4 Discussion
The results of our study document a highly different genetic and phylogeographic structure of diploid and triploid goldfish, particularly reflected in a clear geographic structure in diploids and no obvious association between structure and geographical origin in triploids. Also, and in accordance with our main hypothesis, we found a major difference in patterns of genetic variation between invasive populations of diploids and triploids in Tibet, with decreased variation in diploids and evidence for recent population decline reflecting founder events, but in contrast no detectable loss of variation in triploids. Nevertheless, inbreeding was low in diploids suggesting that multiple introductions from diverse sources have buffered bottlenecks associated with founding. Finally, we found evidence for selective sweeps in invasive diploid goldfish, with genes within outlier regions enriched for functions related to mannosidase activity and embryo development. We discuss these findings in more detail below.