Diversity and Composition of Caddisflies (Insecta: Trichoptera) along an Elevation Gradient in Southeastern Mexico

Round 1

Reviewer 1 Report

·         Statement that β-diversity increases with altitude is something of a simplification. It may not apply across all taxonomic groups and assemblages (see for example see Zootaxa 4590 (1): 001–039 (2019)).

·         The five collection sites correspond to different streams. It might have been better to select the 5 altitude samples from along a single watercourse?

·         Traps (including light traps) sheeting and hand collecting with nets present many problems for collection of quantitative insect abundance data. Exact siting, individual collecting technique etc. can influence the data. This limitation needs to be at least mentioned.

·         P 163. Comparing similarity using Jaccard index is useful as it employs simple binary data (presence / absence). It would be instructive to compare this result with a similar treatment using abundance data (e.g. using Bray Curtis similarity).

·         L 170. “Only male abundances were considered for calculating diversity indices because there is insufficient taxonomic information to sort out females and assign them to the different species”. This seems to present a major issue as only a proportion of taxa sampled were actually analysed. Many others could not be identified and were apparently ignored! Sampling was therefore selective, limited to identifiable males with females of other species discarded. Interpretation is very limited because of this.  Sampling did not reflect true species richness, only a subset of identifiable taxa. Thus the sample comprised a sample of 121 spp (L 206) but we do not know how many unidentifiable species were caught.

1.       This problem needs to be discussed in detail.

2.       Would a morphospecies approach have obviated this problem?

·         Table 2 needs to be corrected. The left column is confusing. “Air” data in one row, “temperature” in another. E.g “temperature” is recorded as a value in brackets (presumably this is (±SE) ?).

·         L207… give taxon authors for all genera mentioned.

·         In Table 3, explain “capture frequency.” All values seem to be multiples of 10. Double spacing of the rows might be changes to single spacing in the interests of clarity.

·         L 224 Change The geographic distribution of the species varied widely between sampling sites to. - The geographic distribution of the species varied widely across sampling sites.

·         It is only necessary to provide taxon authors of species at first mention (so not in both tables and the text… one only).

·         L 257 change Regarding temporality to Regarding seasonality.

·         Throughout mss, change temporality to seasonality.

·         L 258 we learn that During the “nortes” season, 1,697 258 caddisflies were collected, classified into 10 families, 28 genera, and 65 species. Given that many females were collected but not identified, it would be useful to also give an abundance figure that includes this. Obviously, this missing female data cannot be included in the analysis but it is of interest.

·         L 257-72 etc. In discussion of dominant species at different sites, it would be interesting to use measures of overall dominance (e.g. Berger-Parker) and/or evenness at each site for the comparison. Did evenness change with elevation? (as has been found elsewhere).

·         Fig 2. This “dendrogram” might better be referred to as cluster analysis?

·         It would be useful to quote statistical support for the clusters in the “dendrogram” (e.g. By bootstrapping).

·         In Table 5, the parameters a and b need explanation / mention of the model that used them.

·         True α-diversity is mentioned in several places. What is this? Measured or estimated diversity (if so, by which method).

·         Table 7 says north… do you mean nortes (as used elsewhere in the mss.)?

·         e.g Ln 339 ….mean alpha diversity was 8.57 effective species, is quoted. I think this needs explanation. The sample from 5 sites included 121 actual species yet there were only 8.57 effective species. Is 8.57 a diversity index of some kind? Explain please.

·         Ln 378-9. The statement “This study evaluated the alpha, beta, and gamma components of caddisfly diversity 378 in relation to air temperature and relative humidity along an altitudinal gradient” is not really true. The study examined these parameters at different elevations…. the sampling sites were NOT along a gradient. This needs to be corrected.

·         Ln 394 “the urgent need for studies 394 focused on various aspects of this group”. I can find nothing in the mss to suggest that urgent studies are needed. Certainly, the desirability of further studies is demonstrated.

·         Ln 441 “Beta diversity had a significant contribution,” What did it contribute to?

·         In general, discussion of β-diversity in relation to elevation seems a little vague. β-Diversity is a measure of species turnover between different places / seasons etc. So far as I am aware, β-diversity does not relate to point sources (as does α-diversity, for example). When you say that there is greater β-diversity at high altitude, I think you mean that turnover (replacement / substitution / absence) in the highest sites is high when compared with lower sites? Please clarify using simple description of exact meaning.

·         Ln 462--- “These results are consistent with several studies showing the preponderance of temperature over other parameters such as the composition of the vegetation cover, the percentage of shade, and organic matter content in deep sediments, among others [13, 68, 69].”

·         I think this statement applies to the aquatic immatures of Trichoptera. It seems unlikely to hold for many other insects such as terrestrial Diptera for example. It would be helpful to state that this conclusion relates specifically to studies on Trichoptera,

·         In the Discussion, on the subject of future research; it would be good to suggest that studies should use immature stages rather than flying (dispersing) adults.

·         Generally the use of English is adequate although there are a few places where it is awkward. However, the intended meaning is clear and that is the most important issue. However, the authors do need to check for consistent use of past tense when describing the results.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

The research provides interesting insight into the diversity of caddisflies in this transitional region of Mexico. The authors need to explain how all caddisflies arriving at the lights were collected, not merely a subsample of caddisflies. They also need to explain that other collecting methods (e.g., benthic collecting for larvae, Malaise traps for adults) may have produced other results. A more significant problem is the lack of clarity pertaining to sex. The authors explain that they identified species for only males and they also provide data about sex ratios. In addition, they acknowledge that males and females of different species may be attracted to lights at night in ratios different from those of the actual local populations, although the differences are unknown. Therefore, the abstract and results need to be more clear that the diversity results pertain only to male diversity and not to the diversity of the actual local populations.

Comments for author File: Comments.pdf

Author Response

We made all the grammatical changes suggested by the reviewer. Map in figure 1 was modified in order to have concordance among the abreviatures used by site in figure and text.

 The authors need to explain how all caddisflies arriving at the lights were collected, not merely a subsample of caddisflies.

They also need to explain that other collecting methods (e.g., benthic collecting for larvae, Malaise traps for adults) may have produced other results. A more significant problem is the lack of clarity pertaining to sex. The authors explain that they identified species for only males and they also provide data about sex ratios. In addition, they acknowledge that males and females of different species may be attracted to lights at night in ratios different from those of the actual local populations, although the differences are unknown.

In paragraphs 169 to 173 we explain the reason to use only males, due the taxomic problems in the indetified of females. 

Therefore, the abstract and results need to be more clear that the diversity results pertain only to male diversity and not to the diversity of the actual local populations.

We enfatized that our results and discussion are based in the adult males