Genomic Research Supporting Western Conservation

Science Center Objects

In the western United States (U.S.), there are many regionally restricted, rare species resulting from complex demographic and ecological processes through time. In addition to the inherent risks associated with being rare (i.e., having few individuals spread over a limited area that could be disproportionately affected by chance events), anthropogenic disturbances are increasing in magnitude across the region (e.g., energy extraction activities, recreation, livestock, invasive species). These disturbances can threaten the continued persistence of rare species by diminishing habitat, altering ecosystem properties, and changing the climate. Thus, the need to document the historical and contemporary properties of and project the future impacts on rare species is critical. Examples of Genetics for Western Restoration and Conservation (GWRC) group research that facilitates the conservation of species across the western U.S. are highlighted below.

Current Genetics for Western Restoration and Conservation (GWRC) group projects:

Connectivity across the fragmented distribution of Graham’s beardtongue: investigating the factors influencing gene flow

Graham’s beardstongue (Penstemon grahamii)

Graham’s beardstongue (Penstemon grahamii) on the Green River Formation in the Uinta Basin, UT. (Credit: Daniel Winkler, USGS Southwest Biological Science Center. Public domain.)

Graham’s beardtongue (Penstemon grahamii) is a narrowly endemic flowering plant distributed across the Green River geologic formation in the Uinta Basin, Utah. The Green River formation is also an important substrate indicating deposits of energy resources, and development for extraction activities is a common land disturbance. We performed high throughput DNA sequencing to 1) examine population genetic structure across the species’ range and 2) estimate how genetic diversity and rates of gene flow are influenced by various landscape features (e.g., climate, soil, and habitat disturbance). Knowledge of these biological processes may help managers prioritize the protection of important areas of the species’ range to support its continued persistence.

Assessing patterns of genetic differentiation and interactions among rare, closely related milkvetch species

Milkvetches (i.e., plants in the genus Astragalus) comprise the most diverse genus of flowering plants in the world, and many endemic and rare milkvetch species are distributed across the western U.S. A clade of two of these species—Astragalus sabulosus (composed of varieties sabulosus and vehiculus) and A. iselyi—occupies a narrow distribution in southeastern Utah. The distributions of these species and varieties do not overlap, yet they share morphological characteristics that suggest close evolutionary relationships. Given their limited distributions, small population sizes, and impending listing decisions under the U.S. Endangered Species Act, we used genomic data to determine: 1) the rate of gene flow among these taxa; 2) how long they have been isolated from one another; 3) how much genetic diversity is present across each taxon’s range; 4) if signatures of inbreeding depression exist; and 4) whether taxa harbor unique, adaptive genetic variation.

Upcoming Genetics for Western Restoration and Conservation (GWRC) group projects:

Navajo sedge (Carex specuicola)

Navajo sedge (Carex specuicola) growing out of sandstone rockface

Navajo sedge (Carex specuicola) growing in a hanging garden (to left growing out of sandstone rock face) near the Inscription House site on the Navajo Nation, AZ. (Credit: Rob Massatti, USGS Southwest Biological Science Center. Public domain.)

This rare sedge grows where water trickles out of Navajo sandstone and is found in “hanging gardens” on the Navajo Nation in Arizona and Utah. Given this restricted, often disconnected habitat, it is unknown how gene flow affects the genetic identity of plants, and thus how the plant should be managed to protect patterns of genetic diversity.

Arizona willow (Salix arizonica)

Arizona willow has few, widely scattered populations across Arizona, New Mexico, Colorado, and Utah. Not only do these geographic distances make it unlikely that gene flow occurs among populations, but the populations persist across a range of environmental conditions, suggesting the possibility of local adaptation. In addition, gene flow may occur with closely related species, necessitating a genomic perspective to inform appropriate management actions.

Pagosa skyrocket (Ipomopsis polyantha)

Pagosa skyrocket persists in two close but disconnected locations in southwestern Colorado. One location has hundreds of thousands of individuals, while the other only has hundreds. Given that the travel distance of known pollinators is not expected to be far enough to facilitate pollination between the two locations, it is unknown how genetically differentiated the populations are or if the smaller population is genetically healthy (i.e., retains sufficient genetic diversity and has low levels of inbreeding).

Arizona cliffrose (Purshia subintegra)

The endangered Arizona cliffrose is known from four populations across central Arizona. However, previous research suggested that of these four populations, one was a distinct species, Purshia pinkavae, while the remaining three resulted from hybridization events (P. pinkavae x P. stansburiana). While these analyses were informative for the management of P. subintegra, they raised additional questions that need to be addressed before appropriate management actions can be determined. Outstanding questions revolve around the timing of hybridization events that led to the creation of three of the P. subintegra populations, the ongoing nature of gene flow between P. subintegra and P. stansburiana where their ranges overlap, and relationships among P. subintegra, P. stansburiana, and other regional taxa in the genus.