Pleistocene deposits (ca. 2 mya) in areas now located in Texas and Oklahoma (genus Perca) and South Dakota (Percina and Etheostoma) (Cavender 1986). Given the currently available information, it is not possible to distinguish between a dispersal hypothesis, with percids evolving in Europe and then dispersing to North America via the North Atlantic connection, or a vicariance hypothesis, with percids evolving in Laurasia and then being separated by the formation of the North Atlantic Ocean (Carney and Dick 2001). However, given that fossils likely underestimate ages of percids, I have shown the Laurasian origin in Figure 2.4.
The first occurrence of darters in North America is likely far earlier than indicated by the Pleistocene fossils. A molecular phylogeny of the darter family (Percidae), with the rate of genetic change (i.e., the molecular clock) based on a fossil-calibrated phylogeny of centrarchids, shows the separation of darters from nondarter percids occurring 19.8 mya (Carlson et al. 2009). The 18.5 mya age of the most recent common ancestor to the darter genus Nothonotus provides further evidence of at least a Miocene origin of darters (Near and Keck 2005). Finally, a recent molecular phylogeny of logperches (genus Percina) showed that divergence began in the Pliocene (ca. 3–5 mya), although most speciation events in this group did occur within the Pleistocene (Near and Benard 2004).
FUNDULIDAE (34 SPECIES) Members of this group occur in North and Central America as well as Cuba; in North America all but two species occur east of the continental divide (Berra 2001). The oldest fossil evidence in North America dates from the middle Miocene (ca. 16 mya) and perhaps is of the modern genus Plancterus (Cavender 1986). North American fundulids apparently are derived from Central American ancestors (Briggs 1986, 1987) and, in support, phylogenies based on morphological and molecular data are consistent in placing the Central American family Profundulidae as basal to the Fundulidae (Parenti 1981; Wiley 1986; Bernardi 1997).
CYPRINODONTIDAE (35 SPECIES) Cyprinodontid fishes include both marine/estuarine and freshwater forms that are found primarily along coastal regions (with some notable exceptions) in North, Central, and South America, and the Mediterranean region including North Africa (Parenti 1981; Berra 2001). One view is that the distribution of the cyprinodontiform fishes suggests, in part, a reduced Pangean pattern (Figure 2.2), with members of the group absent from Australia and Antarctica (Parenti 1981). Correspondingly, the order Cyprinodontiformes likely existed at least from the late Triassic before the breakup of Pangea (Figure 2.5A), and New World cyprinodontids perhaps date from the early Tertiary (Parenti 1981). An alternative view places the origin of the group at a later time in the early Cretaceous when Africa and South America were only divided by a narrow saltwater passage (Figure 2.5B, C) (Briggs 1986).
The relatively great age of New World cyprinodontids is also supported by molecular studies of the amount of divergence between New and Old World species (Echelle and Echelle 1993). The North American cyprinodontids are likely derived from a marine ancestor (Gilbert 1976; Parker and Kornfield 1995). However, the hypothesis that lineages of inland species of Cyprinodon in North America have been derived independently from the widely distributed coastal species, although initially supported by a reduced data set of western species in the Cyprinodon variegatus complex (Echelle and Echelle 1992), has not been substantiated by a more complete study of the family (Echelle et al. 2005).
In spite of the suggested age of the order and of New World Cyprinodontidae, the fossil record for the family in North America is meager. The only known North American fossil, of the extinct species Cyprinodon breviradius, is from late Miocene/early Pliocene deposits near Death Valley, California (7–9 mya) (Miller 1981; Cavender 1986). However, there are recent phylogenies, based on water-soluble proteins (allozymes) and mitochondrial DNA, that provide times of divergence for North American genera and species (Echelle and Echelle 1992; Echelle et al. 2005). Molecular data suggest that modern New World genera of the Cyprinodontidae began diverging in the Miocene (7–9 mya)—dates that are earlier than those proposed by Miller (1981) based largely on geological inferences. Some species within the family are of much more recent origin, dating to less than one million years (Echelle et al. 2005).
COTTIDAE (30 SPECIES) In terms of the diversity of genera, the sculpins are primarily a marine family. However, the genus Cottus is well represented in North American fresh waters with 28 species, and there are at least two freshwater species of Myoxocephalus. The oldest fossils of the genus Cottus are from late Miocene (ca. 11 mya) deposits of North America in what is now Oregon (Linder 1970; Cavender 1986). Freshwater forms in both genera are derived from marine species (Gilbert 1976; Burr and Mayden 1992). In contrast to the Miocene age of Cottus, freshwater species of Myoxocephalus are more recent, likely invading freshwater habitats in the early to middle Pleistocene around the beginning of the major continental glaciations (ca. 0.9 mya) (Kontula and Väinölä 2003).
ATHERINOPSIDAE (39 SPECIES) The New World silversides are primarily a marine family, although there are five genera that occur widely in freshwater habitats. Fossil silversides are known from Pliocene formations (ca. 4–5 mya)—one in what is now Arizona and the other from the Mesa Central of the Mexican Plateau (Cavender 1986). The Arizona fossils were most likely from a marine or brackish water habitat and have been assigned to the modern species Colpichthys regis (Todd 1976). The Mexican material also represented modern species of the genus Menidia (formerly placed in Chirostoma) (Barbour 1973; M. L. Smith 1981). Freshwater silversides are derived from marine ancestors, with perhaps several independent invasions of fresh water by species groups occupying the Mexican Plateau and those found in more northern regions of North America (Barbour 1973; Gilbert 1976; Burr and Mayden 1992).
SUMMARY
Fish evolution began in the early Paleozoic, perhaps 500–470 million years ago (mya). Modern bony fishes, the teleosts, appeared by the lower Mesozoic (230–206 mya), and by the middle Mesozoic (195 mya), representatives of most major groups of fishes were present. The distribution of marine and freshwater fishes worldwide, and the occurrence and distribution of North American freshwater fishes, have been strongly shaped by the movements of landmasses—plate tectonics.
The diverse fish fauna of North America came to occupy North America over a span of hundreds of millions of years, from as early as the late Paleozoic through the Pleistocene, and continuing into the present as populations respond to changing environmental conditions. Over two-thirds of the fauna, in terms of family origins, has occupied North America since the Paleogene (ca. 24 mya) or earlier, whereas ages of particular species can be much more recent. The minnows and darters, the two most speciose North American families, are also among the more recent (Miocene and Oligocene) arrivals.
Lineages of fishes in North America have various origins as well. Half of North American freshwater fishes have a marine origin, followed by those originating in North America (or in ancient landmasses of Pangea and Laurasia), Central and South America, and Eurasia. Because of the long and varied histories of fish lineages, contemporary assemblages of fishes should be viewed as being composed of suites of species with potentially widely differing histories, with adaptations that have likely been shaped to a greater or lesser extent by interactions in fish assemblages that were greatly different from those they are currently occupying.
SUPPLEMENTAL READING
Cavender, T. M. 1986. Review of the fossil history of North American freshwater fishes, 699–724. In The zoogeography of North American freshwater fishes. C. H. Hocutt and E. O. Wiley (eds.). John Wiley and Sons, New York, New York. An important reference to the fossil history of North American fishes.
Grande, L. 2001. An updated review of the fish faunas from the Green River Formation, the world’s most productive freshwater Lagerstätten, 1–38. In Eocene biodiversity: Unusual occurrences and rarely sampled habitats. G. F. Gunnell (ed.). Kluwer Academic/Plenum Publishers, New York, New York. A comprehensive review of one of the most complete series of fossil fish faunas.
Smith, A. G., D. G. Smith, and B. M. Funnell. 1994. Atlas of Mesozoic and Cenozoic coastlines. Cambridge University Press, Cambridge, United Kingdom. An important reference for understanding
