A new analysis of Hawaiian honeycreeper origins shows that their closest relatives are the rosefinches of the genus Carpodacus.
The Hawaiian honeycreepers have long been known as a fantastically divergent group of island endemics, derived from a fringillid finch ancestor at some time within the last 5.5 million years or so.
Using a dataset of one mitochondrial and 13 nuclear genes, the authors were able to resolve their relationships and demonstrate their origin.
Most lineages of the highly morphologically variable honeycreeper subfamily Drepanidinae evolved after the emergence of Oahu around 4 million years ago and Maui around 2 million years ago, with the former island being the hub of evolution and dispersal of the different forms.
While no new forms or species were discovered by the researchers, their use of outgroup has shown that the oft-quoted ancestors of the group were not the cardueline finches or indeed the crossbills Loxia and Pine Grosbeak, though these have been mooted as behavioural analogues in some respects. Genetically, the honeycreepers' sister group are the rosefinches.
While not an obvious choice, the geographical distribution of rosefinches across Eurasia and North America make them likely candidates to colonise Hawaii, to the south in the Pacific but on a latitude enabling lost birds to arrive en masse when travelling between the two large landmasses. Common Rosefinches often irruptively disperse in large mixed-sex groups to establish new wintering grounds. A large group of Carpodacus-type finches would have enough genetic variation to establish a fairly viable population in a new area and to begin to rapidly radiate when freed from the inter-specific competition of a larger landmass.
Reference
Lerner, H R L, Meyer, M, James, H F, Hofreiter, M, and Fleischer, R C. 2011. Multilocus Resolution of Phylogeny and Timescale in the Extant Adaptive Radiation of Hawaiian Honeycreepers. Current Biology doi:10.1016/j.cub.2011.09.039.
