CLADISTIC-ANALYSIS OF THE ALDERFLIES OF AMERICA NORTH OF MEXICO (MEGALOPTERA, SIALIDAE)

A cladistic analysis of thirty-five morphological characters is used to produce a cladogram for the twenty-four American species of Sialis found north of Mexico, two European species, and three species of Protosialis. Three species groups (americana, californica and infumata) proposed by Ross (1937) are shown to be monophyletic. Sialis, Protosialis, and the aequalis species group as currently constituted, are paraphyletic; S.nevadensis is nested within Protosialis and Protosialis is nested within Sialis. Character evolution is evaluated in the light of a phylogenetic hypothesis, and structural modifications are found to correlate with presumed functional constraints.