| OCR Text |
Show Of the North American leeches, Alboglossiphonia heteroclita, Glossiphonia complanata, Glossiphonia verrucata, Helobdella stagnalis, and Theromyzon tessulatum occur across Eurasia. The northern hemisphere shares many of the leech genera, suggesting speciation in these genera in North America since the breakup of Lauasia. Helobdella stagnalis may have evolved during Pangaea as this species is found in every continent except Australia and Antarctic. The genera of Alboglossiphonia, with its center of diversity in Australasia, likewise could have evolved during Pangaea. Thus, leeches may have occupied suitable habitats in the Great Basin prior to the formation of the Great Basin. In contrast to the widely distributed species, some species are endemic to single sites as Montezuma Well in Arizona, caves, and ancient lakes ( Lake Baikal and Lake Ohrid). Since leeches have been proposed as occurring within the Great Basin since its formative times and since leeches are not a rapid evolving group ( in contrast to fish), leeches may suggest some interesting ancient aquatic connections. Mooreobdella microstoma is found largely in eastern United States and in Mogollon Rim of Arizona, the White River of Nevada, Carico Lake basin in central Nevada, and in the Owens, Walker, Carson, Truckee, Madeline Plains of the Lahontan Basin, Malheur Basin of Oregon, and west of the Sierra Nevada Range. It is absent from the Amargosa drainage and except for Carico Lake basin, from the Humboldt drainage and from Bonneville Basin. This suggests an ancient aquatic basin system extending from eastern United States across the Colorado River basin and northward along the formative Sierra Nevada and Coast Ranges. Nephelopsis obscura is found in eastern Bonneville Basin, one location in Thousand Springs Creek drainage, one location in Goshute Basin ( Big Springs), in Lake Basin, and in Toiyabe Basin, and has not been found in northern California, or Oregon ( but is found in Washington and across northern United States and Canada). This could suggest an ancient drainage connection from upper Snake River to central Nevada. Erpobdella dubia/ parva is common in eastern Bonneville Basin, one location in Thousand Springs Creek drainage, and widely distributed in Goshute and Franklin Basins, suggesting connections between Bonneville Basin and the Relict Dace basins. A variation of these two species is the new species in northwestern Lahontan Basin which could have evolved from eastern Great Basin or west coast populations during the Pleistocene. Table 1. Summary offish ( Hubbs and Miller, 1948), amphibian, and leech distribution. Number of Number of Number of Fishes Amphibians Leeches Bonneville 18 6 15 Lahontan 10 5 12 Death Valley 9 5 7 . Alkali Spring Butte: Gale 1 1 1 Cave 3 Clayton Clover- Independence 2 6 |
