Geology, Geography, and Genetics: The 3 G's of Highly Diverse Southeast Alaska Island Populations of Sockeye Salmon

Southeast Alaska drainages can be divided into two categories: short coastal streams linked to lakes, and large river systems that traverse the coastal mountain range from Canada.  Sockeye Salmon, Oncorhynchus nerka, spawn in many topologically diverse systems within these two drainage categories, employing a variety of life history patterns.  We surveyed 96 SNP markers for 171 Sockeye Salmon spawning aggregates from Prince William Sound south to Washington.  We found low levels of genetic diversity among spawning aggregates within trans-mountain rivers in Southeast Alaska, suggesting high levels of gene flow among these aggregates.  This contrasted with high levels of diversity among coastal spawning groups, even over relatively small distances with F_ST reaching 0.43.  These high levels of genetic diversity suggest low gene flow accompanied by small population sizes. We explore variables that might explain the patterns of genetic variation observed throughout Southeast Alaska including geography, geology, colonization history, and life history.