Commodity-specific punishment for experimentally induced defection in cooperatively breeding fish

Coercion is an important but underrated component in the evolution of cooperative behaviour. According to the pay-to-stay hypothesis of cooperative breeding, subordinates trade alloparental care for the concession to stay in the group. Punishment of idle subordinates is a key prediction of this hypothesis, which has received some experimental scrutiny. However, previous studies neither allowed separating between punishment and effects of disruption of social dynamics, nor did they differentiate between different helping behaviours that may reflect either mutualistic or reciprocal interaction dynamics. In the cooperative breeder Neolamprologus pulcher, we experimentally engineered the ability of subordinates to contribute to alloparental care by manipulating two different helping behaviours independently from one another in a full factorial design. We recorded the treatment effects on breeder aggression, subordinate helping efforts and submissive displays. We found two divergent regulatory mechanisms of cooperation, dependent on behavioural function. Experimental impediment of territory maintenance of subordinates triggered punishment by dominants, whereas prevented defence against egg predators released a compensatory response of subordinates without any enforcement, suggesting pre-emptive appeasement. These effects occurred independently of one another. Apparently, in the complex negotiation process among members of cooperative groups, behaviours fulfilling different functions may be regulated by divergent interaction mechanisms.


Comments to the Author(s)
I maintain that the authors have not analyzed their data appropriately, and that these response variables are indeed not independent. For instance, aggression in one actor shapes submission responses in another, and social interactions are causally linked with both of these other behaviors. These behaviors are causally linked together in a network. Thus, while I appreciate that the authors would like to dissect their analysis behavior-by-behavior, I do not think this is an acceptable method on its own. A combined multivariate test should be conducted first. Following a significant multivariate test, I agree the authors should proceed with a behavior by behavior analysis. Otherwise, they will need to use a modified p-value, which would eliminate some of their more interesting results. I remain firm on this point and do not accept the author's absent argument for rejecting the interdependence of these behaviors.
That aside, it is clear from my reading that there will continue to be interesting results from this paper following a multivariate or network analysis, and that the experiments here are cleverly designed, sound, and deserving of positive attention. I like this paper and these authors are superb writers. They have respected and honored the other major concerns of the other reviewer and myself, and I would like to afford them every opportunity to revise their work.

Review form: Reviewer 2
Is the manuscript scientifically sound in its present form? Yes

Do you have any ethical concerns with this paper? No
Have you any concerns about statistical analyses in this paper? No

Recommendation?
Accept with minor revision (please list in comments)

Comments to the Author(s)
The authors have done a good job of addressing previous comments and clarifying many of the confusions in the first draft of the manuscript. I think the current draft is very clear and wellwritten. I have only a few minor comments: Lines 53-59 and 82-84: I think an example in both these sections would clarify these points.
Line 151: Italics are missing from the species name.
Lines 359-371: I think the authors should explicitly address the fact that there were no fry present in this study here. I know the authors address this in a paragraph earlier in the discussion, but I do not believe it fully addresses the arguments raised in this paragraph, even if their current explanation may still be plausible due to the potential for future reproduction. Figure 2: What type of post-hoc test was used to calculate differences among treatment groups and how did it control for multiple comparisons? I see the authors' response to Reviewer 2's comment about multiple comparisons, but I think this is a separate issue.

11-Nov-2019
Dear Mr Naef, The editors assigned to your paper ("Commodity-specific punishment for experimentally induced defection in cooperatively breeding fish") have now received comments from reviewers. We would like you to revise your paper in accordance with the referee and Associate Editor suggestions which can be found below (not including confidential reports to the Editor). Please note this decision does not guarantee eventual acceptance.
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Once again, thank you for submitting your manuscript to Royal Society Open Science and I look forward to receiving your revision. If you have any questions at all, please do not hesitate to get in touch. Dear authors, Thank you for transferring your manuscript to RSOS. Your revision has been seen by the original reviewers. Reviewer 1 (previously ref. 2) maintains the original criticism of the statistical analysis, and this concern is also picked up by reviewer 2 in their remarks to the editor. Both, however, recommend the manuscript to RSOS. Please follow the suggestions of the referees, and I look forward to receiving your resubmission.

Kind regards, Kristina Sefc
Reviewers' Comments to Author: Reviewer: 1 Comments to the Author(s) I maintain that the authors have not analyzed their data appropriately, and that these response variables are indeed not independent. For instance, aggression in one actor shapes submission responses in another, and social interactions are causally linked with both of these other behaviors. These behaviors are causally linked together in a network. Thus, while I appreciate that the authors would like to dissect their analysis behavior-by-behavior, I do not think this is an acceptable method on its own. A combined multivariate test should be conducted first. Following a significant multivariate test, I agree the authors should proceed with a behavior by behavior analysis. Otherwise, they will need to use a modified p-value, which would eliminate some of their more interesting results. I remain firm on this point and do not accept the author's absent argument for rejecting the interdependence of these behaviors.
That aside, it is clear from my reading that there will continue to be interesting results from this paper following a multivariate or network analysis, and that the experiments here are cleverly designed, sound, and deserving of positive attention. I like this paper and these authors are superb writers. They have respected and honored the other major concerns of the other reviewer and myself, and I would like to afford them every opportunity to revise their work.

Reviewer: 2 Comments to the Author(s)
The authors have done a good job of addressing previous comments and clarifying many of the confusions in the first draft of the manuscript. I think the current draft is very clear and wellwritten. I have only a few minor comments: Lines 53-59 and 82-84: I think an example in both these sections would clarify these points.
Line 151: Italics are missing from the species name.
Lines 359-371: I think the authors should explicitly address the fact that there were no fry present in this study here. I know the authors address this in a paragraph earlier in the discussion, but I do not believe it fully addresses the arguments raised in this paragraph, even if their current explanation may still be plausible due to the potential for future reproduction. Figure 2: What type of post-hoc test was used to calculate differences among treatment groups and how did it control for multiple comparisons? I see the authors' response to Reviewer 2's comment about multiple comparisons, but I think this is a separate issue.

Author's Response to Decision Letter for (RSOS-191808.R0)
See Appendix A.

Recommendation? Accept as is
Comments to the Author(s) First, I must apologize to the editor and authors for my tardy review. I'm in the midst of a longterm field season and I'm only now circling back to honoring my commitment to this review. I am, however, happy to convey that I am pleased with the authors' revised analyses and interpretation. This paper is certainly deserving of publication in Roy Soc Open Science, and I am now happy to give it my most enthusiastic endorsement. I thank the authors for taking the extra effort to address my nagging concerns. They've produced a clever study they can be very proud of.

14-Jan-2020
Dear Mr Naef, It is a pleasure to accept your manuscript entitled "Commodity-specific punishment for experimentally induced defection in cooperatively breeding fish" in its current form for publication in Royal Society Open Science. The comments of the reviewer(s) who reviewed your manuscript are included at the foot of this letter.
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Please see the Royal Society Publishing guidance on how you may share your accepted author manuscript at https://royalsociety.org/journals/ethics-policies/media-embargo/. Comments to the Author(s) First, I must apologize to the editor and authors for my tardy review. I'm in the midst of a longterm field season and I'm only now circling back to honoring my commitment to this review. I am, however, happy to convey that I am pleased with the authors' revised analyses and interpretation. This paper is certainly deserving of publication in Roy Soc Open Science, and I am now happy to give it my most enthusiastic endorsement. I thank the authors for taking the extra effort to address my nagging concerns. They've produced a clever study they can be very proud of.

Response to Referees
Replies to Referee 1 I maintain that the authors have not analyzed their data appropriately, and that these response variables are indeed not independent. For instance, aggression in one actor shapes submission responses in another, and social interactions are causally linked with both of these other behaviors. These behaviors are causally linked together in a network. Thus, while I appreciate that the authors would like to dissect their analysis behavior-by-behavior, I do not think this is an acceptable method on its own. A combined multivariate test should be conducted first. Following a significant multivariate test, I agree the authors should proceed with a behavior by behavior analysis. Otherwise, they will need to use a modified p-value, which would eliminate some of their more interesting results. I remain firm on this point and do not accept the author's absent argument for rejecting the interdependence of these behaviors.
Reply: We have now conducted the non-parametric multivariate tests the reviewer suggested in the first reviewing round (PERMANOVA from the R-package vegan). The results confirm our conclusions, and the respective information was added to the methods and results sections (lines 206-218; 222-226; 252-255). Where the multivariate test did not indicate significant treatment effects, the previous analyses of individual behaviours were removed from the text and the results from the multivariate test was provided instead. This was the case for the "nodemand" control situation (lines 252-255) and for the effect of defence prevention during the manipulation phase (lines 225-226, 236-239 and 247-249).
That aside, it is clear from my reading that there will continue to be interesting results from this paper following a multivariate or network analysis, and that the experiments here are cleverly designed, sound, and deserving of positive attention. I like this paper and these authors are superb writers. They have respected and honored the other major concerns of the other reviewer and myself, and I would like to afford them every opportunity to revise their work.