Effects of Male age and Size on Mating Success in the Bumblebee Bombus terrestris

In social insects, the reproductive strategies adopted by colonies emerge as a complex property of individual behaviours, but as yet we are often unable to fully explain them in evolutionary terms. In bumblebees, colonies adopt either a short-lived strategy specializing in male production, or a longer-lived strategy in which mainly new queens are produced, but this results in males emerging long before mates are available; this strategy can only easily be explained if older males are at a significant reproductive advantage. Here we examine how age and morphological characters influence mating success of male bumblebees. In two separate experiments in which single virgin males and females were confined together, we found that young males and heavy males mated more swiftly and copulated for less time compared to old males or lighter males, respectively. However, in competitive situations age proved to be unimportant and the only factors to influence mating success were the lengths of the fore and hind tibiae, with strong directional selection for long leg length. Fore and hind legs are both used in courtship, so both traits are associated with plausible mechanisms under selection. It has previously been argued that, in times of food stress, bumblebee colonies should produce males as male size is less likely to be strongly correlated with fitness than female size. Our results suggest that this may not be so, since aspects of male size directly impact on their mating success. Our results leave unexplained the emergence of males many days before new queens.     

Effects of Calcium-Loading on Egg Production in Ring-Necked Pheasants

Abstract: Ring-necked pheasants (Phasianus colchicus) are able to store dietary calcium as medullary bone, which they may mobilize for future eggshell synthesis. We define this mechanism as calcium-loading. Previous experiments on pheasants conducted to document the importance of calcium in limiting distribution did not account for calcium-loading. We hypothesized that calcium-loading could override experimental calcium treatments of the diet. We measured egg production, egg characteristics, and femoral mineral content for pheasants that were not calcium-loaded on 7 diets differing in calcium from 0.2% to 4.5% and compared these results to a similar study on calcium-loaded pheasants. We predicted that calcium-loaded pheasants would produce more eggs than those that were not calcium-loaded. We also predicted that there would be no significant difference between femur ash fractions in non-calcium-loaded pheasants, but that the ash fraction in calcium-loaded pheasants would differ significantly between the beginning and end of the experiment. Egg production was higher in calcium-loaded pheasants above 2% dietary calcium. Femur ash fraction was not different in non–calcium-loaded pheasants but differed significantly before and after the experiment and between high (>2%) and low (<2%) dietary levels in calcium-loaded pheasants. Calcium-loading may account for short-term persistence of captive pheasants introduced on calcium-poor soils, followed by their eventual population failure. Managers may improve survival of captive pheasants before introduction by surveying habitat for adequate calcium and by calcium-loading.     

Reduced Mating Vigor in Selection Lines of the Butterfly Bicyclus anynana

Despite its acknowledged value for testing evolutionary theory, artificial selection is vulnerable to artifacts that are difficult to control. Here, we show that lines of the butterfly Bicyclus anynana, being artificially selected for differences in egg size, show considerably reduced mating vigor and male mating success than control lines, which is attributed to presumed differences in the levels of inbreeding. Besides selection line, neither forewing length, body dry mass or fat content of males had a detectable impact on male mating performance. Because artificial selection may (e.g. due to inbreeding) yield inadvertent effects even on traits that seem not to be related to the target trait, their results should be interpreted with caution.     

外源促性腺激素处理后鸡产蛋及孵化研究

目的:探讨促卵泡素(FSH)对低产期肉用种母鸡在产蛋数量和孵化的影响,寻求较佳的用于提高低产期母鸡产蛋的激素剂量。方法:本试验采用同种激素不同剂量的处理方式,比较实验组和对照组产蛋量和孵化情况。结果:注射不同剂量的激素对鸡的产蛋有一定的影响,实验组一的平均产蛋数与对照组接近,其它四组均显著低于对照组(P<0.05),孵化率与健雏率与对照组无显著差异(P>0.05)。结论:小剂量激素处理对鸡产蛋量没有太大的影响,但大剂量会引起鸡生殖系统萎缩,激素处理对受精卵孵化及雏鸡生长并无负面影响。     

Female Fertility and Mating Type Effects on Effective Population Size and Evolution in Filamentous Fungi

The murine agouti locus regulates a switch in pigment synthesis between eumelanin (black/brown pigment) and phaeomelanin (yellow/red pigment) by hair bulb melanocytes. We recently described a spontaneous mutation, hypervariable yellow (A(hvy)) and demonstrated that A(hvy) is responsible for the largest range of phenotypes yet identified at the agouti locus, producing mice that are obese with yellow coats to mice that are of normal weight with black coats. Here, we show that agouti expression is altered both temporally and spatially in A(hvy) mutants. Agouti expression levels are positively correlated with the degree of yellow pigmentation in individual A(hvy) mice, consistent with results from other dominant yellow agouti mutations. Sequencing of 5' RACE and genomic PCR products revealed that A(hvy) resulted from the integration of an intracisternal A particle (IAP) in an antisense orientation within the 5' untranslated agouti exon 1C. This retrovirus-like element is responsible for deregulating agouti expression in A(hvy) mice; agouti expression is correlated with the methylation state of CpG residues in the IAP long terminal repeat as well as in host genomic DNA. In addition, the data suggest that the variable phenotype of A(hvy) offspring is influenced in part by the phenotype of their A(hvy) female parent.     

Male and Female Mating Behavior is Dependent on Social Context in the Butterfly Bicyclus anynana

Reproduction is often more costly to females than it is to males, leading to the evolution of ornamented or competitive males and choosy females. Reproduction costs to females, however, can be reduced through nuptial gifts provided by males. These gifts, by increasing female survival or fecundity, can promote the evolution of mutual mate choice, ornamentation, or competition in both sexes, as well as plasticity in mating behavior dependent on social context. We tested for plasticity in male and female mating behavior in a species of butterfly, Bicyclus anynana, where male spermatophore gifts contribute to female survival and fecundity, and where mutual mate choice and ornamentation were previously established. We examined the effect of a sexual competitor on male–female interactions by observing and comparing the behavior of male–female pairs with that of triads containing either an extra male or an extra female. In the presence of a sexual competitor both males and females copulated less than when in male–female pairs, regardless of the direction of sex-ratio skew. Active males increased their own likelihood to copulate, while active females increased their likelihood of being courted. In addition, there was an effect of social context on relative rates of male and female courting and flying. These results suggest that both males and females change their mating behavior in response to social context in the butterfly Bicyclus anynana.     

产卵次序对山麻雀卵色、卵大小和重量的影响

产卵次序可对鸟类卵黄中的营养成分、卵壳色素以及卵壳厚度等产生影响。一些鸟类可通过产卵次序对不同卵的资源进行分配,从而实现繁殖成效的最大化。本研究对不同产卵次序下山麻雀(Passer cinnamomeus)的卵色、卵大小和卵重量进行分析,结果表明,山麻雀的卵重和卵大小随着产卵次序并无显著变化,卵色与卵的大小和重量均无显著相关性,但卵背景的色度随产卵次序有明显下降趋势,而卵斑点密度则呈相反的变化。卵背景的色度随产卵次序下降可能是山麻雀有限的色素在卵中不均匀分配的结果,而卵斑点密度的增加则可能是对后期卵壳厚度变薄的一种补偿。     

Effects of Chromium Propionate on Egg Production,Egg Quality,Plasma Biochemical Parameters,and Egg Chromium Deposition in Late-Phase Laying Hens

This study was conducted to investigate the effects of chromium propionate on egg production, egg quality, plasma biochemical parameters and egg chromium deposition in late-phase laying hens. Four hundred thirty-two 60-weeks old laying hens were divided into four groups of 108 birds per group according to egg production. The dietary treatments consisted of the basal diet adding with 0, 200, 400, and 600 μg/kg chromium as chromium propionate. All laying hens were given feed and water ad libitum for 8 weeks. The addition of 400 μg/kg Cr as chromium propionate increased egg production (P?<?0.01) during the later 4 weeks, but decreased albumen height, yolk color score, and Haugh unit of eggs. Six hundred micrograms per kilogram Cr as chromium propionate supplementation improved shell thickness (P?<?0.05). 200 μg/kg Cr as chromium propionate supplementation decreased the uric acid concentration by 31 % (P?<?0.05). However, supplemental Cr did not affect the egg chromium deposition of hens (P?>?0.05). These data indicated that feeding of late-phase laying hens with chromium propionate could improve egg production, increase eggshell thickness, but do not result in abnormal levels of chromium deposition in eggs.     

交配和温度对小地老虎雌蛾性信息素产生的影响

研究了交配和温度对小地老虎雌蛾性信息素产生的影响,结果表明,交配对性信息素各组分的滴度无显著影响,因此不影响小地老虎在下一暗期的再次求偶和交配.但环境温度对小地老虎性信息素的含量则有显著的影响,20～25℃最有利于小地老虎性信息素的生物合成,而低温和高温则均不利于小地老虎性信息素的正常产生与释放.     

Ultraviolet Ornamentation and Male Mating Success in a High-Density Assemblage of the Butterfly Colias eurytheme

Ultraviolet (UV) colour patterns, particularly those deriving from surface structures, serve a role in sexual signalling and mate choice in a range of animal groups. In the butterfly Colias eurytheme (Pieridae), male-limited iridescent UV functions in species recognition, and has potential as an intraspecific sexual signal of mate quality. I compared the dorsal colouration and body size of males discovered ‘in-copula’ (N = 95) with a random sample of free-flying individuals (N = 129), both collected from a high density agricultural population located in Chandler, U.S.A. Despite reasonable variance in each trait, I found no among-group differences in UV characters (brightness, hue and angular visibility) or in the coincident pigmentary yellowish-orange (brightness and saturation). Statistical power was sufficient to detect all but the smallest among-group differences, and there was a marginally significant tendency for in-copula males to be larger. These data do not support the hypothesis for intraspecific female choice upon male dorsal colouration. However, I discuss how the density and apparently very young age of individuals in the sampling population may have pre-disposed this result, and thus, how sexual selection on male colouration may operate in a density dependent manner.     

Breeding Strategies in Females of the Parasitoid Wasp Spalangia endius: Effects of Mating Status and Size

Does the mating status or body size of a female parasitoid wasp affect her host size choice or propensity to burrow? In Spalangia endius, using smaller hosts appears to reduce a female's cost of parasitization but not her son's fitness. However, virgin females, which produce only sons, did not preferentially parasitize smaller hosts. Mated females also showed no host size preference. Mated females burrowed more than virgins in the presence of hosts, although not in their absence. Burrowing may reduce a mated female's harassment from males, and not burrowing may increase a virgin female's chance of mating because males avoid burrowing. Mating did not increase female longevity. Greater female size increased the offspring production of mated females burrowing for hosts but not in the absence of burrowing and not in virgin females. A female's size had no significant effect on whether her first drill attempt was on a large or a small host or on the duration of her successful drills.     

Optimal Egg Size in Marine Invertebrates: Theory and Phylogenetic Analysis of the Critical Relationship between Egg Size and Development Time in Echinoids

Life-history models for marine invertebrate larvae generally predict a dichotomy in egg size in different species: eggs should be either minimal in size or large enough to support development fully without larval feeding. This prediction is contradicted, however, by the empirical observation of wide, continuous variation in egg size between these extremes. The prediction of dichotomy rests on the assumption of a negative linear relationship between egg size and development time. Here, I present a simple model in which development time is inversely proportional to egg size. Incorporating this relationship into an optimality model produces predictions of intermediate rather than extreme egg size. Modeled variations in mortality, food availability, fertilization rates, and temperature all produce continuous shifts in the value of the intermediate optimal size, in direct contrast to those produced by previous models, which predict shifts between two extreme optima. Empirical data on echinoid egg size and development time strongly support the model's assumption of an inverse proportional relationship between egg size and development time. A composite phylogeny is constructed of the 37 species for which egg size, development time, water temperature, and phylogenetic relatedness are known. Independent contrasts are made of the evolutionary changes in egg size and development time. This analysis indicates that evolutionary shifts in development time are correlated with the inversely proportional shifts in egg size assumed in the model. The assumption of a negative linear relationship used in previous models is rejected. This model provides a potential explanation for intraspecific variation in egg size along environmental gradients, sympatric differences in egg size among species, and biogeographic trends in egg size and development mode across taxa.     

Pheromone Blend Does not Explain Old Male Mating Advantage in a Butterfly

In several insect species, male mating success is higher in older than in younger males, although condition diminishes dramatically with age. Two hypotheses are under debate to explain the counterintuitive pattern of old male mating advantage: first, an increased eagerness of older males to mate, driven by their low residual reproductive value, and second female preference for older males based on chemical cues such as sex pheromones (female choice hypothesis). In a series of experiments, we manipulated female olfaction, male pheromone blend and female age to test whether old male mating advantage prevails when the influence of male sex pheromones is controlled for, using the tropical butterfly Bicyclus anynana as model. We found that older males had a higher mating success than younger ones irrespective of female scent‐sensitivity and irrespective of male pheromone blend. Interestingly, older males were found to court more often and for longer time bouts than younger males. These results were independent of female age, although younger males courted younger females more often and for longer bouts than older females. Taken together, our results indicate that male courtship activity (1) is higher in older compared to younger males and (2) increases the mating success of older males. Olfaction and sensing pheromones, in contrast, were not a necessary prerequisite for old male mating advantage to occur and may use other cues than pheromones to assess male quality.     

Promiscuous Mating among Blue Monkeys in the Kakamega Forest,Kenya

13 females and 12 of 19 males present in a group of blue monkeys (Cercopithecus mitis stuhlmanni) mated promiscuously during an intense bout of sexual activity. Several aspects of their behavior are considered as mechanisms for determining mating patterns. Estrus synchrony coincided with a multi-male influx, allowing promiscuity. The length of stay and rank of an incoming male were correlated with his number of copulations in the group, while the original resident and highest ranking male was never seen to mate. Thus, although agonistic behavior, especially among males, affected mating success, it did not guarantee copulations. Adjustments of position relative to other individuals also affected who mated with whom. These and earlier observations suggest that there may be more than one way to be successful in mate competition, and lead us to question whether the kinds of behavior we observed have merely a reproductive function.