What caused the narrowing of the nenes' circumstances to the point of near-extinction? Was the isolation of island living to blame for draining their gene pool to a puddle, or was it caused by the 20th century population decline? How did they survive and recover when many other species of flightless Hawaiian birds disappeared altogether before recorded history?
Research reported in today's edition of the journal Science suggests that a boom in the human population between 900 and 350 years ago may have impacted and reduced the population size of the nene during that time, and consequently diminished the species' genetic variation.
A team of scientists from the Conservation and Research Center of the Smithsonian's National Zoological Park and National Museum of Natural History, along with a collaborator from the University of California, Los Angeles, examined DNA from nene on the island of Hawaii from four time periods: Extant captive and wild birds; museum specimens collected between 1833 and 1928; bones from archaeological middens radiocarbon dated at 160 to 500 years ago; and bones from paleontological sites dating from 500 to 2540 radiocarbon years before the present. They were surprised to find the levels of genetic variation typical of contemporary geese only in the paleontological samples.
"We were expecting to see evidence of the loss of genetic variation first in the museum specimens, coincident with the nene population decline that began in the 1800s," said Robert Fleischer, head of the Natural History Museum's genetics laboratory. "Instead, we found the precipitous drop much earlier, in the samples dating from between 500 and 850 years ago, coincident with the expansion of human
Contact: Elizabeth Tait
Smithsonian Tropical Research Institute