Reconstructing the history of intercontinental dispersal in Daphnia lumholtzi by use of genetic markers

After its appearance in 1989, the cladoceran Daphnia lumholtzi rapidly dispersed throughout the southern United States. In the current study, we used allozyme and mitochondrial deoxyribonucleic acid sequence data to infer the past dispersal of this species. Both genetic markers revealed the similarity among all U.S. populations and those from Uganda and Nepal but their divergence from Australian lineages. The extent of genetic divergence among populations, when coupled with estimates of rates of molecular evolution, suggests that the distribution of this species reflects a series of long-distance dispersal events over the last 4 million years.