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Juday, Chancey (ed.) / Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XXI (1924)

Baker, Frank Collins
The fauna of the Lake Winnebago region,   pp. [109]-146 PDF (11.3 MB)


Page 131


Baker-The Fauna of The Lake Winnebago Region.       131
  Table 5 shows the relation of the number of species of Mollusca
to the depth of the water. The greatest variety is found at depths
not exceeding two meters.
  Table 6 shows the relation of the number of species of Mollusca
to the character of the bottom in Lake Winnebago. The maximum
number was found on sand bottom.
  Table 7 shows the variety of the molluscan faunas of three lakes,
namely, Oneida Lake, New York; Maxinkuckee Lake, Indiana; and
Lake Winnebago, Wisconsin.
  One of the interesting features brought out by the study of the
molluscan fauna of the Lake Winnebago region is the difference
in size and shape between the Unionidae of the Fox River and
those of the lakes, a difference which appears to be comparable to
that noted by Grier (1919) between the Naiads of Lake Erie and
the upper drainage of the Ohio River. Grier states that "if we put
a shell in the lake environment we may expect it will change its
morphological features, not at random, but in a distinct, deter-
minate, or orthogenetic direction. " This change in the morphology
of shells that have migrated from a river to a lake is strikingly
shown in the Lake Winnebago fauna, and a study of the two areas
by the methods of Grier would produce the same results as attained
by the study of the Lake Erie shells. It is a significant fact that
the same varietal forms inhabit both Lake Winnebago and Lake
Erie, indicating that the law holds good under similar conditions
in widely separated areas. Dr. Sterki notes that almost all of the
Pisidium of the lake are small and slight, some even depauperate,
and Sphaerium and Musculium are similarly affected. The gastro-
pods of the lake are in the main different from those of the river.
Thus the entire molluscan fauna is affected by the same law of
variation produced by river and lake environment, clearly indi-
cating that ecological station plays a large part in the evolution of
species. A study of the tables and of the systematic list which fol-
lows will bring out additional features of this ecological character-
istic. Just what factors have been potent in producing these
changes does not seem to be definitely known. It is probable that
variation in food supply, in the chemical character of the fluid
medium in which they live, as well as in the general physical
environment, plays a large part in these changes of form.


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