关键词： Dermosimii   Eutheria   Mammalia   phylogeny   primate paraphyly  

摘要： The strict orthology of mitochondrial (mt) coding sequences has promoted their use in phylogenetic analyses at different levels. Here we present the results of a mitogenomic study (i.e., analysis based on the set of protein-coding genes from complete mt genomes) of 60 mammalian species. This number includes 11 new mt genomes. The sampling comprises all but one of the traditional eutherian orders. The previously unrepresented order Dermoptera (flying lemurs) fell within Primates as the sister group of Anthropoidea, making Primates paraphyletic. This relationship was strongly supported. Lipotyphla ("insectivores") split into three distinct lineages: Erinaceomorpha, Tenrecomorpha, and Soricomorpha. Erinaceomorpha was the basal eutherian lineage. Sirenia (dugong) and Macroscelidea (elephant shrew) fell within the African clade. Pholidota (pangolin) joined the Cetferungulata as the sister group of Carnivora. The analyses identified monophyletic Pinnipedia with Otariidae (sea lions, fur seals) and Odobenidae (walruses) as sister groups to the exclusion of Phocidae (true seals).

关键词： bird   frog   grazing   impact   mammal   rangeland   reptile  

摘要： Despite the hegemony of pastoralism over most of Australia's tropical savannas, its impacts upon biodiversity are poorly known. There is even less knowledge about the impacts of military training, a recent, but rapidly expanding, alternative land use. We compare impacts of these land uses upon mammals, birds, reptiles and frogs at a site in north-eastern Australia, with sampling from 24 quadrats stratified by four landscape positions (upper slope to riparian) and three current land-use types (pastoralism, military training and undisturbed). Prior to exclusion in 1967, the whole study area had been subjected to grazing over the course of approximately 100 years, so differences observed strictly reflect responses to changed land use (largely cessation from grazing) over the period of 32 years subsequent to the imposition of the present regime. The four classes of vertebrates showed contrasting responses. Frog distribution was unrelated to land use, but strongly associated with landscape position. Reptiles showed a very strong response to land-use type but not to landscape position. The total abundance and richness of reptiles was greater in ungrazed (i.e. military and undisturbed) than in grazed quadrats. The total abundance and species richness of birds varied strongly with landscape position but was unrelated to land use. However, many individual bird species showed significant responses to land-use type, and bird species composition was significantly related to both land-use type and landscape position. The richness of the mammal fauna was weakly related to landscape position and not related to land-use type. A few individual mammal species showed significant responses to either or both factors, but mammal species composition was significantly (albeit weakly) related only to land-use type. With due regard to some interpretative constraints in the study design, and the history of the site prior to this study, these results suggest that pastoralism leads to a substan

关键词： induced defenses   condensed tannins   Acacia   mammalian herbivory   ants   mutualism  

摘要： Condensed tannins have been considered to be important inducible defenses against mammalian herbivory. We tested for differences in condensed tannin defenses in Acacia drepanolobium in Kenya over two years among different large mammalian herbivore treatments [total exclusion, antelope only, and megaherbivore (elephants and giraffes) + antelope] and with four different ant symbiont species on the trees. We predicted that (1) condensed tannin concentrations would be lowest in the mammal treatment with the lowest level of herbivory (total exclusion), (2) trees occupied by mutualist ants that protect the trees most aggressively would have lower levels of tannins, and (3) if chemical defense production is costly, there would be a trade-off between tannin concentrations, growth, and mechanical defenses. Mean tannin concentrations increased from total exclusion treatments to wildlife-only treatments to megaherbivore + antelope treatments. In 1997, condensed tannin concentrations were significantly lower in trees occupied by the ant Crematogaster nigriceps, the only ant species that actively removed axillary buds. Contrary to our prediction, trees occupied by ant species that protect the trees more aggressively against mammalian herbivores did not have lower overall levels of condensed tannins. There was no consistent evidence of a trade-off between tannin concentrations and growth rate, but there was a positive correlation between mean thorn length and mean tannin concentrations across species of ant inhabitants and across herbivore treatments in 1997. Contrary to our expectation, trees had higher tannin concentrations in the upper parts of the canopy where there is little herbivory by mammals.

关键词： 乙型肝炎表面抗原   中草药   体外试验   树Ju  

摘要： 目的 :筛选具有抑制乙型肝炎表面抗原 (HBs Ag)活性的中草药。方法 :体外试验采用反向间接血凝法 ,动物实验采用本室自己建立的乙型肝炎树鼠句感染模型。结果 :通过体外试验 ,从 2 0 0种常用中草药中筛选出具有较明显抑制 HBs A活性的 5种药物 ,它们分别是珍珠草 (叶下珠 )、桑椹子、五倍子、丹参和仙茅 ,这 5种药物可使 HBs Ag滴度从 1∶ 32 76 8降至1∶ 16。进一步在树鼠句体内进行抗乙肝病毒抑制试验 ,仅有珍珠草和五倍子有清除 HBs Ag的作用。结论 :体外实验及动物实验均表明珍珠草及五倍子有较强抗 HBs Ag作用 。

关键词： escape hypothesis   frugivory   granivory   Procyon lotor   seed predation  

摘要： The Janzen-Connell escape hypothesis predicts that the success of tree propagules increases with distance from the parent tree. Fleshy fruits that are transported in the guts of frugivores are believed to have evolved to facilitate the wide dispersal of seeds. However, some fragivores deposit seeds in latrines, thus creating aggregations of seeds that are large enough to attract seed predators and negate the advantages of dispersal. Raccoons (Procyon lotor) often produce large seed deposits since they habitually defecate in latrines. The survival of wild black cherry (Prunus serotina) seeds in simulated raccoon latrines was monitored in areas with natural levels of food availability and in areas to which supplemental food had been supplied to the primary seed predators. Dispersal of seeds by raccoons did not necessarily provide effective protection from post-dispersal seed predation at natural food levels. Once the resident seed predators had located the latrines, the majority of the seeds were quickly removed. However, seed removal from raccoon latrines was reduced significantly and dramatically by the addition of alternative food. This implies that raccoon latrines may represent safe sites for tree recruitment during periods of high food availability such as during masting events, thus providing conditional support for the escape hypothesis.

关键词： 澳洲   澳大利亚   大洋洲   袋鼠   动物  

摘要： 澳大利亚的天气很特别,很难见到连天的阴雨。有时虽有阵骤风暴雨,可很快雨过天晴,阳光普照,百鸟争鸣了。我后来才知道,澳大利亚地靠南极,四边大洋,山多低矮,气候干燥,阳光充足是世界闻名。特别是季节变化和动、植物的特异更使海外游人吃惊。正像二百多年前一位英国移民在家信中所云.“这里简直是一个不可思议的地方。动物不是走而是跳,树木不落叶子光掉皮。更奇妙的是这里的圣诞节,居然不在寒冬而在酷热的夏天。”客店虽然布置得冰天雪地,而街上却有摄氏三十多度,少女们赤背在路上吃冰淇淋,海滨浴场更是人山人海。澳洲真是个奇妙的大陆。

关键词： HPA axis   Clomipramine   Diazepam   Cortisol   Behaviour   Drug metabolism  

摘要： To improve our knowledge of the causal mechanisms of stress-related disorders such as depression, we need animal models that mirror the situation in patients. One promising model is the chronic psychosocial stress paradigm in male tree shrews, which is based on the territorial behaviour of these animals that can be used to establish naturally occurring challenging situations under experimental control in the laboratory. Co-existence of two males in visual and olfactory contact leads to a stable dominant-subordinate relationship, with subordinates showing distinct stress-induced behavioural and neuroendocrine alterations that are comparable to the symptoms observed during episodes of depression in patients such as constantly elevated circulating glucocorticoid hormones due to a chronic hyperactivity of the hypothalamic-pituitary-adrenal axis. To elucidate whether the chronic psychosocial stress model in tree shrews besides its "face validity" for depression also has "predictive validity", we treated subordinate tree shrews with the tricyclic antidepressant clomipramine and found a time-dependent restoration of both endocrine and behavioural parameters. In contrast, the anxiolytic diazepam was ineffective. Although the chronic psychosocial stress model in tree shrews requires further validation, it has sufficient face, predictive, and construct validity to become an interesting non-rodent model for research on the etiology and pathophysiology of depression.

关键词： FRUGIVORES   FRAGMENTED landscapes   EXTINCTION (Biology)  

摘要： We investigated the effects of forest fragmentation on the disappearance of fruit-eating animals and the recruitment of animal-, wind-, and gravity-dispersed trees in 80-year-old forest patches in the East Us- ambara Mountains of Tanzania. We compared adult and juvenile trees in forest transects in a 3500-ha submontane forest with those in four forest fragments of 521,30,9, and 0.5 ha. Preliminary results show that recruitment of seedlings and juveniles of 31 animal-dispersed tree species was more than three times greater in continuous forest and large forest fragments (greater than or equal to 30 ha) than in small forest fragments (less than or equal to 59 ha), whereas recruitment of eight wind- and gravity-dispersed trees of the forest interior was unaffected. Recruitment of 10 endemic, animal-dispersed tree species was 40 times lower in small fragments than in continuous forest or large fragments. Counts of diurnal primates and birds in all five sites indicated that frugivorous species have declined with decreasing fragment size. These results are consistent with the idea that loss of dispersal agents depresses tree recruitment in the course of forest fragmentation.

关键词： Acacia   seedlings   elephants   fire   ungulates   Botswana  

摘要： Acacia erioloba woodlands provide important forage and shade for wildlife in northern Botswana. Mortality of mature trees caused by browsing elephants has been well documented but the lack of regeneration of new trees has received little attention. Annual growth of new shoots and changes in height were measured to determine the influence of elephants and small ungulate browsers, rainfall and fire on the growth and survival of established A. erioloba seedlings from 1995 to 1997 in the Savuti area of Chobe National Park. All above-ground vegetation was removed from 40% of established seedlings in 1995 and 28% in 1997 by browsing elephants, and the mean height of remaining seedlings decreased from >550 mm to <300 mm. When seedlings browsed by kudu, impala and steenbok but not elephants are considered, mean seedling height increased <50 mm per year, even though mean new shoot growth remaining at the end of the dry season was 100-200 mm. Fires burned portions of the study area in 1993 and 1997, killing above-ground vegetation, but most established A. erioloba seedlings survived, producing coppice growth from roots. While elephants and fire caused the greatest reduction in established seedling height and number, small browsers suppressed growth, keeping seedlings vulnerable to fire and delaying growth to reproductive maturity.

关键词： granivory   herbivory   keystone species   Microtus pennsylvanicus   New York State   old-field succession   Peromyscus leucopus   plant-herbivore interactions   rodents   seed vs. seedling predation   seedling establishment   tree invasion  

摘要： Despite many observations of herbivores and granivores influencing the survival of tree seeds and seedlings, the net effects of these consumers on plant succession remain unclear. We used both experimental herbivore manipulations and observations of changes in vegetation cover to evaluate the longer-term impacts of small-mammal herbivores and granivores on woody plant invasion into old fields in New York State. Over a 5-yr period, we manipulated the density of meadow voles (Microtus pennsylvanicus) within partial enclosures replicated at five study sites. Average vole activity in enclosures with high vole density was significantly greater than that in enclosures with low vole density. In contrast, activity of competitively inferior white-footed mice (Peromyscus leucopus) was significantly greater within enclosures designated as low vole density. Colonization by tree seedlings, as well as shrubs and vines. was significantly greater in enclosures under the low vole density treatment. Further, tree seedling abundance was higher in shrub-dominated enclosures with low vole, but high mouse, activity. Five years of contrasting mouse and vole activity within adjacent enclosures revealed that seedling predation by voles had a greater net effect on changes in woody vegetation cover in old fields than did seed predation by mice, despite studies reporting higher rates of seed vs. seedling predation in these areas. We conclude that short-term measures of predation intensity may not accurately predict the longer-term effects of small-mammal herbivores on vegetation dynamics and suggest that voles may be a keystone herbivore in old-field succession.