Historical and Life History Factors in the Biogeography of Mayflies

Abstract

SYNOPSIS. Cladistic analysis of mayflies suggests that dispersal was very asymmetrical after the new land connection between North and South America. Twenty-one genera apparently moved from South to North and Central America, but there is good evidence for only one North American genus moving into the south. Testable predictions are possible once the boreal (Laurasian) or austral (Gondwanian) designations are made. For example, Paracloeodes , a genus of austral origin, was predicted to be found in South America, and in North America in warm rivers north and east of its known distribution. These predictions have been confirmed. Other characteristics of tropical mayflies, such as length of larval period and emergence and mating patterns, may be used to predict habitats and characteristics of present North American genera. Merger events and consequent dispersal of organisms have profound influences on distributional patterns, and from such information, biologically useful generalities can be made.