Understanding the Colonization History of Chinook Salmon in Patagonia Using Single Nucleotide Polymorphisms (SNPs): Gauging the Effects of Artificial Vs. Natural Propagation

Chinook salmon (Oncorhynchus tshawytscha) in South America have rapidly colonized Patagonian Rivers, likely mediated by both introductions (1970–1991) followed by dispersion from either farmed broodstock or already naturalized populations in more recent years (1991–Present). We genotyped 270 Chinook salmon sampled between 2003 and 2013 from six Pacific and two Atlantic basins through a panel of 190 SNPs developed from the native range in North America. Using population- and individual-based inference, our goals were three-fold: (1) quantify the contribution of donor (native) populations to introduced populations, (2) identify the number of gene pools among introduced populations using Bayesian inference, and (3) test for signals of reduced diversity among Atlantic populations, which were presumably founded from a reduced number of immigrants of Pacific origin. We found (1) variable contributions of donor populations among basins, consistent with early stocking practices and more recent imports for farming; (2) three distinct genetic pools: two in the Pacific and one in the Atlantic; (3) and lower genetic diversity among Atlantic basins than Pacific basins, suggesting a founder effect from Chinook salmon strays from the Pacific. A combination of both artificial and natural propagation might explain the rapid colonization of Chinook salmon in South America.