The transposable portion of the genome of Drosophila algonquin is very different from that in D. melanogaster

Four clones containing different transposable elements were isolated from a genomic library of Drosophila algonquin. Each clone was hybridized to salivary-gland chromosomes of three lines of D. algonquin and two lines of D. affinis. The estimated copy number in D. algonquin of the four element families varied from 59 to 333. The occupancy per site varied from 0.64 to 0.75. Thus the transposable portion of the D. algonquin genome is dominated by a few high-copy-number elements, each characterized by high occupancies. The copy number and occupancy values were very similar in D. affinis. This differs from the situation in D. melanogaster mobile middle-repetitive DNA, which has at least 30 and perhaps as many as 100 different families of mobile elements, with copy numbers ranging from 5 to 100. When several lines have been examined, elements in D. melanogaster are revealed to have very low occupancies. The four D. algonquin elements do not hybridize with D. melanogaster DNA, but they did hybridize with 15 obscura-group species, thereby revealing a pattern that is consistent with concerted evolution.