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Variation in reproductive traits (sexual maturity, clutch size, clutch weight, mean egg mass, newborn weight) was studied during a four year period in a population of the live-bearing lizard Lacerta vivipara . Sexual maturity was associated with attaining a minimum body size. Clutch size increased with female body length and litter weight increased with clutch size. A major component of the within year variation in these reproductive traits was attributable to female size. Analysis of successive clutches in individual females indicated that a significant fraction of the variation in litter size, adjusted for female length, was due to consistent differences between individuals. Newborn weight varied within and among litters, but no relations between hatchling mass or mean egg mass in a litter and other traits were detected.
Size-adjusted reproductive performances remained constant during the course of this study, even though environmental conditions (weather factors, food availability) varied annually. Observed among year variations in reproductive characteristics were attributable to differences in the body size distributions of the adult females. 相似文献
Size-adjusted reproductive performances remained constant during the course of this study, even though environmental conditions (weather factors, food availability) varied annually. Observed among year variations in reproductive characteristics were attributable to differences in the body size distributions of the adult females. 相似文献
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Recent studies indicate that directional female mate choice and order-dependent female mate choice importantly contribute
to non-random mating patterns. In species where females prefer larger sized males, disentangling different hypotheses leading
to non-random mating patterns is especially difficult, given that male size usually correlates with behaviours that may lead
to non-random mating (e.g. size-dependent emergence from hibernation, male fighting ability). Here we investigate female mate
choice and order-dependent female mate choice in the polygynandrous common lizard (Lacerta vivipara). By sequentially presenting males in random order to females, we exclude non-random mating patterns potentially arising
due to intra-sexual selection (e.g. male–male competition), trait-dependent encounter probabilities, trait-dependent conspicuousness,
or trait-dependent emergence from hibernation. To test for order-dependent female mate choice we investigate whether the previous
mating history affects female choice. We show that body size and body condition of the male with which a female mated for
the first time were bigger and better, respectively, than the average body size and body condition of the rejected males.
There was a negative correlation between body sizes of first and second copulating males. This indicates that female mate
choice is dependent on the previous mating history and it shows that the female’s choice criteria are non-static, i.e. non-directional.
Our study therefore suggests that context-dependent female mate choice may not only arise due to genotype-environment interactions,
but also due to other female mating strategies, i.e. order-dependent mate choice. Thus context-dependent female mate choice
might be more frequent than previously thought. 相似文献
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Increased transmission of parasites and diseases is generally considered as a major cost of social life. In this study we
tested the hypothesis regarding ectoparasites as a cost of living in crowded habitats in the common lizard (Lacerta vivipara). We used two approaches to explore this question. First, we tested if ectoparasite load and prevalence are positively correlated
with host density in the field. Second, we experimentally tested if lizards avoid parasitized conspecifics. Contrary to expectation,
we found that (1) ectoparasite load is negatively correlated with lizard density; (2) prevalence does not significantly increase
with density; (3) unparasitized lizards do not avoid parasitized conspecifics but are attracted by them whatever their parasite
load. These findings suggest that ectoparasites cannot be considered as a cost of living at high density in the common lizard,
in spite of the potential negative impact mites may have on lizard fitness.
Received: 18 August 1996 / Accepted: 7 February 1997 相似文献
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Social environments are inherently dynamic, often changing depending on the frequency and outcomes of conspecific interactions – they can be simultaneously the targets and agents of selection. Understanding how organisms settle in heterogeneous social environments and the effects this has on reproductive success is vital to our understanding of the selective forces at work in wild populations. From an intensive behavioural and ecological study of territoriality in the polymorphic white‐throated sparrow (Zonotrichia albicollis), we demonstrate that males of the two morphs inhabit social niches that correspond to their respective alternative reproductive strategies. By integrating molecular ecology and Geographic Information Systems, we generated continuous, socio‐spatial models of local conspecific density and cuckoldry risk. Our results suggest that the morphs segregate their territories based on socio‐spatial variables, creating a heterogeneous social landscape that matches each behavioural phenotype with a favourable social environment. Specifically, the monogamous tan males tended to settle in low‐density areas that were also low for cuckoldry risk, while the opposite was true for the promiscuous white males. This pattern of socio‐spatial heterogeneity, combined with the social niche partitioning we observed, might act as a social niche polymorphism, and play an important role in maintenance of the alternative reproductive strategies of the white‐throated sparrow. Socio‐spatial factors, similar to those observed in the white‐throated sparrow, may play important roles in the evolution of mating systems in other species, even those with more continuous or cryptic variation. 相似文献
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Although negative frequency-dependent fitness is argued to allow the stable coexistence of two alternative reproductive types (such as resource defenders and reproductive parasites), no existing theory has considered a third strategy where resource defenders invest differentially in defence against reproductive parasites. Here, we present the results of a three-strategy game, where reproductive parasites interact with two resource defenders: 'Susceptibles' defend more resources but lose more reproductive success to parasites. 'Immunes' lose less to parasites, but immunity carries a reproductive cost. We show that the inclusion of a third strategy dramatically changes the evolutionary dynamics, such that for a wide range of parameter values, our model predicts the continuous sequential invasion of the three strategies instead of stable coexistence. Our results therefore limit the generality of the prediction that frequency-dependent fitness necessarily allows alternative reproductive tactics to coexist at equilibrium and may also explain the observed dynamics of some multiple-strategy systems. 相似文献
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A major goal in evolutionary biology is to determine how phenotypic variation arises and is maintained in natural populations. Recent studies examining the morphological, physiological and behavioural differences among discrete colour morphotypes (morphs) have revealed several mechanisms that maintain discrete variation within populations, including frequency‐dependence, density‐dependence and correlational selection. For example, trade‐offs over resource allocation to morphological, physiological and behavioural traits can drive correlational selection for morph‐specific phenotypic optima. Here, we describe a ventral colour polymorphism in the wall lizard (Podarcis muralis) and test the hypothesis that morphs differ along multivariate axes defined by trade‐offs in morphological, physiological, and immunological traits. We show that ventral colour is a discrete trait and that morphs differ in body size, prevalence of infection by parasites and infection intensity. We also find that morphs differ along multivariate phenotypic axes and experience different multivariate selection pressures. Our results suggest that multivariate selection pressures may favour alternative optimal morph‐specific phenotypes in P. muralis. 相似文献
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Environmental (i.e. non-genetic) maternal effects have the potential to associate the environmental conditions faced by mothers during gestation or before egg laying with the phenotype of their offspring. For this reason, maternal effects may play a major role in determining offspring phenotype independently of the genotype of the individuals, and can thus be considered a mechanistic basis of phenotypic plasticity. Despite the ecological and evolutionary implications of environmental maternal effects, few studies have experimentally investigated this phenomenon in reptiles. Here we report the results of an experimental laboratory study on the effects of maternal feeding rate and density on offspring locomotor performance in the common lizard (Lacerta vivipara). Lacerta vivipara is a viviparous lizard, and viviparity enhances the probability of a maternal influence on offspring phenotype. We focused on a particular phenotypic trait, maximal sprint running speed, because this trait is thought to be selectively important in squamates. Sprint speed was a repeatable trait, and it varied significantly among families. Maternal feeding rate significantly affected sprint speed, whereas density had no effect on this trait. The effect of maternal feeding rate differed according to the sex of the offspring and their body size, resulting in significant two-way and three-way interactions among these factors. In other words, the maternal feeding rate changed the shape of the allometric relationship between speed and size, but differently for males and females. The complexity of such effects makes it extremely difficult to offer an adaptive interpretation, but emphasizes the role played by the environment in shaping phenotypes among generations. 相似文献
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High levels of testosterone can benefit individual fitness, for example by increasing growth rate or ornament size, which may result in increased reproductive success. However, testosterone induces costs, such as a suppressed immune system, thereby generating trade-offs between growth or mate acquisition, and immunity. In birds and reptiles, females allocate steroids to their eggs, which may be a mechanism whereby females can influence the phenotype of their offspring. To our knowledge, only the benefits of early androgen exposure have been experimentally investigated to date. However, to understand this phenomenon, the costs also need to be evaluated. We manipulated testosterone levels in eggs of the viviparous common lizard and monitored growth, endurance and post-parturient responses to ectoparasites of the offspring. Testosterone-treated individuals had significantly higher growth rates than controls, but suffered a significant decrease in growth rate when exposed to ticks, whereas the corresponding difference for controls was non-significant. There was no difference in observed parasite load or leucocyte count between manipulated and control offspring. Thus, our results suggest that high testosterone levels during embryonic development have detrimental effects on immune function resulting in reduced growth rate, and that this must be taken into consideration when evaluating the potential adaptive value of maternal androgen allocation to eggs. 相似文献
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Socially acquired information is widespread in the animal kingdom.Many individuals make behavioral decisions based on such socialinformation. In particular, individuals may decide to leaveor select their habitat based on social information. Few studieshave investigated the role of density-related information, apotential social cue about habitat quality in dispersal. Here,we tested for the possibility that the phenotype of intrudercommon lizards (Lacerta vivipara) may inadvertently carry informationabout their natal population density. We found that such informationuse is likely. The behavior of focal lizard was influenced bythe natal population density of the intruder it was interactingwith. This suggests that individuals may use the behavior ofothers to acquire appropriate information about surroundingsand to base spatial decisions on this information. Density-relatedinformation may then affect individual movement decisions andthus metapopulation dynamics. 相似文献
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Environmental stress increases the prevalence and intensity of blood parasite infection in the common lizard Lacerta vivipara 总被引:1,自引:0,他引:1
Parasites affect the life-histories and fitness of their hosts. It has been demonstrated that the ability of the immune system to cope with parasites partly depends on environmental conditions. In particular, stressful conditions have an immunosuppressive effect and may affect disease resistance. The relationship between environmental stress and parasitism was investigated using a blood parasite of the common lizard Lacerta vivipara. In laboratory cages, density and additional stressors had a significant effect on the intensity of both natural parasitaemia and parasitaemia induced by experimental infection. Four weeks after infection, crowded lizards had three times more parasites than noncrowded lizards. After 1 month of stress treatment, naturally infected lizards had a significantly higher level of plasma corticosterone and a higher parasite load than nonstressed individuals. In seminatural enclosures, stress induced by the habitat quality affected both the natural blood parasite prevalence and the intensity of parasitaemia of the host. 相似文献
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Belliure J Meylan S Clobert J 《Journal of experimental zoology. Part A, Comparative experimental biology》2004,301(5):401-410
Many animals exhibit dramatic responses when subjected to a stressor. A classic marker of the stress response is an increase in plasma glucocorticoids, but this constitutes only one step in the cascade from experience of a stressor to wider organismal changes, including behavior. The behavioral sensitivity to glucocorticoids would determine the consequences of the stress-related alteration of behavior for the organism. In this study we explored, under laboratory conditions, the prenatal and postnatal effects of corticosterone on activity and thermoregulation of juveniles of the common lizard, Lacerta vivipara. Activity was measured as the time spent moving and the time spent scratching the wall in an empty terrarium. Thermoregulatory behavior was measured as the time spent motionless under a light bulb. Activity and thermoregulation of juveniles of the common lizard showed a different sensitivity to prenatal and postnatal corticosterone treatment, modulated by juvenile sex and maternal condition. Prenatal corticosterone manipulation influenced the time spent moving in both sexes. By contrast, only juvenile females increased the time spent scratching the walls of the terrarium when corticosterone was delivered both at the prenatal and postnatal stage. Prenatal hormone manipulation increased the time spent basking by juveniles issued from large females. These results suggest that, in addition to influencing a variety of behavioral and morphological traits, corticosterone may also play an important role in the regulation of activity and thermoregulation of juvenile lizards, modulated by individual sex and maternal condition. 相似文献
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A Depeiges A Force J P Dufaure 《Comparative biochemistry and physiology. B, Comparative biochemistry》1987,86(2):233-240
From epididymal fluid samples taken at three different times during the reproductive period (early April, late April, mid-May), the soluble proteins were separated with one dimensional electrophoresis on polyacrylamide gel. Their evolution was studied: firstly quantitatively, after staining with Coomassie blue, or, for one protein (the "L" protein), by immunodetection; secondly, according to their glycosylation after transfer to nitrocellulose and treatment with a set of labelled lectins: from Wheat germ, Ricinus communis, Lens culinaris, Asparagus pea or Canavalia ensiformis, with or without use of their specific inhibitor sugars. At least 15 proteins underwent a quantitative and/or qualitative evolution, mainly during the month of April. Protein "L" (19 kDa), which is androgen dependent and which fixates on to spermatozoa during their epididymal transit, appears to be little or not glycosylated. By contrast its accumulation in the epididymal canal increases considerably during the month of April. Five other proteins proved to be especially interesting because of their evolution during this same period, notably the MW 94, 67, 35, 29 and 25.5 kDa proteins. With the exception of the 67 kDa all the others increased quantitatively. All were decisively enriched in mannose or in methyl-mannoside residues. The proteins of MW 29 and 25.5 kDa were also enriched in galactose or N-acetyl galactosamine residues. These findings are of physiological significance since they are set up concomitantly with the acquisition of maximum motility of spermatozoa in the distal segment of the epididymis, and they coincide with a very great increase in testosteronemia. 相似文献
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Summary During the period May to August 1978, individuals of both Lacerta agilis and Lacerta vivipara were observed in a specially constructed out-door vivarium. The daily patterns of behaviour of the two species were recorded along with surface and air temperatures. Daily activity of both species followed a similar basic pattern but was modified by variations in the local weather. Adults of L. vivipara reached a thermal preferendum more quickly and had a longer daily activity period than adults of L. agilis. The larger L. agilis can increase its period of activity by making use of different thermal conditions in a diverse habitat with varied vegetation structure under conditions of high solar radiation. The status of viable populations of L. agilis could be maintained or enhanced by management aimed at modifying the microenvironment of the lizard's habitat. 相似文献
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断尾对胎生蜥蜴运动能力和选择体温的影响 总被引:1,自引:0,他引:1
尾自切是蜥蜴为了降低被捕食危险而采取的一种反捕食适应策略,但断尾可导致体重减轻、热量收支平衡改变,并影响蜥蜴的运动能力和体温调节.为检验断尾对蜥蜴运动能力和选择体温的影响,于2006年5月选取黑龙江省小兴安岭地区的一个胎生蜥蜴种群进行实验.结果表明:在30 ℃和24℃两个实验温度下,断尾后胎生蜥蜴的运动能力均明显下降,表现在停顿次数增多、最大可持续距离和最大疾跑速度减少等方面;断尾、温度和性别对胎生蜥蝎运动能力的影响在一定程度上是相互独立的,断尾是影响胎生蜥蜴运动能力的主要因素;断尾对胎生蜥蝎的选择体温没有显著影响. 相似文献
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Polymorphism often corresponds to alternative mating tactics in males, but much less is known about this relationship in females. However, recent work suggests that selection for alternative reproductive strategies in females can maintain genetic variation in important life-history traits. Brown anole lizards (Anolis sagrei) exhibit a genetically based polymorphism in dorsal pattern that is expressed only by females, which occur in bar (B), diamond (D) and intermediate diamond-bar (DB) morphs. Here, we use a combination of natural history data, captive breeding studies and phenotypic manipulations of reproductive investment to test the hypothesis that this polymorphism corresponds to morph-specific patterns of reproductive investment. Three years of data from wild females and two generations of captive breeding revealed no differences among morphs in the frequency of egg production or in the number, frequency, size or sex ratio of offspring. Manipulations of reproductive investment via surgical ovariectomy revealed significant costs of reproduction with respect to survival, growth, immune function and haematocrit, but the magnitudes of these costs did not differ among morphs. Collectively, our results refute the hypothesis that this sex-limited polymorphism is maintained by selection for alternative reproductive strategies. We compare this finding to other systems in which polymorphic females exhibit alternative reproductive tactics and discuss other selective factors that could maintain polymorphism in anoles. 相似文献
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Dispersal is a complex phenomenon affected by multiple factors. Among the factors that influence dispersal in the common lizard (Lacerta vivipara), poor maternal body condition and stress are known to decrease dispersal propensity of juveniles. But the effect of individual factors on dispersal could change when several of them act concurrently or at different developmental stages. Prenatal factors can affect clutch and/or juvenile characteristics that later affect dispersal. Postnatal influences are mainly exerted on juvenile dispersal behavior. We investigated the role of body condition and stress on dispersal at a prenatal and a postnatal stage. Stress was mimicked by experimentally increasing corticosterone levels in pregnant females and recently born juveniles. We considered (1). the influence of maternal body condition and prenatal corticosterone treatment on clutch, juvenile characteristics and on dispersal behavior and (2). the influence of juvenile body condition and postnatal corticosterone treatment on juvenile dispersal behavior. There was an interaction between maternal condition and prenatal corticosterone treatment on juvenile dispersal. Dispersal decreased with maternal corticosterone increase only in juveniles from the more corpulent females, while it increased with juvenile body condition. Good maternal body condition affected clutch and juvenile characteristics favoring dispersal, while elevation of corticosterone level (stress) exerted the opposite effect. Juvenile body condition favored dispersal, while there was no effect of postnatal corticosterone treatment on juvenile dispersal propensity. 相似文献