Background/Question/Methods The keystone species, Pisaster ochraceus, suffered mass mortalities along the northeast Pacific Ocean as a result of Sea Star Wasting Syndrome (SSWS) outbreaks in 2013-2017. The cause of SSWS is still debated and understanding there are genetic factors influencing which individuals are afflicted with SSWS may help clarify the etiology of the disease. We sampled tissue in sea stars from three populations in Oregon in 2015, one year after the start of the epidemic, and used reduced-representation genome sequencing to compare allele frequencies between symptomatic (susceptible) and asymptomatic (potentially resistant) individuals. Results/Conclusions Using Fst-based analysis of selection, we found three loci that may be associated with SSWS variation. In addition, we used discriminant analyses of principal components tests and identified several regions across the genome demonstrating small genetic differences that successfully distinguishes symptomatic versus asymptomatic sea stars across geographic regions. These data complement prior work that suggests a genetic basis for variation in SSWS resistance, which indicates potential for increased resilience of survivors to future outbreaks. We highlight the importance of assessing genetic variation in parallel with observational monitoring to more proactively understand and mitigate the increasingly present threat of marine disease outbreaks.
