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Pages 24-45

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From page 24... ... Virgin Islancls, Hawaii, American Samoa, and various Micronesian island groups) , the prehistoric and ongoing extinction of numerous populations and species of birds has consequences beyond losing the birds themselves. Read the entire page →
From page 25... ... Many tracts of land in North America are relatively undisturbed, and if biologically feasible, we might try to restore locally extirpated species as part of a recovery program for endangered species. Rather than using past distributions as strict guiclelines for restoration efforts, the data could be part of planning conservation programs, with a goal of preserving plant and animal communities that approach those of a less disturbed state. Read the entire page →
From page 26... ... become extinct worldwide and then dividing the number of regional extinctions by the global number of species in the groups. The resulting estimated global extinction rates which wouici have been larger if other known extinctions were included in the estimate ranged from 10 to 1,000 times the estimates! Read the entire page →
From page 27... ... Cumulative losses of wetlands have attracted much concern and scrutiny (NRC, 1992a) , perhaps because 50% of animals and 33 % of plants listed as endangered or threatened under the Endangered Species Act depend on wetland habitats (Nelson, 19891. Read the entire page →
From page 28... ... Perhaps the most notorious of all exotic fish introductions is that of the Nile perch (Lates nitotica) into Lake Victoria in East Africa, where it has clevastated the diversity of the endemic cichlid fishes. Read the entire page →
From page 29... ... ~ The prehistoric and ongoing extinction of so many populations and species of birds on islands has consequences beyond losing the birds themselves. The losses of land birds, for example, may influence pollination or seed dispersal of indigenous plants. Read the entire page →
From page 30... ... For most endangered species in the United States today, the most serious threat is habitat destruction. Because of this, habitat conservation is the best single means to counter extinction. Read the entire page →
From page 31... ... Island, California. Natural History Museum of Los Angeles County, Science Series 36:319-327. Read the entire page →
From page 32... ... 1989. Wildlife Conservation and the Invasion of Nature Reserves by Introduced Species: a Global Perspective. Read the entire page →
From page 33... ... 1989. Agriculture, wetiancis, and endangered species: The Food Security Act of 1985. Read the entire page →
From page 34... ... Science Series Publication 30. Natural History Museum of Los Angeles County, Los Angeles, Ca. Read the entire page →
From page 35... ... 1987. California condor associated with sprucejack pine woodland in the Late Pleistocene of New York. Read the entire page →
From page 37... ... Nonetheless, the committee concludes that the ESA's inclusion of species, subspecies, and distinct population segments is correct and appropriate. HISTORICAL USE OF THE TERM SPECIES IN IMPLEMENTATION OF THE ENDANGERED SPECIES ACT Introduction Many societies have names for kinds of organisms, usually organisms that are large and conspicuous, or of life-sustaining, life-threatening, or economic importance. Read the entire page →
From page 38... ... Botanical Interpretations of Species When Congress passed the Endangered Species Act in 1973, it explicitly included plants, as well as fish and wildlife. After the ESA was passed, Congress requested that the Smithsonian Institution prepare a list of threatened, endangered, and extinct plants of the United States. Read the entire page →
From page 39... ... ~5) of the Endangered Species Act was amended to state that species on which action had not been taken cluring 2 years after the initial proposal must be withdrawn from consideration. Read the entire page →
From page 40... ... HISTORY OF SPECIES CONCEPTS BEFORE AND AFTER THE ENDANGERED SPECIES ACT Species Concepts Although Darwin's Origin of Species was ostensibly about speciation, the book really is about natural selection, or the changes that take place within species, not about how species arise from other species. Many biologists have extrapolated from Darwin's assumptions about selection to a theory of speciation. Read the entire page →
From page 41... ... Any given island might have entities that systematists would recognize as full species, subspecies, distinct population segments, or even the ancestral species, unaltered. To complicate matters further, a drop in sea level might allow all these isolates to meet-those that had differentiated sufficiently would not interbreed and would thus remain isolated as species, but others might interbreed, spreading their special characteristics into the other populations so that the unique identities of each isolate would be lost. Read the entire page →
From page 42... ... In 1974, Ghiselin's "radical solution to the species problem" restructured the debate to a consideration of the ontological status of those units of nature being called species. Ghiselin's timing was coincident with the establishment of phylogenetics in systematics after 1966, and the general rethinking of many basic assumptions that took place in those years included reexamination of species concepts as well. Read the entire page →
From page 43... ... BOX 3-1 Species concepts in the scientific literature. Despite of the lack of consensus about species concepts, the scientific and popular cultures attach special significance to the rank of species, leading to debates over the importance of groups of organisms ranked below the species level, such as subspecies, varieties, races, or population segments. Read the entire page →
From page 44... ... A CONCEPT OF SPECIES FOR THE PURPOSES OF THE ENDANGERED SPECIES ACT Introduction After centuries of debate, no one doubts that natural groups of organisms exist. Scientists now are concerned with methods of classification and circumscription of taxonomic boundaries. Read the entire page →
From page 45... ... Thus, the following discussion provides a practical approach to identifying distinct population segments. Application of the evolutionary unit concept should result in no substantive change in the application of conservation laws. Read the entire page →

From page 24...

... Virgin Islancls, Hawaii, American Samoa, and various Micronesian island groups) , the prehistoric and ongoing extinction of numerous populations and species of birds has consequences beyond losing the birds themselves.