Allozymic variation and differentiation in naturalized populations of rainbow trout, Oncorhynchus mykiss (Walbaum), from southern Chile

An allozyme survey was conducted in three naturalized populations of rainbo w trout, Oncorhynchus mykiss (Walbaum), from rivers in two Andean lakes of southern Chile. The analysis was based on 32 presumed loci, 10 of which wer e variable, and revealed that the mean percentage of polymorphic loci (P = 21.8%: range = 15.6-28.1%), the mean number of alleles per locus (n = 1.26; range = 1.2-1.3) and the mean observed heterozygosity (H-O = 7.0%; range = 6.0-8.2%) are high, although within the range reported for rainbow trout. Although the mean genetic distance between the samples was low (D = 0.003), and only 5.2% of the total observed genetic variation can be accounted by interpopulation differences (F-ST = 0.052), eight out of 10 polymorphic loc i exhibited significant allelic heterogeneity, Some loci, notably EST-1*, I DHP-3,4*, MEP-1* and PGM-1*, showed considerable discriminatory capacity am ong the samples. Rainbow trout has a longer history in Chilean waters since salmonid introduction started earlier this century. Under current intensiv e farming practices, the preliminary information provided in the present pa per is likely to be helpful in setting up a baseline for further characteri zation and/or monitoring of naturalized populations.