Evolution and systematics

The suborder Percoidei contains more than 70 families and 2,800 species. This chapter and the four Percoidei chapters that follow highlight a representative sample of Percoidei taxa. This chapter focuses on four families:

• Percidae, the perches, with 10 genera and 162 species

• Centrarchidae, the sunfishes, with eight genera and 29 species

• Elassomatidae, the pygmy sunfishes, with one genus and six species

• Moronidae, often grouped under the umbrella descriptor "temperate basses," with two genera and six species

All four families fall within the massive order Perciformes, although the placement of Elassomatidae in this order has been disputed. The current classification positions Percidae, Cen-trarchidae, and Moronidae within the 71-family suborder Per-coidei, and the pygmy sunfishes in the single-family suborder, Elassomatoidei. Some taxonomists have suggested moving the elassomatids out of the percomorphs altogether and placing them into the atherinomorphs, a broad grouping that includes the killifishes (cyprinodonts), but at least one genetic analysis (Jones and Quattro, 1999) discounts this change. Past arrangements had placed the pygmy sunfishes together as a subfamily within Centrarchidae, but their similarities in appearance have since been attributed to evolutionary convergence.

Changes have also occurred in other families. The mo-ronids, for example, now include species formerly within the family Percichthyidae. Some biologists consider them to be most closely related to the snooks and giant perches in the family Centropomidae, because both share two additional lateral lines on the tail, above and below the main lateral line. Little doubt exists that all four families—Percidae, Centrarchidae, Moronidae, and Elassomatidae—will undergo further taxonomic alterations in the future, as scientists learn more about the phylogenetic relationships between species, genera, and higher classifications.

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