The species is endemic to New Zealand, and is predominantly found along southern coasts of the South Island and on Stewart Island, as well as on the subantarctic Snares and Auckland Islands. Based on genetic data, the species appears to have undergone a recent range expansion into the North Island, as it can be found at low frequencies along the Wellington coastline. This range expansion coincides with areas affected by tectonic uplift and landslides caused by historic earthquakes, including the 1855 Wairarapa earthquake. The removal of "D. antarctica" and formation of new coastline by such tectonic disturbance likely provided an ecological opportunity for "D. poha" to successfully colonise coastline north of the Cook Strait.