关键词： Koala   Semi-arid   Resource selection   Spatial distribution   Australia   Home range  

摘要： Background: Conservation strategies derived from research carried out in one part of the range of a widely distributed species and then uniformly applied over multiple regions risk being ineffective due to regional variations in species-habitat relationships. This is particularly true at the edge of the range where information on animal movements and resource selection is often limited. Here, we investigate home range size, movement patterns and resource selection of koalas Phascolarctos cinereus in the semi-arid and arid landscapes of southwest Queensland, Australia. We placed collars with GPS units on 21 koalas in three biogeographic regions. Home range sizes, resource selection and movement patterns were examined across the three regions. Results: Habitat selectivity was highest at the more arid, western edge of the koala's range with their occupancy restricted to riparian/drainage line habitats, while the more easterly koalas displayed more variability in habitat use. There was no significant difference between home range sizes of koalas at the western edge of the range compared to the more easterly koalas. Instead, variability in home range size was attributed to spatial variations in habitat quality or the availability of a key resource, with a strong influence of rainfall and the presence of freestanding water on the home range size of koalas. Within a 580 m spatial range, movement patterns of male and female paths showed a tortuous trend, consistent with foraging behavior. Beyond this spatial range, male paths showed a trend to more linear patterns, representing a transition of movement behavior from foraging to breeding and dispersal. Conclusions: The difference in home range movement patterns and resource use among the different koala populations shows that behavior changes with proximity to the arid edge of the koala's range. Changes in home range size and resource use near the range edge highlight the importance of further range-edge studies for informin

关键词： 北京动物园   雕塑   青年时期   锲而不舍   单簧管   北京人   学习   演奏家  

摘要： 田树民，1956年生，北京人，自幼随父学习绘画，尤喜动物与音乐，先拜解放军军乐团单簧管演奏家张进才学习单簧管，后从吾学习石雕。树民青年时期在北京动物园供职，与鸟兽虫鱼结下不解之缘。在爬虫馆工作时，细心观摩，胸有成竹，刀笔之下，出神入化，至今所镌作品百余件，各臻妙处。京华从吾习雕刻者，卓然有成者惟树民也。树民不慕荣利，穷且益坚、锲而不舍、持之以恒。必成器也。

关键词： burning mosaic   critical weight range   fire impact   post-fire succession   small mammal   vegetation structure  

摘要： Understanding mechanisms underlying fire regime effects on savanna fauna is difficult because of a wide range of possible trophic interactions and feedbacks. Yet, understanding mechanisms underlying fauna dynamics is crucial for conservation management of threatened species. Small savanna mammals in northern Australia are currently undergoing widespread declines and regional extinctions partly attributable to fire regimes. This study investigates mammal trophic and ecosystem responses to fire in order to identify possible mechanisms underlying these declines. Mammal trophic responses to fire were investigated by surveying mammal abundance, mammal diet, vegetation structure and non-mammal fauna dynamics in savannas six times at eight sites over a period of 3 years. Known site-specific fire history was used to test for trophic responses to post-fire interval and fire frequency. Mammal and non-mammal fauna showed only minor responses of post-fire interval and no effect of fire frequency. Lack of fauna responses differed from large post-fire vegetation responses. Dietary analysis showed that two mammal species, Dasyurus hallucatus and Isoodon auratus, increased their intake of large prey groups in recently burnt, compared to longer unburnt vegetation. This suggests a fire-related change in trophic interactions among predators and their prey, after removal of ground-layer vegetation. No evidence was found for other changes in food resource uptake by mammals after fire. These data provide support for a fire-related top-down ecosystem response among savanna mammals, rather than a bottom-up resource limitation response. Future studies need to investigate fire responses among other predators, including introduced cats and dingoes, to determine their roles in fire-related mammal declines in savannas of northern Australia.

关键词： Urban ecology   Arboreal arthropods   Sampling   Trees  

摘要： Large, isolated trees are a prominent part of town planning, and the nature of the urban environment poses unique challenges in sampling the arthropod assemblages found on them. As part of a larger study on the role of these trees in supporting wider biodiversity, we undertook a trial of arthropod sampling methods to compare the relative impact of sampling method versus the species of tree sampled. Using four species of study trees, three sampling methods were trialed: an inverted cone based bole trap, a compact flight intercept trap, and branch bagging and clipping. Total arthropod abundance, richness, and diversity were modeled using generalised linear mixed models, which showed that in many cases the variation between sampling method was larger than that found between tree species. All three of the sampling methods proved to be practical in the field, and overcame the challenges faced in sampling urban trees, thereby providing the opportunity for more detailed study. Our findings also highlight the case for a multifaceted approach to sampling arthropods if a complete picture of the community assemblage is to be gained.

关键词： 身高   动物   长度单位   测量  

摘要： “朋友们，我们测量人和动物的身高时，不是一般都说几米吗。那么测量高度的时候，长度单位是不是只能用m（米）呢？”

关键词： Phylogenetics   molecular clock   sequence evolutionary rate   phenotypic evolution   morphology   genomics  

摘要： Sequence evolution behaves in a relatively consistent manner, leading to one of the fundamental paradigms in biology, the existence of a 'molecular clock'. The molecular clock can be distilled to the concept of accumulation of substitutions, through time yielding a stable rate from which we can estimate lineage divergence. Over the last 50 years, evolutionary biologists have obtained an in-depth understanding of this clock's nuances. It has been fine-tuned by taking into account the vast heterogeneity in rates across lineages and genes, leading to 'relaxed' molecular clock methods for timetree reconstruction. Sequence rate varies with life history traits including body size, generation time and metabolic rate, and we review recent studies on this topic. However, few studies have explicitly examined correlates between molecular evolution and morphological evolution. The patterns observed across diverse lineages suggest that rates of molecular and morphological evolution are largely decoupled. We discuss how identifying the molecular mechanisms behind rapid functional radiations are central to understanding evolution. The vast functional divergence within mammalian lineages that have relatively 'slow' sequence evolution refutes the hypotheses that pulses in diversification yielding major phenotypic change are the result of steady accumulation of substitutions. Patterns rather suggest phenotypic divergence is likely caused by regulatory alterations mediated through mechanisms such as insertions/deletions in functional regions. These can rapidly arise and sweep to fixation faster than predicted from a lineage's sequence neutral substitution rate, enabling species to leapfrog between phenotypic 'islands'. We suggest research directions that could illuminate mechanisms behind the functional diversity we see today.

关键词： Ecological modeling   Alien species   Classification trees   Azolla filiculoides (Lam.)  

摘要： Alien species have the abilities to alter the ecosystems they invade. We used classification trees (CTs) to predict the distribution of an exotic species, Azolla filiculoides (Lam.), at Selkeh Wildlife Refuge located in Anzali wetland, northern Iran. Cover percentages of Azolla were modeled using 33 physico-chemical and structural habitat variables. In total, 7 sampling sites were considered for abiotic and biotic sampling which resulted in 84 datasets. The predictive power of CTs was assessed based on two performance criteria: the percentage of Correctly Classified Instances (CCI %) and Cohen's kappa statistics (kappa). Different Pruning Confidence Factors (PCFs) were tested in order to improve the predictive results with regard to the complexity and accuracy of the predictions. The obtained results showed that Azolla distribution prediction was reliable in terms of both performance criteria (CCI > 70% and kappa > 0.40). Of the 33 variables presented to the model, the validity of 9 variables was confirmed for the prediction of habitat requirement of Azolla. A logical relationship was found between the distribution of Azolla and structural habitat variables such as air temperature, humidity, light intensity and depth of wetland. Besides, orthophosphate and nitrate were found to be two important nutrients for the prediction. The CTs allowed the selection of the most important variables and thus provided critical information to support the implementation of an Azolla management programme in Anzali wetland. More specifically, this kind of models can be used to select parameters that should be sampled at Selkeh wetland in the future. (C) 2012 Elsevier B.V. All rights reserved.

关键词： fire ecology   invertebrates   Kimberley   savanna  

摘要： This paper documents the effects of fire on grass-layer invertebrates in tropical savannas of the Kimberley region of north-western Australia, in the context of resource availability for consumers. Inappropriate fire regimes have been identified as a factor threatening a number of vertebrate groups, including small mammals, across northern Australia, and a possible mechanism might be through the effects of individual fires or fire regimes on food availability. We test for a fire effect on grass-layer invertebrate resources, which may affect insectivorous savanna vertebrates. Wet season sweep-net invertebrate samples were taken in two tropical savanna habitats, with contrasting laterite and sandstone substrates, in 2008, 2009 and 2010. Sites were stratified by post-fire interval to analyse invertebrate successional change after fire. In addition, experimental burns were implemented in 2010 to investigate immediate post-fire invertebrate responses. Total invertebrate numbers declined by 8090% immediately (1 week) following fire, reflecting the loss of grass-layer habitat. Of the commonly sampled invertebrate groups, Araneae, Coleoptera, Hempitera, Lepidoptera, Formicidae and Diptera were all reduced in numbers immediately post-fire, whereas Orthoptera showed no immediate post-fire decline. Invertebrate numbers were rapidly restored to pre-fire levels by the first wet season after fire, and no detectible change was observed in numbers or composition from 1 to 34 years post-fire (the longest post-fire interval available). This suggests that the effects of individual fires on grass-layer invertebrates are very short-lived. Such short-lived post-fire responses among grass-layer invertebrates, plus evidence that most ground-layer invertebrate groups are fire-resilient, suggest that food resource limitation is not a tenable explanation for fire-related declines among insectivorous savanna vertebrates. However, wet season burning could result in significant invertebrate reso

关键词： mammals   monitoring   abundance   population cycle  

摘要： The population dynamics of Clethrionomys voles has a cyclic pattern characteristic of these rodents in Scandinavia (Koshkina, 1966; Okulova and Kataev, 2003; Stenseth, 1999). Among 16 population cycles traced in Cl. rufocanus, there were eight cycles with a 4 year period, six with a 6 year period, and two with a 6 year period.

关键词： ant   fire regime   fire resilience   frequent fire   small mammal  

摘要： Tropical savannas are the world's most fire-prone biome, and savanna biotas are generally well adapted to frequent fire. However, in northern Australia there are concerns that recent increases in the frequency and extent of high-intensity fires are causing substantial declines in regional biodiversity values. In this paper we use two well-studied and contrasting faunal groups, ants and small mammals, as case studies for reviewing faunal responses to fire in Australian savannas. The Australian savanna ant fauna is dominated by arid-adapted taxa that are highly resilient to frequent fire and are not considered to be threatened by prevailing fire regimes. Indeed, frequent fire promotes ant diversity because it maintains an open habit that makes the dominant arid-adapted taxa feel at home. Long-term fire exclusion reduces ant diversity due to a marked decline in arid-adapted taxa, and favours highly generalized, more shade-tolerant taxa. In contrast, many small mammal species of high conservation value are highly sensitive to frequent fire, and there are widespread concerns that their populations are threatened by current fire management. Many of the species have shown dramatic population declines over recent decades, and, although the causes are poorly understood, there is little doubt that fire is an important contributing factor. It is likely that fire is acting synergistically with other underlying causes of decline, particularly predation by feral cats. The overall resilience of most savanna animal species in relation to frequent fire suggests that they are secure under all but the most extreme fire regimes. However, it is clear that more fire-sensitive groups such as small mammals need special fire management attention. This needs to involve less frequent and finer-scale burning, along with the protection of some large, infrequently burnt source areas.