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Referee Comments: Referee 2

Posted by PLOS_ONE_Group on 17 Apr 2008 at 18:06 GMT

Referee 2's Review:

N.B. These are the comments made by the referee when reviewing an earlier version of this paper. Prior to publication the manuscript has been revised in light of these comments and to address other editorial requirements.

What are the main claims of the paper?
This paper examines the maintenance of genetic variation in aggressive behaviour in Drosophila. It uses interactions among individuals with known genetic composition to determine whether variance in aggressive behaviour may be maintained by variance in the best strategy when individuals are faced with others, and also how success in aggressive interactions influence mating success. The paper finds that population means do not necessarily predict the outcome of individual interactions with individuals of other genotypes. Also females do not necessarily prefer winners of all genotypes. Both these outcomes could enhance variation in aggressive behaviour of individuals.

Are the claims properly placed in the context of the previous literature?
Yes, to my knowledge.

Do the experimental data support the claims? If not, what other evidence is required?
The experimental data apparently support the claims but need much better explanation.

Who would find this paper of interest? And why?
This paper would be of broad interest to people studying the genetics of behaviour.
In what further directions would it be useful to take the current research?
It would be interesting to determine what factors other than wins in territorial encounters influence female choice, and the relative importance of these factors in the flies.

Is the manuscript written clearly enough that it is understandable to non-specialists? If not, how could it be improved?
No, the MS is not clearly written, and this is its major fault. (1) It is not clear why "the Winters lines" were included in the experiment with the other two lines. Are they like a whole series of neutral controls? If so, why were the neutral controls singled out? Are they a measure of variation of behaviour in lines with little genetic variation? Spell out their purpose and significance.

(2) The purpose and significance of the 2 time blocks for experiments (if any) are not clearly spelled out. "The significance of variation in territorial success was tested among the lines with a chi-squared test for the difference between the actual success results, relative to the neutral hypothesis of an equal number of wins for each genotype" is not a clear description of the test, and I am not sure why this test was performed. I don't want to reproduce each sentence here, but this entire paragraph, and the one following, are very unclear but are critical to the evaluation of the paper. The last paragraph of the section on female choice is also unclear - what is meant by "differences in relative male mating success"? Relative to what?

Because the methods are so unclear, the meaning of the results and discussion are difficult to follow.

(2) A clear definition of transitive and intransitive as they relate to behaviour are sorely needed in this paper - not just a reference to a paper that has observed intransitive behaviour. What exactly do you mean by these two terms - what do you expect to observe if they are happening?


(3) The words "which" and "that" are not used correctly throughout the text. Please rectify.

Have the authors provided adequate proof for their claims without overselling them?
No, see above comments, this is just not clear, rather than overselling.

Have the authors treated the previous literature fairly?
Yes, fine.

Does the paper offer enough details of its methodology that its experiments could be reproduced?
No, see above comments. Methods for fly culture, dyadic behaviour surveys etc are clear.