Is evolution gradual or rectangular? Evidence from living fishes

摘要: Abstract The traditional view that most evolutionary change is gradual and cumulative within lineages (phyletic gradualism) has recently been challenged by the proposition majority of concentrated speciation events (rectangular evolution). The logical implications these competing hypotheses for means variances genetic distance among living members rapidly slowly speciating phylads are examined. An example a critical test versus rectangular evolution provided electrophoretic analyses genic composition in 69 species North American Cyprinidae (minnows), 19 Centrarchidae (sunfish). Rate protein appears somewhat decelerated, if anything, minnows. Results inconsistent with predictions evolution, but not demonstrably incongruent phyletic gradualism.