Year of Award


Document Type


Degree Type

Doctor of Philosophy (PhD)

Degree Name

Fish and Wildlife Biology

Department or School/College

College of Forestry and Conservation

Committee Co-chair

Dave E. Naugle, Michael K. Schwartz

Commitee Members

Fred W. Allendorf, Jeffrey M. Good, Jon Graham


University of Montana


Wide-ranging species face many threats to genetic connectivity. In light of these threats, one major challenge is the efficient use of scarce resources for the conservation of these species. Setting conservation priorities for landscapes and connectivity can be informed using molecular genetics, and can ensure the efficient use of scare resources to maximize returns in biodiversity conservation.

The greater sage-grouse (Centrocercus urophasianus; hereafter sage grouse) is a species of conservation concern that spans eleven state boundaries, land managed by multiple agencies, and one international boundary. Across the species’ distribution, the threats to the genetic connectivity range from agricultural conversion to energy development, to catastrophic wildfire. In order to prioritize management as threats loom, there is considerable interest in gaining insight into the species’ population genetic substructure, dispersal capabilities, and range-wide genetic connectivity. The insights gained and be used to prioritize management efforts to preserve or restore genetic diversity and connectivity. This dissertation is composed of an investigation of population genetic substructure, breeding season dispersal, and the characterization of a range-wide genetic network for conservation prioritization.

Limitations in greater sage-grouse dispersal have resulted in the existence of five subpopulations across the northeastern range of the species, none of which appears to be genetically isolated. The genetic structure discovered appears to have been shaped by the natural landscape and ecological features. However, recent disturbances associated with human alteration of the landscape may have increased subpopulation divergence. Existing state conservation areas align well with genetic subpopulation structure allowing straightforward translation of management planning to the conservation of genetic diversity and connectivity. Simulation-based evaluation of the analytical methods used to detect subpopulation structure provided insight into interpretation of the evolutionary history of subpopulation divergence.

While many individuals remained philopatric to the same breeding sites (leks) year after year, more individuals dispersed to alternate leks. Evidence for sex-biased dispersal did not exist: either in tendency to disperse nor in distances traveled. Dispersal appears costly, as there was a greater occurrence of mortality among farther dispersing individuals. Individuals dispersed within, into and out of designated conservation areas, providing additional evidence that these areas are not isolated. Breeding dispersal likely counteracts the effect of philopatry, fostering gene flow.

Using network theory, I characterized the patterns of range-wide genetic connectivity among spring breeding congregations (leks), finding that connectivity is greatest among neighboring leks. The entire network is connected such that there are no isolated subunits. Hubs of genetic connectivity exist, evidenced by increased measures of both local and global network centrality, indicative of their importance to maintaining gene flow across the entire species’ iv range. These high-centrality hubs are centrally located within the species’ distribution, with concentrations within the Upper Snake River Basin of Idaho and the Green River Basin of Wyoming. Conservation efforts to protect these areas could prove essential to securing range-wide genetic connectivity into the future. Overall, this research provides insight into how to use molecular genetic analyses of substructure, dispersal, and connectivity of a continuously distributed species across a vast landscape to inform management and prioritize conservation actions.



© Copyright 2017 Todd Bartholomew Cross