SGER: Morphological CT Scan of Notropis megalepis for Phylogenetic and Evolutionary Studies

Saint Louis University, Saint Louis MO

Investigators

Abstract

Historically, the stark contrast in diversity between North America's sunfish and minnow and shiner species served as a fertile research area for studying differential rates of evolution in two groups of equal age (based on fossil record). Cladistic analyses of osteological characters revealed fundamental flaws with previous studies of this nature and classifications of these fishes, thus questioning the accuracy of prior evolutionary studies. Today, phylogenetic relationships of species of Notropis (shiners) and relatives are relatively well known due to recent morphological and molecular analyses by the PI and collaborators as well as other researchers. Relationships of species of Centrarchidae, also soon to be available using morphological and molecular data, will provide the necessary information to begin comparative studies between the sunfish and shiner groups as envisioned by earlier researchers - rate heterogeneity in evolution. However, a notable problem remaining in advancing this research is the phylogenetic placement of the species Notropis megalepis, the species used to date the Notropis lineage, to a clade appropriate for comparison. The PI proposes to conduct high-resolution CT scans of the fossil Notropis megalepis from the Middle Pliocene of western Kansas using the recent technology developed at The University of Texas NSF Multi-user facility maintained by Dr. Tim Rowe. This fossil is fundamental in dating the age of the North American shiner and minnow group to which it belongs and evaluating rate heterogeneity in evolution for these two groups of fishes. Producing accurate estimates of evolutionary relationships is necessary for the overall framework for information retrieval and biological prediction. Uses of such information and predictability include tracking the origins of disease, identifying biological control agents for invasive species, and evaluating risk factors associated with biological conservation.