 While hybridization among sexually reproducing species already provides good counter-examples to our assumptions about the independence of lineages, the bigger challenges have come from  microbiology . More specifically, what we find in microbial genomics are high levels of horizontal (or lateral) gene transfer (HGT or LGT). For readers unfamiliar with microbial genomics, this can be thought of as the microbial analogue to hybridization, though there are important qualitative and quantitative differences.