Here's an interesting breakdown about the genetics of particular strains of specks in some of the streams of the park...(If i get too technical, I apologize)
Not surprisingly, the Sam's Creek and Starkey Creek are the same pure southern strain. There are two distinct Southern strain populations in Silers creek (I guess two extended families cohabitate in this stream, but want very little to do with each other breeding wise) And a stream geographically located between these two, Meigs creek- has a pure strain in it as well, however these are a Northern strain, and the one stream in the park that was surveyed in this particular study that didn't have any southern strain specks detected in the waters.
All of the NC park streams surveyed that had northern strain specks hybridized with one or more population of southern specks in varying degrees of hybridization. What was interesting, is the correlation between the time passed since the last recorded stocking, and degree of genetic hybridization. The streams that had most recently been stocked with Northern Strain specks showed the highest degree of northern genes in the hybrids. The ones that have had several more generations of reproductions since the last stocking, have the least degree of northern genes in the hybrids, suggesting that the native southern genes are better adapted to the climate and that there is some degree of genetic preference against the northern genes and their hybrids, so that over time, the hybrids are becoming more like the native genetically. It doesn't appear that amount of stocking has any correlation to the degree of hybridization.
The one very weird standout that doesn't fit with any of the studies hypotheses is Beech Flats prong. While it was one the most heavily stocked streams of the ones surveyed and one of the more recently stocked streams that were surveyed, it has the lowest genetic proportion of the marker used to differentiate the two strains and no northern strain mitochondrial dna (DNA that is only passed maternally, and is used to trace the maternal lineage of the fish, thus identify which northern strain it is hybridized with as well differentiate between distinct populations of fish). So why the native specks didn't hybridize with the stockers in this stream as much as any of the others, despite a very high opportunity to do so is kind of a mystery. There are three distinct southern populations in this stream as well. Maybe these families are more or less closed societies who apparently can out breed and out compete the stockers and want very little to do with breeding with them.
All in all, the study found 12 genetic populations of southern specks, and 4 genetic populations of northern specks (As well as the hybrids of these)