Ecology of North American Freshwater Fishes. Stephen T. Ross Ph. D.
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Within the Cenozoic, geologic ages refer to epochs; within the Mesozoic and Paleozoic, ages refer to periods. Numbers at the top of each column are the beginning age (mya) of each geologic age or period. Numbers after families indicate sources; gaps in fossil record are not shown.
SOURCES: 1. Carlson et al. (2009), 2. Cavender (1986), 3. Cavender (1991), 4. Grande (1982), 5. Grande (1984), 6. Grande (1999), 7. Grande and Bemis (1991), 8. Grande and Bemis (1996), 9. Grande et al. (2002), 10. Mateos et al. (2002), 11. Meyer and Lydeard (1993), 12. Miller (1981), 13. Murray (2001a), 14. Murray and Wilson (1996), 15. Myers (1966), 16. Near and Keck (2005), 17. Near et al. (2005), 18. Nelson (2006), 19. Webb et al. (2004), 20. Wilson and Williams (1992).
In western North America, a freshwater fauna dominated by teleosts first appeared by the late Paleocene, followed by the expansion of an essentially modern fauna by the Oligocene and Miocene (Minckley et al. 1986). The western fauna during the Eocene (56–34 mya) and Oligocene (34–23 mya) shared forms with an eastern fauna, including paddlefishes, gars, sturgeons, bowfins, salmon and trout, mooneyes, suckers, catfishes, troutperch, and pickerel (Grande 1984; Minckley et al. 1986; Grande and Lundberg 1988; Grande 1999). The Oligocene fauna included elements from the earlier fauna, such as mooneyes, salmon and trout, and pickerel, as well as from more recent groups, such as minnows, atherinopsids, pupfishes, topminnows, sticklebacks, bass and sunfishes, surfperches, and sculpin (Minckley et al. 1986). Of the nonteleosts, sturgeon are represented by extant western forms, but gars, paddlefishes, and bowfin are now absent from the western fauna.
Although ecologists, until recently, have tended to focus more on current faunas and less on historical aspects, knowledge of the varying ages of occupation of fish groups in North America is of paramount importance to our understanding of fish assemblages and the extent and duration of coevolutionary processes. In addition, recent studies have stressed the importance of incorporating information on evolutionary relationships of component species (i.e., phylogeny) into studies of community ecology (Webb et al. 2002).
As is evident from Figure 2.3 and the previous paragraphs, fish groups vary widely in their ages of occupation in North America. Consequently, the forces shaping the evolution of morphology, physiology, and behavior of species making up present-day assemblages are likely not to be found by only looking within the contemporary assemblage. Instead, selective pressures leading to various traits may date to earlier time periods and may not even include the present-day assemblage. As an example, assemblages that have included pike have changed over time since the Paleocene (65–56 mya), when pike would have been part of fish assemblages including osteoglossomorphs, percopsiforms, amiids, gonorynchids, lepisosteids, asineopids (now extinct), osmerids, clupeids, cyprinoids (possibly catostomids), and ictalurids (Wilson and Williams 1992). Although feeding and morphological specializations show little change in pike, the community relationships have since changed a great deal, consequently, and “major adaptations of pike evolved before modern predator-prey systems existed” (Wilson and Williams 1992).
Origins of North American Fish Families
As with differences in ages, North American fish families exhibit a variety of origins, including archaic groups and some more recent groups whose origins can be traced to Pangean and Laurasian faunas (Figure 2.4). Of the 50 North American fish families listed by Burr and Mayden (1992), half show a marine origin. In some groups the radiation from the marine environment into fresh water occurred early, as with the bowfin subfamily Amiinae (family Amiidae) that has occupied freshwater habitats in the Northern Hemisphere since the late Cretaceous, some 90 mya (Grande and Bemis 1999). The second-largest group has a North American origin (including those originating in old landmasses of Pangea or Laurasia), followed by groups originating in Central and South America and Eurasia (Figure 2.4).
FIGURE 2.4. General origins of North American fish families. Phylogenetic and/or fossil information generally does not allow enough resolution to determine modern continental origins listed as arising in Laurasia/Pangea.
SOURCES: 1. Berra (2001), 2. Briggs (1986), 3. Burr and Mayden (1992), 4. Cavender (1986), 5. Cavender (1991), 6. Collette and Banarescu (1977), 7. Echelle and Echelle (1992), 8. S. A. Foster et al. (2003), 9. Gilbert (1976), 10. Grande (1984), 11. Grande (1999), 12. Grande and Bemis (1991), 13. Grande and Bemis (1996), 14. Grande and Bemis (1998), 15. Grande and Bemis (1999), 16. Grande et al. (2002), 17. Hrbek and Larson (1999), 18. Miller and Smith (1986), 19. Moyle and Cech (2004), 20. Parenti (1981), 21. Patterson (1981), 22. G. R. Smith and Stearley (1989), 23. Wiley (1976), 24. Wilson and Williams (1992).
The 15 fish families containing 90% of the modern species have their origins in Eurasia (minnows and suckers); Central America (livebearers and topminnows); North America, including Pangean/Laurasian elements (catfishes, trouts and salmons, goodeids, sunfishes, and perches); the marine environment (New World silversides, pupfishes, sculpins, lampreys, herrings); and South America (cichlids). The histories of these groups are treated in more detail in the following section.
Numerically Dominant Families
Plate Tectonics, Ages, and Origins
This section examines in more detail how potential fish assemblages have changed over time by the addition of new taxa and relates the arrival of these taxa to the positions of major landmasses at various times in the past. It is primarily limited to families composing 90% of the North American fish fauna, although sturgeons and pickerels are included because of conservation interest and past or present economic importance. Families are listed by decreasing age of occurrence (largely as determined from fossils) in North America. For the goal of relating fish distribution to continental positions and connections over geological time, I have followed Cracraft (1974) and Matthews (1998) in portraying landmasses as a series of blocks (Figure 2.5). Although temperatures in Antarctica were generally too cold for the survival of freshwater fishes (Matthews 1998), I have included it in the figure to help with orientation. Simple diagrams might seem to suggest otherwise, but movements of landmasses were not necessarily unidirectional, so that connections between different elements may have been made and broken numerous times. A case in point is the union of eastern North America and Europe during the Jurassic and early Cretaceous when these landmasses were joined and then separated several times (A. G. Smith et al. 1994).
A. Early Triassic (245 mya)
B. Late Jurassic (161 mya)
C. Late Cretaceous (70 mya)
D. Cenozoic-Paleocene (60 mya)
E. Cenozoic-Middle Eocene (45 mya)
F. Cenozoic-Middle Miocene (10-15 mya)
G. Present day
FIGURE 2.5. Schematic diagrams of the relative positions of oceans and landmasses from the early Mesozoic to the present. Arrows indicate possible connections between landmasses. Sources are given in the accompanying text. Landmasses and oceans are not drawn to scale.
Continental Positions
MESOZOIC, EARLY TRIASSIC (245 MYA) The Pangean supercontinent reached its maximum extent in the early Triassic, then began to break apart by the late Triassic (Figure 2.5A). At its maximum, the supercontinents of Laurasia and Gondwana were joined, providing dispersal routes