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i t~ "! 14 DISTRIBUTION AND ZOOGEOGRAPHY become rare, extinct, or established in other drainage systems, the study of the zoogeography of native forms becomes, lamentably, more and more an exercise in past history, where ancient museum specimens and old field notes are more meaningful than populations of live fish. Nevertheless, the subject is still worth pursuing for the insights it can provide into the distributional patterns and speciation of the native fishes. Any summary of the zoogeography of native California fishes is, in large part, a summary of the work of Robert R. Miller and Carl L. Hubbs, who have devoted an extraordinary amount of time and effort to the study of western freshwater fishes (Hubbs and Miller, 1948; Hubbs, Miller, and Hubbs, 1974; R. R. Miller, 1958, 1961, 1965). KLAMATH RIVER SYSTEM The Klamath River system has three distinct parts: (1) the upper Klamath River above Klamath Falls, including the Lost River; (2) the Klamath River below the falls, including the Trinity River; and (3) the Rogue River, with only a few tributary headwaters in California. The distinctness of the fish faunas of the upper and lower Klamath River reflects that the connection between the two systems is geologically recent. They share only two fishes, Klamath speckled dace and marbled sculpin, mainly endemic to the Klamath system. The lower Klamath has only one species or subspecies of its own (Klamath smallscale sucker), while the upper Klamath has seven in California (Pit-Klamath brook lamprey, blue chub, Klamath tui chub, shortnose sucker, Klamath largescale sucker, Lost River sucker, and slender sculpin). The upper Klamath presumably once flowed into the Great Basin, because the closest relatives of Klamath tui chub, speckled dace, and shortnose sucker are found there. There is also evidence of at least headwater connections with the Pit River of the Sacramento-San Joaquin system. The Pit and Upper Klamath rivers share Pit-Klamath brook lamprey and marbled sculpin. In addition, the closest relative of the slender sculpin appears to be the rough sculpin of the Pit River (Robins and Miller, 1957). With the exception of the Pit River fishes and the Klamath largescale sucker, which appears to be close to both the Columbia largescale sucker, Catostomus macrocheilus, and the Sacramento sucker, the upper Klamath fish fauna shows few affinities to the fishes of either the Columbia system on the north or the main Sacramento-San Joaquin system on the south. This is surprising since the Columbia and Sacramento-San Joaquin faunas show some affinities to each other. In any case, the distinctness of the upper Klamath fish fauna indicates a long period of isolation from other faunas. The connection with the lower Klamath probably was created during one of the high rainfall eras of the Pleistocene. The water level of Klamath Lake then rose to a point where it could spill over a low divide into the lower Klamath River system, eventually eroding a permanent connection that would flow even when the Iake level was low, as it is today. Until reservoirs were constructed on the lower Klamath River, upper Klamath fishes were unable to colonize the lower river because of the absence of suitable habitat, although individuals were occasionally washed into downstream areas.