Dissertations and Theses @ UNI


Thesis (UNI Access Only)


Longnose dace--Conservation--Iowa; Longnose dace--Iowa--Genetics;


A pressing issue in conservation is to determine if present day demographic and population genetic patterns are the result of recent anthropogenic impacts or of historical factors such as geologic history. Rhinichthys cataractae, the longnose dace, is a fish species of greatest conservation need listed in the Iowa Wildlife Action Plan. Within Iowa, the distribution of longnose dace is isolated to drainages in the northeastern portion of the state: the Upper Iowa, Yellow, Turkey / Volga, and Maquoketa rivers, as well as small tributaries of the Mississippi River. This distribution largely coincides with the Paleozoic Plateau landform region which was not glaciated during the last glacial maximum. The aim of this study was to use genetic and ecological data to elucidate the spatial genetic patterns of this species and the environmental factors affecting its distribution and population structure in Iowa. Seven DNA microsatellite loci were analyzed for 261 individuals from 15 localities across the Iowa distribution. Broad scale environmental variables including hydrologic, soil, and climatic factors were evaluated with GIS techniques and an ecological niche model (ENM) was constructed with these data to predict suitable habitat and environmental variables influencing suitability of habitat for the longnose dace. The ENM predicted high probability of R. cataractae occurrence in the known distribution, with very low likelihood of distribution outside of this region. This model suggested that geologic factors (e.g., geologic history, depth to bedrock, in-stream substrate type) play a key role in determining the distribution of R. cataractae in Iowa. In situ habitat data such as in-stream substrate composition and channel shade were collected and analyzed with multiple regressions and hierarchical stepwise corrected Akaike Information Criterion (AICc) in an effort to identify combinations of habitat variables significantly correlated with R. cataractae abundance. None of the habitat variable models evaluated with AICc were statistically significant predictors of R. cataractae relative abundance. However, the habitat variable model with stream width was highest ranked based on AICc, suggesting a potential correlation between stream width and R. cataractae abundance. Population genetic data revealed isolation by distance impacts on genetic differentiation as well as high levels of within locality diversity and two moderately distinct genetic clusters: The Upper Iowa – Yellow River complex and the Turkey/Volga – Maquoketa and Mississippi River tributary assemblage. These two unique groups suggest deep ties to the geologic and glacial history of the region.

Year of Submission


Degree Name

Master of Science


Department of Biology

First Advisor

Peter Berendzen, Chair, Thesis Committee

Date Original


Object Description

1 PDF file (viii, 67 pages)



File Format


Off-Campus Download