Human Disturbance Affects Dung Beetle Assemblages in French Guiana Forests

Round 1

Reviewer 1 Report

In my opinion, this is an interesting paper that includes a research question relevant and meaningful. Nevertheless, there are some important issues that should be addressed and improved.

First of all, although English is not my first language, I found poor phrasing throughout the manuscript, some parts being difficult to understand and to follow. I thus recommend the ms to be reviewed by a native English speaker. Given that I am not native and that there are many things that need to be corrected, I have not included comments regarding language.

Abstract

I think there is a lack of information in the abstract. Some information on the context (introduction) is missing.

Introduction

The paper does not provide a strong enough context for why these types of studies are important. It is not clear what motivates this work. How can studying changes in dung-beetle assemblages against forest loss or climatic variations help achieve conservation goals? How can the results be applied to ongoing conservation or management issues? Why are the studied ecosystems important in particular? This must be made clear in more detail.

In my opinion, the introduction section needs to be refocused and restructured. I have some additional comments:

L 23-29: Ideas within this paragraph are very unconnected.

L 26: I think that the idea of dung beetles as ecological indicators deserves to be developed in more detail.

L 26: What do you mean with wildlife? Please, be more specific.

L 33: Could you give more information on parasite? I do not understand well this ecosystem service.

L 40-41: This is not well connected to the previous idea.

L 51-78: This is not introduction, but methodology.

Materials and methods

I found that this section sometimes contains superfluous information that make it difficult to understand in some points. Experimental design needs to be clarified, because at its current state it is not clear.

L 83: This is the annual rainfall range? I think that information on dry and rainy season mean rainfall worth to be included.

L 93: What was the sampling site selection based on? Forest cover? Distance to the city? Please, specify.

L 88-106: Please, revise and, when necessary, restructure this section. As it is currently written the experimental design is difficult to understand.

L 113-126: Please, revise and restructure this section, the experimental design is difficult to understand.

L 113: I am surprised that you use data from other authors. Please, consider to mention these authors in the Acknowledgements section.

L 115: Just seen the figure 1 the process and methods used are not clear. Please, explain it well.

L 128: are there differences in forest coverage among sites? Please, make this information clearer in the text.

L 137 (Table 1): Add information on % cover of forest and distance to the city. In addition, why do you not provide information on SGO1, SGO2, SGO4 and SGO7, which are the sites that you selected to carry out dung beetle sampling?

L 144: Why did you not sample in nov-dec 2018?

L 165-167: Why did you select Kruscal-Wallis test and Spearman correlation test instead of using a GLM with a poisson distribution?

L 175: Why 10?

L 179: Did the data comply with normality and homoscedascity?

Results

L216-219: This paragraph can be moved to the methods section.

Discussion

I found the discusion too shallow. I think the authors must to refocus the discussion and should try to interpret the results in greater depth on the basis of the results of previous studies. The discussion in its current form seems to be an extension of the results more than a discussion. There are only 10 references in this section.

Conclusion

In my opinion, there is also a lack of depth in the conclusion. Do your findings have any important implication? Is there any conservation issue? Conclusions sound very local.

Author Response

Dear reviewer 1,

Thanks for your comments and requests. We did answer to all your comments (In italic below each of them) and hope to satisfy all of them. You will find our reply attached as a .doc.

Sincerely.

Eric

Author Response File: Author Response.docx

Reviewer 2 Report

The impact of anthropogenic pressure on beetle diversity is high, but poorly known. The article is interesting and present new original data in this field. The methods of the research are appropriate, and the manuscript is well written. However, some parts of the text could be improved.

General comments

1. Species richness and abundance of dung beetles depend directly on the richness of mammal fauna. Is anything known about the richness of mammal fauna in the studied area? Does mammal species richness also increase with the distance to the nearest city? Please, discuss it in the “Discussion” section.

2. Why dung beetle species richness decreases near cities? Could you please propose an explanation? How do cities affect beetles?

 3. Dung beetles are very diverse and abundant in agricultural landscape, in particular, in pastures. The distribution of farms could affect dang beetle richness. Please, indicate the distance from the collecting sites to the nearest farms.

Specific comments

Line 33. How do dung beetles contribute to the pathogen control?

 Lines 113-136. The description of study sites is difficult to read because of many details. I would recommend to remove some details from the description and to add them to the table 1 or to make another additional table. 

Line 141. The human feces were used as a bait. It is a not appropriate bait for many dung beetle species. For example, some dang beetles feeding on horse dang could not be attracted with human feces. I would recommend to discuss the food specialization of species in the Discussion. The information about food specialization of each species could be added to the table in the supplementary material. 

Line 158. Please, add the year of Feer & Boissier's study here.

Line 250. It is quite possible that the increase of species richness of dung beetles could be explained by the larger number of farms. More cows and poultry – more dung beetles. Please, discuss possible impact of nearest farms on dung beetle diversity.

Author Response

Dear reviewer 2,

Thanks for all your comments and requests. We replied to your comments (in italic below each of them) and hope to satisfy all of them, in the .doc downloaded.

Sincerely,

Eric

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

First of all, I greatly appreciate the efforts and the work of the authors, I think that the manuscript has been improved substantially. However, I still have a couple of considerations.

I am not completely confident about the combination of sampling design and data analysis applied. Some sampling sites are very far apart and also correspond to different years. The question is whether the differences obtained between sites could be driven by a regional and/or temporal effect in addition to the effect of the evaluated factors.

This is difficult to solve with the type of analyses used (Kruskal-Wallis test and Spearman correlation test), since they are more limited than other methods.

Authors state that "non-parametric tests are more appropriate" because "data are not normally distributed, except Simpson index, even after transformation. Second, the results of the model are not significant and the residuals are still correlated”. However, assumptions should be reached by the residuals (Zuur et al., 2009).

I understand that with the number of observations available it is difficult to apply other techniques, but it is also true that the analyses used do not allow to discount the possible effect of the site/period itself. However, this is only a reflection; the selected procedures, although less robust, may be valid.

 

L203. “Abundances were weighted according to the number of traps used for sampling in each site to ensure the same representativeness of samples”.

Please, explain how abundances were weighted. Richness is also affected by differences in sampling efforts and higher richness values are overall obtained with increasing sampling efforts. Did you consider this point?

Author Response

Dear reviewer 1, Thanks for your fruitful comments! We did answered to them in the .doc attached, and added in the manuscript sentences to consider them, and then, hopfully to improve the manuscript.

Eric

Author Response File: Author Response.docx

Reviewer 2 Report

I would recommend to accept the manuscript in its present form.

Author Response

Dear reviewer 2, Thanks for the help in improving our manuscript! As no more comment was done, we did not add any modification to the ms.

Eric