It’s a scenario with a basis in evolutionary theory. Males increase their fitness by acquiring more mates; however, this is often not the case for females – and therein lies the conflict.
Researchers at Binghamton University and the University of Arizona studied sexual conflict in water striders, an insect that’s a common model system. They found that, given a choice, females will group themselves around the gentlemen.
The results of the groundbreaking experiment – in which the insects had a freedom of movement not possible in most studies of sexual conflict – appear in the Nov. 6 edition of the prestigious journal Science.
“The original title of the paper was ‘Nice Guys Don’t Always Finish Last,’” lead author Omar Tonsi Eldakar said. “I find that statement to be quite descriptive of the project.”
Previous studies of sexual conflict generally have limited individual movement, emphasizing local competition, noted Eldakar, a 2008 PhD graduate of Binghamton University and a post-doctoral fellow with the Center for Insect Science at the University of Arizona.
Eldakar said he perceives sexual conflict as an example of the “tragedy of the commons,” a situation in which the most exploitive strategy benefits the individual at the expense of the group. (The classic example is of a shepherd who adds another animal to his herd even though the shared pasture is overgrazed.) Few researchers have framed sexual conflict in these terms; however, Eldakar sees a parallel between that shared pasture and the availability of females.
“When you pit exploitation against prudence in direct competition over a shared resource, you’re putting them into a scenario that favors the short-term, exploitative strategy, making it difficult to observe the advantage of prudence,” he said. “This does not accurately reflect what occurs in natural populations. But given a choice, females look for a way to get away from persistent males. If you allow individuals to self-organize, females find these nice guys and group around them, changing the landscape of competition.”
Eldakar and his colleagues have shown through previous studies that groups in which a more gentlemanly approach to mating prevails do better on the whole, even though jerks generally outperform the nice guys when they have to compete one-on-one.
Eldakar thought of the insects as “nice guys” vs. “jerks;” his adviser, David Sloan Wilson, a co-author of the paper and a distinguished professor of biological sciences at Binghamton, termed them “gentlemen” vs. “psychopaths.”
“The presence of psychopaths dramatically reduced the productivity of the population,” Wilson said. “When all the males were gentlemen, the females laid about three times more eggs than they did when all the males were psychopaths. And yet within each group the psychopaths were doing better than the gentlemen. How do the gentlemen persist if they’re disadvantaged within the group?”
Once the females could move between groups, the researchers had their answer. Eldakar and Michael J. Dlugos, then also a Binghamton graduate student, devised a wading pool equipped with special doors that could restrict movement between groups or allow the insects to move freely.
“When they opened the doors, the females would leave whenever a psychopath came around,” Wilson said. “The whole thing resulted in a heterogeneity in which the females were clustered with the gentlemen. It’s the movement of individuals that creates these differences between groups that favor nonaggressive males.”