关键词： 迪翁   努特   学习委员   蹄兔   小鼯鼠   幼鸟   灰树蛙   令人   太远   夜行性  

摘要： 在树栖班,新学期就像学生们内心的一道坎,因为除了不能再尽情享受愉快的假期外,它们还要在开学第一天交上令人头疼的暑假作业。然而,不管同学们多么不乐意,新学期还是如期而至了……"我说过多少次了,迪翁校长布置的作业必须按时完成,而且要精益求精,这学期咱们班绝不能落在其他班级后面!"

关键词： Dispersal limitation   Diversity maintenance   Predation limitation   Seed dispersal   Seed limitation   Seed predation   Small mammals   Tropical forests  

摘要： Recruitment limitation of trees in tropical forests can occur because of high rates of seed predation or low rates of seed dispersal, but the degree to which limitation is influenced by variation in seed predator abundance, and hence variation in seed predation and dispersal, is not well understood. We experimentally reduced the density of a granivorous small mammal (Heteromys desmarestianus) by 90 % to assess the degree to which its rates of seed predation and dispersal limit seed to seedling survival of nine species of trees in a Neotropical lowland forest. Overall, the proportion of seeds that germinated was influenced more by high rates of predation than by limited dispersal. Reduction in density of H. desmarestianus resulted in an order of magnitude decrease in fruit removal rates and an order of magnitude increase in both the absolute and relative numbers of seeds that germinated. However, the proportion of seeds that were cached remained relatively constant across all periods and between control grids and removal plots. In removal plots, H. desmarestianus dispersed and cached about 10 % of the fruits they handled, of which approximately 25 % germinated. This was 2 to 3 times greater than the germination rates of undispersed seeds, and for two species dispersed seeds were the only ones that germinated. The results suggest the simultaneous occurrence of both seed predation and dispersal limitation for trees with animal-dispersed seeds, but there may also be a hierarchy of importance in the relative strength of these two mechanisms that is determined by the dynamics of seed predator populations.

关键词： exclusion   growth   nitrogen   phosphorus   tannin  

摘要： Impacts of large herbivores (>5kg) on woody plants in African savannas are potentially most severe among plants shorter than 1.6m. It is well established that severe browsing leads to longer shoots, yet prevents saplings from recruiting into adult size-classes in African savannas. Increased shoot length, indicating faster shoot growth, is often associated with reduced concentrations of tannins and increased nutrient concentrations, suggesting carbon limitation. We hypothesized that, on average, large herbivores suppress stem height or circumference, but increase shoot length. We also hypothesized that if there were concomitant positive effects on nutrients, or negative effects on tannin concentrations, they would be greatest early in the wet season. We sampled saplings of four deciduous woody species (Acacia grandicornuta, Dichrostachys cinerea, Combretum apiculatum and Grewia flavescens) at different stages of the wet season in a large-scale, long-term herbivore exclusion experiment in Kruger National Park, South Africa. Plant height, shoot length and stem circumference were generally not adversely affected by large herbivores, suggesting C limitation is rarely present among deciduous saplings in semi-arid African savannas, allowing them to tolerate browsing. Time since first rainfall emerged as a predominant factor consistently affecting nutrient and tannin concentrations, rather than large herbivores. Nitrogen and phosphorus generally decreased (by 20-50%), while condensed tannin concentration increased (150-350%) during the wet season, except for one species. We postulate that *** is less prone than other species to accumulating tannins during the wet season because of high investment of C in spines. Although nutrient and tannin concentrations were generally not affected by large herbivores, species-specific responses were evident very early in the wet season, which is when herbivore populations are most likely to be affected by differential forage q

关键词： Constitutive and inducible defences   extrafloral nectar   EFN   juvenile plants   invasion ecology   specialists   generalists   tallow tree   Triadica sebifera   caterpillars   Noctuidae   Limacodidae  

摘要： Invasive plants can be released from specialist herbivores and encounter novel generalists in their introduced ranges, leading to variation in defence among native and invasive populations. However, few studies have examined how constitutive and induced indirect defences change during plant invasion, especially during the juvenile stage. Constitutive extrafloral nectar (EFN) production of native and invasive populations of juvenile tallow tree (Triadica sebifera) were compared, and leaf clipping, and damage by a native specialist (Noctuid) and two native generalist caterpillars (Noctuid and Limacodid) were used to examine inducible EFN production. Plants from introduced populations had more leaves producing constitutive EFN than did native populations, but the content of soluble solids of EFN did not differ. Herbivores induced EFN production more than simulated herbivory. The specialist (Noctuid) induced more EFN than either generalist for native populations. The content of soluble solids in EFN was higher (21 times), with the specialist vs. the generalists causing the stronger response for native populations, but the specialist response was always comparable with the generalist responses for invasive populations. These results suggest that constitutive and induced indirect defences are retained in juvenile plants of invasive populations even during plant establishment, perhaps due to generalist herbivory in the introduced range. However, responses specific to a specialist herbivore may be reduced in the introduced range where specialists are absent. This decreased defence may benefit specialist insects that are introduced for classical biological control of invasive plants.

关键词： ant exclusion   biological control   Ectatomma ruidum   herbivores   indirect resistance   insect-plant interactions   myrmecophilic timber trees  

摘要： Successful reforestation of tropical pastures can be facilitated or impeded depending on the interactions between native timber trees and arthropod communities. We assessed arthropod abundance on Tabebuia rosea (Bignoniaceae), a Central American extrafloral nectary-bearing timber tree, in a plantation of native trees on former pasture in Panama, and we excluded ants from branches of T. rosea to determine ant impact on arthropod assemblages and on leaf damage. The trees' ant fauna was dominated by ground-nesting species and ants were scarce in tree crowns, constituting only 2% of all arthropods collected by branch beating. Leaf damage was principally caused by caterpillars (mainly the pyralid Eulepte gastralis) and by beetles (mainly the chrysomelid Walterianella inscripta). Sugar baits at tree trunks revealed that rewarding food resources recruited high ant numbers to some tree individuals. Activity of the dominant ant, Ectatomma ruidum, at baits was negatively related to leaf damage by E. gastralis, suggesting that trees might be better protected from this herbivore when ant abundance is high. Exclusion of ants resulted in increased beetle diversity. The key herbivore W. inscripta was significantly more abundant on ant-exclusion branches at the beginning, but not towards the end of the rainy season, when beetle density increased. Overall leaf damage and arthropod abundance were not significantly affected by ant exclusion. In conclusion, ant abundance on native timber trees in plantations recently established on former pasture can be low, and ant assemblages may be dominated by ground-nesting generalist species, as shown in this study. This may explain the lacking protection of the timber trees from insect herbivory by ants. Increased protection of establishing timber trees by ants probably requires plantation management measures that increase the abundance of more specialized tree-visiting and tree-nesting ants.

关键词： abiotic gradients   community structure   East Africa   exclosure experiment   herbivory   livestock-wildlife interactions   plant species richness   plant-herbivore interactions   wildlife decline  

摘要： Herbivores influence the structure and composition of terrestrial plant communities. However, responses of plant communities to herbivory are variable and depend on environmental conditions, herbivore identity and herbivore abundance. As anthropogenic impacts continue to drive large declines in wild herbivores, understanding the context dependence of herbivore impacts on plant communities becomes increasingly important. Exclosure experiments are frequently used to assess how ecosystems reorganize in the face of large wild herbivore defaunation. Yet in many landscapes, declines in large wildlife are often accompanied by other anthropogenic activities, especially land conversion to livestock production. In such cases, exclosure experiments may not reflect typical outcomes of human-driven extirpations of wild herbivores. Here, we examine how plant community responses to changes in the identity and abundance of large herbivores interact with abiotic factors (rainfall and soil properties). We also explore how effects of wild herbivores on plant communities differ between large-scale herbivore exclosures and landscape sites where anthropogenic activity has caused wildlife declines, often accompanied by livestock increases. Abiotic context modulated the responses of plant communities to herbivore declines with stronger effect sizes in lower-productivity environments. Also, shifts in plant community structure, composition and species richness following wildlife declines differed considerably between exclosure experiments and landscape sites in which wild herbivores had declined and were often replaced by livestock. Plant communities in low wildlife landscape sites were distinct in both composition and physical structure from both exclosure and control sites in experiments. The power of environmental (soil and rainfall) gradients in influencing plant response to herbivores was also greatly dampened or absent in the landscape sites. One likely explanation for these observed d

关键词： Agriculture   Biology   Botany   Community ecology   Conservation science   Ecology   Forestry   Global change ecology   Microbial ecology   Microbiology   Mycology   Plant ecology   Research Article   Soil ecology   Systems ecology  

摘要： Biological invasions are often complex phenomena because many factors influence their outcome. One key aspect is how non-natives interact with the local biota. Interaction with local species may be especially important for exotic species that require an obligatory mutualist, such as Pinaceae species that need ectomycorrhizal (EM) fungi. EM fungi and seeds of Pinaceae disperse independently, so they may use different vectors. We studied the role of exotic mammals as dispersal agents of EM fungi on Isla Victoria, Argentina, where many Pinaceae species have been introduced. Only a few of these tree species have become invasive, and they are found in high densities only near plantations, partly because these Pinaceae trees lack proper EM fungi when their seeds land far from plantations. Native mammals (a dwarf deer and rodents) are rare around plantations and do not appear to play a role in these invasions. With greenhouse experiments using animal feces as inoculum, plus observational and molecular studies, we found that wild boar and deer, both non-native, are dispersing EM fungi. Approximately 30% of the Pinaceae seedlings growing with feces of wild boar and 15% of the seedlings growing with deer feces were colonized by non-native EM fungi. Seedlings growing in control pots were not colonized by EM fungi. We found a low diversity of fungi colonizing the seedlings, with the hypogeous Rhizopogon as the most abundant genus. Wild boar, a recent introduction to the island, appear to be the main animal dispersing the fungi and may be playing a key role in facilitating the invasion of pine trees and even triggering their spread. These results show that interactions among non-natives help explain pine invasions in our study area.

关键词： 规模化饲养   动物模型   实验动物   动物资源   云南省   繁殖   成果展示   应用  

摘要： 由中国医学科学院医学生物学研究所代解杰课题组联合昆明理工大学生命科学与技术学院共同完成的“树鼢饲养繁殖种群建立及其在HCV动物模型中的应用”项目历时7年，获得2012年云南省科学技术进步一等奖，开创了云南省特色实验动物资源一一树鼢研究的里程碑，彰显了云南省在树嗣饲养繁殖和运用树鼢建立人类疾病动物模型研究领域的顶尖实力，标志着云南省树胸规模化饲养繁殖与应用研究已达到国际先进水平。

关键词： elephant shrew   tree shrew   Macroscelididae   Tupaiidae   Cryptococcus spp.   Gongylonema spp.   arteriosclerosis  

摘要： Investigations into the cause of mortality and other important findings at necropsy were made into two families of small mammals at the Smithsonian National Zoological Park (SNZP;USA). Necropsy reports from 1976 through 2008 were reviewed for all elephant shrews in family Macroscelididae (n = 118) and all tree shrews in family Tupaiidae (n = 90) that lived for greater than 30 days at the SNZP. Causes of mortality were classified by body system and etiology to identify prevalent diseases and trends across demographics for each family. In elephant shrews, gastrointestinal disease (n = 18) and respiratory disease (n = 22) were important causes of mortality with an increased prevalence of pneumonia in adult males. Trauma was a common cause of mortality in tree shrews (n = 22). Cryptococcosis was an important cause of mortality in both families (n = 8 elephant shrews;n = 13 tree shrews). Bacterial infections, often systemic at time of mortality, were also common (n = 16 elephant shrews;n = 17 tree shrews). Arteriosclerosis was a common comorbid pathology noted at necropsy in certain populations, seen only in Elephantulus rufescens in the family Macroscelididae (n = 22) and in only males in the family Tupaiidae (n = 11). Gongylonemiasis was seen commonly in tree shrews (n = 15), as a comorbid finding, or in 5 cases directly leading to mortality. Awareness of the prevalence of these diseases can help guide prevention and intervention strategies.

关键词： late Miocene   Europe   Palaeoenvironments   Mammalian palaeocommunity   Body mass   Biomass  

摘要： Western European Turolian mammalian faunas and palaeoenvironments are less well known than middle and early late Miocene ones for which more data exist at a time when major climate events occurred (Middle Miocene Climatic Optimum followed by Late Middle Miocene Climatic Cooling). In this respect, rich faunas represent exceptional windows into mammalian diversity and biogeography. They constitute key points to understand local palaeoenvironments and refine larger-scale patterns. Dorn-Durkheim 1 is one of the richest mammalian faunas of Western Europe with at least 79 species of mammals. We investigate this fauna and compare its composition to the faunal and biogeographic context of the European late Miocene. A community-based analysis of body masses of the constituent species together with an original approach on predator-prey biomasses are also attempted to reconstruct its palaeoenvironment. While its composition reflects the known late Miocene context and fits in the biogeographic North-South pattern evidenced by earlier studies, the reconstructed landscape is different from previous hypotheses of densely forested habitats. Our results suggest the presence of a savanna-woodland biome more open than previously thought, in a subtropical-like and seasonal climate. Other palaeoecological studies on elements of the large mammal fauna confirm this interpretation.