Rather than getting a gene for its original function, a horizontal gene transfer provides the raw material for evolutionary innovation.
Zebras evolved stripes to prevent pesky biting flies from landing on them, a study finds.
April 4, 2014|
WIKIMEDIA, PAUL MARITZResearchers have suggested many reasons for the zebra’s stripes, including that they serve as protective camouflage, a way to confuse predators, to manage body heat, or some kind of social function. According to a study published this week in Nature Communications, the most likely reason for the stripes is to keep biting insects like horseflies and tsetse flies from landing.
A team led by Tim Caro from the University of California, Davis, tested the five most popular theories. They mapped striped zebras and a few close equid relatives, geographically, and compared the animals’ ranges with factors related to each theory: large predators, average temperature, proximity to woodland areas, and the ranges of horseflies and tsetse files. The only theory the team could not rule out was that of the flies.
“I was amazed by our results,” Caro said in a statement. “Again and again, there was greater striping on areas of the body in those parts of the world where there was more annoyance from biting flies.”
Previous studies have reported that horseflies avoid striped surfaces, but further research will be necessary to understand exactly how zebra stripes keep flies at bay. “The story is likely to be much more complex, and this is unlikely to be the last word on the subject,” Brenda Larison, of the University of California, Los Angeles, told National Geographic’s Weird and Wild blog. “We really need to know what happens with live zebra in the field before we can be sure.”
April 4, 2014
I am sure that there is room for more research, but I am astonished; I thought this was settled decades ago. I can no longer remember when I first encountered the idea.
One of the early persuasive arguments was that the extinct "Quagga" (actually a Burchell's zebra in mufti) occurred in the far south where tsetse flies did not occur.
I cannot remember whether I ever read of any analysis of the ability of bloodsucking flies to recognise and resolve stripes at particular distances; such an analysis should be able to suggest constraints on the relevance of stripes to the attractiveness of zebras to tsetse flies at various distances.