Elevational and Oceanic Barriers Shape the Distribution, Dispersal and Diversity of Aotearoa’s Kapokapowai ( Uropetala ) Dragonflies

Mountains and islands provide an opportunity for studying the biogeography of diversification and population fragmentation. Aotearoa (New Zealand) is an excellent location to investigate both phenomena due to alpine emergence and oceanic separation. While it would be expected that separation across oceanic and elevation gradients are major barriers to gene flow in animals, including aquatic insects, such hypotheses have not been thoroughly tested in these taxa. Here, we show that mountains and oceanic separation function as semi-permeable barriers for Kapokapowai ( Uropetala ) dragonflies. Although Te Moana o Raukawa (Cook Strait), is likely responsible for some of the genetic structure observed, speciation has not yet occurred in populations separated by the strait. We find no evidence that they are an impervious barrier, but Kā Tiritiri-o-te-Moana (the Southern Alps) significantly restrict gene flow between named species. Our data support the hypothesis of an active colonization of Kā Tiritiri-o-te-Moana by the ancestral population of Kapokapowai, followed by a recolonization of the lowlands. These findings suggest that aquatic insects could be an exciting new frontier in the study of the biogeography and population fragmentation in the landscape of Aotearoa.