Undesirable evolutionary consequences of trophy hunting

Phenotype-based selective harvests, including trophy hunting, can have important implications for sustainable wildlife management if they target heritable traits. Here we show that in an evolutionary response to sport hunting of bighorn trophy rams (Ovis canadensis) body weight and horn size have declined significantly over time. We used quantitative genetic analyses, based on a partly genetically reconstructed pedigree from a 30-year study of a wild population in which trophy hunting targeted rams with rapidly growing horns, to explore the evolutionary response to hunter selection on ram weight and horn size. Both traits were highly heritable, and trophy-harvested rams were of significantly higher genetic 'breeding value' for weight and horn size than rams that were not harvested. Rams of high breeding value were also shot at an early age, and thus did not achieve high reproductive success. Declines in mean breeding values for weight and horn size therefore occurred in response to unrestricted trophy hunting, resulting in the production of smaller-horned, lighter rams, and fewer trophies.     

True paternal care in a multi-male primate society

Although male parental care is rare among mammals, adult males of many cercopithecine primate species provide care for infants and juveniles. This care is often in the form of grooming, carrying, support in agonistic interactions, and protection against infanticide. For these behaviours to be interpreted as true parental care, males must selectively direct care towards their own offspring and this care must result in fitness benefits. With the exception of males defending probable offspring from infanticide, male primates living in multi-male, multi-female social groups have not been shown to selectively direct care towards their own offspring. We determined paternity for 75 juveniles in a population of wild savannah baboons (Papio cynocephalus) and collected data on interventions in agonistic disputes by adult males on behalf of juveniles as a form of male care. Here we show that adult males differentiate their offspring from unrelated juveniles and selectively support their offspring in agonistic disputes. As support in agonistic disputes is likely to contribute to rank acquisition and protect juveniles from injury and stress, this can be considered true parental care.     

雄激素与鼠类的社会行为

雄激素引起的社会行为包括杀婴行为、攻击行为、交配行为和社会识别行为等 ,雄激素首先引起脑结构的性差 ,是雌雄个体社会行为发生差异的基础 .雄激素引起的杀婴行为目前还有争议 ,多数学者认为还与孕酮有关 ;雄激素引起的攻击行为还受年龄、生殖状态 (泌乳时期 )、婚配制度、父本扶养还是母本扶养等各种因素的影响 ;雄激素引起的交配行为、社会识别行为还与化学感觉系统有关 ,社会识别主要由抗利尿激素依赖雄激素而产生 .     

Female transference and mate choice among Tana River red colobus.

Red colobus are one of a small number of primate species in which females have been reported to transfer between breeding groups more commonly than males. Several authors have hypothesised that in such species transference may serve to reduce the risk to females of producing offspring of lower fitness through inbreeding. The hypothesis offers no explanation of why females rather than males are responsible for outbreeding in these species, but remains plausible so long as male membership of breeding groups is relatively stable; for once members of one sex have evolved dispersal mechanisms reducing the risk of inbreeding, pressures on the other sex to do likewise will be lowered. Hence, if both sexes commonly migrate, the hypothesis is weakened. I describe here the membership dynamics of a group of Tana River red colobus, Colobus badius rufomitratus, which provide the first evidence of high rates of membership turnover by both sexes in primates, and speculate that the function of female transference in this case may be related to mate choice and the avoidance of infanticide.     

Outbred embryos rescue inbred half-siblings in mixed-paternity broods of live-bearing females

Females commonly mate with more than one male, and polyandry has been shown to increase reproductive success in many species. Insemination by multiple males shifts the arena for sexual selection from the external environment to the female reproductive tract, where sperm competition or female choice of sperm could bias fertilization against sperm from genetically inferior or genetically incompatible males. Evidence that polyandry can be a strategy for avoiding incompatibility comes from studies showing that inbreeding cost is reduced in some egg-laying species by postcopulatory mechanisms that favour fertilization by sperm from unrelated males. In viviparous (live-bearing) species, inbreeding not only reduces offspring genetic quality but might also disrupt feto-maternal interactions that are crucial for normal embryonic development. Here we show that polyandry in viviparous pseudoscorpions reduces inbreeding cost not through paternity-biasing mechanisms favouring outbred offspring, but rather because outbred embryos exert a rescuing effect on inbred half-siblings in mixed-paternity broods. The benefits of polyandry may thus be more complex for live-bearing females than for females that lay eggs.     

一种局部搜索能力增强的狮群算法

狮群算法作为一种新型群智能优化算法,其进化过程多依据狮群猎食、交配等动物本性出发,因此难免会存在收敛速度慢并且不容易发现全局极值等缺点.针对当前基本狮群算法存在的缺点,提出一种局部搜索能力增强的狮群算法(Enhanced Local Search Lion Optimization Algorithm,ELSLOA).为增强种群局部搜索效率,对所有领地狮引入对立搜索方法提高寻优能力,并对优良个体执行Levy flight操作,提高个体局部开采能力,最后利用Tent混沌搜索对领地狮和流浪狮执行混沌操作.对算法进行了函数的仿真对比分析,充分验证了所提出算法的优良性能.     

Female transfer and inbreeding avoidance in social mammals

In most social mammals, males leave their natal group to breed in other groups whereas females commonly remain in the same group throughout their lives. In a few species however, females usually transfer between groups during adolescence. The functional significance of sex differences in dispersal and their connection, if any, to the avoidance of inbreeding is disputed. Here I show that in polygynous mammals where females commonly remain to breed in their natal group, their average age at first conception typically exceeds the average period of residence of adult males in breeding groups. In contrast, where females usually transfer to breed in other groups, the average residence of breeding males or of resident male kin groups typically exceeds the average age of females at first conception. These results support the suggestion that female mammals commonly transfer to avoid inbreeding with their father or other close relatives, although female dispersal may also occur for other reasons.     

Induction of vitellogenin and growth of implanted oocytes in male cockroaches

Vitellogenins are yolk protein precursors that are synthesised in the liver of lower vertebrates in response to ovarian hormones, and in the fat body tissue of insects, under the influence, in most species, of juvenile hormone (JH) from the corpora allata (CA). Vitellogenins are normally restricted to females, although in male amphibians and roosters their synthesis can be induced artificially by the injection of oestrogens. Thus female specificity is maintained by hormonal differences between adult males and females. In insects, on the other hand, because the CA of adults of both sexes are active, it appeared that male fat body could not normally respond to JH by synthesising vitellogenin. However, precise JH synthetic rates of male CA are only known in Schistocerca gregaria and Diplopterapunctata, in which species they are low compared to the rates in the female glands. The absence of vitellogenin in adult males could thus be due to inadequate JH titres. We report here that synthesis of vitellogenin can indeed be induced in males of Diploptera by implantation of female CA or application of Diploptera by implantation of female CA or application of a JH analogue, ZR512 (Zoecon), and that implanted oocytes take up the vitellogenin.     

Sexually antagonistic genetic variation for fitness in red deer

Evolutionary theory predicts the depletion of genetic variation in natural populations as a result of the effects of selection, but genetic variation is nevertheless abundant for many traits that are under directional or stabilizing selection. Evolutionary geneticists commonly try to explain this paradox with mechanisms that lead to a balance between mutation and selection. However, theoretical predictions of equilibrium genetic variance under mutation-selection balance are usually lower than the observed values, and the reason for this is unknown. The potential role of sexually antagonistic selection in maintaining genetic variation has received little attention in this debate, surprisingly given its potential ubiquity in dioecious organisms. At fitness-related loci, a given genotype may be selected in opposite directions in the two sexes. Such sexually antagonistic selection will reduce the otherwise-expected positive genetic correlation between male and female fitness. Both theory and experimental data suggest that males and females of the same species may have divergent genetic optima, but supporting data from wild populations are still scarce. Here we present evidence for sexually antagonistic fitness variation in a natural population, using data from a long-term study of red deer (Cervus elaphus). We show that male red deer with relatively high fitness fathered, on average, daughters with relatively low fitness. This was due to a negative genetic correlation between estimates of fitness in males and females. In particular, we show that selection favours males that carry low breeding values for female fitness. Our results demonstrate that sexually antagonistic selection can lead to a trade-off between the optimal genotypes for males and females; this mechanism will have profound effects on the operation of selection and the maintenance of genetic variation in natural populations.     

Sperm death and dumping in Drosophila

Mating with more than one male is the norm for females of many species. In addition to generating competition between the ejaculates of different males, multiple mating may allow females to bias sperm use. In Drosophila melanogaster, the last male to inseminate a female sires approximately 80% of subsequent progeny. Both sperm displacement, where resident sperm are removed from storage by the incoming ejaculate of the copulating male, and sperm incapacitation, where incoming seminal fluids supposedly interfere with resident sperm, have been implicated in this pattern of sperm use. But the idea of incapacitation is problematic because there are no known mechanisms by which an individual could damage rival sperm and not their own. Females also influence the process of sperm use, but exactly how is unclear. Here we show that seminal fluids do not kill rival sperm and that any 'incapacitation' is probably due to sperm ageing during sperm storage. We also show that females release stored sperm from the reproductive tract (sperm dumping) after copulation with a second male and that this requires neither incoming sperm nor seminal fluids. Instead, males may cause stored sperm to be dumped or females may differentially eject sperm from the previous mating.     

Sperm competition between Drosophila males involves both displacement and incapacitation.

Females in almost all animal groups copulate with multiple males. This behaviour allows different males to compete for fertilization and gives females the opportunity to mediate this competition. In many animals and most insects, the second male to copulate with a female typically sires most of her offspring. In Drosophila melanogaster, this second-male sperm precedence has long been studied but, as in most species, its mechanism has remained unknown. Here we show, using labelled sperm in doubly mated females, that males can both physically displace and incapacitate stored sperm from earlier-mating males. Displacement occurs only if the second male transfers sperm to the female, and in only one of her three sperm-storage organs. Incapacitation can be caused by either fertile or spermless second males, but requires extended intervals between matings. Sperm from different males are not 'stratified' in the storage organs but mix freely. Many animal species may have multiple mechanisms of sperm competition like those observed here, and revealing these mechanisms is necessary to understand the genetic and evolutionary basis of second-male sperm precedence in animals.     

Post-mating clutch piracy in an amphibian

Female multiple mating and alternative mating systems can decrease the opportunity for sexual selection. Sperm competition is often the outcome of females mating with multiple males and has been observed in many animals, and alternative reproductive systems are widespread among species with external fertilization and parental care. Multiple paternity without associated complex behaviour related to mating or parental care is also seen in simultaneously spawning amphibians and fishes that release gametes into water. Here we report 'clutch piracy' in a montane population of the common frog Rana temporaria, a reproductive behaviour previously unknown in vertebrates with external fertilization. Males of this species clasp the females and the pair deposits one spherical clutch of eggs. No parental care is provided. 'Pirate' males search for freshly laid clutches, clasp them as they would do a female and fertilize the eggs that were left unfertilized by the 'parental' male. This behaviour does not seem to be size-dependent, and some males mate with a female and perform clutch piracy in the same season. Piracy affected 84% of the clutches and in some cases increased the proportion of eggs fertilized, providing direct fitness benefits both for the pirate males and the females. Sexual selection--probably caused by a strong male-biased sex ratio--occurs in this population, as indicated by size-assortative mating; however, clutch piracy may reduce its impact. This provides a good model to explore how alternative mating strategies can affect the intensity of sexual selection.     

Population density drives the local evolution of a threshold dimorphism

Evolution can favour more than one reproductive tactic among conspecifics of the same sex. Under the conditional evolutionarily stable strategy, individuals adopt the tactic that generates the highest fitness return for their status: large males guard females, whereas small males sneak copulations. Tactics change at the status at which fitness benefits switch from favouring one tactic to favouring the alternative. This 'switchpoint' is expressed in many species as a threshold between divergent morphologies. Environmental and demographic parameters that influence the relative fitness of male tactics are predicted to determine a population's switchpoint and consequently whether the population is monomorphic or dimorphic. Here we show threshold evolution in the forceps dimorphism of the European earwig Forficula auricularia and document the transition from completely monomorphic to classical male-dimorphic populations over a distance of only 40 km. Because the superior fighting ability of the dominant morph will be more frequently rewarded at high encounter rates, population density is likely to be a key determinant of the relative fitness of the alternative tactics, and consequently the threshold. We show that, as predicted, population density correlates strongly with the shift in threshold, and that this factor drives the local evolution of the male dimorphism in these island populations. Our data provide evidence for the origin of phenotypic diversity within populations, through the evolution of a switchpoint in a conditional strategy that has responded to local population density.     

Mortality profiles of the large herbivores from the Lingjing Xuchang Man Site, Henan Province and the early emergence of the modern human behaviors in East Asia

This paper presents the results of a detailed study of mortality profiles of the large herbivores from the Middle Palaeolithic （MP） bone assemblage of the Lingjing Xuchang Man Site, Henan Province. Based on the analysis of the crown heights of fossil teeth from this assemblage, we come to a conclusion that aurochs （Bos primigenius） and horse （Equus caballus） are the major prey species in this assemblage and the age structures of these animals can be best described as the ＂prime-dominated pattern＂. This study confirmed the well-established notions at many Middle and Upper Palaeolithic sites across Eurasia and Africa that MSA/MP foragers were fully effective in hunting aggressive prey species, particularly aurochs and horse. This find indicates that the hunting behaviors and subsistence strategies were not significantly different between MP and UP （the Upper Palaeolithic） humans in East Asia and hence suggests the early emergence of the modern human behaviors in this area.     

Sexual selection for sensory exploitation in the frog Physalaemus pustulosus

The sensory bases of species and population mate preferences are well known; in frogs properties of the female auditory system influence such preferences. By contrast, there is little understanding of how sensory characteristics could result in sexual selection within a population. One possible mechanism is that females are more sensitive to male courtship signals that deviate from the population mean. We document this mechanism in the frog Physalaemus pustulosus. Female basilar papilla tuning is biased toward lower-than-average frequencies in the 'chuck' portion of the male's call, explaining female preference for the lower-frequency chucks produced by larger males. The tuning does not differ between P. pustulosus and its close relative P. coloradorum, a species in which males never evolved the ability to produce chucks; thus the female tuning evolved before the chuck and therefore the chuck played no role in the evolution of the preference. This allows us to reject two popular hypotheses for the evolution of this female preference (runaway sexual selection and natural selection) in favour of a third: sexual selection for sensory exploitation.     

Sex differences in emigration and mortality affect optimal management of deer populations

Populations of red deer that are limited by food, like those of many other ungulates, commonly include more females than males. We assessed the contribution of variation in sex- and age-specific rates of mortality and emigration to density-dependent changes in the adult sex ratio, using long-term observations and demographic experiments involving the red deer population on Rum, Scotland. We incorporated these effects in a stochastic model of local populations under different management regimes to show here that, when female numbers are allowed to increase to more than 60% of the ecological carrying capacity, the sustainable annual harvest of males from local deer populations will fall. Because males are typically culled by fee-paying hunters and generate more income than females, income will decrease as the male harvest falls. Because numbers of female deer throughout much of the Highlands probably exceed the threshold at which male density starts to be affected, many managers might be able to raise income from local deer populations by reducing female numbers, with potential benefits to the vegetation of Scottish Highland environments.     

Female mimicry in garter snakes

In many diverse taxa, males of the same species often exhibit multiple mating strategies. One well-documented alternative male reproductive pattern is 'female mimicry', whereby males assume a female-like morphology or mimic female behaviour patterns. In some species males mimic both female morphology and behaviour. We report here female mimicry in a reptile, the red-sided garter snake (Thamnophis sirtalis parietalis). This form of mimicry is unique in that it is expressed as a physiological feminization. Courting male red-sided garter snakes detect a female-specific pheromone and normally avoid courting other males. However, a small proportion of males release a pheromone that attracts other males, as though they were females. In the field, mating aggregations of 5-17 males were observed formed around these individual attractive males, which we have termed 'she-males'. In competitive mating trails, she-males mated with females significantly more often than did normal males, demonstrating not only reproductive competence but also a possible selective advantage to males with this female-like pheromone.     

Directional postcopulatory sexual selection revealed by artificial insemination

Postcopulatory sexual selection comprises both sperm competition, where the sperm from different males compete for fertilization, and cryptic female choice, where females bias sperm use in favour of particular males. Despite intense current interest in both processes as potential agents of directional sexual selection, few studies have attributed the success of attractive males to events that occur exclusively after insemination. This is because the interactions between pre- and post-insemination episodes of sexual selection can be important sources of variation in paternity. The use of artificial insemination overcomes this difficulty because it controls for variation in male fertilization success attributable to the female's perception of male quality, as well as effects due to mating order and the relative contribution of sperm from competing males. Here, we adopt this technique and show that in guppies, when equal numbers of sperm from two males compete for fertilization, relatively colourful individuals achieve greater parentage than their less ornamented counterparts. This finding indicates that precopulatory female mating preferences can be reinforced exclusively through postcopulatory processes occurring at a physiological level. Our analysis also revealed that relatively small individuals were advantaged in sperm competition, suggesting a possible trade-off between sperm competitive ability and body growth.     

高速列车蛇行运动稳定性研究概述

高速列车长期服役的可靠性是高铁建设的首要保证,自激蛇行运动是轨道车辆所特有的一种失稳形式,为了保证车辆的运动稳定性,确保其高速、安全行驶,以高速列车蛇行失稳的理论研究方法为背景,概述了蛇行失稳研究中的主要研究方法及其存在的不足,对近期的研究热点方向进行了概述并对非光滑分岔、非对称运行稳定性等方向进行了展望。对于高速列车的确定性和稳定性而言,在不考虑车辆非线性特性的情况下,一般可以采用特征根法、Routh-Hurwitz准则判定法、最小阻尼系数等方法进行分析;当必须考虑轮轨接触以及悬挂系统等非线性特征时,可以采用特征值变化法、QR算法+二分法、中心流形法、打靶法、延续算法等方法。对于车辆的随机稳定性而言,可以采用随机非线性动力学Hamilton理论、蒙特卡洛法、半隐式的Milstein随机数值模拟、小数据量等方法对随机稳定性、随机分岔以及分岔类型进行分析。由于能够考虑自身结构参数激励、轮轨接触不平顺激励,能得到更接近真实运行条件下的失稳临界速度,随机稳定性、随机分岔的理论研究和试验研究逐渐得到研究人员的关注,成为高速列车蛇行失稳研究的热点方向。     

Female mate-choice drives the evolution of male-biased dispersal in a social mammal

Dispersal has a significant impact on lifetime reproductive success, and is often more prevalent in one sex than the other. In group-living mammals, dispersal is normally male-biased and in theory this sexual bias could be a response by males to female mate preferences, competition for access to females or resources, or the result of males avoiding inbreeding. There is a lack of studies on social mammals that simultaneously assess these factors and measure the fitness consequences of male dispersal decisions. Here we show that male-biased dispersal in the spotted hyaena (Crocuta crocuta) most probably results from an adaptive response by males to simple female mate-choice rules that have evolved to avoid inbreeding. Microsatellite profiling revealed that females preferred sires that were born into or immigrated into the female's group after the female was born. Furthermore, young females preferred short-tenured sires and older females preferred longer-tenured sires. Males responded to these female mate preferences by initiating their reproductive careers in groups containing the highest number of young females. As a consequence, 11% of males started their reproductive career in their natal group and 89% of males dispersed. Males that started reproduction in groups containing the highest number of young females had a higher long-term reproductive success than males that did not. The female mate-choice rules ensured that females effectively avoided inbreeding without the need to discriminate directly against close kin or males born in their own group, or to favour immigrant males. The extent of male dispersal as a response to such female mate preferences depends on the demographic structure of breeding groups, rather than the genetic relatedness between females and males.