OCR Text |
Show most ranges although Erpobdella punctata was absent from Albion and Uinta Ranges. Nephelopsis obscura was prevalent in the Uinta Range. Many mid- elevation leeches do not occupy high- elevation lakes, suggesting selective species barriers. Post- pluvial movement of leeches into the Bonneville basin shows that of the 14 species of leeches, only two ( the mammal and amphibian leeches) did not penetrate into the area formerly occupied by Lake Bonneville. Three leeches ( Helobdella fusca, H. triserialis, and Alboglossiphonia heteroclita) were not found above Lake Bonneville levels, and these leeches were found in only one location in Bonneville Basin. Thorough sampling of river systems in mid- elevational habitats should locate these species. The Bonneville Basin was examined on a drainage subbasin level. The Bear ( 11 species), Weber ( 10 species), Jordan ( 10 species) and Sevier ( 9 species) constituted the most species rich region in the Bonneville Basin and the Great Basin, a finding that is similar for fishes and amphibians as well. Shoal Creek ( 1 species), Snake ( also including Deep Creek, Tule, and Fish Springs) subbasin ( 7 species), Thousand Creek ( also including Pilot, and Pilot Creek) subbasin ( 7 species), and North Great Salt Lake ( 1 species) were depauperate with 4 of 7 species in Thousand Creek and Snake subbasins found in only one location, suggesting relict populations. Within the Great Basin, some 43 basins were surveyed for leeches with 25 basins having leeches. Seven Ashless basins ( Cave, Jakes, Ralston, Mono, Lake, Spring, Deep Spring) contained leeches and 3 leechless basins ( Columbus Salt Marsh, Dixie, Grass) contained fish. In the analysis of the log of basin area versus log of species, the leech ( excluding the vertebrate blood host leeches) distribution gives a Z value ( slope) of 0.27. Using the fish and amphibian ( excluding the xeric spadefoot toad) distributions, the Z value is 0.61 and 0.39, respectively. Values of Z above 0.4 suggest that colonization is not compensating for extinction and values below 0.2 characterize samples representing different areas within a continent. This analysis arises from treating the basins in the Great Basin as islands. Thus fishes, and to a lesser extent amphibians, suggest that extinction is occurring without colonization ( an island biogeography phenomena) whereas leeches are behaving as belonging to continental fauna. With respect to fishes and amphibians, extinctions may have occurred in formative Great Basin, and colonization is a Pleistocene occurrence. Fishes require direct aquatic connections for interbasin movement while amphibians require mesic summer climates and leeches require aquatic connections of longer duration and with hyporheic or water- saturated meadow environments. Conditions that allow for leech interbasin movement could readily be utilized by amphibians and fish. Leech, fish, and amphibian distributions suggest that differential interbasin environments occurred for each group. Although leeches are viewed as " cosmopolitan," they are not found everywhere. The Sonora and Mojave desert aquatic systems are largely absent with respect to leeches. Of the North American leeches, only Erpobdella punctata, Gloiobdella elongata, Helobdella stagnalis, and#. triserialis are found in the Caribbean, Mexico, and/ or South America. This would suggest that a region between United States and Mexico would be depauperate with respect to leeches. Other areas of depauperation include the Atacama and Rio Loa region of Chile and the Xinjiang and Qinghai Provinces of western China, both regions of extreme aridity and active orogenesis. |