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Recent declines and extinctions of amphibian populations have been reported in many areas of the world. A majority of the documented declines are in easily detectable anuran species. In eastern North America, flatwoods salamanders (Ambystoma cingulatum) have declined and have recently been added to the threatened species list, and southern dusky salamanders (Desmognathus auriculatus) have disappeared at some sites (Dodd, 1998). A decline has been reported in a small part of the range of green salamanders (Aneides aeneus; Snyder, 1991). However, other published reports indicate little change in eastern salamander populations (e.g., Pechmann et al., 1991; Hairston and Wiley, 1993; Pechmann and Wilbur, 1994). In contrast, my data indicate widespread declines in eastern North American populations of the most common woodland salamander genus—Plethodon, the largest genus of salamanders in the United States (53 presently recognized species). Since 1951, I have done a great deal of fieldwork in eastern North America in the course of studies on the life histories, systematics , population genetics, and molecular evolution of the plethodontid genus Plethodon. In the late 1980s, I noted a decline in the number of salamanders seen at some sites where several species previously had been common, as well as a reduction in the number of salamanders encountered at new sites in areas where species of Plethodon were generally abundant . In the 1990s, I returned to 127 of my sites in order to investigate the apparent declines in salamander populations and to estimate the extent of the declines. Data are available for 205 populations of 38 species. Background Information and Methods of Analysis I began my studies of the genus Plethodon by taking collections of several species throughout the seasons of their surface activity in order to investigate the life histories of these salamanders (Highton, 1956, 1962b; Sayler, 1966; Angle, 1969). When it was discovered during the 1960s and 1970s that there are far more than the 16 species of Plethodon previously recognized (Highton, 1962a), molecular studies were made in order to clarify the taxonomy of the genus before publishing the results of the life history studies on the remaining eastern North American species. There are now 53 species recognized in the genus, including 45 in eastern North America (Highton and Webster, 1976; Larson and Highton, 1978; Duncan and Highton, 1979; Highton and Larson, 1979; Highton and MacGregor, 1983; Highton, 1984, 1989, 1995b, 1997, 1999a; Wynn et al., 1988; Lazell, 1998; Highton and Peabody, 2000). I have 109 life history sites in 22 eastern and central states, which include 169 populations of 44 of the 45 eastern species (all but the recently described Bay Springs salamander [also termed Catahoula salamander; Crother et al., 2000], Plethodon ainsworthi; Lazell, 1998). Most of the populations were selected for life history analysis because of the abundance of one or more of the species present at the site. Salamanders from these sites were also used in molecular studies. Most of my fieldwork for the life history studies was accomplished before the end of the 1970s, although some populations were sampled into the first half of the 1980s. I became familiar with the patterns of seasonal activity and relative abundance at sites throughout the range of each species. My records from this period indicate consistent patterns of surface activity from year to year. When season, surface moisture, and temperature conditions were taken into account, the abundance of salamanders was usually predictable. When multiple collections were made at many sites during the 1950s through the mid-1980s, I never observed a consistent change in abundance at any of the sites. At one site (Cunningham Falls State Park, Frederick County, Maryland) an exceptionally large number of salamanders was collected from 1956–76 (3,473 eastern red-backed salamanders [P. cinereus] and 654 northern slimy salamanders [P. glutinosus]); however, both of these species appeared to be just as abundant at the end of the studies (Highton, 1962b, 1972, 1977; Sayler, 1966; Semlitsch, 1980b) as they were initially. During the 1950s and 1960s, I made extensive field studies on patterns of geographic interactions among, and geographic variation within, each of the Plethodon species occurring in five states: Delaware, Maryland, Pennsylvania, Virginia, and West Virginia (Highton, 1972, 1977). Collections were made at over 1,700 sites, with many visited repeatedly in order to obtain adequate sample sizes for statistical analyses. One species, Valley and Ridge salamanders (P. hoffmani), was later found to be composed of two morphologically similar species, valley and ridge salamanders and Shenandoah Mountain salamanders (P. virginia; Highton, 1999a). During...

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