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Becker, George C. / Fishes of Wisconsin
(1983)

Wisconsin waters,   pp. 3-17 PDF (5.6 MB)


Page 5

 
Wisconsin Waters      5 
0     25    50     75 Mi 
0   25  50  75 100 K. 
              LD~ R_ TR 
                          i0 
                               A      A        LU 
                                       CARTOGRAPHIC LABORATORY, UNIVERSITY
OF WISCONSIN-MADISON 
The glacial lobes at the Wisconsin stage of glaciation and their relation
to the driftless area (after 
Martin 1932:87) 
describing an area of youthful streams; such streams and their associated
swamps 
and lakes are characterized by relatively constant volumes of water. 
   Because isolation is a known mechanism in the formation of new species
of 
animal organisms, it has been suggested that new forms may have evolved within
waters of the driftless area and may have been added to the varieties that
moved 
in as the glacier retreated. The evolution of the largescale stoneroller
(Campos- 
toma oligolepis) has been ascribed to isolation within the driftless area
of a sto- 
neroller (Campostoma sp.) ancestor, and Greene (1935) argued that the driftless
area was the center of distribution of the largescale stoneroller. 
Water Resources 
On the geological time scale, the Great Lakes are very young, their beginnings
dating from only about 20 thousand years ago (Ragotzkie 1974). In area, Lake
Superior, the largest and deepest of the Great Lakes, is the largest freshwater
lake in the world. Superior is also the purest of the Great Lakes, its water
con- 


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