共查询到20条相似文献,搜索用时 31 毫秒
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1IntroductionWildlifetradeisamain~mpetustoutilizewildlife.Thechangeinspeciesandvolumein-volvedinthewildlifetrademayreflectconservationstatus,dynamicsandexploitedlevelofwildliferesources.Thestudyonwildlifetradeisthetheoriticalbasisonwhichproposalsastolimittradeonrareorendangeredspeciescanbemade,andwithwhichfuturemonitoringofthetradecanbecompared.Theresultalsocanbeusedtoevaluateconservationeffectsofprotectionmeasuresandlawsforbiodiversityconservation.Itisofgreatsignificanceinguid-ingsustainable… 相似文献
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Hlasny V 《Journal of economic entomology》2011,104(3):764-772
Invasions of nonindigenous organisms have long been linked to trade, but the contribution of individual trade pathways remains poorly understood, because species are not observed immediately upon arrival and the number of species arriving annually is unknown. Species interception records may count both new arrivals and species long introduced. Furthermore, the stock of invasive insect species already present is unknown. In this study, a state-space model is used to infer the stock of detected as well as undetected invasive insect species established in the United States. A system of equations is estimated jointly to distinguish the patterns of introduction, identification, and eradication. Introductions of invasive species are modeled as dependent on the volume of trade and arrival of people. Identifications depend on the public efforts at invasive species research, as well as on the established stock of invasive species that remain undetected. Eradications of both detected and undetected invasive species depend on containment and quarantine efforts, as well as on the stock of all established invasive species. These patterns are estimated by fitting the predicted number of invasive species detections to the observed record in the North American Non-Indigenous Arthropod Database. The results indicate that agricultural imports are the most important pathway of introduction, followed by immigration of people. Expenditures by the U.S. Department of Agriculture and the Agricultural Research Service are found to explain the species identification record well. Between three and 38 invasive insect species are estimated to be established in the United States undetected. 相似文献
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W. B. RUDMAN 《Zoological Journal of the Linnean Society》1986,86(2):101-184
The genus Glossodoris Ehrenberg is reviewed and 28 species are placed in the genus. Seventeen species are fully described and of these, seven are named as new species. Four others are considered new to science, but insufficient material is available to name them. Published information on a further 11 species is included as is a discussion on phylogenetic trends within the genus. 相似文献
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A new argument that species are individuals has recently been presented based on the way species names are used and systemic logic. The alternate idea that species are a categorical item, i.e., collections of individuals, was rejected. We wanted to evaluate this approach by establishing concepts that apply to individuals in order to examine if they are also applicable to a species viewed as a categorical item. It is our thinking that if species are not such, then concepts applicable to individuals will not be applicable to species so viewed. Individuals and species are similar in the presence of conceptual boundaries, unidirectional change and the presence of past and future time. These are all central, and salient, biological phenomena. But, these are concepts that apply also to populations which, for the most part, are not the same as species. Thus, these considerations infer that species, when viewed as a collection of individuals, do not share relevant concepts with individuals. Our conclusion is that a species is a 'unity' rather than an 'individual'. 相似文献
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N D Levine 《The Journal of protozoology》1987,34(4):362-363
About 447 species of coccidia have been named from the 1687 living, known species of rodents; 207 host species, 92 host genera, and 15 host families are represented; this is about 12% of the known species of rodents. About 4600 species of apicomplexan protozoa have been named. Assuming that the same proportion of the total number of apicomplexan species has been named as of the coccidian species, there must actually be about 38,333 species of apicomplexan protozoa. There are 5.4 times as many protozoan genera as of apicomplexan genera. Assuming that the number of species in each genus is the same for all the protozoa as it is for the Apicomplexa, there may actually be 206,998 species of protozoa. This may be too conservative an estimate. Based on other criteria, an estimate of over 20 million species could be made. 相似文献
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Michael Griffin 《Biodiversity and Conservation》1998,7(4):483-494
Namibia's extant mammal fauna of 250 species represents about 75% of the southern African region's species richness, 83% of generic richness and 98% of familial richness. Fourteen species are presently recognized as endemic (75% or more of the global population occurring within Namibian borders). These endemics occur in the Namib Desert, pro-Namib transition zone and adjoining escarpment, and are primarily rupicolous. The Namibian endemic mammal fauna is characterized by the monotypic Petromuridae, and the rodent genera Gerbillurus and Petromyscus. The distribution of smaller species has probably not changed significantly over the past 200 years, but species such as lion and plain zebra have undergone range reductions of 95% or more, and five species are listed as recently extinct. Approximately 50% of all Namibian mammal species are provisionally listed as 'secure'. However, due to patchy data, 94 species (38%) are classified as under possible or probable threat. Nineteen species (8%) are classified as under definite threat. Over 13% of Namibia is set aside by the state for conservation purposes. Ninety-five percent of mammal species occur in at least one park, over 80% occur in three or more parks, and 59 species (28%) occur in ten or more parks, although for most species nothing is known of their population viability there. Major threats to mammals in Namibia are invasive aliens, including the risk of genetic pollution, and habitat alteration, especially wetland degradation. 相似文献
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Mark Ridley 《Biology & philosophy》1989,4(1):1-16
The correct explanation of why species, in evolutionary theory, are individuals and not classes is the cladistic species concept. The cladistic species concept defines species as the group of organisms between two speciation events, or between one speciation event and one extinction event, or (for living species) that are descended from a speciation event. It is a theoretical concept, and therefore has the virtue of distinguishing clearly the theoretical nature of species from the practical criteria by which species may be recognized at any one time. Ecological or biological (reproductive) criteria may help in the practical recognition of species. Ecological and biological species concepts are also needed to explain why cladistic species exist as distinct lineages, and to explain what exactly takes place during a speciation event. The ecological and biological species concepts work only as sub-theories of the cladistic species concept and if taken by themselves independently of cladism they are liable to blunder. The biological species concept neither provides a better explanation of species indivudualism than the ecological species concept, nor, taken by itself, can the biological species concept even be reconciled with species individualism. Taking the individuality of species seriously requires subordinating the biological, to the cladistic, species concept. 相似文献
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With 61 species occurring mostly in the Andes and adjacent lowland areas, Stenocercus lizards represent one of the most widespread and well-represented Andean vertebrate groups. Phylogenetic relationships among species of Stenocercus are inferred using different datasets based on mitochondrial DNA sequence data of 35 species and morphological data of 59 species. Among morphological data, polymorphic and meristic/morphometric characters are coded under the frequency parsimony and gap-weighting methods, respectively, and the accuracy of these methods is tested. When both types of characters are included, the resulting tree topology is more similar to the topologies obtained from analyses of DNA sequence data than those topologies obtained after exclusion of one or both types of characters. The phylogenetic hypotheses inferred including 59 species of Stenocercus (dataset 1) and excluding those species for which DNA data were not available (dataset 2) are generally congruent with each other, as well as with previously published hypotheses. The most parsimonious tree obtained from analysis of dataset 2 is used in a dispersal-vicariance analysis to infer ancestral areas and major biogeographical events. Species of Stenocercus are divided into two major clades. Clade A has diversified mostly in the central Andes, with a few species in the northern Andes and one species in the southern Andes. Clade B is more widespread, with species in the northern, central, and southern Andes, as well as in the Atlantic lowlands and Amazon basin. The most recent common ancestor of Stenocercus is inferred to have occurred in the eastern cordillera of the central Andes. Given morphological similarity and altitudinal distribution of some species nested in a northern-Andes clade, as well as the relatively recent uplift of this Andean region, it is possible that species in this clade have diverged as recently as the mid-Pliocene. 相似文献
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Based on independent interviews with 25 persons we report 44 edible species of plants used by the Batemi of Sale Division, Ngorongoro District, Tanzania. Thirty-one of these are specifically consumed as food; six species are chewed as thirst quenchers; seven species of gums and resins are chewed; two species are added to food as flavorants; and one species is used in the preparation of honey beer. We report 8 species used as tooth brushes by the Batemi. An additional 35 species of food and beverage plants were observed under cultivation by the Batemi. With these plants the Batemi ingest phytochemicals in a manner that could have positive health effects. 相似文献
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中国千斤拔属植物的初步研究 总被引:7,自引:0,他引:7
本文叙述了千斤拔属名的拉丁学名的变换和研究情况,并研究该属植物国产种的分类、地理分布及其特点。进而对该属植物的习性和苞片、花序、花和叶等诸器官演化趋势作初步探讨,并对该属6个类群之间可能的演化关系、属的起源、分布中心和迁移路线等问题提出初设想。 相似文献
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Richard L. Mayden and Kevin de Queiroz have devised and developed ‘a hierarchy of species concepts’ and ‘a unified species concept’, respectively. Although their integrated frameworks of species concepts are rather different as to how to integrate the diverse modern concepts of species, the end result is that they are likely to agree on species recognition in nature, because they virtually share the same major components (i.e. evolutionary or lineage concept of species; same way of delimiting species), and have the same important consequences. Both the hierarchical and unified frameworks, however, are interpreted to have shortcoming regarding the way of integrating the modern species concepts. I reformulate these ideas into a framework of species concepts as follows: It treats the idea of species as population‐level evolutionary lineages (sensu Wiley 1978 ) as the concept for species category, and it adopts the contingent biological properties of species (e.g. internal reproductive isolation, diagnosability, monophyly) as operational criteria in delimiting species. I also suggest that existing and revised versions of the integrated framework of species concepts all are not new species concepts, but versions of the evolutionary species concept, because they treat the evolutionary (or lineage) species concept as the concept for species category. 相似文献
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Engen S 《Mathematical biosciences》2007,210(2):490-507
There is often large variation in traits across the species of a community. In particular, variation in life history traits affecting population dynamics is likely to affect the species abundance distribution. Applying a dynamic and heterogeneous species abundance model we study how differences in extinction time for species in a community act as a force changing the distribution of dynamic parameters across species. This process may generate communities that are more heterogeneous then the heterogeneity measured as the species enter the community. Analytical results for some versions of the lognormal and gamma species abundance model are given as exemplifications of this process, together with stochastic simulations demonstrating the temporal changes in number of species and community heterogeneity through time. 相似文献
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Species concepts and species delimitation 总被引:7,自引:0,他引:7
De Queiroz K 《Systematic biology》2007,56(6):879-886
The issue of species delimitation has long been confused with that of species conceptualization, leading to a half century of controversy concerning both the definition of the species category and methods for inferring the boundaries and numbers of species. Alternative species concepts agree in treating existence as a separately evolving metapopulation lineage as the primary defining property of the species category, but they disagree in adopting different properties acquired by lineages during the course of divergence (e.g., intrinsic reproductive isolation, diagnosability, monophyly) as secondary defining properties (secondary species criteria). A unified species concept can be achieved by treating existence as a separately evolving metapopulation lineage as the only necessary property of species and the former secondary species criteria as different lines of evidence (operational criteria) relevant to assessing lineage separation. This unified concept of species has several consequences for species delimitation, including the following: First, the issues of species conceptualization and species delimitation are clearly separated; the former secondary species criteria are no longer considered relevant to species conceptualization but only to species delimitation. Second, all of the properties formerly treated as secondary species criteria are relevant to species delimitation to the extent that they provide evidence of lineage separation. Third, the presence of any one of the properties (if appropriately interpreted) is evidence for the existence of a species, though more properties and thus more lines of evidence are associated with a higher degree of corroboration. Fourth, and perhaps most significantly, a unified species concept shifts emphasis away from the traditional species criteria, encouraging biologists to develop new methods of species delimitation that are not tied to those properties. 相似文献
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Lang Kai-Yung 《植物分类学报:英文版》1988,26(3):173-188
Herminium is a genus of about 26 species, mainly distributed in the temperate and
subtropical regions of Asia and Europe. Yunnan, Sichuan and Xizang in China are the present distribution centre as well as differentiation centre of the genus. In the present paper, taxa
of Herminium hitherto recorded in China are taxonomically and phytogeographically discussed
and revised, and, as a result, 18 species are recongnized, including two newly recorded species, H. angustilabre King et Pantl. and H. quinquelobum King et Pantl., and 12 species endemic to China. A full list of synonyms is given, a key to the species is provided and the
distribution areas of all taxa are mapped. 相似文献
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Elvira Hörandl 《Folia Geobotanica》1998,33(3):335-348
The application of different current species concepts to the predominantly apomicticR. auricomus complex (goldilocks) is discussed. As with other uniparental reproducing organisms, biological species concepts are hardly applicable in apomictic groups. Information on reproductive systems, phenetic and ecological differentation, and evolutionary traits favour an “agamospecies” concept. It is argued that agamic lineages in goldilocks can be treated neither as subspecific taxa, nor as hybrids. A general viewpoint is proposed that species are stable phases within a continuous process of diversification of ancestral-descendent lineages. Constancy of progeny, similarity of phenotype, and ecogeographical niches of organisms are regarded as the most important operational criteria for grouping and ranking of species. Mode of reproduction is seen as a feature of a species — not as a criterion for its definition. Internal stability of features is regarded as more important for species definition than the features themselves. 相似文献
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Few comprehensive works have investigated non-indigenous snails and slugs as a group. We compiled a database of non-indigenous
gastropods in Israel to explore how they arrived and spread, characteristics of their introduction, and their biological traits.
Fifty-two species of introduced gastropods are known from Israel (of which nine species subsequently went extinct): 19 species
of freshwater snails and 33 species of terrestrial gastropods. The majority of these species are found only in human-dominated
habitats. Most of those found in natural habitats are aquatic species. Most snails are introduced unintentionally from various
parts of the Holoarctic region, reaching Israel as stowaways with horticultural imports and the aquarium trade, but some are
brought intentionally to be used as pets or for food. Because the study of this group in Israel is very limited, information
regarding their distribution in the country and their effects on other species is incomplete. Though only nine species of
non-indigenous snails have been found to date in natural habitats, some of these are very abundant. More information and research
is required to enable effective management schemes. 相似文献
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M. C. DAY 《Zoological Journal of the Linnean Society》1984,80(2-3):83-101
The hypothesis that males of certain species of the pompilid genus Cryptocheilus Panzer are polymorphic, first proposed by H. Wolf, is examined critically in the light of modern knowledge of the mating systems of Hymenoptera and the known biology of Cryptocheilus species. Speculations are made as to the likely selection pressures operating to produce this phenomenon; nine Old World species of Cryptocheilus are identified as probable examples. The taxonomic implications of the hypothesis are considered; one new generic and nine new specific synonymies are listed, and lectotypes are designated for three nominal species. Two names are retrieved from synonymy for species here recognized as valid. A key is provided for the extreme forms of the males of these species; more detailed treatment must await full revision of Cryptocheilus. 相似文献