Landscape restoration supports genetic connectivity among populations of a keystone species

Background/Question/Methods

Restoration of habitats that minimize dispersal costs could be essential for supporting population connectivity and the recovery of wildlife species. In the Chihuahuan Desert of southern New Mexico, grasslands have been replaced with shrubs due to overgrazing, drought, and lack of fire. We tested the hypothesis that landscape-scale restoration of grasslands affects gene flow among populations of banner-tailed kangaroo rats (Dipodomys spectabilis). Dipodomys spectabilis is a keystone species that creates habitat heterogeneity and alters plant and animal communities. Restoration treatments are known to reduce shrub cover and increase grass cover, and the density of D. spectabilis responds positively to treatments. However, the response of D. spectabilis is strongly time-lagged due to inadequate connectivity to source populations. Insight into effects of landscape structure on dispersal could be helpful for targeting areas for future restoration treatments. We used seven microsatellite markers and landscape resistance models to examine whether restored grasslands and other landscape features (e.g., waterways, roads, slope) affect the degree of genetic divergence among 20 D. spectabilis populations. 

Results/Conclusions

Pairwise genetic divergence (F_ST) varied from 0–0.18, suggesting that the level of gene flow varied widely across the landscape. There was a strong pattern of isolation by distance using a simple model of Euclidean distances. However, landscape resistance models were generally more supported than a Euclidean distance model for explaining variation in genetic divergence. The most-supported resistance model accounted for restored grasslands and no other landscape features, suggesting restoration treatments facilitate gene flow. There was also some evidence that gene flow was restricted by roads and waterways. Populations east and west of the Rio Grande and Interstate-25 corridor were strongly differentiated. Overall, our results suggest that landscape-scale efforts to restore grasslands support dispersal and gene flow among populations of D. spectabilis. Targeting future restoration sites near other treated areas may be an effective approach for facilitating the recovery of D. spectabilis populations.