Evolutionary Genetics of the New Zealand Cyanoramphus Parakeets

Abstract

The Genus Cyanoramphus (kakariki) is one of the three groups of New Zealand parrots, having come to New Zealand via dispersal from New Caledonia between 450-625,000 years ago. Kakariki then radiated out into the Pacific. However, the taxonomic status, phylogenetic relationships and population genetics of several Cyanoramphus taxa still remain unknown. This research uses a number of molecular methods, (specifically mtDNA control region sequencing, trace and ancient DNA techniques, microsatellite genotyping and PCR-RFLP analysis), in combination with morphological, geological and historical data in a multidisciplinary analysis to investigate the evolutionary genetics of Cyanoramphus. The main areas the thesis focuses on are the biogeography and the origin(s) of Cyanoramphus parakeets on the Kermadec archipelago; population genetics and conservation of the Antipodes Island green parakeet (AnGP, Cyanoramphus unicolor) and Reischek’s parakeet (ReRCP, Cyanoramphus hochstetteri); origins and hybridisation of the Auckland Islands Cyanoramphus taxa; and the historical status of mainland New Zealand Cyanoramphus taxa. The results have shown that because they originated from two separate colonisations, the Kermadec Islands red-crowned parakeet (currently C. novaezelandiae cyanurus) populations on Macauley Island and Raoul Island/Meyer Island are geographically isolated and genetically distinct, indicating a possible subspecies C. n. cyanurus and C. n. ssp. nov. A respectively. The Macauley Island population is more genetically diverse at microsatellite loci than the Raoul Island/Meyer Island population. Wild populations of AnGP and ReRCP on Antipodes Islands' exhibit comparable levels of genetic variation at microsatellite loci. The captive breeding programme for AnGP has preserved the majority of the genetic variation present in the source wild population, but lacks rare alleles. The Auckland Islands' red-crowned parakeet is identical to the mainland New Zealand red-crowned parakeet (RCP, C. n. novaezelandiae) and has high levels of genetic variation. In contrast, the Auckland Islands' yellow-crowned parakeet represents a geographically isolated and paraphyletic clade of yellow-crowned parakeet, indicating a possible subspecies, C. auriceps ssp. nov. A. It shows little or no genetic variation. Interestingly, there is mtDNA evidence of an extinct subspecies of orange-fronted parakeet, C. malherbi ssp. nov. A on the Auckland Islands. Finally, trace and ancient DNA techniques have shown first that historically, there has been extensive genetic exchange of mtDNA lineages between morphologically defined mainland Cyanoramphus taxa through hybridisation; and second, that previously, the orange-fronted parakeet (C. malherbi) morphotype may have comprised of two cryptic taxa. One is now an extinct colour morph of yellow-crowned parakeets (YCP, C. auriceps) and the other, an extant orange-fronted parakeet that obtained an mtDNA haplotype via hybridisation with ancestral RCP The results of this research represent a significant addition to our present knowledge of Cyanoramphus and help to clarify the taxonomic status, phylogenetic relationships and population genetics of Cyanoramphus taxa.