Abstract:
Population genetics is an extremely powerful field of study, as it informs conservation management, taxonomy, and biogeography, among other questions. Tītipounamu or the rifleman (Acanthisitta chloris), New Zealand’s smallest bird, is one of two members of the suborder Acanthisitti, which is sister to all other passerines. Tītipounamu have a widespread but discontinuous distribution. Population numbers are in decline, and many populations are severely endangered, potentially undermining the long-term viability of the species. Building on a previous mitochondrial DNA analysis, this study used two mitochondrial DNA loci and twelve nuclear microsatellite loci to analyse demography, phylogeny, connectivity, and population divergences in nine populations of tītipounamu from the North and South Islands. This dataset was also used to test the current taxonomy, which divides tītipounamu into North Island (Acanthisitta chloris granti) and South Island (Acanthisitta chloris chloris) subspecies. The most basal divergence within tītipounamu appears to be between the populations from the West Coast of the South Island and all other tītipounamu, and was likely caused by the uplift of the Southern Alps. Therefore, a three-lineage model (North Island, Western South Island, and Eastern South Island) is better supported than a North Island vs. South Island model. No taxonomic change is currently advised due to a paucity of morphological data, but the three groupings have been designated Evolutionarily Significant Units (ESUs). The Hauturu (Little Barrier Island) population is highly divergent from other North Island tītipounamu, and has also been designated an ESU. Two insular populations, Hauturu and Codfish Island, appear to have very low genetic diversity and have likely experienced bottlenecks. Despite this, both have been used as source populations for translocations. These examples indicate the importance of undertaking population genetic studies before performing translocations. To this end, appropriate source populations for translocation have been designated.
