Distribution of the DNA transposon family， Pokey in the Daphnia pulex species complex.

The Pokey family of DNA transposons consists of two putatively autonomous groups， PokeyA and PokeyB， and two groups of Miniature Inverted-repeat Transposable Elements (MITEs)， mPok1 and mPok2. This TE family is unusual as it inserts into a specific site in ribosomal (r)DNA， as well as other locations in Daphnia genomes. The goals of this study were to determine the distribution of the Pokey family in lineages of the Daphnia pulex species complex， and to test the hypothesis that unusally high PokeyA number in some isolates of Daphnia pulicaria is the result of recent transposition. To do this， we estimated the haploid number of Pokey， mPok， and rRNA genes in 45 isolates from five Daphnia lineages using quantitative PCR. We also cloned and sequenced partial copies of PokeyA from four isolates of D. pulicaria.