关键词： SAVANNA ecology   HERBIVORES   ECOLOGY   LANDSCAPES  

摘要： Areas within regional landscapes that make a disproportionate contribution to supporting large herbivore populations have been interpreted as key resource areas, hotspots, buffers, stepping stones or serving other functional roles. We investigated the role that the restricted extent of habitat types exploited at different stages of the seasonal cycle might play in limiting the abundance of a blue wildebeest subpopulation in the Kruger National Park, South Africa. GPS collars enabled the space use patterns of the animals to be related to available habitat types, and faecal nutrient concentrations to be related to the habitats exploited at that time. Wildebeest herds occupied primarily grazing lawn grasslands associated with gabbro uplands or sodic lowlands through the wet season into the early dry season. During the late dry season, they switched to seep-zone grasslands in mid slope regions of granitic landscapes. Use of recently burned areas enhanced forage quality at the beginning of the wet season. The seasonal habitat shifts enabled wildebeest to obtain adequate nitrogen, phosphorus and sodium throughout the year. Lawn and seep-zone grasslands combined constituted 10% of the available area. Grazing lawns, which encompassed only 3% of the study area, appeared to be the primary limitation on the abundance of wildebeest. However, the greater security from predation provided by the open vegetation cover in the grazing lawns is not easily disentangled from the resource benefits that they yield. Nevertheless, findings indicate how local abundance can be restricted by the extent of portions of the landscape providing crucial benefits during particular phases of the seasonal cycle. Hence the key resources concept needs to be expanded to accommodate the functionally distinct contributions made by different habitats towards supporting local herbivore populations.

关键词： 树鼩   肝脏疾病   动物模型  

摘要： 肝病的危害,尤其是肝炎的流行以及肝癌的高死亡率已经成为国内外共同关注的重要卫生问题之一,由于缺乏理想的动物模型,某些肝炎及肝癌目前尚未清楚其发病的生理学机制,为了寻找有效的防治方法,建立合适的动物模型显得极其重要。树鼩在医学研究中的价值近年来受到越来越多的关注。国内外的研究发现,人们利用树鼩成功建立了多种肝脏疾病的动物模型,多数研究集中在人类病毒性肝炎及肝癌方面。本文主要介绍肝脏疾病树鼩动物模型的国内外新进展。

关键词： 实验动物   树鼩   疾病动物模型   灵长类动物   种属差异   药靶  

摘要： 创新药物的研发依赖优良的实验动物和疾病动物模型。中科院昆明动物所的科技人员最近研究发现,树鼩作为新型实验动物在特定药物研发中有着独特优势。目前药物研发中广泛使用啮齿类动物(大鼠,小鼠),由于与人种属差异较大,获得的研究结果经常与人相距甚远,造成药物研发在大量投入后的最终失败。树鼩是灵长类动物的近亲。

关键词： Arthropods   Biodiversity   Ecosystem function   Herbivore control   Identity effects   Spiders  

摘要： Stand diversification increasingly emerges as a promising means for improving the multi-functionality and sustainability of management in plantation forests. Increasing tree species richness might potentially also benefit natural enemies, which can substantially contribute to sustainable forest management via top-down control of forest pests. However, there is little empirical evidence on how tree species richness affects the diversity and abundance of predators, as the majority of analyses to date have rarely gone beyond comparisons of monocultures and two species mixtures. Here, we analyzed the performance of spiders as important generalist predators in a tree diversity experiment that uses four of the economically most important broadleaved and coniferous tree species in Europe. We tested the extent to which tree species richness and the identity of the planted tree species affect the abundance, biomass, species richness and functional diversity of spiders. Whereas tree species richness in general had no significant effect, tree species identity strongly affected spider biomass and abundance-with a particularly strong negative effect of the non-native Douglas fir (Pseudotsuga menziesii (Mirb.) Franco). Our results indicate that increasing tree species richness does not necessarily promote characteristics of natural enemy assemblages relevant for pest control in forests and thus not all functions that may be important in a multi-functional management context. Rather, tree species composition and identity will often be of crucial importance in determining forest ecosystem functions and services. The fact that the severe impact of Douglas fir persisted even in diversified tree species mixtures suggests that stand-level predator efficiency can be reduced for tree species growing adjacent to or in mixture with this species. This calls for a more thorough examination of the ecological consequences of the increasing use of this species in forestry across Europe, in part

关键词： functional heterogeneity   grazers   Kruger National Park   microclimates   plant-available nutrients   plant-soil (below-ground) interactions   resource limitation   spatial heterogeneity  

摘要： 1. Savannas are highly heterogeneous tree-grass mixtures, and the structural variation imposed by a discontinuous canopy cover results in spatial variation in soil properties such as plant-available nutrients, temperature and soil moisture. Many savannas are also dominated by large vertebrate herbivores, which impose a different suite of effects on soil properties related to consumption, excretion and physical disturbance. 2. In nutrient-poor, water-limited systems, variation in soil resource availability may play a fundamental role in structuring plant communities, but the relative and interactive effects of key drivers of heterogeneity have received little attention in savanna ecosystems. 3. We investigated the independent and interactive effects of herbivores and tree canopy cover on multiple soil properties up to a depth of 10 cm, including bulk density, soil C pools, total and plant-available nutrients, moisture dynamics and temperature at two contrasting sites in Kruger National Park, South Africa. We analysed samples from locations under and between adult tree canopies and inside and outside long-term herbivore exclosures using a nested design. 4. We found strong positive effects of tree canopies on total and labile pools of soil C and N and negative effects on plant-available P and soil temperature. Tree canopy effects on soil moisture availability were small but clearly detectable. During precipitation events, trees increased moisture inputs on granite soils but decreased moisture inputs on basalt soils compared to open sites. 5. Conversely, we found mixed evidence for herbivore effects on soil chemistry and temperature, but a clearer effect on soil moisture, with areas outside exclosures experiencing higher soil moisture retention, particularly immediately following precipitation events. Soil bulk density, a driver of both nutrient and soil moisture dynamics, was lower under trees and when herbivores were excluded. 6. Synthesis. Our results suggest that va

关键词： agricultural landscape   central place   home range   multinomial logit model   semi-arid  

摘要： Understanding factors that influence habitat selection in heterogeneous landscapes is fundamental for establishing realistic models on animal distribution to inform rangeland management. In this study, we tested whether seasonal variation in habitat selection within the home range of a large herbivore was influenced by constraints such as, distances from water and central place using semi-free range cattle (Bos taurus) as a case study. We also tested whether shifts in space use over time were dependent on spatial scale and on the overall abundance of resources. We predicted that distance from water significantly influenced dry season habitat selection while the influence of the central place on habitat selection was season-independent. We also predicted that shifts in space use over time were spatial scale-dependent, and that large herbivores would include more diverse habitats in their home ranges during the dry season, when water and food resources are less abundant. Multinomial logit models were used to construct habitat selection models with distances from water and central place as habitat-specific constraints. Results showed significant variations in habitat selection between the dry and wet season. As predicted, the effect of distance from central place was season-independent, while the effect of water was not included in the top dry season models contrary to expectation. A diverse range of habitats were also selected during the dry season including agricultural fields. Results also indicated that shifts in space use were spatial scale dependent, with core areas being more sensitive to changes than the home range. In addition, shifts in space use responded to temporal changes in habitat composition. Overall, our results suggest that semi-free range herbivores adopt different foraging strategies in response to spatial-temporal changes in habitat availability.

关键词： Crocuta crocuta   Leptailurus serval   lion   Odzala-Kokoua   Panthera leo   Republic of Congo   serval   spotted hyena  

摘要： The catchment of the Congo River basin contains an extensive forest-savanna mosaic, which once harbored significant populations of lions (Panthera leo), African wild dogs (Lycaon pictus), and spotted hyenas (Crocuta crocuta). The mosaic's northern part, stretching across the Republic of Congo and southern Gabon, is today geographically isolated. Uncontrolled hunting has led to a gradual decrease in its ungulate populations, and today African wild dogs are considered extinct within the Congo Basin. Lions and spotted hyenas suffered an extreme collapse of their respective former ranges, and in the Republic of Congo both species are believed to survive exclusively in the Odzala-Kokoua National Park (OKNP). We surveyed all extensive savanna areas within this park, to determine the current status of savanna carnivores. We conducted 460 km of track searches on foot, and operated 25 remote camera traps across the survey area over 424 trap-days. We detected no sign of lion presence in the park. Spotted hyena tracks were widespread, and our camera traps recorded 154 hyena photographs, representing 46 different individuals. We also recorded leopard (Panthera pardus), serval (Leptailurus serval), and African golden cat (Caracal aurata) within the survey area. Although lions are likely extinct in the Republic of Congo and neighboring Gabon, our results highlight the importance of OKNP for the regional conservation of spotted hyenas and smaller savanna carnivores.

关键词： MAMMALS -- Research   SAVANNA animals   RESEARCH   MAMMAL ecology   BIRDS of prey   SAVANNA ecology  

摘要： Little is known about the dynamics of small mammals in tropical savanna: a critical gap in our understanding of Africa's best known ecosystems. Historical evidence suggested small mammals peak in abundance (outbreak) in Serengeti National Park (SNP), as in agricultural systems. We asked 1) what are bottom-up drivers of small mammals and 2) do predators have top-down effects? We documented dynamics of small mammals, birds of prey, and mammalian carnivores in SNP and agricultural areas. We used climatic fluctuations and differences between unmodified and agricultural systems as perturbations to examine trophic processes, key to understanding responses to climate change and increasing human pressures. Data were derived from intermittent measures of abundance collected 1968-1999, combined with systematic sampling 2000-2010 to construct a 42-year time series. Data on abundance of black-shouldered kites (1968-2010), eight other species of rodent-eating birds (1997-2010), and 10 carnivore species (1993-2010) were also collated. Outbreaks occurred every 3-5 years in SNP, with low or zero abundance between peaks. There was a positive relationship between rainfall in the wet season and 1) small mammal abundance and 2) the probability of an outbreak, both of which increased with negative Southern Oscillation Index values. Rodent-eating birds and carnivores peaked 6-12 months after small mammals. In agricultural areas, abundance remained higher than in natural habitats. Abundances of birds of prey and mammalian carnivores were extremely low in these areas and not related to small mammal abundance. Small mammals are an important food resource for higher trophic levels in the Serengeti ecosystem. Changes in climate and land use may alter their future dynamics, with cascading consequences for higher trophic levels, including threatened carnivores. Although outbreaks cause substantial damage to crops in agricultural areas, small mammals also play a vital role in maintaining some of

关键词： Metazoa   phylogeny   body plan   scenario  

摘要： A renewed emphasis on the gaps in organization that exist between the crown-group body plans of higher-level animal taxa is a hallmark of the emerging consensus in metazoan phylogenetics. Bridging these gaps is the greatest hurdle that stands in the way of translating our knowledge of phylogeny into a renewed understanding of the macroevolution of animal body plans. Unless a good fossil record is available, there is little hope that we will be able to bridge many of these gaps empirically. We have, therefore, little choice but to resort to our more-or-less informed imagination to produce the historical narratives that are the ultimate goal of our studies of animal evolution. Only by fully engaging with the challenges of devising testable scenarios will we be able to tell where along the spectrum of science and fiction our understanding of animal body plan evolution will finally come to rest.

关键词： carbon   Cerrado   Desmodus rotundus   food chain   nitrogen  

摘要： Carbon and nitrogen stable isotopes were used to track major dietary variations in arthropods found in a cave located in a neotropical savanna in Central Brazil. We determined the delta C-13 and delta N-15 for cave crickets, cockroaches, spiders, guano of a hematophagous bat, and leaf litter found on the ground near the cave entrance. The delta C-13 and delta N-15 for the cricket and cockroaches showed that bat guano was not the only food item for these arthropods. They had intermediate delta C-13 and delta N-15 between bat guano and leaf litter, which means that they consumed additional food resources other than guano in their diet, independent of distribution of guano deposits in the cave. The spiders, predators with great mobility, seemed to not have a preferential diet item since their isotope signals indicated they hunt both crickets and cockroaches. The delta C-13 of the bat guano (-15.4 parts per thousand) indicated that the diet of these hematophagous bats relied on animals fed with C-4 plants. The conversion of native savanna vegetation of which the debris is mostly from C-3 plants, to pasture, based on C-4 African grass, a remarkably common land use transformation in the region, is indirectly influencing the diet of hematophagous bats, which basically relied on exotic fauna. The C and N stable isotope ratios showed that the arthropods inside the cave do not rely solely on bat guano for their diet, but interact directly with the external environment, through litter debris, indicating a significant exchange of energy and matter between the cave environment and the surrounding area.