communities will shift upward and amphibians must either move with them or acclimate until adaptation occurs. Even small increases in temperature lead to significant metabolic depression in montane salamanders (Bernardo and Spotila, 2006). Impacts of the different warming scenarios are all dramatic and severe [see fig. TS.6 in Parry et al. (2007)]. The first event predicted by the IPCC panel, “Amphibian Extinctions Increasing on Mountains,” is now an empirical fact.
In previous publications, we showed that many tropical plethodontid salamanders have very narrow altitudinal limits and are often restricted to single mountains or local mountain ranges (Wake et al., 1991). With few exceptions, species found above 1,500–2,000 m have narrow distributional limits. We have surveyed extensively a mountainous segment of eastern Mexico from the vicinity of Cerro Cofre de Perote (≈4,000 m) in central western Veracruz in the north to Cerro Pelon (≈3,000 m) in northern Oaxaca in the south. These two peaks, separated by ≈280 km, lie along the eastern crest of the Sierra Madre Oriental, a nearly continuous range that is broken only by Rio Santo Domingo (Fig. 2.4). Otherwise the crest lies above 1,500 m, with many peaks that rise to ≈2,000 m or higher. There are 18 species of plethodontids on both Cofre de Perote and Pelon, but only two species—widespread lowland members of Bolitoglossa—are shared. To determine the geographical limits of the other species, we have been surveying the entire crest area since the 1970s. We have learned that most of the species on each mountain are endemic to it. When we searched in the intervening region, expecting to expand the known distributional ranges for different species, we instead discovered numerous undescribed species (many since named) almost every time we explored an isolated peak at >2,000 m. On a single short trip just 5 years ago to the Sierra de Mazateca, north of the Rio Santo Domingo (Fig. 2.4), we discovered two new species of Pseudoeurycea and at least one new species of Thorius (Parra-Olea et al., 2005). We suspect that many species disappeared without ever having been discovered because the area is heavily populated and has experienced extensive habitat modification. Furthermore, the newly discovered species are endangered and survive in what appear to be suboptimal, disturbed habitats or in small fragments of forest. The majority of species along altitudinal transects in this area are found at >2,000 m in cloud forests that are being forced upward by global warming. On Cerro Pelon, eight of the species are found only at >2,200 m, and six of them range to the top of the mountain. Global warming threatens to force them off the mountain and into extinction.
The section of the Sierra Madre Oriental we have been studying is home to 17 named and 3–5 as yet unnamed species of the plethodontid salamander genus Thorius, the minute salamanders. All but four of these species occur exclusively at >2,000 m, often on mountains that rise only