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

• Published in: Ecology and evolution Vol. 8; no. 11; pp. 5394 - 5412
• Main Authors: Cross, Todd B., Schwartz, Michael K., Naugle, David E., Fedy, Brad C., Row, Jeffrey R., Oyler‐McCance, Sara J.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.06.2018; John Wiley and Sons Inc
• Subjects: Centrocercus urophasianus; Conservation; Disintegration; Exchanging; Gene flow; Genetic diversity; graph theory; Hubs; Landscape preservation; Local population; multiscale conservation prioritization; Nodes; Original Research; Population genetics; Population number; Species; Spokes; Wildlife conservation; Wyoming; United States > US; Centrocercus urophasianus; graph theory; multiscale conservation prioritization
• DOI: 10.1002/ece3.4056
• ISSN: 2045-7758

Genetic networks can characterize complex genetic relationships among groups of individuals, which can be used to rank nodes most important to the overall connectivity of the system. Ranking allows scarce resources to be guided toward nodes integral to connectivity. The greater sage‐grouse (Centrocercus urophasianus) is a species of conservation concern that breeds on spatially discrete leks that must remain connected by genetic exchange for population persistence. We genotyped 5,950 individuals from 1,200 greater sage‐grouse leks distributed across the entire species’ geographic range. We found a small‐world network composed of 458 nodes connected by 14,481 edges. This network was composed of hubs—that is, nodes facilitating gene flow across the network—and spokes—that is, nodes where connectivity is served by hubs. It is within these hubs that the greatest genetic diversity was housed. Using indices of network centrality, we identified hub nodes of greatest conservation importance. We also identified keystone nodes with elevated centrality despite low local population size. Hub and keystone nodes were found across the entire species’ contiguous range, although nodes with elevated importance to network‐wide connectivity were found more central: especially in northeastern, central, and southwestern Wyoming and eastern Idaho. Nodes among which genes are most readily exchanged were mostly located in Montana and northern Wyoming, as well as Utah and eastern Nevada. The loss of hub or keystone nodes could lead to the disintegration of the network into smaller, isolated subnetworks. Protecting both hub nodes and keystone nodes will conserve genetic diversity and should maintain network connections to ensure a resilient and viable population over time. Our analysis shows that network models can be used to model gene flow, offering insights into its pattern and process, with application to prioritizing landscapes for conservation. Genetic networks characterize complex genetic relationships among groups of individuals. We modeled a genetic network across the entire range of the greater sage‐grouse—genotyping 5,950 individuals, from 1,200 leks, at 15 microsatellite loci—and described the underlying structure of the network. We identified hubs and keystone nodes (nodes with greater contribution to network connectivity than would be expected given the population size of the node) that are likely of increased conservation value given their centrality to the network.