As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.

Friday 26 January 2018

Genetic drift caught in action in invasive birds



Studies of island bird populations have taught us a lot about evolution, but it's hard to catch birds in the act of naturally colonizing new islands. Instead, a new study from The Auk: Ornithological Advances examines what's happened by looking at the genetics of a species that arrived in Hawaii in the twentieth century through decidedly unnatural means—us.

Japanese Bush-Warblers were introduced to Oahu in 1929 and have since become established on all the main islands of Hawaii, providing a unique opportunity to follow post-invasion evolution on a known, recent timescale. Northern Arizona University's Jeffrey Foster and his colleagues took blood and muscle samples from 147 bush-warblers living on five islands between 2003 and 2005. Their results indicate genetic drift is occurring—Oahu's birds have higher genetic diversity than those on other islands, whose populations were founded by smaller groups of individuals, just as population genetic theory predicts. Kauai bush-warblers, however, appear to be on a distinct genetic trajectory from those on other islands. Kauai is three times as far from Oahu as the closest other islands, and appears to have received a unique subset of the overall genetic diversity found elsewhere, but it remains to be seen whether the trend on Kauai will continue in the future or if continued dispersal of birds among islands will blur these differences. "This study nicely showed genetic divergence for a very short period using the artificially introduced Japanese Bush-Warblers," according to Shoji Hamao of Japan's National Museum of Nature and Science, an expert on the species.

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