Deep mtDNA subdivision within Linnean species in an endemic radiation of tiger beetles from New Zealand (genus Neocicindela).

The invertebrate fauna of New Zealand is of great interest as a geologically tractable model for the study of species diversification, but direct comparisons with closely related lineages elsewhere are lacking. Integrating population-level analyses with studies of taxonomy and clade diversification, we performed mtDNA analysis on Neocicindela (Cicindelidae, tiger beetles) for a broad sample of populations from 11 of 12 known species and 161 specimens (three loci, 1883 nucleotides), revealing 123 distinct haplotypes. Phylogenetic reconstruction recovered two main lineages, each composed of 5-6 Linnean species whose origin was dated to 6.66 and 7.26 Mya, while the Neocicindela stem group was placed at 10.82 ± 0.48 Mya. Species delimitation implementing a character-based (diagnostic) species concept recognized 19 species-level groups that were in general agreement with Linnean species but split some of these into mostly allopatric subgroups. Tree-based methods of species delimitation using a mixed Yule-coalescence model were inconclusive, and recognized 32-51 entities (including singletons), splitting existing species into up to 8 partially sympatric groups. These findings were different from patterns in the Australian sister genus Rivacindela, where character-based and tree-based methods were previously shown to produce highly congruent groupings. In Neocicindela, the pattern of mtDNA variation was characterized by high intra-population and intra-species haplotype divergence, the coexistence of divergent haplotypes in sympatry, and a poor correlation of genetic and geographic distance. These observations combined suggest a scenario of phylogeographic divergence and secondary contact driven by orogenetic and climatic changes of the Pleistocene/Pliocene. The complex evolutionary history of most species of Neocicindela due to the relative instability of the New Zealand biota resulted in populations of mixed ancestry but not in a general loss of genetic variation.