关键词： ANIMAL migration   EFFECT of climate on animal migration   SAVANNAS   FOOD chains (Ecology)   AFRICA   SERENGETI Plain (Tanzania)  

摘要： The article discusses importance of animal migration for sustenance of Africa's freshwater food webs. Topics include effect of climate and man-made walls on great migrations, effect of extinction of animal migrations, mass drownings of Serengeti wildebeest in Mara river, animal carcasses adding to river biomass being pathway to carbon and nitrogen production.

关键词： brush management   cattle   endozoochory   Prosopis glandulosa   seeds   woody plant invasion  

摘要： The dispersal of woody plant seeds by livestock has been implicated as one of the causes of woody plant encroachment in semiarid ecosystems worldwide. In the southern Great Plains, United States, cattle are suspected to have increased encroachment of the woody legume honey mesquite (Prosopis glandulosa Torr.) because they are effective consumers of mesquite pods and pass viable seed from those pods through their digestive systems. Since other animal species also consume or gather mesquite pods and seeds, our objective was to compare the removal of mesquite pods by cattle, other vertebrate herbivores, and insects. Mature pods were collected from trees in late summer and placed within each level of a hierarchical exclusion design using fences and cages that blocked cattle;other large vertebrates (deer, feral hogs);smaller vertebrates (rabbits, birds, rodents);and insects at replicate sites in north and south Texas locations. Pod removal was quantified during 60-d trials in the fall of each of 3 yr. The treatment that allowed cattle to have access to pods had the greatest or tied for the greatest pod removal at trial end in all trials. Final pod removal in the feral hog and white-tailed deer treatments was numerically lower but statistically similar (P <= 0.05) to cattle. However, the rate of pod removal during the first 20 din several of the trials was greatest (P <= 0.05) in the cattle treatment at both locations. Pod removal by rodents was high in 1 yr at both locations, which we attributed to high growing season precipitation at both locations during that year. Results may have implications regarding seed-centric grazing management decisions and keeping cattle out of pastures when mesquite pods are abundantly present on the ground. (C) 2017 The Society for Range Management. Published by Elsevier Inc. All rights reserved.

关键词： Rule extraction   Reproduction   Animal personality   Animal behavior   Internal states   Fitness  

摘要： The connection between reproductive fitness and animal personality is not fully understood. Using computer simulations and machine learning, we found high accuracy rules that predict which personalities are associated with fitness for two correlated measures of components of fitness applied a posteriori for classificatory purposes: fitness component (1) in terms of survival and short-term reproductive success, and fitness component (2) in terms of long term reproductive success which is indirectly related to survival of the parents. Animals are represented in the abstract as individuals with a genome that through time develops into certain characteristic behaviors and personalities. To the best of our knowledge, this is the first simulation study of its kind that extracts rules to investigate the link between personality and fitness. Clearly separated behaviors between fit and non-fit individuals emerged through the evolution of the population over time without top-down processing. Moreover, we did not employ a pre-defined fitness function, in order to minimize any possible biases toward a specific type of behavior. With respect to fitness component (1), we found that individuals with one of two extreme values of a personality trait (either bold or fearful) tend to be most fit, which agrees with empirical studies. With respect to fitness component (2), we found that when resources are low, fit individuals search for food whereas if food is abundant, they focus on reproduction, thereby suggesting the context dependence of fitness related behaviors. Once again, these results agree with empirical studies.

关键词： defaunation   density-dependent transmission   exclosure   nematode   population regulation   wildlife decline  

摘要： Biodiversity loss can alter disease transmission;however, the magnitude and direction of these effects vary widely across ecosystems, scales, and pathogens. Here we experimentally examine the effects of one of the most globally pervasive patterns of biodiversity decline, the selective loss of large wildlife, on infection probability, intensity and population size of a group of common rodent-borne parasites - macroparasitic helminths. Consistent with previous work on vector-borne pathogens, we found that large wildlife removal causes strong and systematic increases of rodent-borne parasites, largely due to increases in rodent density, as rodents are released from competition with larger herbivores. Although we predicted that increased host density would also increase per capita infection among all directly transmitted parasites, this additional amplification occurred for only two of three examined parasites. Furthermore, the actual effects of large mammal loss on per capita infection were mediated by the complex suite of abiotic and biotic factors that regulate parasite transmission. Thus, while these results strongly suggest that large wildlife loss will cause systematic increases in rodent parasite populations, they also underscore the difficulty of making more specific predictions for a given parasite based on simple attributes such as transmission mode or life history strategy. Instead, detailed information on the ecology of each parasite species would be necessary to make more accurate predictions of how biodiversity loss will affect infection.

关键词： Blood-brain barrier   stroke   focal ischemia   neurovascular unit   endothelium  

摘要： Stroke-induced blood-brain barrier breakdown promotes complications like cerebral edema and hemorrhagic transformation, especially in association with therapeutical recanalization of occluded vessels. As arteries, capillaries and veins display distinct functional and morphological characteristics, we here investigated patterns of blood-brain barrier breakdown for each segment of the vascular tree in rodent models of embolic, permanent, and transient middle cerebral artery occlusion, added by analyses of human stroke tissue. Twenty-four hours after ischemia induction, loss of blood-brain barrier function towards FITC-albumin was equally observed for arteries, capillaries, and veins in rodent brains. Noteworthy, veins showed highest ratios of leaky vessels, whereas capillaries exhibited the most and arteries the least widespread perivascular tracer extravasation. In contrast, human autoptic stroke tissue exhibited pronounced extravasations of albumin around arteries and veins, while the pericapillary immunoreactivity appeared only faint. Although electron microscopy revealed comparable alterations of the arterial and capillary endothelium throughout the applied animal models, structural loss of arterial smooth muscle cells was only observed in the translationally relevant model of embolic middle cerebral artery occlusion. In light of the so far available concepts of stroke treatment, the consideration of a differential vascular pathophysiology along the cerebral vasculature is likely to allow development of novel effective treatment strategies.

关键词： 转基因树   世界   动物   昆明   中科院   体外培养体系   精原干细胞   中国科学院  

摘要： 据2017年1月5日《中国科学报》报道，中国科学院昆明动物所郑萍、赵旭东和姚永刚三个课题组共同建立了树嗣精原干细胞体外培养体系，并利用体外培养的树嗣精原干细胞获得世界首只转基因树嗣，实现了树驹基因修饰技术的突破。相关成果发表在《细胞研究》杂志。

摘要： A new nematode Parapharyngodon hugoi n. sp. (Oxyuroidea: Pharyngodonidae) is described parasitising the large intestine of the tree frog Trachycephalus typhonius (Linnaeus) (Anura: Hylidae) from the wetlands of Pantanal, State of Mato Grosso do Sul, Brazil. The new species exhibits a unique structure of the posterior cloacal lip in males, which is supported by a rigid V-shaped structure. Parapharyngodon hylidae parasitic in hylid frogs, including T. typhonius, from Mexico, is the most similar congener to P. hugoi n. sp. but is distinguished from the new species by the presence of a gubernaculum (vs absence), by the lateral alae in males ending far anterior to cloacal opening (vs near to it) and because in gravid females the ovaries encircle the oesophageal corpus. Additionally, the new species differs from its congeners as well as from species of Thelandros Wedl, 1862, a very closely related genus, by the combination of features such as spicule length, number of caudal papillae, morphology of the anterior cloacal lip, which is echinate, and position of ovaries. The geographical distribution of hosts seems to play an important role in the speciation process of Parapharyngodon spp.;however, due the lack of molecular data this issue along with the validity of both Thelandros and Parapharyngodon are still questions to be solved in the future, after improvement of the genetic database. A key to the species of Parapharyngodon parasitic in amphibians from the American continent is provided.

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.