关键词： Animals   Biodiversity   Biodiversity   Ecosystem   Ecosystem   Environment   Evolution   Insects/physiology   Meristem/growth & development   Peru   Plant Leaves/growth & development   Seedling/growth & development   Soil   Trees/growth & development   Tropical Climate  

摘要： In an edaphically heterogeneous area in the Peruvian Amazon, clay soils and nutrient-poor white sands each harbor distinctive plant communities. To determine whether a trade-off between growth and antiherbivore defense enforces habitat specialization on these two soil types, we conducted a reciprocal transplant study of seedlings of 20 species from six genera of phylogenetically independent pairs of edaphic specialist trees and manipulated the presence of herbivores. Clay specialist species grew significantly faster than white-sand specialists in both soil types when protected from herbivores. However, when unprotected, white-sand specialists dominated in white-sand forests and clay specialists dominated in clay forests. Therefore, habitat specialization in this system results from an interaction of herbivore pressure with soil type.

关键词： Varying environments   Neotropical forest   Habitat selection   Tropical   forest   Central panama   Meadow voles   Wet forest   Costa-rica   Seed   rain   Diversity.  

摘要： Variation in food resource availability can have profound effects on habitat selection and dynamics of populations. Previous studies reported higher food resource availability and fruit removal in treefall gaps than in the understorey. Therefore, gaps have been considered "keystone habitat" for Neotropical frugivore birds. Here we test if this prediction would also hold for terrestrial small mammals. In the Amazon, we quantified food resource availability in eleven treefall gaps and paired understorey habitats and used feeding experiments to test if two common terrestrial rodents (Oryzomys megacephalus and Proechimys spp.) would perceive differences between habitats. We live-trapped small mammals in eleven gaps and understorey sites for two years, and compared abundance, fitness components (survival and per capita recruitment) and dispersal of these two rodent species across gaps and understorey and seasons (rainy and dry). Our data indicated no differences in resource availability and consumption rate between habitats. Treefall gaps may represent a sink habitat for Oryzomys where individuals had lower fitness, apparently because of habitat-specific ant predation on early life stages, than in the understorey, the source habitat. Conversely, gaps may be source habitat for Proechimys where individuals had higher fitness, than in the understorey, the sink habitat. Our results suggest the presence of source-sink dynamics in a tropical gap-understorey landscape, where two rodent species perceive habitats differently. This may be a mechanism for their coexistence in a heterogeneous and species-diverse system.

关键词： cavity-nester habitat   Trichaptum abietinum   Fomitopsis cajanderi   tree topping, rifle and shotgun inoculation   internal decay  

摘要： A total of 188 Douglas-fir trees were treated to determine whether fungal inoculation with rifle or shotgun promoted stein decay and subsequent use by cavity-nesting birds in the Coast Range in Oregon. Inoculated trees were either live or killed by topping. Topped trees were climbed and severed just below the lowest whorl of live branches. Fungal inoculum was delivered by either a 0.45-70 caliber rifle or a 12-gauge shotgun to tree trunks at a height of about 8 in aboveground. Inoculum of either Phellinus pini or Fomitopsis cajanderi was grown on small wooden dowels or sawdust and fitted into the rifle slug (dowels) or behind the shotgun slug (sawdust). Sterile dowels or sawdust were used as a control. After 5 years, all topped trees had died, and at least 50% had sap rot as indicated by the presence of conks of Trichaptum abietinum. Conks of Crytoporus volvatus, Fomitopsis pinicola, or P. pini were sometimes observed on topped (dead) trees. Almost half of the topped trees had evidence of wildlife activity including foraging holes, nest cavities, or bark removal. There was no difference in sap rot incidence or subsequent wildlife activity among three treatments (rifle, shotgun, or not shot) or among three inoculum types (P. pini, F. cajanderi, or sterile). None of the untopped (live) but artificially inoculated trees had conks or evidence of wildlife use. Of seven live and shot trees that were destructively sampled, there was an average of 68.7 cm(2) of decay area on each wood disc that was associated with each bullet. There was no apparent difference in internal decay area between sterile and viable inoculum, but sample size was small. It appears that tree killing by topping below the live crown is a faster method of creating wildlife habitat than ballistic inoculation of live Douglas-fir trees in the Oregon Coast Range. Topped and dead trees had more avian foraging holes, deep cavities, and bark removed than did live inoculated trees. Based on the seven live shot

关键词： biodiversity   legacy tree   biological legacy   forest management   managed forests   Northwestern California   redwood   Sequoia sempervirens   basal hollows   wildlife communities   bats   small mammals   birds  

摘要： Old-growth forests provide important habitat elements for many species of wildlife. These forests, however, are rare where lands are managed for timber. In commercial forests, large and old trees sometimes exist only as widely-dispersed residual or legacy trees. Legacy trees are old trees that have been spared during harvest or have survived stand-replacing natural disturbances. The value of individual legacy trees to wildlife has received little attention by land managers or researchers within the coast redwood (Sequoia sempervirens) region where 95% of the landscape is intensively managed for timber production. We investigated the use of individual legacy old-growth redwood trees by wildlife and compared this use to randomly selected commercially-mature trees. At each legacy/control tree pair we sampled for bats using electronic bat detectors, for small mammals using live traps, for large mammals using remote sensor cameras, and for birds using time-constrained observation surveys. Legacy old-growth trees containing basal hollows were equipped with 'guano traps';monthly guano weight was used as an index of roosting by bats. The diversity and richness of wildlife species recorded at legacy trees was significantly greater than at control trees (Shannon index = 2.81 versus 2.32;species = 38 versus 24, respectively). The index of bat activity and the number of birds observed was significantly greater at legacy trees compared to control trees. We found no statistical differences between legacy and control trees in the numbers of small mammals captured or in the number of species photographed using remote cameras. Every basal hollow contained bat guano and genetic methods confirmed use by four species of bats. Vaux's swifts (Chaetura vauxi), pygmy nuthatches (Sitta pygmaea), violet-green swallows (Tachycineta thalassina), and the long-legged myotis (Myotis volans) reproduced in legacy trees. As measured by species richness, species diversity, and use by a number of diff

关键词： Amazon   bees   Brazil   Dipteryx   Jacaranda   model   pollination   sensitivity analysis   trees  

摘要： Animals, especially insects, are principal pollen vectors of tropical trees and have behavior patterns that affect gene dispersal. Here, we explore complex pollination systems using a new simulation model Eco-Gene and considering, among other factors, flowering synchrony. spatial distribution of trees, degree of selfing, population densities, pollinator flight distances, pollen deposition, and pollinator response to floral display size. Sensitivity analyses using two contrasting tree data sets (Jacaranda copaia and Dipteryx odorata) determined the importance of each parameter on three response variables: the proportion of seeds from self-pollination, effective population size, and pollen dispersal. Spatial considerations and attractiveness of floral displays were prominent features determining the population genetic result of pollinators, and some biological implications of the results are discussed.

关键词： Acacia   herbivory   rodent   savanna   seedling   seedling predation   small mammal   tree recruitment   ungulate  

摘要： Trees of the genus Acacia are widespread and important components of savanna ecosystems. Factors or organisms that influence the survival of Acacia seedlings are likely to affect tree recruitment and therefore community and ecosystem dynamics. In African savannas, large mammals, especially elephants, have been considered the most important agents of mortality for adult trees, but their impacts on tree seedlings are not well known. We investigated the effects of large mammals on Acacia seedling survival by excluding large mammals from replicated 4-ha plots. Approximately twice as many seedlings were killed in plots with large mammals absent as on plots with large mammals present. Rodents and some invertebrates were more abundant on plots without large mammals and were responsible for these higher predation rates. Seedlings in areas with large mammals were more likely to die of desiccation;however, net seedling survival was approximately twice as high in the presence of large mammals. Our results indicate that large mammals may indirectly increase Acacia seedling survival and thus accelerate, rather than inhibit, tree recruitment.

关键词： allometry   coexistence   diet breadth   guild relations   large carnivores  

摘要： 1. A long-term (13-year) data set, based on > 4000 kills, was used to test whether a sympatric group of large predators adheres to the theoretical predictions that (1) mean prey body size and (2) prey diversity increase as functions of predator body size. 2. All kills observed by safari guides are documented routinely in Mala Mala Private Game Reserve, South Africa. We analysed these records for lion (Panthera leo, Linnaeus), leopard (Panthera pardus, Linnaeus), cheetah (Acinonyx jubatus, Schreber) and African wild dog (Lycaon pictus, Temminck). Males and females of the sexually dimorphic felid species were treated as functionally distinct predator types. Prey types were classified by species, sex and age class. 3. Prey profiles were compared among predator types in terms of richness and evenness to consider how both the range of prey types used and the dominance of particular prey types within each range may be influenced by predator size. No significant size-dependent relationships were found, so factors separate from or additional to body size must explain variation in prey diversity across sympatric predators. 4. A statistically strong relationship was found between mean prey mass and predator mass (r(2) = 0.86, P= 0.002), although pairwise comparisons showed that most predators killed similar prey despite wide differences in predator size. Also, minimum prey mass was independent of predator mass while maximum prey mass was strongly dependent on predator mass (r(2) = 0.71, P= 0.017). The ecological significance is that larger predators do not specialize on larger prey, but exploit a wider range of prey sizes.

关键词： GABA   calcium binding proteins   olfactory marker protein   glomerulus   nidus   confocal laser scanning microscopy  

摘要： We immunohistochemically examined the organization of the main olfactory bulbs (MOBs) in seven mammalian species, including moles, hedgehogs, tree shrews, bats, and mice as well as laboratory musk shrews and rats. We focused our investigation on two points: 1) whether nidi, particular spheroidal synaptic regions subjacent to glomeruli, which we previously reported for the laboratory musk shrew MOBs, are also present in other animals and 2) whether the compartmental organization of glomeruli and two types of periglomerular cells we proposed for the rat MOBs are general in other animals. The general laminar pattern was similar among these seven species, but discrete nidi and the nidal layer were recognized only in two insectivores, namely, the mole and laboratory musk shrew. Olfactory marker protein-immunoreactive (OMP-IR) axons extended beyond the limits of the glomerular layer (GL) into the superficial region of the external plexiform layer (EPL) or the nidal layer in the laboratory musk shrew, mole, hedgehog, and tree shrew but not in bat, mouse, and rat. We observed, in nidi and the nidal layer in the mole and laboratory musk shrew MOBs, only a few OMP-IR axons. In the hedgehog, another insectivore, OMP-IR processes extending from the glomeruli were scattered and intermingled with calbindin D28k-IR cells at the border between the GL and the EPL. In the superficial region of the EPL of the tree shrew MOBs, there were a small number of tiny glomerulus-like spheroidal structures where OMP-IR axons protruding from glomeruli were intermingled with dendritic branches of surrounding calbindin D28k-IR cells. Furthermore, we recognized the compartmental organization of glomeruli and two types of periglomerular cells in the MOBs of all of the mammals we examined. These structural features are therefore considered to be common and important organizational principles of the MOBs. (C) 2004 Wiley-Liss, Inc.

关键词： 久视   实验   动物模型   树鼩   睫状肌   视力疲劳  

摘要： 目的:从神经-受体-受体介导睫状肌细胞内反应角度探讨肝劳发生的机制。方法:选用与猿猴解剖特点极其接近的动物树鼠句,对其限定照明时间并予以形觉刺激诱视,造成树鼠句持续近视状态以模拟肝劳的病理变化。在实验的第3,6,9天分别处死模型组及正常对照组动物,取睫状体检测其中β-肾上腺素受体(β-AR),环磷酸腺苷(cAMP),环磷酸鸟苷(cGMP)和Na+-K+-ATP酶;以确定造模3,6,9d3个不同时段对动物的影响。结果:造模6d时,树鼠句睫状肌中β-AR发生了上行调节;造模6d时,β-AR睫状肌中cAMP含量显著升高,cGMP含量降低;造模6d时,β-AR睫状肌中Na+-K+-ATP酶活力升高。结论:持续近视状态下睫状肌双重神经支配的异常为肝劳发病的重要原因之一。

关键词： parasites   Monogenea   Trematoda   Nematoda   parasite prevalence  

摘要： As part of broader study on the helminth parasites of amphibians in the different bioclimatic zones of Nigeria, a study of the the helminth parasites of amphibians at New Bussa in the Guinea savanna zone of Nigeria was undertaken. Amphibian hosts examined included Bufo regularis, B. maculatus, Dicroglossus occipitalis and Rana galamensis. The cestode Cylindrotaenia sp. was recovered from Bufo regularis and B. maculatus. Monogeneans were represented by Eupolystoma alluaudi and Polystoma galamensis and trematodes by Haematoloechus exoterorchis, H. micrurus, Mesocoelium monodi and Diplodiscus fischthalicus. Nematode parasites included Rhabdias bufonis, Amplicaecum africanum, Camallanus dimitrovi, Cosmocerca ornata and the larvae of an ascaridoid nematode. Eupolystoma alluaudi, which has been shown to have low prevalence rates in other savanna locations, had high prevalence rates in B. regularis (68.4%) and B. maculatus (82.3%). A few Bufo specimens, which had over-dispersed infection with adult worms and the whole range of developing stages represented, confirm the internal cycle of re-infection already observed by other investigators for E. alluaudi in Bufo spp.