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Thank you for addressing the additional queries of Reviewer 1. The manuscript reads very well now and I am happy to accept it for publication.
[# PeerJ Staff Note - this decision was reviewed and approved by Jennifer Vonk, a PeerJ Section Editor covering this Section #]
A reviewer has some additional suggestions to make your presentation clearer. And also, importantly, the reviewer suggests adding a citation supporting the claim that body mass is the "strongest proxy" of body size in burying beetles as well as adding a citation or unpublished data supporting the claim that beetles in the wild arrive at a carcass within minutes of each other (as per your original reply to Reviewer 2).
This revision has addressed many of my comments. Some additional comments below.
L23: Splitting two traits (body size and weapons) with the priority effects in this sentence form seems to suggest that priority effects are also traits. A better structure may be to swap the clause referring to priority effects with the weapons clause.
L35: If body size was the only predictor, then it should state “the largest beetles won”.
L186: It would be more accurate to say just species identity here, as no other traits were measured.
L285: This statement needs a citation. Mass fluctuates with water/food consumption and is therefore not constant for the same individual over time. Mass is fine to use as a proxy, but the statement that it is “the strongest proxy” seems excessive.
L344: Thank you for the explanation about priority effects. I do think an experimental manipulation of priority would have better tested the ideas put forward in the manuscript. I think this methodology would be strengthened yet again if the authors presented some published data concerning the time between visitors to carcasses in nature, as they alluded in their response to reviewers (specifically query 4 from reviewer 2): “…with beetles arriving within minutes of each other…”.
All data are code are presented and well annotated.
No comments.
Both reviewers were positive about several aspects of your manuscript while also raising some important points that need to be addressed.
First, Reviewer 1 raises an important issue - this manuscript is very similar in many respects to Schrempf et al. 2021 PeerJ 9:e10797. I would think a larger publication studying the interactions of all species would be a stronger paper than publishing what seem to be least-publishable units.
Second, both reviewers question the measurement and use of "priority" in these current study given that members were simultaneously introduced in each trial. Your methodology and interpretation of the observed effect of this variable need to be justified.
Third, Reviewer 1 requires some discussion of the potential biases in using wild-caught individuals in the study.
Finally, Reviewer 2 raises a number of statistical issues that need to be addressed. I look forward to reading a revised version of your manuscript.
[# PeerJ Staff Note: Please ensure that all review and editorial comments are addressed in a response letter and any edits or clarifications mentioned in the letter are also inserted into the revised manuscript where appropriate. #]
The manuscript was well written. The authors used clear hypotheses and a good structure. I have some concerns about the manuscript, however. First, it seems like a carbon copy of a paper from the same group published in this same journal in 2021 (Schrempf et al. 2021 PeerJ 9:e10797), but using a different burying beetle species. The introduction and literature cited seem identical. On this point alone it is not worthy of rejection, however. The science is sound, but one wonders if a paper will result from replicating this study with every species pair that coexist at the authors’ field site.
Second, in the introduction the authors discuss weaponry as a species-level trait that could influence the outcomes of behavioural interactions. While a good example, I think the authors laboured this point—burying beetles do not possess weaponry that is fundamentally different between species. Mandibles are used in fights, but different species do not have drastically different mandibles.
Third, priority is not a trait but is referenced as one throughout the manuscript. In addition, there is nothing in the methods or results about these priority effects. How was it measured or manipulated? I expected the experimental design to include some period of time where an individual was left alone on a carcass to mimic arriving first, with the competitor (smaller or larger) introduced later. Were both individuals introduced at the same time? Any information about priority needs to be rewritten and framed appropriately.
As noted above, the design of the experiment is not clear regarding the priority effect aspect of the manuscript. If the beetles were introduced at the same time, and priority measured by the first to the carcass, I would not interpret this data as any priority effect.
All the beetles used in this manuscript were wild caught individuals. The authors did not have any knowledge of whether the individuals they caught were mated or not, or their previous experience with fighting for resources. Could the authors speculate about how these factors, while unknown, could contribute to the variation in the results they found? With a relatively small sample size, it is possible by chance that their smaller individuals were less likely to have mated which may have been driving the pattern over and above the effect of body size. Some acknowledgement of these issues would be welcome. Why were lab-reared individuals not used?
L150: How did carcass size influence the rate of interactions? Are larger carcasses more fiercely fought over?
L159: Did the individuals have any time in the lab to acclimate?
L170: I do not understand the mass measurement; why is it multiplied by 10g?
L174: Why is 1cm the threshold used for an interaction? Is there any data on the distance when behaviours change in these species? Individuals more than 1cm away might already exhibit different behaviours if they are aware of heterospecifics.
This manuscript replicates a previous paper from the same group but has replaced one of the burying beetle species with another. There is little discussion about why the species pair in this manuscript should differ in the mechanism underlying dominance to the previous species pair of N. tomentosus and N. orbicollis, where similarly body size alone was the significant predictor of dominance.
The first three paragraphs of the discussion have considerable repetition about body size and dominance. This information should be one paragraph maximum. The discussion is also lacking in broader conclusions. Are the two species tested here very similar in size, or closely related phylogenetically relative to previously published work? What does this paper add to the understanding of mechanisms of dominance?
All data and code are provided and well annotated.
No comments.
This manuscript is clearly written and provides a nice summary of the basic questions it attempts to answer. The authors provide sufficient background to put the manuscript in a broader context. The paper follows a standard structure and the raw data has been provided (along with a README file). The manuscript I also self contained and for the most part, the conclusions follow from the results.
There is a typo on line 320: "influences" should be "influence".
The study design is generally sound and the methods are fairly easy to follow. I do have a few comments / suggestions for the authors.
1. I suggest dropping trial 152… it is the only one in which the two beetles were not of the same sex. I imagine that this trial involved a mis-sexed beetle (this happens!). In any case, I suggest removing it form the dataset.
2. Line 157- this suggests that the bicycle light was in the container with the beetles and the carcass. Is this correct?
3. It is not clear how the pairs were established for their trials. Were the they assigned randomly or were they chosen to generate variation in the body size ratios. I assume the former, but this is not made clear.
4. It sounds as though the beetles were placed in the container at the same time. Doesn’t this simulate arriving at the carcass simultaneously (or at least nearly so)? In a more natural situation, the beetles might arrive at the carcass hours apart, thus one species may have begun to prepare the carcass before the other arrives. I wonder whether the authors experiment really simulates that type of priority effects that occur in nature.
5. This is kind of a minor point, but the authors refer to their study as an "experiment", however nothing is actually manipulated here. Instead, it is an observational study that is conducted under controlled lab conditions.
The analyses and results seem sound. However, I have a few general comments / questions.
1. Lines 248-253: there is a multiple testing issue here (e.g. using three different measures of relative body size, all of which are probably highly correlated, in different models). Have the authors considered adjusting their alpha for this? More generally, I would suggest just picking one measure of size or perhaps constructing a multi-variate measure of size from a PCA.
2. 291-299: A related issue- the authors only present the AIC's for the mass model (Table 3). Is there a reason for this? They also note that for all interaction types the results were the same using different measures of body size. They then restrict the analysis to only aggressive interactions. However, when they do this, they only show the mass results. In general, if the authors are going to use all three measures of size, they should conduct and present parallel analyses on them.
3. I suggest restructuring table 3 so that the linear model corresponding to each row is specified (instead of using the + / - coding that is currently employed. I also suggest that the intercept and parameter estimates be put closer to one another. Having the effect size for the mass ratio surrounded by the codes for whether a variable is present or absent in the model is slightly confusing.
4. 3. Line 320-322: the authors suggest that N. pustulatus is dominant to N. orbicollis when the two species have similar body sizes. I am not sure that I see this in the figure. Can you specify what range of ratios you consider to be similar body sizes?
5. Lines 36-362: It is not clear what is meant here. Can you clarify a bit?
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