Year of Award


Document Type


Degree Type

Master of Science (MS)

Degree Name

Organismal Biology and Ecology

Department or School/College

Division of Biological Sciences

Committee Co-chair

Winsor H. Lowe, H. Arthur Woods

Commitee Members

Michael K. Schwartz


death valley model, population genetics, stream networks, Dicamptodon aterrimus, stream hierarchy model


University of Montana


Stream network structure constrains population processes of freshwater organisms, with individual, population and community level consequences. This consistent structure provides a framework in which examination of life-history influences on population genetic structure may provide general insight. I examined how stream network structure affects gene flow and genetic structure of the facultatively paedomorphic Idaho Giant salamander, Dicamptodon aterrimus in Idaho and Montana, USA. I used microsatellite data to test population structure models by (i) examining hierarchical partitioning of genetic variation in stream networks and (ii) testing for genetic isolation by distance along stream corridors versus overland pathways. Replicated sampling of streams within catchments within three river basins revealed that stream hierarchical scales had strong effects on gene flow and genetic structure. AMOVA identified significant structure among all hierarchical levels (among streams, among catchments, among basins), and divergence among catchments had the greatest structural influence. Isolation by distance was detected within catchments, and in-stream distance was a strong predictor of genetic divergence. Patterns of genetic divergence suggest that differentiation among streams within catchments was driven by limited migration according to the stream hierarchy model, but divergence among catchments and among basins was due to genetic drift, consistent with the death valley model of population structure (Meffe and Vrijenhoek 1988). These results show the strong influence of stream networks on population structure and genetic divergence of a salamander with contrasting effects at different hierarchical scales.



© Copyright 2009 Lindy Beth Mullen