关键词： Chromolaena odorata   habitat selection   Invasive species   large herbivores   savanna  

摘要： AimHabitat loss and fragmentation is one of the main drivers of defaunation, that is the loss of large mammals. Biological invasions could be drivers of such phenomenon. However, their impact on large herbivore communities has not been studied to our knowledge. We made use of a landscape-scale control programme of one of the world's worst invaders, the shrub Chromolaena odorata, as a natural experiment to assess how this alien invader affects habitat use by 14 species of ungulates in an African savanna. LocationHluhluwe-iMfolozi Park, KwaZulu-Natal, South Africa. MethodsAt the height of the invasion in 2004, a large-scale control programme was initiated that successfully reduced densities of *** across the park. We estimated mammalian herbivore habitat and patch use by dung counts and the presence and density of *** along 24 line transects with a total length of 190km during the peak of the invasion (2004) and a decade after the initiation of a successful control programme (2014). To account for differences in herbivore assemblies between habitats and the preferential invasion of closed savanna woodlands, we analysed the recolonization of previously invaded patches by herbivores based on the change in dung abundance. ResultsHerbivore species differed in how they responded to invaded patches of this non-native shrub. Grazers were the most negatively affected, especially those that avoid predators by running. Browsers were negatively impacted only at the highest invasive shrub densities. Some species, especially bushpig, positively selected invaded patches. Main conclusionsLarge herbivores varied in their response to invasion with differences in impact depending on feeding strategy and predator avoidance strategy, but the majority of ungulates responded positively to the removal of this invasive shrub.

关键词： Invasive plant   Insect herbivory   Individual-based model   JABOWA-II forest simulator   Melaleuca quinquenervia   Native species recovery  

摘要： Melaleuca quinquenervia (Cav.) Blake (hereafter melaleuca) is an invasive tree from Australia that has spread over the freshwater ecosystems of southern Florida, displacing native vegetation, thus threatening native biodiversity. Suppression of melaleuca appears to be progressing through the introduction of insect species, the weevil, Oxiops vitiosa, and the psyllid, Boreioglycaspis melaleucae. To improve understanding of the possible effects of herbivory on the landscape dynamics of melaleuca in native southern Florida plant communities. We projected likely future changes in plant communities using the individual based modeling platform, JABOWA-II, by simulating successional processes occurring in two types of southern Florida habitat, cypress swamp and bay swamp, occupied by native species and melaleuca, with the impact of insect herbivores. Computer simulations show melaleuca invasion leads to decreases in density and basal area of native species, but herbivory would effectively control melaleuca to low levels, resulting in a recovery of native species. When herbivory was modeled on pure melaleuca stands, it was more effective in stands with initially larger-sized melaleuca. Although the simulated herbivory did not eliminate melaleuca, it decreased its presence dramatically in all cases, supporting the long-term effectiveness of herbivory in controlling melaleuca invasion. The results provide three conclusions relevant to management: (1) The introduction of insect herbivory that has been applied to melaleuca appears sufficient to suppress melaleuca over the long term, (2) dominant native species may recover in about 50 years, and (3) regrowth of native species will further suppress melaleuca through competition.

关键词： Equus caballus   facilitation   habitat modification   invasive species   Rattus   Ziziphus mauritiana  

摘要： In an ecosystem under simultaneous threat from multiple alien species, one invader may buffer the impact of another. Our surveys on a remote floodplain in the Kimberley region of north western Australia show that invasive chinee apple trees (Ziziphus mauritiana) provide critical refuge habitat for native rodents (pale field rats, Rattus tunneyi). Feral horses (Equus caballus) have trampled most of the remaining floodplain, but are excluded from the area around each chinee apple tree by thorny foliage. Although chinee apple trees constituted <10% of trees along our transects, they represented >50% of trees that harboured rat burrows. The mean number of burrows under each chinee apple tree was twice as high as under most other tree species, and we trapped more than seven times as many rats under chinee apple trees as under other types of trees. The extensive burrow systems under chinee apple trees contained female as well as male rats, whereas we only captured males around the smaller burrow systems under other tree species. Our data suggest that this invasive tree plays a critical role in the persistence of pale field rat populations in this degraded ecosystem, and that managers should maintain these trees (despite their alien origins) at least until feral horses have been removed.

关键词： Philoscia muscorum   Betula populifolia   Populus deltoides   Urban brownfield   Metal contamination   Fluctuating asymmetry  

摘要： Fluctuating asymmetry (FA) refers to random, small and non-directional deviations from ideal bilateral symmetry is proposed as a bio-indicator. of abiotic stress in both animals and plants. We investigated the effect of heavy metal stress on FA levels of morphological traits in a terrestrial isopod (Philoscia muscorum) as well as in the leaves of two hardwood tree species: Gray birch (Betula populifolia) and eastern cottonwood (Populus deltoides), in an urban brownfield in New Jersey. FA levels measured for five traits (length of two segments of antennae and three segments of the seventh legs) were compared in male and female populations of P. muscorum sampled from three low and three high soil metal load sites within the brownfield. FA levels measured for leaf width (perpendicular distance from a midpoint on midrib to the widest point of the lamina in right and left half in a leaf) were compared for both gray birch and eastern cottonwood leaves collected from the same low and high soil metal load sites. Contrary to the hypothesis that FA increases with higher heavy metal stress in isopods and trees, our results revealed that true asymmetry in gray birch and for some isopod traits (2nd antenna article, 3rd antenna article and merus of males and females, carpus and prodopus in females) did not differ between low and high metal contaminated sites. Furthermore, FAs measured in eastern cottonwood leaves and other isopod traits (carpus and prodopus in males) were found to be even lower at high metal contaminated sites than the low metal load sites. The overall effect of metal stress was shown as reduction in growth (measured as body size for a given head width in an individual) of isopods at high metal load sites as compared to the low metal load sites. Various hypotheses including induction of detoxification mechanisms in response to metal stress, selection against individuals with presumably lower fitness (high FA), difference in sensitivity of traits to stress, and pl

关键词： 序列分析   系统进化树   节肢动物   α- 淀粉酶   Alpha-amylase   Arthropod   Phylogenetic Tree Construction   Sequence Analysis   序列分析   系统进化树   节肢动物   α- 淀粉酶   Language of Keywords: English   Chinese  

摘要： Objective: To investigate the evolutionary relationship of alpha-amylases among different arthropods by constructing phylogenetic tree and to find the specific sequences of the alpha-amylases in the phylogenetic tree. Methods: 56 amino acid sequences encoding alpha-amylase of different species indexed in Arthropoda were downloaded from National Center for Biotechnology Information (NCBI). CLUSTALX2.0 was used for sequence alignment, and MEGA6. 0 was used to establish the phylogenetic tree. By using the BOXSHADE, the clusters of alpha-amylase specific sequence were explored. Results:The 56 amino acid sequences encoding alpha-amylases were grouped into four major clusters in phylogenetic tree, which were named as A, B, C, D. The specific sequence are VD (NHD)NQ for Cluster A, ID(NHD) NX Cluster B, are ID (NHD) NQ Cluster C, and XGN (NHD) X for Cluster D. The conserved sequences are NHD (Asn-His-Asp) for all of these amino acids sequences. Conclusion:The amino acid sequences encoding arthropod alpha-amylase were divided into four major clusters. Each cluster has its own special sequence. All the sequences have the conserved NHD. [ABSTRACT FROM AUTHOR]

关键词： abiotic gradients   bottom-up effects   foundation species   grazing lawn   mega-herbivore   meso-herbivore   plant dominance   plant-herbivore interactions   top-down effects   wildlife decline  

摘要： 1. Productivity and herbivory often interact to shape plant community composition and species richness with levels of production mediating the impact of herbivory. However, differences in herbivore traits such as size, feeding guild and dietary requirements may result in different impacts of diverse herbivore guilds across productivity gradients. 2. We used size-selective herbivore exclosures to separate the effects of herbivory by larger herbivores, such as elephant, Burchell's zebra and blue wildebeest from those of medium/smaller herbivores, such as impala and warthog, on herbaceous plant communities. These exclosures were established along a 10-fold productivity gradient, ranging from 90 to 950 g m(-2) of standing plant biomass in the Kruger National Park, South Africa. 3. Exclusion of all herbivores generally increased plant species richness at low productivity, but decreased richness at high productivity. Exclusion of medium/smaller herbivores (e.g. impala, warthog) showed stronger effects on plant richness, particularly loss of forbs, at higher productivity rather than at lower productivity. In contrast, exclusion of larger herbivores had stronger effects on plant richness, typically with increasing forb richness, at low rather than high productivity. 4. The change in species richness appeared linked to changes in light availability following herbivore exclusion. Strong increases in shading led to declines in species richness while more moderate increases in shading led to increases in species richness, possibly due to amelioration of heat and water stress by modest increases in shading. 5. Increasing plant dominance, which likely alters multiple mechanisms of plant interactions, was correlated with declines in plant richness following herbivore exclusion. The impact of increasing dominance on plant richness operated independent of productivity, with the exclusion of impala appearing particularly important in driving this relationship. 6. Synthesis. We show t

关键词： Agrilus planipennis   diversity   forest   foundation species   Fraxinus   invasive species  

摘要： 1 Emerald ash borer (EAB) Agrilus planipennis Fairmaire is an invasive non-native woodboring beetle that has killed hundreds of millions of ash trees (Fraxinus spp.) in North America. Identifying the arthropod community associated with ash trees has been highlighted as an important research requirement in understanding the wider effects of EAB. 2 We harvested live ash trees infested with EAB at 37 sites in Maryland from 2011 to 2014 and collected a total of 2031 arthropods. All arthropods were identified to order and 94.6% were identified to family or below. The community comprised 13 orders, 60 families and 41 genera, with 28 arthropod species identified. Coleoptera, Diptera, Hymenoptera and Lepidoptera accounted for 98.3% of arthropods collected. 3 Data on changes in richness and diversity over time were fitted to second-order polynomial models, corresponding with a transition in the dominant taxa from woodboring beetles (Cerambycidae) to parasitoids (Braconidae and Eulophidae). This resulted in changes to community composition as the EAB infestation intensified. 4 The findings of the present study provide further evidence of the diversity of arthropods at risk from EAB. Given the number of invasive non-native insects threatening North American forests, establishing what taxa are present is important for predicting the likely broader impacts of these invasions.

关键词： Savannas   Comment   aluminium   herbivores  

摘要： The article evaluates a study which examines how the loss of vertebrate herbivore affects plant species richness in African Savanna. Topics discussed include the herbivore impact on plant species richness along a productivity gradient, the need for new approaches to predict hervibore impact, and the functional grouping of herbivores.

关键词： Sabellida   High-throughput sequencing   Mitogenome   Sequence evolution   Gene length evolution   Gene order  

摘要： Here we describe, for the first time, the mitochondrial genome of Spirobranchus giganteus (Annelida: Serpulidae) and compare it with all available annelid mitogenomes. The entire mitogenome has 22,058 bp in length and bears 12 protein-coding genes (the ATP8 gene is missing), two rRNA, and 24 tRNA genes. The nucleotide composition and GC-skew are surprisingly different from those reported for other annelids. In addition, the pairwise genetic distances between the mitogenomes of S. giganteus and other annelids are higher than the distances for all annelid taxa analyzed. This result is consistent with a faster rate of mitochondrial sequence evolution in S. giganteus, which may explain the difficulty in obtaining PCR products with the available primers. The mitochondrial gene order of S. giganteus was remarkably different not only from that of the Sedentaria lineage, which includes S. giganteus, but also from the mitochondrial gene order of other major annelid lineages. The mitogenome of S. giganteus has no repetitive motifs despite its long control region (4769 bp), but genes are shorter and have a lower AT content than other members of Annelida. Finally, we show that mitochondria( gene order rearrangements can directly correlate to variations in gene length. (C) 2016 Elsevier B.V. All rights reserved.

关键词： 树鼩   肝脏疾病   动物模型   灵长类动物  

摘要： 肝脏疾病尤其是肝炎及肝癌已成为国内外重要的健康问题。探索有效的防治方法需要构建合适的动物模型。与传统普遍使用的啮齿类动物模型相比,非人灵长类动物树鼩与人类亲缘关系更近,更能反映各种人类疾病的发生、发展和转归,应用潜力巨大。目前国内外利用树鼩初步建立了包括肝细胞癌、各型病毒性肝炎及肝脏代谢性疾病在内的多种人类肝脏疾病模型,但仍存在建模周期长、模型稳定性欠佳、缺乏肝硬化模型等问题,未来有待改进。