Active Sampling and Understory Traps Can Cost-Effectively Detect Changes in Butterfly Communities after Hydroelectric Dam Construction

Round 1

Reviewer 1 Report

This study investigate butterfly communities before and after constructing a dam in the Brazilian Amazon, the conclusions are well described and relevant in the biodiversity crisis that we meet. The purpose of this study is clear and the M&M and analysis are well designed to answer to the research questions. However, I suggest to the authors to add more informations for the entomological point of view: interesting species, genera or families collected ? Some are on red lists (if they exists of course) ? Ecological or agronomic interests of some of these feeding-fruits species ?

I also suggest to the author to more deeply analyze the species diversity estimates in decomposing better the sampling effort.

 

24: Write some examples of optimal monitoring. 

 

72-75:I find that the dam issue in the Amazon and their impact on the biodiversity is well introduced. However, you introduce just with one paragraph the butterfly of this study, even it is well defined, I proposed to add more details on the overall butterfly communities issue in the Amazon, the other butterfly that could be sampled and so on. What are the main families in these forest and their ecological features ?

 

143-144: Do you have pictures of your trapping systems ? It could be nice to add it in the paper.

 

148-157: From which protocol did you prepare your butterfly specimen ? Did some fruit-feeding butterfly were identified by expert ? What are the principal butterfly families in your study ?

 

175-178: Why you do not use the q = 1 and q = 2 of Hill index diversity framework, with Hill-Shannon and Hill-Simpson you could better estimate the mean rarity of your samples ? I think that could be relevant to add these supplementary analysis to your paper. 

 

172-... : Please add R version used and its reference

 

192 : Add justification on the selection of the negative binomial distribution

 

231 : I do not have a view on the Table S1...; how many genera and families ?

 

231-234 : Why beginning by the description of Figure 2b and not first on the species diversity estimates according to before/after constructing the dam ? I suggest that you need to follow the hierarchy of your research question.

 

233-235 : It seems that could be in the M&M.

 

309-310 : I am not sure that the hydroelectric dam has little effect on the species diversity, maybe you could deeply analyse that by each plotting site on each localities ? I think the results of figure are too general to asses that argument, prove us that by decompising better your analysis.

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

This paper reports on a carefully designed case study on the impact of flooding an area after a hydroelectric plant was taken into function in tropical Amazonia. The target group is butterflies, with a focus on rotting fruit-feeding species that have in many studies shown to be suitable indicators of environmental change and impacts. The paper is very well written. Data collection and statistical data analysis are fine and use up to date methodology. I also emphasize the unusually good taxonomic resolution of the data, in comparison to many other studies on tropical insects. The main outcome is that species composition well reflects faunal change, whereas species richness or species incidences alone are not that informative in this case. Moreover, it is shown that understory bait traps are sufficient to capture this impact information, suggesting that for standardized monitoring this method alone is sufficient. While I generally agree on that, I also emphasize (and this might be worth considering in the discussion) that this bait method captures only a rather small fraction of the diversity of butterflies. Large species rich families go completely unnoticed (e.g. Lycaenidae, Riodinidae) – and any faunal losses that occur in these often highly specialist taxa (just think of their complex interactions with ants!) will go completely unnoticed if only fruit-bait traps are employed in environmental monitoring. I do not say one should include the latter in monitoring – this would be hopeless. But as always: if you select just one single guild of animals with just one single method of assessment, any extrapolations beyond that guild are critical and often potentially misleading.

I have very few points where I suggest some consideration during revision.

L 74: should likely better read “attraction to ...” instead of ‘attractive’; the traps are per se not ‘attractive’

L 114: spelling: Köppen or Koeppen, not Koppen

L 175: because with q=0 these estimates may be strongly affected by singleton specimens (e.g. stray individuals), I strongly suggest to cross-check whether results on species/diversity accumulation might change at q=1 (exponential Shannon diversity = effective number of species). I would expect this to be the case, since the still increasing curves (especially before the flooding) might have substantially lower curvature at q=1.

L 231-237: looking at Fig. 2, species richness WAS highest in the first time period before filling the dam. If you combine all sampling methods, as a proxy for total butterfly community richness BEFORE the impact, this pattern might even become more obvious (and statistically significant?). As noted above, however, the geometry/curvature of the curves might substantially change if looking at effective number of species, or in other words: the high values of mere richness in the earliest samples might rather indicate more influx of stray singleton individuals from neighbouring forest prior to flooding the dam.

L 266: rather: individual-based curves??  At least this is what the text at the x-axis suggests to be the case…

L 271: is that really true?? My impression is: extrapolation goes well beyond the size of the largest sample.

L 293: what about implementing an FDR control for multiple hypothesis testing here, in view of the Bonferroni inequality? I am pretty sure that after such a correction, all “significant” effects based on species incidences will vanish – and only with the abundance-based considerations most results will persist as robust. This also has an important corollary: namely, that for such an impact assessment and monitoring abundance data are required, whereas mere presence/absence data could be too coarse in ecological resolution. This should then also be emphasized in the discussion.

L 297: perhaps again explain explicitly what the abbreviation SDR means in that particular context... Later in the same line, should rather read "and" instead of “e”?

L 463: Journal name missing; Journal of Insect Conservation

L 471: Journal name missing: Revista Colombiana de Entomología

L 481: delete “Publishing Group”

L 520: Journal name missing; Frontiers in Forests and Global Change

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thanks for you answers, for me it is OK. It is a really good work.

 

Kinds regards,

 

Grégoire