Low neutral genetic diversity in isolated Greater Sage-Grouse (Centrocercus urophasianus) populations in northwest Wyoming

Abstract

Identifying small, isolated populations is a conservation priority, not only because isolation may result in negative fitness consequences, but these populations may also harbor unique genetic diversity. The Greater Sage-Grouse (Centrocercus urophasianus) is a widespread obligate species of the sagebrush biome in western North America that has experienced range-wide contraction over the past century. To prevent local extirpation, efforts have been made to identify isolated populations. Here, we analyzed 16 microsatellite loci from 300 Greater Sage-Grouse individuals to assess genetic structure among populations in Wyoming and southeast Montana, particularly with the Jackson Hole and Gros Ventre populations in northwest Wyoming. Four genetic clusters were observed with Pinedale (central-west) and Casper (central) populations forming a cluster, Powder River Basin (central-north) and southeast Montana forming a second cluster, and both Jackson Hole and Gros Ventre forming distinct population clusters. All but the Jackson Hole and Gros Ventre genetic differentiation correspond with designated ecoregions and possessed an isolation-bydistance pattern of differentiation. Both Jackson Hole and Gros Ventre were identified as separate populations with asymmetrical dispersal into Gros Ventre. Both populations also possessed significantly reduced genetic diversity and low effective number of breeders (N b ). Because both populations are surrounded by extensive forested mountain ranges nearly devoid of sagebrush habitat, the Jackson Hole and Gros Ventre populations may have long been isolated from other Greater Sage-Grouse populations; however, only a few alleles were unique to the Jackson Hole and Gros Ventre populations. The observed genetic differentiation was largely due to allele frequency differences rather than private alleles, suggesting some historical gene flow. More work is needed to determine the timing of isolation and whether managers should focus on maintaining and increasing adequate sagebrush habitat, allowing the population to increase in size, or population supplementation to increase genetic diversity.

The genetic network of greater sage‐grouse: Range‐wide identification of keystone hubs of connectivity

“…Similarly, there was a correlation between conditional genetic distance and geographic distance. These results support prior findings of isolation by distance across the species’ range (Bush et al., ; Cross et al., ; Davis, Reese, Gardner, & Bird, ; Fedy, Row, & Oyler‐McCance, ; Oyler‐McCance, Taylor, & Quinn, ; Schulwitz, Bedrosian, & Johnson, ). However, nodes with greater centrality, important to both local and network‐wide genetic exchange, are located across the species’ range.…”

“…Schulwitz et al. () found that the subpopulations in southern and southeastern Montana and the Dakotas were both highly connected to leks in northern Wyoming. We also found the same pattern of connectivity, evident in the hub‐and‐spoke topology of the minimum spanning tree.…”

Full Issue

“…Oyler-McCance et al 2005a, Bush et al 2011, Schulwitz et al 2014, the Bi-State population(Oyler-McCance et al 2014), and Gunnison Sage-Grouse(Oyler-McCance et al 2005b). Even so, clustering of individuals within the Gunnison Sage-Grouse and the Bi-State groups in this study (Figure 3) are evident and are consistent with previous microsatellite data.…”

Declining recruitment of Gunnison Sage-Grouse highlights the need to monitor juvenile survival

“…Johnson et al (2010) emphasized the importance of managing populations according to their specific population dynamics and not assuming that the same management will be optimal across a species. The small, isolated San Miguel population represents unique genetic diversity for Gunnison Sage-Grouse (Oyler-McCance et al 2005), which similarly has been found for isolated populations of Greater SageGrouse (Schulwitz et al 2014, Davis et al 2015c, OylerMcCance et al 2015. These genetic differences may be related to different processes exhibited by the different populations, and highlight the need to preserve the genetic diversity that is present in isolated populations.…”