Expanded niche for white sharks.

Until the advent of electronic tagging technology, the inherent difficulty of studying swift and powerful marine animals made ecological information about sharks of the family Lamnidae difficult to obtain. Here we report the tracking of movements of white sharks by using pop-up satellite archival tags, which reveal that their migratory movements, depth and ambient thermal ranges are wider than was previously thought.     

菠菜性别差异NUPTs序列的克隆及分析

质体DNA向核基因组转移能够形成核质体DNA,核质体DNA序列的插入是推动动植物基因组及染色体组演化的重要动力.但是核质体DNA的插入和植物性染色体起源及演化之间的关系仍不清楚.以雌雄异株植物菠菜为材料,利用基因组消减杂交技术筛选分离菠菜雌雄基因组差异的NUPTs序列,并进行验证和分析.结果表明,从构建的菠菜消减杂交文库中共得到39条长度为75~308 bp的雌雄差异序列,其平均长度约为154 bp.对获得的序列进行Blastn同源比对发现了12条序列为叶绿体基因组来源序列,这些序列与菠菜叶绿体基因组相似度在98%以上,说明所获得的差异片段为核质体DNA序列.将筛选出的核质体DNA序列进行进一步验证后获得了两个稳定的长度分别为146 bp和199 bp的雄性偏好核质体DNA序列,说明所获得的两个NUPTs序列在菠菜雄性基因组中有更多的累积.     

Seed dispersal. Directed deterrence by capsaicin in chilies

The primary function of ripe, fleshy fruit is to facilitate seed dispersal by attracting consumers, yet many fruits contain unpleasant-tasting chemicals that deter consumption by vertebrates. Here we investigate this paradox in the chili (Capsicum) and find that capsaicin, the chemical responsible for the fruit's peppery heat, selectively discourages vertebrate predators without deterring more effective seed dispersers.     

Convergent evolution in mechanical design of lamnid sharks and tunas

The evolution of 'thunniform' body shapes in several different groups of vertebrates, including whales, ichthyosaurs and several species of large pelagic fishes supports the view that physical and hydromechanical demands provided important selection pressures to optimize body design for locomotion during vertebrate evolution. Recognition of morphological similarities between lamnid sharks (the most well known being the great white and the mako) and tunas has led to a general expectation that they also have converged in their functional design; however, no quantitative data exist on the mechanical performance of the locomotor system in lamnid sharks. Here we examine the swimming kinematics, in vivo muscle dynamics and functional morphology of the force-transmission system in a lamnid shark, and show that the evolutionary convergence in body shape and mechanical design between the distantly related lamnids and tunas is much more than skin deep; it extends to the depths of the myotendinous architecture and the mechanical basis for propulsive movements. We demonstrate that not only have lamnids and tunas converged to a much greater extent than previously known, but they have also developed morphological and functional adaptations in their locomotor systems that are unlike virtually all other fishes.     

Parents suppress reproduction and stimulate dispersal in opposite-sex juvenile white-footed mice.

Juvenile dispersal is sex-biased in many mammals and birds: one sex often disperses more often or farther than the other. Two hypotheses are generally presented for sex-biased dispersal. The first holds that juvenile dispersal reduces reproductive and/or resource competition between parents and same-sexed offspring. If so, presence of a parent on the natal home range should both promote dispersal of same-sex offspring and suppress reproduction of those that remain. The second is that juvenile dispersal reduces matings between parents and offspring, thus decreasing the likelihood of inbreeding depression. If so, presence of a parent should favour dispersal and reproductive suppression of offspring of the opposite sex. Here I present evidence that juvenile dispersal in white-footed mice, Peromyscus leucopus, is due to inbreeding avoidance. When population density was high, experimental removal of one parent delayed dispersal of opposite-sexed offspring and only the presence of the parents of opposite sex suppressed juvenile reproduction.     

2.5MaB.P.真马快速扩散事件在中国的表现

通过对甘肃庆阳巴家嘴第四系底部地层中发现的２种真马化石研究得出，其地质年龄为２．５Ｍａ Ｂ．Ｐ，是欧亚大陆发现最早真马化石的地点之一。认为：第四纪初真马从北美向欧亚大陆快速扩散的背景，是全球冰期气候的出现；中国与整个欧亚大陆一样，在一系列年龄为 ２． ５ Ｍａ Ｂ．Ｐ．的地点发现了最早的真马；这些化石显示出种级单元丰富的多样性，即在同一生态区域内常常同时有２种真马共同生活，还有三趾马共生；这是在气候突变条件下动物快速扩散事件产生的适应辐射，为区域叠覆成种理论提供了大型动物成种的证据。     

木本克隆植物中国沙棘种群林缘扩散规律研究

通过对中国沙棘林缘扩散过程和规律进行分析,揭示了中国沙棘的克隆生长过程.结果显示:中国沙棘以年龄最大的分株为中心向两侧实施克隆扩散,形成中间分株大、密度小以及越向两侧分株越小、密度越大的双向“阶梯式”种群外貌.然而,种群向两侧的扩散并不对称,其原因在于扩散过程受到土壤水分状况的影响.向土壤水分条件较好的一侧,林缘扩散种群以分株较大、密度较高为特征,克隆生长格局倾向于“聚集型”;向土壤水分较差的一侧,林缘扩散种群以分株较小、密度较低为特征,克隆生长格局倾向于“游击型”.由此表明在不同的土壤水分状况下,中国沙棘通过克隆生长调节形成与之相适应的克隆生长格局,即觅养对策.     

科学大家关于创新之问

 一些杰出的中国科学家,不仅取得了出色的科学成就,对中国的科技与教育发展也极为关切。在专业研究之外,在科学与社会之间,他们同样遗留下了丰富的思想遗产。以“科学大家关于创新之问”为视角,梳理了彭桓武、杨振宁、周光召、郝柏林、李政道、冯端等几位著名科学家围绕中国科技创新话题所做的深思与探索。     

Diversity and dispersal interactively affect predictability of ecosystem function

Theory and small-scale experiments predict that biodiversity losses can decrease the magnitude and stability of ecosystem services such as production and nutrient cycling. Most of this research, however, has been isolated from the immigration and emigration (dispersal) processes that create and maintain diversity in nature. As common anthropogenic drivers of biodiversity change--such as habitat fragmentation, species introductions and climate change--are mediated by these understudied processes, it is unclear how environmental degradation will affect ecosystem services. Here we tested the interactive effects of mobile grazer diversity and dispersal on the magnitude and stability of ecosystem properties in experimental seagrass communities that were either isolated or connected by dispersal corridors. We show that, contrary to theoretical predictions, increasing the number of mobile grazer species in these metacommunities increased the spatial and temporal variability of primary and secondary production. Moreover, allowing grazers to move among and select patches reduced diversity effects on production. Finally, effects of diversity on stability differed qualitatively between patch and metacommunity scales. Our results indicate that declining biodiversity and habitat fragmentation synergistically influence the predictability of ecosystem functioning.     

Strong effect of dispersal network structure on ecological dynamics

A central question in ecology with great importance for management, conservation and biological control is how changing connectivity affects the persistence and dynamics of interacting species. Researchers in many disciplines have used large systems of coupled oscillators to model the behaviour of a diverse array of fluctuating systems in nature. In the well-studied regime of weak coupling, synchronization is favoured by increases in coupling strength and large-scale network structures (for example 'small worlds') that produce short cuts and clustering. Here we show that, by contrast, randomizing the structure of dispersal networks in a model of predators and prey tends to favour asynchrony and prolonged transient dynamics, with resulting effects on the amplitudes of population fluctuations. Our results focus on synchronization and dynamics of clusters in models, and on timescales, more appropriate for ecology, namely smaller systems with strong interactions outside the weak-coupling regime, rather than the better-studied cases of large, weakly coupled systems. In these smaller systems, the dynamics of transients and the effects of changes in connectivity can be well understood using a set of methods including numerical reconstructions of phase dynamics, examinations of cluster formation and the consideration of important aspects of cyclic dynamics, such as amplitude.