Faunal Diversity
FISH 7380
Dr. e. irwin
Objectives
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Understand the basic structure of riverine communities
Learn broad patterns of faunal diversity across N.AM.
river systems
Understand mechanisms contributing to and underlying
differences in species richness among river systems
Know the “big five”, and other especially diverse N.AM.
fish families
Wrestle with "ecological consequences of diversity"
Riverine communities: webs of the really wellknown (fishes) and the totally undescribed (fungi
& bacteria)
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Functional Groups
Heterotrophy vs. Autotrophy
Food webs
Diversity: "the variety and variability among
living organisms and the ecological complexes in
which they occur (Office of Technology
Assessment 1987)"
Food webs
Microbes
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Bacteria, protists and fungidecomposers of POM, retain and transform
DOM
Meiofauna
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pass through 500 micron, retained 40 micron
sieve
58-82% of species in streams
Rotifers (Bdelloidae=benthic group 2,500 species
30% planktonic)
Gastrotrichs (Chaetonotida (mainly FW 350
species)
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e.g. rotifers, harpaticoids, cyclopoid copepods,
flatworms. gastrotrichs, young insects….
Interstitial, burrowing, epibenthic
Meiofauna
Macroinvertebrates
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> 15,000 aquatic invertebrates described, including:
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4665 Diptera
1640 Coleoptera
1340 Trichoptera ("The queen order of insects")
400 Hemiptera
50 Megaloptera
635 Lepidoptera (aquatic!)
575 Ephemeroptera
550 Plecoptera
415 Odonates - 170 in AL (Krotzer abstract)
386 Crayfishes - 70 in AL (Johnson thesis)
500 Gastropoda
320 Bivalva
Diptera
Coleoptera
Tricoptera
Hemiptera
Megaloptera
Lepidoptera
Odonata
Plecoptera
Decapoda
Bivalvia
Gastropoda
Fat pocketbook- Potamilus capax
Interrupted rocksnail Leptotoxis formeani
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“New species are described annually, and a total
head count never will be complete” (Williams
and Neves 1992)
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"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.
Fishes
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About 800 spp in North America, excluding
Mexico, mostly riverine
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compared to (best available underestimates!):
about 10250 freshwater spp worldwide
South America
Africa
North America (& Mexico)
Europe
Australia
Alabama
2800 spp
2000 spp
1100 spp
250 spp
230 spp
328 spp
Floodplain rivers are diverse
Patterns of diversity of fishes in North
America: Why?
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The mighty Mississippi, the southeast, and
the west
Ecological stability + geographic
instability = spp diversity
Drainages are not equally blessed
NA drainages
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Mississippi-Missouri-Ohio : richest, 375 spp, 31
families;
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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)
NA fishes
 N. Am. fishes a relatively young fauna
 60% Miocene or younger (about 26-23
mya)
 (Miller, cited in Hocutt and Wiley, p
443).
Sabretooth salmon (3 mya)
The big five
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Nearly 80% comprise 5 families 
Cyprinidae 302 spp
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Percidae
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This number is already out of date!)
(This one is, too!)
Ictaluridae
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165 spp
Catostomidae 70 spp
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(largest family of fishes; 1600 spp worldwide)
48 spp
(endemic to N Am; 27 spp are madtoms)
Centrarchidae 32 spp
Western Rivers
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Small fishes rule, except out west
Stability-diversity
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.
Imperilment