Sex differences in learning in chimpanzees

The wild chimpanzees in Gombe National Park, Tanzania, fish for termites with flexible tools that they make out of vegetation, inserting them into the termite mound and then extracting and eating the termites that cling to the tool. Tools may be used in different ways by different chimpanzee communities according to the local chimpanzee culture. Here we describe the results of a four-year longitudinal field study in which we investigated how this cultural behaviour is learned by the community's offspring. We find that there are distinct sex-based differences, akin to those found in human children, in the way in which young chimpanzees develop their termite-fishing skills.     

陕西省鹿类动物的数量估计和资源保护与利用问题的探讨

通过７４个样方共５５．１７ｋｍ２，分别对陕西分布的４种鹿类动物中的３种的种群数量进行了调查，借助数理统计学方法，对其资源贮存量进行了估计．结果表明，林麝（Ｍｕｓｃｈｕｓｂｅｒｅｚｏｖｓｋｉ）１９８５年的密度是２．４９±０．３７只／ｋｍ２，秦巴山区的资源估计贮存量为８５２００±１０４００只；１９８３～１９８４年黄麂（Ｍｕｎｔｉａｃｕｓｒｅｖｅｓｉ）的密度为９．８０±０．７５只／ｋｍ２，安康地区１０县黄麂资源存量为６４７００±４９００只，年种群自然增长率为３５％，适宜猎取量为１３０００～１４０００只；陕北黄土高原狍（Ｃａｐｒｅｏｌｕｓｃａｐｒｅ－ｏｌｕｓ）１９７６年的密度为６．０２±０．８３只／ｋｍ２，资源贮存量为８１２００±１１２００只．１９８１年狍的密度为５．０９±０．６１只／ｋｍ２，资源存量为６８７００±８２００只，狍的年种群自然增长率为３８％，适宜猎取量为１２０００～１５０００只．文中对陕西省鹿类动物资源的保护、管理和利用进行了探讨．     

Genetic diversity among Chinese sika deer （Cerrus nippon） populations and relationships between Chinese and Japanese sika deer

Sika deer （Cervus nippon） is a cervid endemic to mainland and insular Asia and endangered. We analyzed variation in the mitochondrial DNA （mtDNA） control region for four subspecies to understand the genetic diversity, population structure and evolutionary history in China. 335 bp were sequenced and eight haplotypes were identified based on 25 variable sites among the populations. Sika deer in China showed lower genetic diversity, sug- gesting a small effective population size due to habitat fragmentation, a low number of founder individuals, or the narrow breeding program. AMOVA analysis indicated that there was significant genetic subdivision among the four populations, but no correlation between the genetic and geographic distance. PhyIogenetic analyses also revealed that Chinese sika deer may be divided into three genetic clades, but the genetic structure among Chinese populations was inconsistent with subspecies designations and present geographic distribution. Including the sequence data of Japanese sika deer, the results indicated that Chinese populations were more closely related to Southern Japanese populations than to the Northern Japanese one, and the Taiwan population was closer to populations of Northeastern China and Sichuan than to those of Southern China.     

The optimal sex ratio in cooperatively breeding populations

In some cooperatively breeding species, elder siblings remain within their home ranges to assist their parents in raising their younger siblings by providing protection or food. Previous attempts to model the popu- lation sex ratios of such species have assumed that helping is cost-free and only involves benefits to parents, resulting in offspring sex ratio biases towards the helping sex. However, parents may also incur costs in maintaining helpers. We incorporated costs and benefits of helping to predict the sex ratio of offspring in a theoretical model. Our model showed that the evolutionary stable strategy （ESS） sex ratio strongly depends on three parameters： （1） the average number of helpers per female; （2） the benefits that a helper brings to its mother＇s offspring production （MOP）; and （3） the cost-benefit ratio of helping. When one sex of elder siblings provides help, the ESS sex ratio is biased towards the helping sex if MOP costs are less than the benefits, （i.e., the cost-benefit ratio 〈1）. However, the ESS sex ratio becomes biased towards the non-helping sex if MOP costs exceed the benefits （i.e., the cost-benefit ratio 〉1）. Additionally, our model shows that the ESS sex ratio becomes biased in favor of the more helpful sex when both male and female elder siblings provide help. These results explain why sex ratios may become biased towards the helping sex, as well as the non-helping sex, in some species.     

Genetic basis of fitness differences in natural populations

Genomics profoundly influences current biology. One of many exciting consequences of this revolution is the potential for identifying and studying the genetic basis of those traits affecting fitness that are key to natural selection. Recent studies using a multitude of genomic approaches have established such genotype-phenotype relationships in natural populations, giving new insight into the genetic architecture of quantitative variation. In parallel, an emerging understanding of the quantitative genetics of fitness variation in the wild means that we are poised to see a synthesis of ecological and molecular approaches in evolutionary biology.     

GENETIC DIVERSITY AMONG CHINESE SIKA DEER (CERVUS NIPPON) POPULATIONS AND RELATIONSHIPS BETWEEN CHINESE AND JAPANESE SIKA DEER

SIKA DEER,CERVUS NIPPON,WAS HISTORICALLY WIDE-SPREAD THROUGHOUT NORTHEASTERN ASIA,FROM THE USSURI REGION TO VIETNAM,INCLUDING THE KOREAN PENINSULA,MAINLAND CHINA AND TAIWAN,AND THE JAPANESE ARCHI-PELAGO,AND UP TO13SUBSPECIES HAVE BEEN DESCRIBED[1].THE FOS…     

Sex increases the efficacy of natural selection in experimental yeast populations

Why sex evolved and persists is a problem for evolutionary biology, because sex disrupts favourable gene combinations and requires an expenditure of time and energy. Further, in organisms with unequal-sized gametes, the female transmits her genes at only half the rate of an asexual equivalent (the twofold cost of sex). Many modern theories that provide an explanation for the advantage of sex incorporate an idea originally proposed by Weismann more than 100 years ago: sex allows natural selection to proceed more effectively because it increases genetic variation. Here we test this hypothesis, which still lacks robust empirical support, with the use of experiments on yeast populations. Capitalizing on recent advances in the molecular biology of recombination in yeast, we produced by genetic manipulation strains that differed only in their capacity for sexual reproduction. We show that, as predicted by the theory, sex increases the rate of adaptation to a new harsh environment but has no measurable effect on fitness in a new benign environment where there is little selection.     

Maternal investment. Sex differences in avian yolk hormone levels

It has been suggested that female birds put more resources into eggs fathered by attractive males by laying larger eggs or by adding more testosterone, but this inference could be undermined if eggs of different sex are provisioned differently, as these studies did not control for sex differences. Here we compare hormone concentrations in the yolks of male and female eggs and find that these are significantly different. Our results indicate that it is premature to conclude that female birds invest more in eggs sired by a preferred male, and raise the possibility that yolk sex steroids may be part of the sex-determining process in birds.     

Patterns of mortality and age at first reproduction in natural populations of mammals

There is great variation in the age at which females of different mammalian species first breed. Recent comparative analyses have focused on the relationship between age at first reproduction and body size, but differences in patterns of mortality experienced by natural populations are expected to have major effects on selection for age at first reproduction. Here we show that the age at which females first reproduce is strongly correlated with expectation of life at birth, after the effects of body size have been removed, within and among species of mammals living in natural populations.     

Fine-scale recombination rate differences between sexes, populations and individuals

Meiotic recombinations contribute to genetic diversity by yielding new combinations of alleles. Recently, high-resolution recombination maps were inferred from high-density single-nucleotide polymorphism (SNP) data using linkage disequilibrium (LD) patterns that capture historical recombination events. The use of these maps has been demonstrated by the identification of recombination hotspots and associated motifs, and the discovery that the PRDM9 gene affects the proportion of recombinations occurring at hotspots. However, these maps provide no information about individual or sex differences. Moreover, locus-specific demographic factors like natural selection can bias LD-based estimates of recombination rate. Existing genetic maps based on family data avoid these shortcomings, but their resolution is limited by relatively few meioses and a low density of markers. Here we used genome-wide SNP data from 15,257 parent-offspring pairs to construct the first recombination maps based on directly observed recombinations with a resolution that is effective down to 10 kilobases (kb). Comparing male and female maps reveals that about 15% of hotspots in one sex are specific to that sex. Although male recombinations result in more shuffling of exons within genes, female recombinations generate more new combinations of nearby genes. We discover novel associations between recombination characteristics of individuals and variants in the PRDM9 gene and we identify new recombination hotspots. Comparisons of our maps with two LD-based maps inferred from data of HapMap populations of Utah residents with ancestry from northern and western Europe (CEU) and Yoruba in Ibadan, Nigeria (YRI) reveal population differences previously masked by noise and map differences at regions previously described as targets of natural selection.     

开放式渔业的最优管理

以目标泛函为基础,应用最大值原理讨论了开放式渔业的最优控制问题.进而得出了鱼群的最优种群密度和最优收获率h*;并进一步分析了贴现率对最优收获量的影响.最后应用了一个建立在Schaefer模型上的例子.     

开放式渔业的最优管理

以目标泛函为基础,应用最大值原理讨论了开放式渔业的最优控制问题．进而得出了鱼群的最优种群密度z^＊和最优收获率h^＊;并进一步分析了贴现率δ对最优收获量的影响．最后应用了一个建立在Schaefer模型上的例子．     

非损伤技术研究天山马鹿性别比与冬季家域

 利用5对微卫星对331 堆粪便进行个体识别,发现喀拉乌成山小渠子地区73 堆粪便来自32 头马鹿,白杨沟64 堆粪便来自28 头马鹿,哈密东天山国家森林公园的白石头地区87 堆粪便来自66 头马鹿,松树塘地区41 堆粪便来自32 头马鹿,寒气沟地区66 堆粪便来自42 头马鹿。利用SRY基因鉴定的天山马鹿雌雄比是1.78:1~2.89:1,粪便形态鉴定的结果是1.62:1~2.40:1,两种方法获得的结果无统计学差异。冬季雌雄马鹿家域范围分别是1.24~1.71 km²和1.02~1.57 km²,雌雄性家域范围差异不大,这是由天山马鹿自身习性决定的。