sampling error. In order to assess the likelihood the population is non-hybridized, we determine the chances of 

 not detecting as little as a one percent genetic contribution of a non-native taxon to a hybrid swarm. This is 

 simply 0.99 "^'^ where N is the number of fish in the sample and X is the numberof marker loci where the/) allele 

 is characteristic of the non-native taxon. 



In samples showing evidence of hybridization, that is; fragments characteristic of a non-native taxon were 

 detected at two or more marker loci, we used two approaches to determine if the population appeared to be a 

 hybrid swarm. First, contingency table chi-square analysis was used to test for heterogeneity of allele frequencies 

 among the marker loci. Next, we compared the observed distribution of the number of loci per individual at 

 which non-native fragments were detected to the expected random binomial distribution based on the estimated 

 native and non-native genetic contributions to the population. If both analyses were non-significant we 

 concluded the population came from a hybrid swarm. 



Heterogeneity of allele frequencies among marker loci could arise from a couple of factors. In very old hybrid 

 swarms the frequencies over time may diverge from each other due to genetic drift or the sample may have 

 contained individuals from multiple populations with different amounts of hybridization. These possibilities are 

 generally distinguishable from each other. Under the first scenario, the non-native fragments will still be 

 randomly distributed among individuals while in the latter scenario they will not. 



Another factor that can result in a non-random distribution of non-native fragments among individuals is 

 relatively recent hybridization. Unlike in mixed population samples, however, in this situation the allele 

 frequencies among marker loci are expected to be statistically homogeneous because they can all still be traced to 

 a common origin or origins. 



Results and Discussion: .' t. j . 



Sample # 2924 Details: 



PINE fragments characteristic of only Westslope were detected. 



■■ ■,; ,; '■"■■ ' '"' ' ' '" TABLE 1 



Diagnostic PINE markers for westslope cutthroat, 

 Yellowstone cutthroat, and rainbow trout. X 

 indicates the fragment is present in the particular 

 taxon. 



J. Markers Yellowstone Westslope Rainbow 



'i'-'- 



