The goal of this research is to understand the origin of a closely-related complex of 21 species of fishes, in the genus Semionotus, in relation to the formation, expansion and subsequent evaporation of a large fossil lake (Lake P4) preserved in the Newark Basin of eastern North America. Specific objectives are to: (1) determine which species were unique to Lake P4 by mapping the occurrences of these species in 8 distinct lake basins and through 33 million years of time, (2) analyze the genealogical (phylogenetic) history of these species, and (3) test the hypothesis that those species which are unique to P4 (and thus probably originated in that lake) will be more derived and appear later in the historical record of the lake than those species which have widespread distributions and presumably colonized Lake P4 during its early history. This study will have significant implications for our understanding of the fundamental pattern of the origin of species and of the relation between environmental change and organic evolution.
