Ducks and the Coevolution of Genitalia
In class, we've discussed some interesting examples of both sexual selection and coevolution. A recent study of the genitalia of a strange species of duck provides a fascinating example of sexual coevolution.
The duck in question - the Meller's Duck from Madagascar, is certainly a rare breed. While 97% of all bird species don't even have phalluses, the Meller's Duck has incredibly long phalluses, sometimes as long as the length of its entire body.
Previous scientists assumed this long phallus evolved as a result of competition between males who wanted to get their sperm in as far as possible during forced copulation to increase their chances of producing offspring. Dr. Brennan, however, points instead to the strong correlation between long male phalluses and elaborate female genital defenses in the same species, and argues that male and female Meller's Ducks are locked in a constant sexual arms race that has resulted in the development of such unusual structures. The females have evolved elaborate oviducts with pockets and spirals to limit the success of forced copulation, and the males have in response evolved longer phalluses that allow them to force copulation despite the females' defensive measures.
Dr. Brennan's study is the clearest example of genital coevolution in vertebrates uncovered so far, though Dr. Brennan believes that more subtle examples of coevolution are likely to be discovered in other species with further research.
Read the full New York Times article here, it's quite interesting!