Dr. e. irwin
Understand the basic structure of riverine communities
Learn broad patterns of faunal diversity across N.AM.
Understand mechanisms contributing to and underlying
differences in species richness among river systems
Know the “big five”, and other especially diverse N.AM.
Wrestle with "ecological consequences of diversity"
Riverine communities: webs of the really wellknown (fishes) and the totally undescribed (fungi
Heterotrophy vs. Autotrophy
Diversity: "the variety and variability among
living organisms and the ecological complexes in
which they occur (Office of Technology
Bacteria, protists and fungidecomposers of POM, retain and transform
pass through 500 micron, retained 40 micron
58-82% of species in streams
Rotifers (Bdelloidae=benthic group 2,500 species
Gastrotrichs (Chaetonotida (mainly FW 350
e.g. rotifers, harpaticoids, cyclopoid copepods,
flatworms. gastrotrichs, young insects….
Interstitial, burrowing, epibenthic
> 15,000 aquatic invertebrates described, including:
1340 Trichoptera ("The queen order of insects")
635 Lepidoptera (aquatic!)
415 Odonates - 170 in AL (Krotzer abstract)
386 Crayfishes - 70 in AL (Johnson thesis)
Fat pocketbook- Potamilus capax
Interrupted rocksnail Leptotoxis formeani
“New species are described annually, and a total
head count never will be complete” (Williams
and Neves 1992)
"The conditions for speciation of stream dwelling
animals has been nearly ideal in eastern North
America for many million years. One of the
results has been the origin of what is probably the
richest freshwater mollusk fauna in the world."
David H. Stansbery, 1970.
About 800 spp in North America, excluding
Mexico, mostly riverine
compared to (best available underestimates!):
about 10250 freshwater spp worldwide
North America (& Mexico)
Floodplain rivers are diverse
Patterns of diversity of fishes in North
The mighty Mississippi, the southeast, and
Ecological stability + geographic
instability = spp diversity
Drainages are not equally blessed
Mississippi-Missouri-Ohio : richest, 375 spp, 31
SE Province: Atl and Gulf Slope drainages,
Savannah R to Ponchartrain, 268 spp, 31 families
Western systems: fewer spp, but high endemism.
Why impt from a management perspective?
e.g., Colorado River Basin 32 spp, 7 families - 69%
spp endemic (22)
N. Am. fishes a relatively young fauna
60% Miocene or younger (about 26-23
(Miller, cited in Hocutt and Wiley, p
Sabretooth salmon (3 mya)
The big five
Nearly 80% comprise 5 families
Cyprinidae 302 spp
This number is already out of date!)
(This one is, too!)
Catostomidae 70 spp
(largest family of fishes; 1600 spp worldwide)
(endemic to N Am; 27 spp are madtoms)
Centrarchidae 32 spp
Small fishes rule, except out west
N. M. Burkhead, S. J. Walsh, B. J. Freeman and J. D.
Williams, 1997. Status and restoration of the Etowah
River, an imperiled southern Appalachian ecosystem. In
Aquatic Fauna in Peril: The Southeastern Perspective, G.
W. Benz and D. E. Collins, eds.