Phylogeography of the New Zealand cicada Maoricicada campbelli based on mitochondrial DNA sequences: Ancient clades associated with cenozoic environmental change

New Zealand's isolation, its well-studied rapidly changing landscape, and i ts many examples of rampant speciation make it an excellent location for st udying the process of genetic differentiation. Using 1520 base pairs of mit ochondrial DNA from the cytochrome oxidase subunit I, ATPase subunits 6 and 8 and tRNA(Asp) genes, we detected two well-differentiated, parapatrically distributed clades within the widespread New Zealand cicada species Maoric icada campbelli that may prove to represent two species. The situation that we uncovered is unusual in that an ancient lineage with low genetic divers ity is surrounded on three sides by two recently diverged lineages. Using a relaxed molecular clock model coupled with Bayesian statistics, we dated t he earliest divergence within M. campbelli at 2.3 +/- 0.55 million years. O ur data suggest that geological and climatological events of the late Plioc ene divided a once-widespread species into northern and southern components and that near the middle of the Pleistocene the northern lineage began mov ing south eventually reaching the southern clade. The southern clade seems to have moved northward to only a limited extent. We discovered five potent ial zones of secondary contact through mountain passes that will be examine d in future work. We predict that, as in North American periodical cicadas, contact between these highly differentiated lineages will exist but will n ot involve gene flow.