Mitochondrial DNA sequence variation and phylogeography of oceanic insects(Hemiptera : Gerridae : Halobates spp.)

Relatively few insects have invaded the marine environment, and only five s pecies of sea skaters, Halobates Eschscholtz (Hemiptera: Gerridae), have su ccessfully colonized the surface of the open ocean. All five species occur in the Pacific Ocean, H. germanus White also occurs in the Indian Ocean, wh ereas N. micans Eschscholtz is the only species found in the Atlantic Ocean . We sequenced a 780 bp long region of the mitochondrial cytochrome oxidase subunit I gene (COI) for a total of 66 specimens of the five oceanic Halob ates species. Our purpose was to investigate the genetic variation within s pecies and estimate the amount of gene how between populations. We defined 27 haplotypes for N. micans and found that haplotype lineages from each of the major oceans occupied by this species are significantly different, havi ng sequences containing five to seven unique base substitutions. We conclud e that gene flow between populations of H. micans inhabiting the Atlantic, Pacific, and Indian Ocean is limited and hypothesize that these populations have been separated for 1 to 3 million years. Similarly, there may be limi ted gene flow between H. germanus populations found in the Pacific and Indi an Ocean and between N. sericeus populations inhabiting the northern and so uthern parts of the Pacific Ocean. Finally, we discuss our findings in rela tion to recent hypotheses about the influence of oceanic diffusion on the d istribution and population structure of oceanic Halobates spp.