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From page 46... ... is usually associated with sufficient genetic divergence to ensure an inclependent evolutionary future. Measures of genetic divergence or genetic distance between populations can be user! Read the entire page →
From page 47... ... As a consequence, average levels of genetic divergence can be estimated from reasonably large samples of genes that determine protein products. In addition, the isozyme method is relatively easy to implement, and it is not difficult for an experienced laboratory to screen several hundred individuals per day. Read the entire page →
From page 48... ... , and a change in fragment pattern must therefore be clue to a mutational change in a recognition site. A recent innovation in the PCR method, know as the RAPD method, is based on short random primers (usually 10 nucleotides in length) Read the entire page →
From page 49... ... other vocalizations often lead to reproductive isolation (e.g., Lack, 1971~. The degree to which population segments in the wild are independent units or part of a larger genetic entity is often unclear because of difficulties in ascertaining historical and current levels of gene flow. Read the entire page →
From page 50... ... is another problematic case. There is very little genetic variation in the Big Cypress panthers, and those in the Everglades, which were introduced from stock descended from Latin American populations, have hybridized with those in the Big Cypress area (Roelke et al., 1993; Barone et al., 1994~. Read the entire page →
From page 51... ... A biologically sound methoc! of identifying distinct population segments does not recognize political boundaries, although it does recognize the validity of asking whether a particular population within a political boundary (e.g., a country) Read the entire page →
From page 52... ... on scientific evidence. To help provide scientific objectivity in identifying these population segments, the concept of the evolutionary unit (KU) Read the entire page →
From page 53... ... There is no scientific reason to exclude any EUs of invertebrate animals and plants from coverage under the ESA. � Although the way organisms are divided into kingdoms has changed since the ESA was enacted in 1973, current scientific knowledge about how species concepts apply in practice to many of these organisms does not lead us to recommencI that coverage be extended to prokaryotes and most single-celled eukaryotes, such as yeasts. Read the entire page →
From page 54... ... 1991. Policy on applying the definition of species under the En(langere(1 Species Act to Pacific salmon. Read the entire page →
From page 55... ... Evolutionarily significant units and the conservation of biological diversity under the Endangered Species Act. Read the entire page →
From page 56... ... 56 Science and the Endangered Species Act Woolfenclen, G Read the entire page →
From page 57... ... Habitat is one of the four components of a species' environment, along with climate variables, nutrients, and other interacting organisms (Andrewartha and Birch, 1954~. The fact that habitat serves a multitude of organisms is critical to understanding its full role in the Endangered Species Act. Read the entire page →
From page 58... ... Ancl habitat protection is a prerequisite for conservation of biological diversity. Habitat protection is essential not only to protect those relatively few species whose endangerment is established, it is also in essence a pre-emptive approach to species conservation that can help to avoid triggering the provisions of the Endangered Species Act. Read the entire page →
From page 59... ... regulations concerning the act's prohibition An, against taking an endangered species, in this case, the northern spotted owl. Take is defined in the ESA to include harm, and FWS has defined harm to include significant habitat modification that adversely affects an endangered species. Read the entire page →
From page 60... ... The standard of habitat protection provides an important point of focus for those outside of government, including the scientific community, to help protect areas at least until recovery plans are developed that will clarify the needs of endangered species and provide more fully for their recovery. Importantly, critical habitat designation can be beneficial to other listed and nonlisted species living in the clesignated area, especially for those species for which satisfactory long-term recovery plans have not been implemented. Read the entire page →
From page 61... ... Because in our recommendation essential survival habitat is identified without reference to economic impact, and because it might not be sufficient to ensure long-term survival and recovery of endangered species, the committee views it as an emergency, stop-gap measure until critical habitat can be designated and a recovery plan can be completed, not as a substitute for those measures. To avoid harm that indefinite delays in designating critical habitat and formulating recovery plans might cause to economic interests and to the endangered species itself, the implementation of this recommendation needs to include ways of preventing those delays from occurring. Read the entire page →
From page 62... ... HABITAT-CONSERVATION PLANS In Section 7 of the ESA, Congress offered relief from Section 9 prohibitions against taking endangered species where the government's actions were "not likely to jeopardize the continued existence of any endangered! or threatened species." Similar relief was not available to nonfederal parties when federal permits were not required for development or other activities. Read the entire page →
From page 63... ... . 63 RECOVERY PLANNING The ultimate goal of the ESA is to recover threatened and endangered species. Read the entire page →
From page 64... ... In the absence of adequate data, "educated guesswork" has anti will continued to rule the clevelopment of the "central pillar" of recovery plans. Moreover, few scientists agree on the data and analyses that are required to produce a reliable population viability analysis for conservation planning purposes. Read the entire page →
From page 65... ... A final desired feature is that recovery plans reflecting the best judgment of science from decisions made before listing through consultation and habitat planning bear some relationship to decisions affecting the future of the species. We recommend, therefore, that all recovery planning inclucle an element of "recovery plan guidance,'' particularly with regard to activities anticipated to be reviewed under sections 7, 9, and 10 of the ESA. Read the entire page →
From page 66... ... . NATURAL COMMUNITY CONSERVATION PROGRAM AND COASTAL SAGE SCRUB COMMUNITY OF SOUTHERN CALIFORNIA Recent listings of the northern spotted owl, desert tortoise, fish species from the Sacramento-San Joaquin delta estuary, and California gnatcatcher have affected economic activity in several regions of California. Read the entire page →
From page 67... ... Some data available in some portions of the planning area were of substantial immediate value to subregional planning, but the amounts of information then available by and large were not adequate to identify the physical characteristics of management areas necessary to protect ecosystem functioning through time, to identify minimum viable population sizes for target species, or to describe effective landscape corridors that would facilitate ecological interaction and gene flow among organisms that occupy the coastal sage scrub community. The scientific review pane! Read the entire page →
From page 68... ... The ability of individual patches of coastal sage scrub habitat to be effectively managed over the long term will be a critical factor in prioritizing of conservation efforts. For these reasons and in recognition of the critical role of restoration activities in the Natural Communities Conservation Planning Program, the scientific review pane} encouraged the immediate creation of a committee to address central issues in management and restoration to focus on I Read the entire page →
From page 69... ... Because threats to the persistence of species were viewed as so pressing, conservation planning should result in no net loss of habitat value, defined as the ability of the coastal sage scrub habitat to support target species in a subregion over the long term. Expected incremental losses of habitat therefore must be mitigated with habitat restoration activities and effective management planning. Read the entire page →
From page 70... ... A guideline policy for local government treatment of the higher, intermediate, and lower potential value lands during the interim period includes six assessment criteria that address (in order) the presence of natural vegetation, the presence of coastal sage scrub, the size of the scrub patch, its proximity to higher value lands, its role as a potential landscape linkage or corridor, the densities of target species. Read the entire page →

From page 46...

... is usually associated with sufficient genetic divergence to ensure an inclependent evolutionary future. Measures of genetic divergence or genetic distance between populations can be user!