Every creature is an expression of its native environment; a creation of the land, created in the image of the land. Nothing is arbitrary. The signature of the land is written in the phenotypes of her children, and even in the phenotypes of exotics that have come from abroad and found the land suitable to their particular characteristics, like immigrants who abandon their homeland only to discover a truer homeland.
Excessive movement of species can, as we are discovering of late, lead to genetic hegemony and extinction. If irresponsibly transported by humans, a small number of species can out-compete native species into nonexistence. The mutual isolation of the lands of the past had spawned a wonderful variety of species that are presently marching to oblivion.
Human cultures are similarly crafted by isolation. California, a land of substantial internal isolation, is itself isolated from surrounding lands by ocean, deserts, and mountains. Thus it was that early Californian cultures were not homogenized due to technological influences of other early American cultures, and Californians sustained a rich cultural diversity until they were driven to the brink of extinction during the European pandemic.
The Pacific Coast is home to a familiar species of trout that remains nameless save for its subspecies, the steelhead and the rainbow trout. The two subspecies occupy distinct habitats; one lives at sea and spawns in Pacific tributaries, and the other lives an entirely landlocked, freshwater existence.
Pacific streams present varying degrees of isolation from the ocean and from each other. The Kern River, when it was wild, was an extraordinary case, as its waters reached the ocean only in spring, when flows were high enough to breach the natural spillways of the Sink. When the Kern was a free river, it would first flow into Kern Lake, at the base of the Range. If the river waxed high enough, Kern Lake would spill over into Buena Vista Lake. When Buena Vista Lake filled, it would overflow into Goose Lake, and the overflow would continue from there to Tulare Lake. Tulare Lake would sometimes fill the Sink until it overflowed into the San Joaquin River.
At high flows, fish had an opportunity to migrate up and down the basin waterways, but the sloughs would dry quickly, and the lakes would recede and even dry as summer and autumn progressed. Streams that flowed directly from the Range into Tulare Lake, such as the Kaweah River, were not as isolating as the Kern. A fish that ascended up the Kern from Tulare Lake, on the other hand, would have a much longer journey through a chain of three smaller, intermittent basins.
Once fish got above Kern Lake, they might manage to ascend the Kern rapid by rapid, subsisting in pools through the months of low flows, and ascending more quickly up spring and winter torrents. The falls and cascades dropping off the Kern Plateau presented the final barrier. Beyond that barrier live the California golden trout, offspring of isolation.
The domain of the golden trout is the upper Kern River watershed. The golden trout that populate the Kern itself are similar to the common rainbow, whereas the golden trout in more isolated Kern tributaries are more distinctive. The Little Kern subspecies is the most endangered, and perhaps the most visually striking. The subspecies of the Kern Plateau is more purely golden in color and thus the best-known variety of golden trout.