North American Population
When three populations were defined in North America (Eastern US, Middle US and Western US) there is no distinct population structure based on the F ST analysis. The comparison of these three regions shows little genetic differentiation (Table 3). These findings are consistent with an earlier investigation of this population, which found that there was no population structure based on allozyme data in the North American starling population (Cabe, 1998). Banding efforts in North America have shown that the starlings are found to migrate in unpredictable ways, not always in the North and South direction, but also in the East and West directions (Brewer, 2000). The absence of the population subdivision in North America is likely due to the high dispersal rates and the unpredictable and latitudinal migration patterns.
Since the introduction of European starlings into North America, novel haplotypes may have arisen, in addition to the native range haplotypes identified here (Figure 4). These haplotypes are UKK, UKC and UKE as described in the native population sampled from Monks Wood, UK (Rollins et al, 2011). However, because our native-range data are limited, it is likely that there are more shared haplotypes between North America and the UK than we have identified. Remarkably little is known about starling population genetics in the native range.
Consistent with our findings based on mitochondrial data, a recent study using genome-wide SNPs to investigate North American starlings did not find evidence of population structure (Hofmeister et al., 2019). However, those data do indicate that there are genotypes associated with specific environmental features such as precipitation and/or temperature. This suggests that over time, population structure may develop in this invasive population, despite apparent high levels of dispersal.