Comment on "Impacts of the Cretaceous Terrestrial Revolution and KPg extinction on mammal diversification"

Meredith et al. (Reports, 28 October 2011, p. 521) question three findings of our delayed-rise hypothesis for present-day mammals made with reference to the Cretaceous-Paleogene (KPg) boundary, based on their new time tree of the group. We show that their own data do not support their objections and that the macroevolutionary patterns from the respective phylogenies are not statistically different.     

A Late Jurassic digging mammal and early mammalian diversification

A fossil mammal from the Late Jurassic Morrison Formation, Colorado, has highly specialized teeth similar to those of xenarthran and tubulidentate placental mammals and different from the generalized insectivorous or omnivorous dentitions of other Jurassic mammals. It has many forelimb features specialized for digging, and its lumbar vertebrae show xenarthrous articulations. Parsimony analysis suggests that this fossil represents a separate basal mammalian lineage with some dental and vertebral convergences to those of modern xenarthran placentals, and reveals a previously unknown ecomorph of early mammals.     

An Early Cretaceous tribosphenic mammal and metatherian evolution

Derived features of a new boreosphenidan mammal from the Lower Cretaceous Yixian Formation of China suggest that it has a closer relationship to metatherians (including extant marsupials) than to eutherians (including extant placentals). This fossil dates to 125 million years ago and extends the record of marsupial relatives with skeletal remains by 50 million years. It also has many foot structures known only from climbing and tree-living extant mammals, suggesting that early crown therians exploited diverse niches. New data from this fossil support the view that Asia was likely the center for the diversification of the earliest metatherians and eutherians during the Early Cretaceous.     

Multiple causes of high extinction risk in large mammal species

Many large animal species have a high risk of extinction. This is usually thought to result simply from the way that species traits associated with vulnerability, such as low reproductive rates, scale with body size. In a broad-scale analysis of extinction risk in mammals, we find two additional patterns in the size selectivity of extinction risk. First, impacts of both intrinsic and environmental factors increase sharply above a threshold body mass around 3 kilograms. Second, whereas extinction risk in smaller species is driven by environmental factors, in larger species it is driven by a combination of environmental factors and intrinsic traits. Thus, the disadvantages of large size are greater than generally recognized, and future loss of large mammal biodiversity could be far more rapid than expected.     

气候变化对青藏高原陆地生态系统的影响研究进展

气候变化对陆地生态系统的影响及其反馈是当前全球变化研究的重要内容,青藏高原是全球气候变化的敏感区和启动区,气候变化对青藏高原陆地生态系统的影响是当前全球气候变化的重要研究领域。系统总结了目前关于气候变化对青藏高原陆地生态系统的影响与反馈的相关研究,最后根据当前研究中存在的问题,讨论了未来的研究方向。     

Sudden extinction of the dinosaurs: latest Cretaceous, upper Great Plains, USA

Results of a three-year field study of family-level patterns of ecological diversity of dinosaurs in the Hell Creek Formation of Montana and North Dakota show no evidence (probability P < 0.05) of a gradual decline of dinosaurs at the end of the Cretaceous. Stratigraphic reliability was maintained through a tripartite division of the Hell Creek, and preservational biases were corrected for by comparison of results only from similar fades as well as through the use of large-scale, statistically rigorous survey and collection procedures. The findings are in agreement with an abrupt extinction event such as one caused by an asteroid impact.     

河北承德地区哺乳动物区系研究

1993年3月至2001年10月对承德地区哺乳动物资源进行了调查研究,共查明哺乳动物53种,隶属于7目17科40属,其中占北种28种,东洋种4种,广布种21种,占河北省哺乳动物总数的67．9％。其中国家二级保护哺乳动物1种,国家二级保护种类7种,河北省保护种类19种,该地区分布有河北省仅存的野生马鹿种群。     

哺乳动物卵巢移植研究进展

随着器官移植及冷冻保存技术的发展,卵巢移植近年来成为生殖生物学、生殖医学的研究热点.研究表明,新鲜或冻存卵巢移植后其功能可恢复,并能保持较长时间的功能.文章就卵巢移植的历史、依据、技术及存在的问题和发展前景进行了综述.     

Costs and the diversification of exaggerated animal structures

Sexual selection can favor production of extravagant ornaments and weapons in the contest for access to the opposite sex. Existing explanations for the diversity of sexually selected structures focus on reproductive benefits conferred by particular ornament or weapon morphologies. Here, I show that costs of weapon production also may drive patterns of weapon evolution. In beetles, production of horns reduces the size of neighboring morphological structures (antennae, eyes, or wings, depending on the location of the horns), and these tradeoffs reveal unexpected functional associations between ecology and horn morphology. This study illustrates a critical but overlooked role of costs in sexual selection and has implications for understanding the evolution of animal morphology.     

云南省危害烟草陆生贝类的调查研究

 对云南省27个市、县进行了危害烟草的陆生贝类(蜗牛和蛞蝓)的调查研究。获得1纲2亚纲2目8科15属21种的标本153号。制订出云南省危害烟草陆生贝类的分科检索表,描述了21种烟草害螺的形态、分布和危害,并提出综合防治措施。     

An aegialodontid upper molar and the evolution of mammal dentition

The most obvious key synapomorphy of the therian mammals is the tribosphenic pattern of their molars. Tribosphenic teeth are capable of both shearing and grinding, which substantially increase effectiveness of food processing and, in turn, permit evolution of a wide range of dietary specializations. Functional tribospheny developed repeatedly during mammalian evolution but was successful only in the Boreosphenida. The earliest stage in the development of boreosphenidan tribospheny has remained poorly understood, being documented only by lower molars of aegialodontids. Here, we report a known upper molar of an aegialodontid mammal, Kielantherium, from the Early Cretaceous of Mongolia.     

Mammal population losses and the extinction crisis

The disappearance of populations is a prelude to species extinction. No geographically explicit estimates have been made of current population losses of major indicator taxa. Here we compare historic and present distributions of 173 declining mammal species from six continents. These species have collectively lost over 50% of their historic range area, mostly where human activities are intensive. This implies a serious loss of ecosystem services and goods. It also signals a substantial threat to species diversity.     

Nonrandom extinction and the loss of evolutionary history

The hierarchical nature of phylogenies means that random extinction of species affects a smaller fraction of higher taxa, and so the total amount of evolutionary history lost may be comparatively slight. However, current extinction risk is not phylogenetically random. We show the potentially severe implications of the clumped nature of threat for the loss of biodiversity. An additional 120 avian and mammalian genera are at risk compared with the number predicted under random extinction. We estimate that the prospective extra loss of mammalian evolutionary history alone would be equivalent to losing a monotypic phylum.     

Lancefield swamp and the extinction of the Australian megafauna

Excavations into the Australian swamp of Lancefield show that a bone bed dated at 26,000 years ago contains perhaps 10,000 giant extinct animals. Associated artifacts suggest that humans were in the area, but the direct cause of death of the animals is, on present evidence, not explicable. Such a recent date for the classic megafauna shows that it was living together with humans for at least 7000 years in southeast Australia. This enduring association argues against a catastrophic and rapid overkill in the Australian Pleistocene.     

水电站开发对陆生动植物的影响及保护建议

水电站开发在解决能源问题、促进经济发展的同时,给库区的陆生动植物带来了深远的影响.对水电站开发对流域内陆生动植物的影响进行了阐述,并提出了生态影响削减和恢复的几点建议,以期为水电站开发提供理论依据.     

Avian extinction and mammalian introductions on oceanic islands

The arrival of humans on oceanic islands has precipitated a wave of extinctions among the islands' native birds. Nevertheless, the magnitude of this extinction event varies markedly between avifaunas. We show that the probability that a bird species has been extirpated from each of 220 oceanic islands is positively correlated with the number of exotic predatory mammal species established on those islands after European colonization and that the effect of these predators is greater on island endemic species. In contrast, the proportions of currently threatened species are independent of the numbers of exotic mammalian predator species, suggesting that the principal threat to island birds has changed through time as species susceptible to exotic predators have been driven extinct.     

哺乳动物胚胎干细胞研究进展

胚胎干细胞(embryonic stem cells, ES)是指从桑椹胚或附植前囊胚内细胞团分离的多潜能细胞,它具有体外培养无限增殖、自我更新和多向分化的特性。无论在体外还是体内环境,ES细胞都能被诱导分化为机体几乎所有的细胞类型。自1981年Evans和Kaufman首次成功分离小鼠ES细胞,国内外研究人员已在仓鼠、大鼠、兔、猪、牛、绵羊、山羊、水貂、恒河猴、美洲长尾猴以及人类都分离获得了ES细胞,而且已经证明小鼠ES细胞可以分化为心肌细胞、造血细胞、卵黄囊细胞、骨髓细胞、平滑肌细胞、脂肪细胞、软骨细胞、成骨细胞、内皮细胞、黑素细胞、神经细胞、神经胶质细胞、少突胶质细胞、淋巴细胞、胰岛细胞、滋养层细胞等。人类ES细胞也可以分化为滋养层细胞、神经细胞、神经胶质细胞、造血细胞、心肌细胞等。ES细胞不仅可以作为体外研究细胞分化和发育调控机制的模型,而且还可以作为一种载体,将通过同源重组产生的基因组的定点突变导入个体,更重要的是,ES细胞将会给人类移植医学带来一场革命。