Galápagos Islands finches that helped Charles Darwin develop his theory of natural selection are showing clear signs of further evolutionary development.
The latest study by researchers from the Flinders University Bird Lab has further shown that the birds commonly known as Darwin’s finches are the world’s fastest-evolving vertebrates, with their appearance and behaviour quickly adapting to rapidly changing environments.
Researchers Dr Katharina Peters and Professor Sonia Kleindorfer, from the Research Centre for Animal Behaviour at Flinders, found that the critically endangered female medium tree finches, that only occur on Floreana Island on the Pacific Ocean archipelago, are mating with male small tree finches, a common species that occur across the Galápagos Islands.
Female birds generally choose a male partner and males will put in considerable effort to attract a choosy female. But why would a female choose a male from a different species?
The research study showed this cross-species choice pattern is very strong in tree finches on Floreana Island. However, while females of the critically endangered medium tree finch species are selecting males from both finch species, the common finch females will only pair with their common species male counterparts.
Hybrid females from finch cross matings also choose to pair with small tree male finches or other hybrid males. It means that the gene flow is skewed towards the more genetically vigorous small tree finch species and away from the endangered medium tree finch.
Darwin’s Finches are under attack from an introduced parasitic fly, which has been killing the birds for at least two decades – and Dr Peters suspects that hybrid finches may have an advantage when dealing with the parasitic fly.
“Our research aims to shed light on the possible evolutionary benefits of hybridisation by analysing breeding success across species,” says Dr Peters.
“Based on our study, we recommend that the tree finch group on Floreana Island should be treated as a single conservation management unit due to their intertwined evolutionary trajectories and the frequent natural occurrence of hybridisation in this system.”
The Galápagos Islands are one of the world’s foremost destinations for wildlife viewing. The province of Ecuador lies about 1,000km off its coast and its isolated terrain shelters a diversity of plant and animal species, many found nowhere else.
Charles Darwin visited in 1835, and his observation of the rich array of Galápagos species later inspired his theory of evolution.
View the Flinders Bird Lab research paper, ‘Females drive asymmetrical introgression from rare to common species in Darwin’s tree finches,’ Journal of Evolutionary Biology KJ Peters, SA Myers, RY Dudaniec, JA O’Connor, S Kleindorfer here