Suckers of subfamily Ictiobinae (Teleostomi: Catostomidae) are large, deep-bodied, long-finned fishes native to large rivers and lakes in eastern North America, inclusive of Mexico.  Seven species of ictiobines are currently recognized in the two extant genera, Carpiodes and Ictiobus.  The group is poorly studied and is believed to be much more diverse than presently recognized.  Most of the species have wide, highly overlapping distributions, and may show similar (replicated) patterns of speciation.  Most species of ictiobines are readily diagnosable by morphological characters.  However, as a consequence of the overlapping distributions and human alteration of the large rivers these fishes inhabit, a number of the species are hybridizing, and this may be complicating efforts to understand diversity and evolutionary history of the group.

We propose to revise the two extant ictiobine genera to assess morphological and genetic diversity within currently recognized species.  We will test the hypothesis that current nominal species are complexes of biological/evolutionary species.  We will formally describe all newly discovered diversity and establish morphological characters and taxonomic keys to aid others in identification of new and existing forms. We will sequence portions of the mitochondrial and nuclear genomes, and use these data to establish phylogenies at the levels of all ictiobines, genera Carpiodes and Ictiobus, and species complexes within these genera.  We will use molecular techniques that enable us to screen large numbers of individuals to assess population-level genetic variation and cytonuclear disequilibria, identify interspecific hybrids, and individuals that should be sequenced to develop phylogenetic hypotheses.  Lastly, we will use the derived phylogenies to examine speciation and dispersal patterns, and (by comparing our results to those based on studies of small stream fishes) assess differences in patterns and rates of evolution between large and small stream habitats. 

This project combines expertise in traditional (morphology-based) and modern (molecular) methods of systematics.  It involves analysis and synthesis of data from both of these areas.  It will provide unique insights into the connections between morphological and genetic differentiation in large-river environments.  As is true for ictiobines, species representing separately evolving lineages typically come together in large-river environments, and populations within species tend to have higher degrees of connectedness than those of small stream species.  In addition to resolving taxonomic problems in an important group of large-river fishes, this study will increase general understanding of dispersal, speciation and maintenance of reproductive isolating mechanisms in large-river environments.  Students at two stages of professional development (undergraduate and graduate) - including participants in a minority undergraduate research-training program - will receive training in this project.

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