关键词： Agriculture   Cattle ranching   Cropland   Fire   Shrub/woody encroachment  

摘要： Grasslands and savannas are among the most degraded biomes in the world. These biomes face a diverse number of anthropogenic threats, and despite this scenario, little attention is given to their conservation and sustainable use. This meta-analysis aims to analyze the effect of anthropogenic activities on the abundance of native mammals in these grassy ecosystems. A systematic research in the literature was carried out in order to find studies that analyzed variations in abundance of mammals in response to an anthropogenic activity in any grassland, savanna or shrubland environment around the world. After filtering, 24 studies were analyzed, generating 202 effect sizes for five anthropogenic factors: cropland activities (32 effect sizes - ES);cattle ranching (58 ES);fire (30 ES);shrub/woody encroachment (56 ES) and urbanization (26 ES). Analyzed papers included field data from all continents. In general, mammalian abundance is decreasing under anthropogenic disturbance, as shown by the general effect size. This result highlights the need for more intense conservation programs in grasslands and savannas, since its species are under threat. When comparing the different anthropogenic threats, only cropland activities affected mammals significantly, reducing their abundance. The estimate of the mean effect of cattle ranching, fire, shrub/woody encroachment and urbanization on abundance of mammals did not differ from zero. However, for cattle ranching, fire and shrub/woody encroachment the mean effects measured had large confidence intervals, indicating that these mean effects could not be estimated accurately. Cattle ranching, fire and shrub/woody encroachment effects on mammalian abundance probably depend on their intensity and on the environmental characteristics of each ecosystem, and therefore each case must be analyzed in an ecosystem-specific perspective. Urbanization did not affect mammals, although this anthropogenic activity was analyzed only in two ecosystems

关键词： Aging   Comparative biology   Complexity   Disposable soma   Diversity   Model organism  

摘要： Use of model organisms in aging research is problematic because our ability to extrapolate across the tree of life is not clear. On one hand, there are conserved pathways that regulate lifespan in organisms including yeast, nematodes, fruit flies, and mice. On the other, many intermediate taxa across the tree of life appear not to age at all, and there is substantial variation in aging mechanisms and patterns, sometimes even between closely related species. There are good evolutionary and mechanistic reasons to expect this complexity, but it means that model organisms must be used with caution and that results must always be interpreted through a broader comparative framework. Additionally, it is essential to include research on non-traditional and unusual species, and to integrate mechanistic and demographic research. There will be no simple answers regarding the biology of aging, and research approaches should reflect this. This article is part of a Special Issue entitled: Animal models of aging - edited by Houtkooper Riekelt.

关键词： extinction risk   fire management   Melville Island   native mammal diversity   northern Australia   pyrodiversity   threatened species   tropical savanna  

摘要： 1. The increasing awareness that a fire regime that promotes biodiversity in one system can threaten biodiversity in another has resulted in a shift away from fire management based on vague notions of maximising pyrodiversity, towards determining the optimal fire regime based on the demonstrated requirements of target species. 2. We utilised a long-running, replicated fire experiment on Melville Island, the largest island off the northern Australian coast, to test the importance of pyrodiversity for native mammals in a northern Australian savanna landscape. We first developed statistical models to determine how native mammal abundance has responded to nine years of experimentally-manipulated fire frequency. Next, given each species' modelled response to fire frequency, we identified the level of pyrodiversity and optimal mix of fire frequencies that would be expected to maximise mammal diversity and abundance, and minimise extinction risk. This was done for both the entire mammal assemblage and for the mammal species currently declining on Melville Island. 3. Fire frequency was a significant predictor of abundance of the northern brown bandicoot Isoodon macrourus, black-footed tree-rat Mesembriomys gouldii, brush-tailed rabbit-rat Conilurus penicillatus, grassland melomys Melomys burtoni, pale field-rat Rattus tunneyi, and mice/dunnarts but not for the common brushtail possum Trichosurus vulpecula. 4. The geometric mean abundance (GMA) of the entire mammal assemblage was positively associated with pyrodiversity, but peaked at an intermediate value. Hence, maximising pyrodiversity would reduce native mammal assemblage GMA below its potential maximum. The fire history for an area that maximised the entire native mammal assemblage GMA consisted of 57% long-unburnt, 43% triennially burnt and <1% annually burnt. Pyrodiversity did not reduce the extinction risk, nor increase the GMA of declining mammals above that predicted in areas entirely annually or triennially burnt.

关键词： competition   grazing facilitation   livestock-wildlife interactions   nutrient-rich foraging hotspots   Odontotermes   resource selection  

摘要： African savanna termite mounds function as nutrient-rich foraging hotspots for different herbivore species, but little is known about their effects on the interaction between domestic and wild herbivores. Understanding such effects is important for better management of these herbivore guilds in landscapes where they share habitats. Working in a central Kenyan savanna ecosystem, we compared selection of termite mound patches by cattle between areas cattle accessed exclusively and areas they shared with wild herbivores. Termite mound selection index was significantly lower in the shared areas than in areas cattle accessed exclusively. Furthermore, cattle used termite mounds in proportion to their availability when they were the only herbivores present, but used them less than their availability when they shared foraging areas with wild herbivores. These patterns were associated with reduced herbage cover on termite mounds in the shared foraging areas, partly indicating that cattle and wild herbivores compete for termite mound forage. However, reduced selection of termite mound patches was also reinforced by higher leafiness of Brachiaria lachnantha (the principal cattle diet forage species) off termite mounds in shared than in unshared areas. Taken together, these findings suggest that during wet periods, cattle can overcome competition for termite mounds by taking advantage of wildlife-mediated increased forage leafiness in the matrix surrounding termite mounds. However, this advantage is likely to dissipate during dry periods when forage conditions deteriorate across the landscape and the importance of termite mounds as nutrient hotspots increases for both cattle and wild herbivores. Therefore, we suggest that those managing for both livestock production and wildlife conservation in such savanna landscapes should adopt grazing strategies that could lessen competition for forage on termite mounds, such as strategically decreasing stock numbers during dry periods.

关键词： Tree cavities   Forestry   Conservation planning   Hollow-using fauna   Management prescriptions   Habitat trees  

摘要： Hollow-using fauna are thought to be particularly vulnerable to timber harvesting, and habitat for these species is often managed by retaining single hollow-bearing trees or patches of hollow-bearing trees within the harvested area. This study examined tree retention, survival and use by arboreal mammals in 27 small clumps of trees (0.04-0.21 ha) retained at ten partial harvest sites and 24 clumps of trees in nearby unharvested sites in Tasmania, Australia. Harvested sites were assessed on three occasions (1999, 2005-06 and 2014) and unharvested sites on two occasions (2005-06 and 2014). Of the retained clumps in harvested areas, 96% contained at least two habitat trees at the time of first survey (one year after harvest) which is the minimum required under the Tasmanian Forest Practices Code. Loss of retained trees in clumps between 2005-06 and 2014 was higher in harvested sites (average of 11.7% of all trees and 1.5% of habitat trees per clump) than unharvested sites (average of 2.8% of all trees and 0.3% of habitat trees per clump), but was comparable to or lower than rates of loss in many other studies. Trees were more likely to fall if they were dead and had little burn damage at the time of last survey. Factors found to influence tree death included the interaction between burn damage and the size of the tree, with the likelihood of a heavily burnt, average sized tree dying being twice that of an unburnt tree. Scratch marks from arboreal mammals were more prevalent in large trees with visible hollows, particularly in the clumps in harvested areas. In conclusion, the Tasmanian Forest Practices Code provisions were generally implemented as required and the evidence suggests the retained clumps of trees survive and are effective to some degree at providing habitat and promoting recolonisation by fauna in partial harvest coupes. However, further work is required to assess the adequacy of the clump provisions, when combined with management for other values in produ

关键词： agriculture   cropland   epigaeic spider species   food security   food web   functional diversity   functional traits   pest control  

摘要： Predators play a disproportionately positive role in ensuring integrity of food webs, influencing ecological processes and services upon which humans rely. Predators tend to be amongst the first species to be affected by anthropogenic disturbance, however. Spiders impact invertebrate population dynamics and stabilise food webs in natural and agricultural systems (potentially mitigating against crop pests and reduced yields). Africa's savannas are undergoing continent-wide conversion from low-density rangelands to villages and croplands, as human populations burgeon. Despite limited research, and evidence of deleterious impacts to biodiversity, African savannas are earmarked by prominent international organisations for conversion to cropland. Given the key role of spiders in food webs, they can have beneficial impacts in agroecosystems. Furthermore, functional diversity (FD) reflects ecosystem pattern and processes better than species diversity, so we evaluated impacts of large-scale landuse change on both species richness and FD. We surveyed spiders using pitfall traps at 42 sites (14 replicates each in rangeland, cropland, and villages) in South African savannas, investigating effects of landuse, season, and habitat variables on spider species diversity and FD. Species richness was lowest in villages. FD was lowest in cropland, however, with reduced representation of traits associated with hunting of larger invertebrates. Furthermore, there were fewer specialists in croplands. These findings suggest that even when cropland does not impact species diversity, loss of FD can still occur. As savanna systems transform, impacts on invertebrate population dynamics may increase the possibility of a breakdown in pest control in natural and agricultural systems, given changes in FD of invertebrate predators.

关键词： Pastoralism   Coexistence   Rangelands   Heterogeneity   Community based conservation   Resilience  

摘要： Wildlife and livestock have coexisted across East African rangelands for millennia, tracking seasonal forage availability across large landscapes. More recently however, free-ranging movements have been increasingly restricted by land use changes, reducing the ability of livestock and wildlife to access necessary grazing resources, leading to both homogenization and degradation of the rangeland. This in turn has led to losses in productivity of both livestock and wildlife. This study describes wildlife and livestock interactions in response to pasture in one of the few remaining areas of mixed wildlife-livestock use with unrestricted movements. We ask if pastoral management systems can create and maintain spatial and temporal heterogeneity of pasture, through the seasonal movement of livestock. Furthermore, does this heterogeneity create a diverse, productive and resilient assemblage of both domestic and wild ungulates? Our results provide evidence to support the notion that traditional pastoral systems which continue to manage for heterogeneity of pasture can still support not only livestock but also substantial numbers of wildlife. The results highlight the need for wildlife and livestock to retain both mobility and access to both wet and dry season areas to maintain ecosystem resilience and promote coexistence in mixed livestock-wildlife landscapes.

关键词： 树鼩   病毒感染性疾病   动物模型  

摘要： 病毒感染是我国传染病致死的主要病因。建立一种能有效模拟人类感染病毒的动物模型,对病毒感染性疾病的致病机制和防治研究具有重要意义。树鼩作为灵长类动物的近亲,是近年建立和发展起来的新型动物模型,在病毒感染性疾病模型研究中突显优势和潜能。本文从树鼩的分类学、生理学和免疫学等生物学特征方面阐述了其应用于病毒感染性疾病动物模型研究的优势,并对树鼩在肝炎病毒、单纯疱疹病毒、流感病毒、肠道病毒等多种人类病毒感染性疾病模型应用中的最新研究进展予以比较和概述。

关键词： Chromatin-based mechanisms   Genotypic variation   Insect herbivore   Phenotypic plasticity   Tree defence  

摘要： The interaction of plants and their herbivorous opponents has shaped the evolution of an intricate network of defences and counter-defences for millions of years. The result is an astounding diversity of phytochemicals and plant strategies to fight and survive. Trees are specifically challenged to resist the plethora of abiotic and biotic stresses due to their dimension and longevity. Here, we review the recent literature on the consequences of phytochemical variation in trees on insect-tree-herbivore interactions. We discuss the importance of genotypic and phenotypic variation in tree defence against insects and suggest some molecular mechanisms that might bring about phytochemical diversity in crowns of individual trees.

关键词： Acacia nilotica   digestibility   nitrogen balance   protozoa   rumen enzymes   sheep  

摘要： This study was conducted to evaluate the effect of supplying two levels of Acacia nilotica (***) pods to rations of sheep on nutrient digestibility, nitrogen balance and rumen liquor parameters (pH, total protozoa count, protein concentration and enzymes activity). Twelve mature rams (50 +/- 1.25 kg B.W.) were distributed into three groups, each with four rams. Animals in group one were considered as a control which fed a basal diet, consisting of concentrate mixture and Egyptian clover. The second group and the third one received the same basal diet with supplying the concentrate mixture by 1.5% and 3.0% of *** pods meal respectively. The experiment lasted for 3 weeks. It was found that supplementation of *** pods to the concentrate mixture at a rate of 1.5% and 3.0% significantly improved the total feed intake compared to the control. The digestibility of dry matter and crude fibre was significantly reduced with *** supplements, whereas the digestibility of crude protein was significantly improved. All of nitrogen intake and N-retained were significantly increased in rams fed on concentrates with 1.5% and 3.0% A. nilotica pods when compared to the control. The pH of ruminal fluid was not affected by the dietary treatments. Nevertheless, the total rumen protozoa count was significantly decreased in *** pods supplemented groups. Also, the rumen protein concentration and the ruminal enzymes activity, especially alpha-amylase, cellulase and protease, were lower in *** pods supplemented treatments. In conclusions, inclusion of low levels of *** pods (1.5% and 3.0%) in the concentrates can be used as a natural protein protectant in ruminants by forming tannin protein complexes in the rumen to maximize the amino acids available in the lower digestive tract. Also, these levels can increase the protein digestibility as well as the N-retained in the body .