NANFA-- glaciers, etc.

Christopher Scharpf (
Wed, 20 Aug 2003 22:45:27 -0400

> Now, how about the role of glaciation and the development of North American
> fishes? There are plants found in the Appalacians found usually in arctic
> regions. A glance at a number of darter distribution maps suggests that they
> may have accompanied the melting lines north.

While continental drift explains the presence of several fish groups in
North America, it does not explain their distribution patterns across the
continent. A major explanation for this is Pleistocene glaciation. During
this period, which began about 2.5 million years ago and ended (we think)
about 10,000 years ago, as much as a third of North America was covered with
glaciers. As glaciers advanced (grew) they killed just about everything in
their path. As glaciers retreated (shrunk), they carved new lakes and rivers
in the bedrock, rerouted some river systems, and altered the land by
widening or deepening river valleys and forming waterfalls, all of which had
profound effects on fish distributions. In fact, it's glaciers that largely
account for why most North American fish species are concentrated in the
central and southeastern U.S. and comparatively few species are located in
the north. The Mississippi Basin, for example, contains the richest fish
diversity in North America because it served as a refuge and major center of
fish evolution when glaciers covered points north. In contrast, the Hudson
Bay and North Appalachian provinces were fishless just 14,000-15,000 years
ago; their fishes began moving in from the south once the ice started to
melt. Such colonization is slow, depending largely on stream capture

> Would the work above address these things?


> Would any other works come to mind which especially deal with the effects of
> glaciation?

There are several zoogeography textbooks that do; I think the one by Brown
and Inlimo (sp.?) is considered to be the best. Beyond that I don't know.

Chris Scharpf
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