关键词： Antechinus   Agilis   Swainsonii   Fuscipes   Habitat loss   Relative abundance   Performance indices   Conditional inference tree   Random forests  

摘要： Anthropogenic habitat loss, fragmentation and degradation often co-occur in a landscape and their relative influence on a native animals' health and survival can be difficult to determine. We examined the influence of these environmental variables on the estimated relative abundance of some small mammal species in a large area (similar to 2500 km(2)) of southeastern Australia. Using the agile antechinus (Antechinus agilis) as a model, we also examined the association between these variables and three population performance indices, mass-size residuals (MSR;indexing fat reserves), the neutrophil/lymphocyte ratio (N:L;indexing physiological stress) and red blood cell counts (RBC;indexing regenerative anaemia). Study sites were in either highly disturbed and fragmented, or relatively undisturbed, continuous Eucalyptus forest. We generated conditional inference tree statistical models to identify the relative importance of up to 49 ecological variables in explaining variation in small mammal abundance and performance indices. Habitat loss was important in explaining small mammal abundance, as were the abundances of the same species in neighbouring study sites. The models also suggested that the habitat area required to support a 'healthy' population was greater in the larger species examined. Autocovariates of neighbouring site same-species abundances and habitat fragmentation were the next most important influences on small mammal relative abundance, implying that metapopulations may be important for population persistence, especially in bush rats (Rattus fuscipes). Habitat degradation, reflected in structural and floristic features, was less important, but explained some variance in relative abundances. For agile antechinus populations, time of year, degree of forest fragmentation and extent of native tree cover were important in explaining performance indices. Results indicated that habitat reduction per se was a significant threatening process for small mammals. Hab

关键词： Aspen   Birch   Climate change   Plant-insect interactions   Malacosoma disstria   Temperature  

摘要： As the world's climate warms, the phenologies of interacting organisms in seasonally cold environments may advance at differing rates, leading to alterations in phenological synchrony that can have important ecological consequences. For temperate and boreal species, the timing of early spring development plays a key role in plant-herbivore interactions and can influence insect performance, outbreak dynamics, and plant damage. We used a field-based, meso-scale free-air forest warming experiment (B4WarmED) to examine the effects of elevated temperature on the phenology and performance of forest tent caterpillar (Malacosoma disstria) in relation to the phenology of two host trees, aspen (Populus tremuloides) and birch (Betula papyrifera). Results of our 2-year study demonstrated that spring phenology advanced for both insects and trees, with experimentally manipulated increases in temperature of 1.7 and 3.4 A degrees C. However, tree phenology advanced more than insect phenology, resulting in altered phenological synchrony. Specifically, we observed a decrease in the time interval between herbivore egg hatch and budbreak of aspen in both years and birch in one year. Moreover, warming decreased larval development time from egg hatch to pupation, but did not affect pupal mass. Larvae developed more quickly on aspen than birch, but pupal mass was not affected by host species. Our study reveals that warming-induced phenological shifts can alter the timing of ecological interactions across trophic levels. These findings illustrate one mechanism by which climate warming could mediate insect herbivore outbreaks, and also highlights the importance of climate change effects on trophic interactions.

关键词： nutrient release rate   phosphorus   termites   nutrient cycling   dung beetles   dung deposition   carbon   nitrogen   faeces   African herbivores  

摘要： Although dung of mammalian herbivores is an important pathway for nutrient return in savanna ecosystems, differences in dung decomposition rates among species have been little studied. We measured the rates of dung deposition and decomposition for various herbivores in a moist Tanzanian savanna and the related differences among species to nutrient concentrations and the activities of soil macrofauna (e.g. different mesh sizes of decomposition bags, or presence and absence of dung beetles). Dung C:N:P stoichiometry varied widely among species, which could in part be explained by differences in feeding strategy (browsers vs. grazers) and digestive physiology (ruminants vs. non-ruminants). Rates of both decomposition and nutrient release were influenced by the C:N:P stoichiometry of dung, with lower relative losses of the least abundant nutrient in the dung. Surprisingly, soil macrofauna increased the relative losses of the least abundant nutrient, thereby stabilizing the ratio of N loss to P loss. Dung beetles increased rates of N and P release from wildebeest dung significantly and also increased N availability in the soil. We conclude that rates of nutrient return in dung depend not only on where herbivores deposit their dung, but also on its C:N:P stoichiometry, the activity of soil macrofauna and interactions between these factors. These factors may therefore influence the relative availabilities of N and P in the soil and hence the functioning of savanna ecosystems.

关键词： canopy sampling   phytophagous   natural enemies   pollinators  

摘要： Acacia mangium (Fabales: Fabaceae) is broadly used in restoration process of degraded lands in tropical and subtropical regions. Thus, our aim was to assess the spatial distribution of arthropods on tree crown (vertical- upper, median and lower canopy and horizontal-north, south, east and west) and leaf surfaces (adaxial and abaxial) of A. mangium trees. Phytophagous arthropods and natural enemies were quantified biweekly in 20 trees during three years. The Shannon index (H') of phytophagous insects were higher on the abaxial surface of leaves on branches facing the west side and basal thirds, while the lowest index was found on the adaxial surface of leaves on branches facing north and on trunk of A. mangium. The natural enemies and pollinators presented the highest H' indexes on the abaxial surface of leaves on branches facing north on basal thirds of A. mangium, while the lowest index values were found on the adaxial surface of leaves on branches facing the other sides. Trigona spinipes Fabricius (Hymenoptera: Apidae, Meliponinae), Aethalion reticulatum (Hemiptera: Aetalionidae) and Pentatomidae sp.1 (Hemiptera) were the most abundant and with the lowest k-dominance on different parts of A. mangium trees. Camponotus sp.2 (Hymenoptera: Formicidae), Tetragonisca angustula (Latreille) (Hymenoptera: Apidae) and Polistes sp. (Hymenoptera: Vespidae) had higher abundance and lower k-dominance. These results may be a support for programs of pest control and maintenance of natural enemies and pollinators in future plantations of A. mangium. For instance, application of biopesticides may reach better results if aimed directly to the preferred sites of target organisms, beyond minimizing possible negative effects on non-target ones.

关键词： conservation   ecology   land-use management   plant-animal interactions   tropical ecosystems  

摘要： African savannas are home to an abundant and diverse assemblage of wild herbivores, but the very grasses that sustain these wild herds also make savannas attractive to humans and their livestock We used the Kenya Long-term Exclosure Experiment to investigate the ecological effects of different combinations of native and domestic grazers. The experimental removal of large grazing mammals set into motion a cascade of consequences, beginning with the doubling in abundance of a small grazing mammal, the pouched mouse (Saccostomus mearnsi). The presence of abundant mice attracted venomous snakes such as the olive hissing snake (Psammophis mossambicus);devastated seedlings of the dominant tree (Acacia drepanolobium);and doubted the abundance of fleas, which potentially increased the risk of transmission of flea-borne pathogens. Together, these results show the potential for the loss of large mammals to have cryptic consequences for African savannas, with important and often undesirable repercussions for humans.

关键词： Animal phylogenetics   Biology and life sciences   Computational biology   Evolutionary biology   Evolutionary processes   Evolutionary systematics   Genetics   Genome analysis   Genome evolution   Genome sequencing   Genomic databases   Genomics   Mammalogy   Molecular biology   Molecular biology techniques   Phylogenetics   Research Article   Sequence analysis   Sequence databases   Sequencing techniques   Speciation   Zoology  

摘要： One of the major challenges in the analysis of closely related species, speciation and phylogeography is the identification of variable sequence markers that allow the determination of genealogical relationships in multiple genomic regions using coalescent and species tree approaches. Rodent species represent nearly half of the mammalian diversity, but so far no systematic study has been carried out to detect suitable informative markers for this group. Here, we used a bioinformatic pipeline to extract intron sequences from rodent genomes available in databases and applied a series of filters that allowed the identification of 208 introns that adequately fulfilled several criteria for these studies. The main required characteristics of the introns were that they had the maximum possible mutation rates, that they were part of single-copy genes, that they had an appropriate sequence length for amplification, and that they were flanked by exons with suitable regions for primer design. In addition, in order to determine the validity of this approach, we chose ten of these introns for primer design and tested them in a panel of eleven rodent species belonging to different representative families. We show that all these introns can be amplified in the majority of species and that, overall, 79% of the amplifications worked with minimum optimization of the annealing temperature. In addition, we confirmed for a pair of sister species the relatively high level of sequence divergence of these introns. Therefore, we provide here a set of adequate intron markers that can be applied to different species of Rodentia for their use in studies that require significant sequence variability.

关键词： agonistic behavior   anuran   assessment   playback   signaling   strategic behavior  

摘要： Animal contests can greatly impact individual fitness;therefore, the behavioral strategies used during contests have received much interest in both theoretical and empirical studies. Recent reviews of animal contest behavior have clarified the predictions for contest dynamics when individuals' behavioral strategies are based on influences of self, opponent, or both. These predictions mostly apply to natural or staged interactions between 2 competing animals, but studies of aggressive signaling behavior often use other methodologies. In particular, playback tests have been heavily utilized because they provide the investigator with powerful control over experimental conditions. My aims in this paper are 2-fold. First, I discuss how playback tests can be used to study animal contest dynamics. Specifically, I develop predictions for individuals' responses to playback tests that will allow investigators to discriminate between different contest strategies. By monitoring individual persistence, resource-holding potential (or its correlates as reflected in signal structure), and other behaviors in appropriately designed playback tests, I show that strategies based on influences of self, opponent, and both self and opponent can be discriminated. Second, I illustrate these methods with data from a playback experiment on male responses to acoustic signals in the gray tree frog, Hyla versicolor. Males' responses to playbacks of synthetic advertisement and aggressive calls that varied in call frequency indicated that both self and opponent characteristics influenced persistence in contests.

关键词： demographic variability   plant-herbivore interactions   herbivory   grass   browsing   tree   savanna   large mammal   elephant   browse trap  

摘要： Despite widespread acknowledgement that large mammal herbivory can strongly affect vegetation structure in savanna, we still lack a theoretical and practical understanding of savanna dynamics in response to herbivory. Like fire, browsing may impose height-structured recruitment limitations on trees (i.e. a 'browse trap'), but the demographics of herbivore effects have rarely been considered explicitly. Evidence that cohorts of trees in savannas may establish during herbivore population crashes and persist long term in savanna landscapes is anecdotal. Here, we use an experimental approach in Hluhluwe iMfolozi Park in South Africa, examining the response of grass biomass and tree populations to 10years of graduated herbivore exclusion, and their subsequent response when exclosures were removed. We found that grazer exclusion increased grass biomass and that, despite presumable increases in fire intensity and grass competition, herbivore - especially mesoherbivore, including impala and nyala - exclusion resulted in increases in tree size. After herbivore reintroduction, grazers reduced grass biomass over short time-scales, but tree release from browsing persisted, regardless of tree size. Synthesis. This work provides the first experimental evidence that release from browsing trumps grazer-grass-fire interactions to result in increases in tree size that persist even after browser reintroduction. Escape from the 'browse trap' may be incremental and not strictly episodic, but, over longer time-scales, reductions in browsing pressure may lead to tree establishment events in savanna that persist even during periods of intense browsing. Explicitly considering the temporal demographic effects of browsing will be the key for a much-needed evaluation of the potential global extent of herbivore impacts in savanna.

关键词： Acari   Ailanthus altissima   Collembola   Litter   Invasive species   Riparian ecosystem  

摘要： Invasive species are a major threat to global biodiversity because they alter the functioning of affected ecosystems by displacing the native vegetation and fauna. This study evaluated the effect of the invasive species Ailanthus altissima on soil properties and the microarthropod community, compared to the native species Populus nigra. Soil samples were taken in riparian forests, an ecosystem with high risk of colonisation by invasive tree species, on a stretch of the Henares River (Madrid, Spain) under the canopy of both tree species. In addition, controlled laboratory experiments were performed to evaluate the effects of litter on the arthropod community. Some groups of springtails (Entomobryomorpha, Poduromorpha and Symphypleona), mites (Gamasida and some Oribatida) and other arthropods groups (spiders, pseudoscorpionids, isopods and insects) were more abundant under the native species, while Actinedida mites were more abundant under ailanthus. Differences in porosity, pH and organic matter content were also observed between soils. In the laboratory experiments, the Arthropleona springtails and a few Oribatida mites preferred poplar leaf extract, and the Actinedida mites preferred ailanthus leaves. The invasion of A. altissima could be influencing soil fauna through their litter and also could be changing several soil properties which consequently affect soil microarthropod communities. This study reveals the clear disturbance of ecosystems that the invasion by exotic species produces at many levels of the soil system. (C) 2014 Elsevier Masson SAS. All rights reserved.

关键词： Animals   Biodiversity   Biodiversity   Forests   Herbivory/physiology   South Africa   Trees  

摘要： Forest fragmentation and plant diversity have been shown to play a crucial role for herbivorous insects (herbivores, hereafter). In turn, herbivory-induced leaf area loss is known to have direct implications for plant growth and reproduction as well as long-term consequences for ecosystem functioning and forest regeneration. So far, previous studies determined diverging responses of herbivores to forest fragmentation and plant diversity. Those inconsistent results may be owed to complex interactive effects of both co-occurring environmental factors albeit they act on different spatial scales. In this study, we investigated whether forest fragmentation on the landscape scale and tree diversity on the local habitat scale show interactive effects on the herbivore community and leaf area loss in subtropical forests in South Africa. We applied standardized beating samples and a community-based approach to estimate changes in herbivore community composition, herbivore abundance, and the effective number of herbivore species on the tree species-level. We further monitored leaf area loss to link changes in the herbivore community to the associated process of herbivory. Forest fragmentation and tree diversity interactively affected the herbivore community composition, mainly by a species turnover within the family of Curculionidae. Furthermore, herbivore abundance increased and the number of herbivore species decreased with increasing tree diversity in slightly fragmented forests whereas the effects diminished with increasing forest fragmentation. Surprisingly, leaf area loss was neither affected by forest fragmentation or tree diversity, nor by changes in the herbivore community. Our study highlights the need to consider interactive effects of environmental changes across spatial scales in order to draw reliable conclusions for community and interaction patterns. Moreover, forest fragmentation seems to alter the effect of tree diversity on the herbivore community, and thus,