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291.
The occurrence of cannibalism in mammals was studied during a general review of cannibalism (Polis, 1981). In total, there were 146 references documenting intraspecific predation in 75 species of mammals distributed between seven orders. Of these references, 138 refer to cannibalism whereas eight studies refer to intraspecific killing unaccompanied by cannibalism. Of the papers that specified the identity of both the predator and the prey, approximately 80% referred to infanticide (including cannibalism). It appears that infanticide often functions as part of a reproductive strategy. Juveniles and adults are occasional intraspecific prey for some species of Insectivora, Chiroptera, Primates, Lagomorpha, Rodentia, Carnivora, and Artio-dactyla. Cannibalism was best documented for the carnivores, rodents and primates. In general, cannibalism often occurs during normal predatory activities and is a function of low food availability, environmental stress, and a high density of conspecifics. 相似文献
292.
DAVID W. STANLEY-SAMUELSON RUSSELL A. JURENKA GARY J. BLOMQUIST WERNER LOHER 《Physiological Entomology》1987,12(3):347-354
ABSTRACT. When injected into the haemolymph of newly emerged adult males of the field cricket, Teleogryllus commodus (Walker), [3 H]arachidonic acid is incorporated into tissue phospholipids. Two reproductive tissues, testes and accessory glands, incorporate and preserve the labelled arachidonic acid for at least 49 days. With onset of circadian rhythm-controlled spermatophore production, radioactive arachidonic acid is incorporated into spermatophore phospholipids. After mating with untreated females, radioactivity was detected in spermathecae and in haemolymph from females. Some of the transferred radioactive arachidonic acid is subsequently converted into prostaglandins. Hence, males of T. commodus transfer prostaglandin synthetase activity and substrate by way of spermatophores during mating 相似文献
293.
294.
Phylogenetic diversity: a quantitative framework for measurement of priority and achievement in biodiversity conservation 总被引:3,自引:0,他引:3
GARY M. BARKER 《Biological journal of the Linnean Society. Linnean Society of London》2002,76(2):165-194
The value of biodiversity lies in its option value for the future, the greater the complement of contemporary biodiversity conserved today, the greater the possibilities for future biodiversity because of the diverse genetic resource needed to ensure continued evolution in a changing and uncertain world. From this perspective, biodiversity option value can be equated with richness in the different features expressed by species. An individual species of greater value is one contributing more novel features to a given subset. The feature diversity of species and communities is difficult to estimate directly, but can be predicted by the phylogenetic relationships among the species. The ‘Phylogenetic Diversity’ measure (PD) (Faith, 1992a) estimates the relative feature diversity of any nominated set of species by the sum of the lengths of all those branches spanned by the set. These branch lengths reflect patristic or path‐length distances. This study first reviews and expands on some of the properties of PD, and develops simple modifications of the measure (δnPD and enPD) to enable capture of both the phylogenetic relatedness of species and their abundances in each sample. Then the application of PD, δnPD and enPD to a wide range of conservation and resource management issues is demonstrated using avian case studies. Supertree construction procedures (matrix representation using parsimony analysis; average consensus) were used to combine the extensive DNA‐DNA hybridization tree of Sibley & Ahlquist (1990) with numerous, recently published phylogenetic reconstructions to derive a phylogenetic tree for the global avian fauna. Using this supertree as a systematic framework, the utility of PD was demonstrated in four case studies: (i) state of the environment reporting, with changes in avian faunas resulting from extinctions quantified as indicators of the state of biodiversity at Global, New Zealand and Waikato region scales, and changes in available habitat quantified as indicators of pressures on biodiversity in the Waikato region; (ii) setting priorities for threatened species management, with PD as a measure of option value integrated with information on survivorship expectations to develop a ranking among threatened New Zealand forest bird species; (iii) monitoring biotic response to management, with data from 5‐minute counts used to analyse changes in forest bird communities under three management regimes in New Zealand; and (iv) selection of indicator species, with PD used to objectively identify subsets of species in the Global, New Zealand and Waikato avian faunas that comprise a high proportion of the option value in those faunas. 相似文献
295.
Tests (pupal covers) of twenty-eight species of male Coccidae, representing fifteen genera from America north of Mexico, are described and illustrated. Tests of each of the species exhibit morphological differences which are useful in identification. Terminology is given for the sutures, corresponding plates, and related structures of the generalized test and a key is provided for separation of the described species. 相似文献