Analysis of Egg and Larval Characters for Their Use in the Systematics of Ostariophysan Fishes.

Revival of the theory of recapitulation has kindled an interest in using larval characters for inferring phylogenetic relationships among organisms. If the tenet of von Baerian recapitulation is true, larval characters should make strong contributions toward defining relationships. The difficulty lies in finding differences between larvae of related species in the face of the morphological similarity implied by von Baer's law. This study examines egg and larval characters for their contribution to the systematics of ostariophysans. The method involves construction of phylogenetic trees with these characters. Accepting the limits and relationships of the taxa based on adult characters, the usefulness of egg and larval characters is established by comparison of the independently derived trees. Specific goals include the use of a phylogenetic reconstruction method to assemble a suite of characters shared by each taxon of interest. Relative value of each of five types of characters is determined. Evolutionary trends in egg and larval characters, suggested by suites of characters, are outlined. Phylogenetic reconstructions are generated by the cladistic Wagner tree method for several taxonomic levels within the Ostariophysi. Character types include: egg, morphometric, meristic, ontogenetic, and presence/absence. Results show that larval characters contain important phyletic information. Groups of species defined by adult characters cluster together on the basis of larval characters. Larval characters preserve the interrelationships of groups in those instances where adult-based phylogenies are supported strongly. The major difficulty is the inability to unite all group members into a monophyletic unit. This, and many reversals and independent acquisitions of derived states, reflects considerable among-group variation in many larval characters. The relative value of the different character types changes with taxonomic level. Presence/absence characters are rather neutral to taxonomic level. Egg and meristic characters have low value at the ordinal and familial levels but are important for subfamilial grouping. Morphometric and ontogenetic characters express their greatest contribution at the ordinal level. Although the characters and species studied occasionally support recapitulation, it is hardly a prevailing influence. Further, the inability of larval characters to demonstrate monophyly of related species contradicts the implication of von Baer's law.PhDZoologyAquatic sciencesUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/159736/1/8402280.pd