did not alter our findings in a sample subset with available data. Overall, our results suggest that constitutive immune components have limited net costs for fitness and that variation in immune maintenance relates to individual differences more closely.  相似文献   

9.
Optimisation of reproductive investment is crucial for Darwinian fitness, and detailed long-term studies are especially suited to unravel reproductive allocation strategies. Allocation strategies depend on the timing of resource acquisition, the timing of resource allocation, and trade-offs between different life-history traits. A distinction can be made between capital breeders that fuel reproduction with stored resources and income breeders that use recently acquired resources. In capital breeders, but not in income breeders, energy allocation may be decoupled from energy acquisition. Here, we tested the influence of extrinsic (weather conditions) and intrinsic (female characteristics) factors during energy storage, vitellogenesis and early gestation on reproductive investment, including litter mass, litter size, offspring mass and the litter size and offspring mass trade-off. We used data from a long-term study of the viviparous lizard, Lacerta (Zootoca) vivipara. In terms of extrinsic factors, rainfall during vitellogenesis was positively correlated with litter size and mass, but temperature did not affect reproductive investment. With respect to intrinsic factors, litter size and mass were positively correlated with current body size and postpartum body condition of the previous year, but negatively with parturition date of the previous year. Offspring mass was negatively correlated with litter size, and the strength of this trade-off decreased with the degree of individual variation in resource acquisition, which confirms theoretical predictions. The combined effects of past intrinsic factors and current weather conditions suggest that common lizards combine both recently acquired and stored resources to fuel reproduction. The effect of past energy store points out a trade-off between current and future reproduction.  相似文献   

10.
生态免疫学研究进展   总被引:2,自引:0,他引:2  
徐德立  王德华 《生态学报》2012,32(19):6251-6258
随着整合生物学思想的发展,生态学与免疫学的相互渗透与交叉,产生了生态免疫学这一崭新的学科,自从其诞生虽然只有短短的十几年时间,但发展迅速。生态免疫学主要从免疫代价的视角来解释生活史权衡、性选择和种群动态变化等生态学问题。动物的免疫功能对其抵抗疾病和最终的生存起至关重要的作用,影响动物免疫的因素具有多样性和复杂性的特点,而研究动物免疫功能变化的原因和结果一直是生态免疫学研究的重要内容。免疫防御是否具有能量或资源代价,这种代价是否昂贵是生态免疫学需要回答的基本问题之一,大量的实验已表明免疫防御的代价是昂贵的。由于能量或资源不是无限的,有限的能量或资源必须在多种经常相互竞争的生理功能间进行分配,这导致了免疫功能与动物的生长、繁殖等生活史组分之间的权衡,很多的研究表明增加一个过程的投资会降低对另一过程的投资。免疫同样在性选择特征进化以及维持雌性偏爱性修饰的雄性中发挥至关重要的作用,免疫功能障碍假说认为睾丸激素负责第二性征的产生并同时具有免疫抑制作用,表达性征的代价是降低了免疫功能,这使得宿主对病原体或寄生物攻击的易感性增加,因此只有高质量的雄性个体才能充分表达性征同时又不遭受大量寄生负荷。综述了生态免疫学的概念、研究内容以及未来研究需要关注的领域。  相似文献   

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