关键词： Animal   Arthropods: Classification   Arthropods: Physiology   Biology:Methods   DNA   Ribosomal: Genetics   Invertebrates: Classification   Invertebrates: Physiology   Models   Biological   Phylogeny  

关键词： HERBIVORES   PLANT conservation   ACACIA  

摘要： High mortality and poor recruitment in Acacia tree populations in many parts of the Middle East may result in loss of biodiversity. Human activities in recent decades have caused drastic changes in the water regime and the abundance of wild and domestic ungulates, which may negatively affect these trees. We studied the effects of large mammalian herbivores on the establishment of young Acacia raddiana and A. tortilis in the Arava Valley between the Red Sea and the Dead Sea, Israel. Seed accumulation under trees was high when large herbivores were excluded, and direct observations confirmed that ungulates were the main seed dispersers of these Acacia species. Insect seed predators (bruchid beetles) damaged more than 95% of seeds not consumed by ungulates. seed germination was facilitated by gut passage through ungulates. Seedling survival was determined largely by water availability and was independent of herbivore density. Under present conditions, several years of high rainfall are necessary for successful establishment of young trees. under severe browsing pressure by ungulates, growth in juvenile trees was delayed and smaller sizes were overrepresented. There was no evidence, however, of effects on the long-term demography of Acacia trees, perhaps because ungulates increased seedling densities by enhancing the viability and germination of seeds. We conclude that large mammalian herbivores are essential components of arid Acacia savannas and that wild and domestic ungulates must be included in future conservation plans.

摘要： Many creatures use chemical signals (pheromones) as sources of information about the world around them. For example, a sex pheromone produced by one sex (usually the female) of a particular species induces an immediate behavioural response in the opposite sex of the same species. However, very little is known about amphibian pheromones. We have now discovered and characterized an aquatic, female-attracting pheromone from the parotoid and rostral glands of a male frog, the magnificent tree frog, Litoria splendida. To our knowledge, this pheromone, which we have named splendipherin, is the first pheromone from an anuran (frog or toad) to be identified.

关键词： Australia   birds   diversity   frogs   mammals   rainfall gradient   reptiles   savanna   soil  

摘要： The abundance, richness and species composition of frog, reptile, bird and mammal faunas varied along an extensive gradient from 470 to 1406 mm annual rainfall, and between three contrasting soil types (clay, loam and sand) in northern Australia. Patterns varied between and within vertebrate classes. In general, the most fertile soils in the highest rainfall sites supported the greatest species richness and abundance, but this association with fertility broke down at lower rainfall sites. Frogs were richest and most abundant at high rainfall sites, especially on clay soils, presumably because these had greatest water availability. Clay soils supported few reptile species, but these were often at relatively high abundance. High rainfall sites supported the richest reptile faunas. On sand and loam soils, bird species richness varied little along the rainfall gradient, but richness declined very substantially on clay soils. This was probably largely due to the far more marked vegetation structural change on clay soils than on other substrates. Few mammals were reported, and no clear trends were associated with either rainfall gradient or soil texture. Turnover in species composition along the rainfall gradient was gradual and limited on sand and loam soils, but far more marked on clay soils. There were few cases of replacements of ecologically comparable species along the gradient. These patterns reflect the disparate history, fragmentation and landscape positioning of clay soil environments, relative to the far more homogeneous eucalypt-dominated vegetation on sand and loam soils. Although comparable studies are lacking on other continents, patterns revealed here may be idiosyncratic due to the virtual monopolisation by eucalypts of the environment across the very extensive rainfall gradient.

关键词： 意大利   地震前兆   合欢树  

摘要： 叙述了在意大利那波利动物园内用树龄达５０ ａ 的两棵合欢树生物电位进行地震前兆观测的方法、装置等；给出了１９９０ 年５ 月１ 日至３１ 日坎帕尼亚地区２４ 次３ 级～５ 级地震前合欢树地震观测的资料；分析了这些地震前合欢树生物电位的异常形态；指出，合欢树生物电位可作为预测预报地震的首选树种。

关键词： edaphic macroarthropods   table-land Atlantic forest   Eucalyptus grandis   Acacia mangium   intertropical region   community structure   biological indicators  

摘要： This study compares the edaphic macroarthropod communities from experimental plantations of Acacia mangium and Eucalyptus grandis, both 7 years old, and from the primary forest, all located on the table-land region in the state of Espirito Santo (Brazil). Most of the taxonomic groups analyzed reach densities as high, or higher, in the plantations as in the primary forest. Four points however differentiate the communities of both plantations from that of the forest: the absence of Diplura and Pseudoscorpionida;the lower relative abundance of ants;the dominance of some non-social arthropods;and the concentration of a great percentage of macroarthropods in the litter layers. All these features seem to reflect a higher complexity in the decomposition subsystem of the primary forest, which is expected since it is a natural ecosystem. Regarding agroecosystems, the community under A. mangium shows a lower seasonal variation of total densities and a higher density of Blattaria, Isopoda, Coleopteran larvae and Lepidopteran larvae. These differences are apparently a consequence of the greater quantity of leaf litter, rich in nutrients, accumulated on the soil in this plantation. Therefore, both plantations create a propitious environment for macroarthropod communities. But A. mangium seems to provide better conditions to the soil communities, and thus it seems to be an important alternative to conciliate the wood production and the recuperation of edaphic communities in areas surrounding the remnants of the Atlantic forest. (C) 2000 Editions scientifiques et medicales Elsevier SAS.

关键词： defaunation   rumen protozoa   Sesbania sesban  

摘要： Nine different accessions of Sesbania sesban were examined for their toxicity to ciliate protozoa from sheep receiving a mixed grass hay-barley/fishmeal concentrate in Aberdeen, Scotland, Several accessions were much more toxic than those (ILRI 10865, ILRI 15036) identified and tested in a previous study. Two highly toxic accessions and one less toxic accession were compared with ILRI 15036 in a feeding trial in Debre Zeit, Ethiopia with sheep receiving a sululta hay-wheat bran diet. No suppression of protozoal numbers occurred in response to S. sesban supplementation (200 g/day). When rumen fluid removed from sheep on the supplemented diet was tested in vitro, protozoal activity appeared to be inhibited less by S. sesban in the mixed population than in either washed protozoa from the same rumen fluid or than had occurred in Scottish sheep. It was concluded that dietary, microbial or animal factors in the Ethiopian sheep had caused the destruction of the antiprotozoal material present in even the most potent accessions of S. sesban. (C) 1999 Elsevier Science B.V. All rights reserved.

关键词： Animals   Evolution   Fossils   Mammals/classification   Phylogeny   Phylogeny   Skeleton  

摘要： An exceptionally complete skeleton that dates to roughly 140-150 million years ago offers the closest look yet at the last common ancestor of modern mammals.

关键词： Taxa   Maximum parsimony   Cladistics   Topology   Monotremes   Evolution   A posteriori knowledge   Computer software  

摘要： Click to increase image sizeClick to decrease image size

关键词： Botswana   group size   Kalahari   ostrich   rainfall  

摘要： Large herbivores, including livestock and ostrich, were counted alone a 200-km long track in south-western Kalahari. Botswana. Altogether, 37 counts were made during different seasons. The number of animals seen and group size were recorded. These variables were compared with monthly and accumulated rainfall (number of animals and group size) and distance to pans (number of animals). Observations of game and livestock were also related to distance to villages. In four of the seven studied species, most animals were seen during the wet season. Group size also varied between seasons apart from the non-gregarious steenbok and duiker, Number of animals and group size were in some cases correlated with rainfall during the month of observation or with accumulated rainfall during the preceding months. The various species were more often observed close to pans than further away from the pans. Compared to livestock. game was on average observed >10 km further au ay from the villages. Few observations of game were made between village centres and the livestock observations most distant from the village.