关键词： biogeography   determinants of plant community diversity and structure   disturbance   dominant species   drought   fire   functional traits   grass community   grazing   phylogeny  

摘要： Grazing and fire are disturbances integral to the evolution and maintenance of savanna grasslands. Humans are altering or completely eliminating these disturbance regimes at a global scale, with important consequences for savanna ecosystem structure and function. It is unknown whether the alteration of these disturbance regimes will have similar effects on grass communities of savanna grasslands in different geographic regions that vary in their biogeographic and evolutionary histories, as well as in the diversity of extant grazers. Here, we examined the effects of large herbivore loss on different aspects of grass community structure - taxonomic, phylogenetic and functional - across a range of fire frequencies in C-4-dominated mesic savanna grassland sites of North America (Konza Prairie Biological Station, Kansas, USA) and South Africa (Kruger National Park). The goal of the study was to determine whether the loss of large herbivores exerted a consistent effect on the grass communities of two physiognomically similar grasslands with different biogeographic and grazing histories. The removal of large herbivores resulted in divergent responses in the grass communities at Konza and Kruger that was consistent across fire treatments. At Konza, there was a rapid and significant response to grazing exclusion while the response was muted and transient at Kruger. Functional syndromes associated with grazing resistance were generally conserved across sites, and it was the functional strategies of the dominant species at each site that drove the divergent responses. Further, our study supports the hypothesis that grazing and aridity may be selective forces that act in parallel as those species that were grazing resistant also occupied drier ***. Our study demonstrates that savanna grassland communities with different biogeographic and grazing histories respond differently to the removal of large herbivores and that climate, fire and grazing are interactive force

关键词： Euarchonta   Euarchontoglires   phylogenomics   tree shrews  

摘要： The well-accepted Euarchonta grandorder is a pruned version of Archonta nested within the Euarchontoglires(or Supraprimates)*** present,it includes tree shrews(Scandentia),flying lemurs(Dermoptera)and primates(Primates).Here,a phylogenomic dataset containing 1912 exons from 22 representative mammals was compiled to investigate the phylogenetic relationships within this *** analyses and hypothesis testing suggested that tree shrews can be classified as a sister group to Primates or to Glires or even as a basal clade within *** analyses of both modified and original previously published datasets found that the phylogenetic position of tree shrews is *** also found that two of three exonic indels reported as synapomorphies of Euarchonta in a previous study do not unambiguously support the monophyly of such a ***,the monophyly of both Euarchonta and Sundatheria(Dermoptera+Scandentia)are *** dating and divergence rate analyses suggested that the ancestor of Euarchontoglires experienced a rapid divergence,which may cause the unresolved position of tree shrews even using the whole genomic data.

关键词： Brazil   cerradao   Cerrado   fire ecology   Gracilinanus agilis   Rhipidomys macrurus   survival  

摘要： Fire is a major form of disturbance in terrestrial ecosystems, mainly in tropical savannas. In these ecosystems, the effects of large wildfires are potentially high on small and relatively less mobile animals, like small mammals. We investigated the effects of an extensive wildfire (approximate to 6,240 ha) in September 2011 on populations of 2 arboreal-scansorial small mammals-the gracile mouse opossum, Gracilinanus agilis, and the long-tailed climbing mouse, Rhipidomys macrurus-in 4 savanna woodland patches (1 burned, 3 unburned) of the highly threatened Brazilian Cerrado. We assessed population densities from 2009 to 2013 and for G. agilis, we estimated apparent survival and recapture probabilities with Cormack-Jolly-Seber models. Both species showed strong, negative fire responses, including sudden collapse and slow recovery (at least more than 1 year). These observed responses were probably a consequence of both the phytophysiognomic features of the habitat and severity of the fire with the resulting changes on the vertical structure of vegetation. The studied species of Cerrado forested formations were not as resilient to fire disturbance as typical species from savanna or temperate woodlands. As a consequence of human activities and climate changes, fire events are predicted to become larger and more frequent in the Brazilian Cerrado. Therefore, it is imperative to create new management strategies to protect forested physiognomies from fire, especially cerradao, which is very fire sensitive and has a limited and scattered distribution in the landscape.

关键词： Biological invasion   establishment   exotic   natural enemy release   pollination syndrome   pre-dispersal seed predation   weed  

摘要： AimInteractions with pollinators and pre-dispersal seed predators are important determinants of reproductive output and could influence the success of plant species introduced to areas outside their native range. We identified the role of these interactions in determining reproductive output and invasion outcomes for species of Australian Acacia introduced to New Zealand. LocationAustralia and New Zealand. MethodsWe studied three species of Australian Acacia with different invasion success in New Zealand. In both Australia and New Zealand, we measured pollination success as the number of pods per inflorescence and the proportion of aborted seeds per pod, determined losses to pre-dispersal seed predators, and measured overall seed output. For each species, we compared performance in New Zealand with that in Australia, then examined whether there was any variation among species in their relative performance in each country. ResultsThe number of pods per inflorescence and proportion of seeds aborted were similar in each country and among species. There was little difference in pre-dispersal seed predation rate between Australia and New Zealand for Acacia dealbata, an invasive species, and Acacia baileyana, a species widely naturalized in New Zealand. However, pre-dispersal seed predation rate was lower in New Zealand for Acacia pravissima, currently considered to be a casual species there. Both the invasive A. dealbata and the casual A. pravissima produced more seeds per tree in New Zealand than Australia. Main conclusionsDifferences in reproductive success between the native and introduced range could not explain the differences in invasion success among the three Acacia species. Although per capita reproductive output was higher in New Zealand for two species, neither mutualistic interactions with pollinators nor antagonistic interactions with pre-dispersal seed predators explained those differences. The high seed output of A. pravissima suggests it has the potential

关键词： 环境科学专业   环保科技   观鸟   二至   参与人员   知识目标   鸟叫   在乡下   记录单   细节特征  

摘要： 一、活动名称＂初夏的动静＂——探访动物园中的鸟和树二、参与人员1.儿童：5人,小学二至四年级学生,以二年级为主;2.教师：1人,环境科学专业、环保科技教师;3.其他：随行家长4人、活动配合工作人员2人。三、活动目标1.知识目标（1）在水禽湖附近观鸟窝、听鸟叫、观察鸟,识别出鸟及鸟巢的类型,巩固相关知识。

关键词： diversity   euglossinen   biogeography   neotropics   pollinators  

摘要： The Neotropical savanna is characterized by a set of different phytophysiognomies occurring in a wide expanse of Brazilian lands. Based on the known higher diversity of orchid bees in forests rather than in savanna formations, we hypothesized that the occurrence of forest formations inside the Brazilian savanna increases the diversity of euglossine bees in that domain and that there are species more associated with these environments. To test this hypothesis, we sampled the euglossine fauna in eight forest and woody savanna remnants and analyzed their community structure. We sampled 1,010 males of 13 species of orchid bees. Bee abundance and species richness ranged from 30 to 341 individuals and from 4 to 12 species, respectively. The forest remnants showed the highest diversity indices and species richness. Our data suggest that some species of Euglossa are mainly associated with forest remnants. We concluded that environmental heterogeneity in the Neotropical savanna contributes to higher diversity of euglossine and that some species are more frequently found in forested habitats. Additionally, considering that some sampled species are typical of the Atlantic and Amazon forests, our data reinforce the hypothesis that forest environments inside the Brazilian savanna can be considered bio-corridors for orchid bees.

关键词： Boosted regression tree   Soil fauna effect   Climate   Plant litter quality   Litter decomposition   Biomes  

摘要： Extensive studies have been conducted to evaluate the effect of soil fauna on plant litter decomposition in terrestrial ecosystems. However, scholars have reported inconsistent results on the direction and magnitude of the soil fauna effect. We present a global synthesis of 75 papers that cover 197 plant species with 543 cases of plant litter decomposition experiments and soil fauna effects on plant litter decomposition. By using a boosted regression tree model (BRT), we aim to provide a synthesis of existing data that comprehensively and quantitatively evaluates how climate, plant litter quality, and study methods interact with soil fauna in affecting plant litter decomposition. Global average effect size (ES) is -0.426, which indicates a 35% lower decomposition rate when soil fauna is excluded by physical or chemical exclusion techniques. The final model explains 32.3% of the variation in ES. The predictors that substantially account for the explained variation include mean annual temperature (MAT, 37.1%), mean annual precipitation (MAP, 9.7%), phosphorus (12.4%), nitrogen (5.6%), and lignin content (5.5%). By contrast, the heterogeneity of the study duration and soil fauna exclusion technique have negligible contributions (each <5%). Log effect size strongly decreases with both MAT and MAP. Plant litters with high quality have stronger soil fauna effect because the log effect size is negatively related to nitrogen and phosphorus content and positively related to lignin content. Our analysis demonstrates the critical role of climate and plant litter quality in determining the soil fauna effect on plant litter decomposition in terrestrial ecosystems. However, the large unexplained variation (67.7%) in ES in the BRT model indicates undiscovered mechanisms underlying the soil fauna effect in our analysis. We call for further studies on this topic in the future. (c) 2015 Elsevier Ltd. All rights reserved.

关键词： herbivore exclosures   mesic   plant defenses   semi-arid   trade-off  

摘要： Five sets of herbivore exclosures situated in mesic and semi-arid savannas in Hluhluwe-iMfolozi Park, South Africa were used to investigate the effects of mammal browsers and savanna type on plant traits relating to leaf nutrient content, defense, and growth in seven Acacia species. Mostly, browsing did not significantly affect leaf nutrient content but for a few species (i.e., increasing foliar N and P, decreasing C/N, and total polyphenols). Browser effects on structural defenses tended to be more pronounced than for leaf nutrient content and chemical defenses, particularly for semi-arid species, resulting in longer, thicker, and denser spines, and a lower bite size index on browsed plants for most semi-arid species. Browsing had no significant effect on growth rates for all species. Secondly, we investigated the effect of savanna type (mesic vs. semi-arid) on the same set of plant traits and growth rates. A trade-off in defense strategy was evident where mesic species had lower quality leaves and invested more heavily in growth and chemical defenses, while semi-arid species generally had higher nutrient content leaves and invested more in structural defenses and higher levels of ramification. These findings suggest that the previously documented trade-off in plant growth, resprouting ability and architecture between herbivore versus fire-adapted savanna woody species can possibly be extended to include browse quality and defense type.

关键词： biodiversity   insects, phytophagous   natural enemies and pollinators  

摘要： Our aim was to assess the seasonal abundance and diversity of arthropods on Acacia mangium Willd. (Fabales: Fabaceae) trees. Phytophagous arthropods, natural enemies and pollinators were quantified biweekly in 20 trees during 3 years. The Shannon biodiversity index (H') of arthropods was greater in the summer and smaller in the winter and spring on A. magium. The diversities of species and abundances of individuals of all arthropod taxa were greater in the autumn and smaller in the winter and in the spring. The H' index of arthropods was greater in 2005 and smaller in 2007. The diversity of species and abundance of individuals of phytophagous taxa were greater in 2005 and 2006, respectively, whereas those of natural enemies and pollinators was greater in 2006. Aethalion reticulatum L. (Hemiptera: Aetalionidae) was the most abundant phytophagous species found in the various seasons, while Camponotus sp. 2 (Hymenoptera: Formicidae), Trigona spinipes Fabricius (Hymenoptera: Apidae, Meliponini), Tetragonisca angustula Latreille (Hymenoptera: Meliponinae, Meliponini) and Polistes sp. (Hymenoptera: Vespidae) were the most abundant natural enemies and pollinators. The great diversity of predators on this tree species can explain the little damage to its leaves. These results may be applied to support programs of pest control and maintenance of natural enemies and pollinators in future plantations of A. mangium.