Assessing the need for and impact of translocation as a means of genetic rescue for Wisconsin's sharp-tailed grouse population

Background/Question/Methods

Loss of genetic diversity is a major factor in extinction for small populations. Populations with high levels of genetic diversity are less likely to suffer the negative effects of inbreeding that can cause a population to decline. Translocating individuals into a critically small population mimics natural gene flow and can increase genetic diversity and lead to population growth. The sharp-tailed grouse (Tympanuchus phasianellus) population in Wisconsin (WI) has experienced a 50% decline since 1991. Because this population consists of several small, isolated subpopulations, inbreeding was identified as a possible threat to its persistence. We used 8 microsatellite loci to analyze genetic variation and gene flow in the WI subpopulations, as well as a contiguous population that spans throughout Nebraska, North and South Dakota, and which is considered demographically healthy. 

Results/Conclusions

The WI subpopulations had lower allelic diversity (A=3.3), lower heterozygosity (H=0.34), and higher inbreeding (F_IS=0.412) than the contiguous population (A=8.0; H=0.75; F_IS=0.185). F_ST values were high between WI subpopulations (0.25) compared to sampling sites in the contiguous population (0.002), indicating relatively low levels of gene flow among WI subpopulations. We conclude that Wisconsin's sharp-tailed grouse population is suffering from a lack of genetic diversity and reduced interpopulation dispersal that is not typical for this species. During spring of 2010 and 2011, 30 sharp-tailed grouse hens were translocated between WI subpopulations with the goal of increasing gene flow and reducing inbreeding. Hens translocated in 2010 were not monitored and so survival is not known. Out of the 11 hens translocated in 2011, only two are known to have survived to reproduce at the release population. Despite the low number of successfully translocated individuals, it is still possible that genetic variation in the population increased. Future work should assess post-translocation inbreeding to determine the efficacy of translocation as a management tool for Wisconsin's current sharp-tailed grouse population.