A study done by Omar Tonsi Eldakar at the University of Arizona Research Laboratories on stream-dwelling water striders (Aquarius remigis) contradicts a popular view that the most sexually aggressive males are most successful in terms of reproduction. He began his study due to the observation that nature is not overrun by ‘hyperagressive males,’ meaning that females must not be choosing for such a trait. Eldakar ended up finding that the less aggressive male water striders actually mated more with females than did the aggressive males.
To come to this conclusion Eldakar simulated the natural environment of water striders, therefore doing away with many of the variables that have lead scientists to false conclusions on this topic. The methods included collecting these insects from the wild during breeding season, categorizing aggressive and non-aggressive males, marking each insect, and observing different combinations of males and females. Six males and six females were used per experiment and all twelve insects were places in a tank of water that was similar to their natural habitat. Behaviors were then observed in all insects present and recorded for each of the experimental trials. When giving the chance to move around, it was observed that female water striders preferred staying in areas with less aggressive males since they would not be harassed. Due to such a location, mating occurred between the female and these more low-key males more often. These results were as expected and coincided with the original observation that most male water striders were not overly aggressive.
As explained by colleagues of Eldakar , this shows that communication between groups is different than communication between two individuals. If put in a circumstance of choosing between aggressive or non-aggressive males, most females would most likely choose an aggressive male, yet in this case, the groups of aggressive males make it too overwhelming for the female.
It is proposed by Eldakar and his co-writer, Pepper, that such selection of the females is due to their perception of the signals communicated by non aggressive males that display cooperation. No follow-up experiments to review this however, were discussed.
The major take-home message in this article, I think, is that evolution and natural selection do not always favor the most brutal, unfriendly adaptations, communications, and behaviors. The real drive of such phenomenon is what works the best for that species in its environment. One more point that I want to highlight is that females are able to process certain behavior cues from males that allow them to make decisions on aggression, such as to say “okay this guy is harassing me, I’m totally walking away…gosh” It would be interesting too, to understand what causes the variations in aggressiveness and maybe to explore the males ability to control such inappropriate acts. Lastly, I would just like to point out one more idea, which I am sure those of you reading have already thought of, but, what does this say about our species? I guess we are still a little behind on evolving ….
Posted by Jackie Connolly ( 3rd post)
Good post. Do you think this is sort of similar to the birds we learned about and their lekking? In that case, from what I remember, they weren't choosing the most brutal or largest or best fighters... they were choosing the best dancers! That's kind of nice, right? It's like frikking Justin Timberlake is at the top of food chain in more than just humans- now he's got birds too. Asshole.
ReplyDeleteBut, about your last comment... I think the idea about the most brutal or inappropriate humans is a proper thought at first, but lets be real... if we were to take any data whatsoever, those dudes would NOT show the highest "reproductive success"... if you know what I'm saying. I mean, jeez, even if you DO give in, they don't even put out! At one of those SWEET frat parties where they ask you to flash them to be let in and get a CUP, I willingly obliged and all I got was thrown down the stairs! WTF!
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I think there are a lot of instances where females are the driving force of evolution of a species. After all, many species won't mate with a male unless that male has some favorable trait. Did the article happen to mention what sort of behavior was 'aggressive' versus what sort of behavior was 'non-aggressive'?
ReplyDeletePosted by Bethany Rappleyea
As you both pointed out here, the reason I thought this article was so relevant was because it showed just how powerful female choice can be. The strange part about this article was that the females did choose the more aggressive males when it was just a simple choice between a non-aggressive and an aggressive male. It was only in large populations that female choice of a non-aggressive mate came into play. So, it seems that it’s not that the females are really choosing a non- aggressive mate but rather choosing to not get ambushed or taken advantage of.
ReplyDeleteThe article did not mention what these behaviors specifically were but I am guessing it was more likely that in both cases it was the same behavior just more forceful. I found a YouTube video showing the mating ritual (http://www.youtube.com/watch?v=FXh8P5INUQQ), which basically entails the male jumping onto the females back and ‘griping her to get her into the mating position.’ So a possible assumption could be that in large populations, if a group of “aggressive” males are present, this might get a little overwhelming for the female. In this case, the “aggressive” or “non-aggressive” mannerisms may be referring more to how forward the male is, or rather how quick they are to jump on the female.
As far as my comment about female choice in our own species, as much as I would love to believe “those guys” are not successful, as Alex just proved, he even ‘obliged’ to their orders (hah).
Hope this made things a little clearer. Thanks for the comments!
Posted by Jackie Connolly