Review History


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Summary

  • The initial submission of this article was received on October 16th, 2014 and was peer-reviewed by the Academic Editor.
  • The Academic Editor made their initial decision on October 16th, 2014.
  • The first revision was submitted on February 20th, 2015 and was reviewed by 2 reviewers and the Academic Editor.
  • A further revision was submitted on April 15th, 2015 and was reviewed by the Academic Editor.
  • A further revision was submitted on May 5th, 2015 and was reviewed by the Academic Editor.
  • The article was Accepted by the Academic Editor on May 6th, 2015.

Version 0.4 (accepted)

· · Academic Editor

Accept

Thank you for your work on the various iterations of this MS. And thank you to the excellent referees for excellent reviews as well. This paper is now acceptable for publication.

Version 0.3

· · Academic Editor

Minor Revisions

This paper is nearly ready for publication. However I would like the authors to reply more thoroughly to a number of comments from the reviewers, particularly from Reviewer #2. I have uploaded a PDF of the authors' rebuttal letter and have appended text in red in places that still need better coverage in the reply.

In addition, in the 2nd half of that uploaded PDF I have marked up the MS from the authors to make a few extra suggestions and edits.

As noted above, this paper is almost ready for publication, but just requires a few small changes and some more thorough replies to reviewers.

Thanks to the authors for their work on this.

Version 0.2

· · Academic Editor

Major Revisions

Both reviewers (both who have opted for public review) suggest revisions. One suggest minor revisions, the other major.

Please attend carefully to these suggestions and supply a revision and rebuttal for further consideration.

In the case of the combined reviews, some of the biggest issues that need to be considered are (partly cut and pasted from the reviews):

-careful editing on a number of points

-more specificity in analyses (mentioned by both reviewers)

-more specificity in terms of your hypothesis/hypotheses (particularly as suggested by Dr. Brehm)

-inclusion of a "A full species-site matrix (as electronic appendix)" would really add value

-Better referencing and consideration of the relevant primary literature

-A large variety of other questions/comments

Please take your time to consider these suggestions, as I believe that they would really add to the overall interest and value of this MS. As noted by Dr. Smith, "Le Cesne and co-authors have compiled a large and interesting data set on the Hemiptera of mountains in Papua New Guinea."

I fully agree with that assessment, an I look forward to receiving the revised version.

·

Basic reporting

More details in the "General Comments to Author"

Experimental design

Change altitude to elevation. See McVicar and Korner 2013 Oecologia (2013) 171:335–337.

“Malaise trap sampling cannot provide a complete survey of the insect fauna” – True – and true of ANY sampling methodology. I would broaden this sentence so it doesn’t read as a criticism of Malaise traps.

Validity of the findings

One element that I think needs to be included in your discussion relates to your use of LOW or LOWEST and the elevational range you sampled. “At the lowest elevation (< 1000 m) the” and “The greatest plant diversity occurs at the lowest elevations with three other pla” – I think that some comment on the author’s capacity to identify mid-elevational peaks when sampling begins at 1000m is warranted. This may, in fact, be a mid-elevation peak with the lowest elevation sites not present in the inventory.

Comments for the author

Le Cesne and co-authors have compiled a large and interesting data set on the Hemiptera of mountains in Papua New Guinea. This manuscript version (which I am seeing for the first time after separate set of revisions) is an interesting paper that warrants consideration for publication after a few minor edits are considered. One small procedural element: I’m not sure what the yellow highlighting in the text refers to, but I presume it has something to do with changes from an earlier version.

General Point:
One element that I think needs to be included in your discussion relates to your use of LOW or LOWEST and the elevational range you sampled. “At the lowest elevation (< 1000 m) the” and “The greatest plant diversity occurs at the lowest elevations with three other pla” – I think that some comment on the author’s capacity to identify mid-elevational peaks when sampling begins at 1000m is warranted. This may, in fact, be a mid-elevation peak with the lowest elevation sites not present in the inventory.

Specific Points:

Change altitude to elevation. See McVicar and Korner 2013 Oecologia (2013) 171:335–337.

“ About half of the studies evaluated” – be specific with the percentage.

Consistently capitalise Malaise trap (remove all incidences of malaise).

“At each elevation a few species were relatively abundant” – be specific here. (avoid words like ‘few’.
Results – “Morphospecies richness.” – The linear equations should be reported here in text. Specify the test (linear regression) the R2 and the p value.
“however, one cicadellid morphospecies represented 73.5% of all Cicadomorpha collected at this elevation” – if this is to be removed as an outlier – I that further support for this decision is warranted.

“As well, at the highest elevations pressure, oxygen availability, ultraviolet radiation, and winds may also affect insect distribution (Hodkinson, 2005), however, we had no means of evaluating these factors.” – Consider re-thinking including this sentence without data. The range you have sampled is unlikely to include significant changes in pressure and O2 – and this is speculation with out any data to support.

“Malaise trap sampling cannot provide a complete survey of the insect fauna” – True – and true of ANY sampling methodology. I would broaden this sentence so it doesn’t read as a criticism of Malaise traps.

“The difference between the relative proportion of Cicadomorpha and Fulgoromorpha with increasing elevation may be a mere artifact of collecting or, if not, may be due to differences in host plant communities or larval habitats among other factors.” – I would consider re-wording this final paragraph/sentence. Consider phrasing this in terms of what you have actually done (the inventory) and what it suggests (the negative trend). That some questions remain unanswered is fine but can be phrased in terms of work that remains to be done.

·

Basic reporting

see General comments to the author

- English still needs improvement
- study design ok but must be better explained
- statistic methods inappropriate

Experimental design

see General comments to the author

Validity of the findings

see General comments to the author

Comments for the author

General comments

The overall patterns documented by the authors are certainly worth publishing, but the authors must invest much more effort in writing an interesting, state of the art manuscript that clearly addresses hypotheses, includes the most relelvant literature on insects in tropical elevational gradients and discusses the outcomes in a framework of other studies conducted in the same area and of other studies of their study organisms globally. Moreover, a major methodological approach (i.e. the use of pure observed species richness as richness measure) is inappropriate, and the documentation of the raw data must be ensured.
I recommend the authors to collaborate with a community ecologist who is familiar with state of the art analyses of diversity patterns along environmental gradients.

Language: should be carefully checked by another native speaker, there are numerous smaller errors or language is often not as precise as it should be.

Introduction
l 22 ‘Hemiptera had a decrease in morphospecies richness’; better: Hemiptera morphospecies richness decreased with elevation’
l 33 what about fungi and bacteria? Better ‘organismic diversity’
use consistently ‘elevation’ (not altitude)


Introduction:
Currently is not well focused, lacks important references and a clear hypothesis to be tested. For example, the second sentence is more or less meaningless (‘One type of pattern that emerges is the change in species richness and differences in the composition ofinsect communities with increasing altitude’). I cannot think of any environmental gradient that will not result in such a change.

Suggested: Rewrite and focus, for example like this: 1) rain forests are very species rich, 2) elevational gradients even increase regional diversity, 3) the most common pattern found are hump shaped patterns or linear decreases (Rahbek etc.), but there are exceptions (increase, constant diversity), 4) continue with line 39–45 but find better references than a textbook and Lawton 1987), 5) continue with line 46 but find more references of current work conducted at Mt. Wilhelm (Novotny etc.); there have certainly been some very important studies on herbivorous insects in PNG in the last years. 6) from line 51 on: can you think of any group of herbivores in which feeding is not linked to the vegetation? I cannot follow why Auchenorrhyncha are more suitable than other groups because ‘they include species that feed xylem, phloem, or mesophyll’. Many groups of herbivores were used as ‘indicators’ and the arguments delivered are not convincing. What about specialisation? This could be an argument why a group is particularly closely linked to vegetation – everything else appears trivial. I cannot imagine that nobody has ever performed diversity studies of the study organisms in other places in the world. What were the results? What is then the expectation for PNG – use this as a working hypothesis.
Furthermore, the introduction does not introduce diversity measures that were performed in this study (concept of alpha diversity, beta diversity / turnover), and more meaningful measures must be applied.

Material and Methods
- A full species-site matrix (as electronic appendix) is required in order to allow anybody to re-analyse and proof the results.
- Study area: Table with precise locations of all sampling sites is requried (long, lat, exact elevation). x axis label should be: elevation (m. a.s.l.)
- Figure 1: Map lacks longitude/ latitude information. Better would be a map of the whole island of Guinea with the two major sampling areas, and an inserted map of Mt. Wilhelm with the precise location of the sampling sites in this area. There may be copyright issues with the graph as currently presented.
- forest: are all forst sites intact primary forests or are they disturbed to a varying extent?
- Wrong term hygroscopy: is ‘the ability of a substance to attract and hold water molecules from the surrounding environment’ – certainly not meant here but humidity?
- Temperature data are remarkably inprecise. There will be exact data from weather stations in PNG from similar sites (e.g. average temperature at 200 m a.s.l. is 25.2°C and not between 25 and 30°C), and this should be presented in a table.
- References are lacking or not precisely assigned to support information on the vegetation.
- The sampling period was rather short. Is coverage similar in all samples? Data on coverage must be provided.
- Logistics: How did you manage to to to every sampling location at every of the 16 days of the sampling period between 200 and 3700 m? Is there a road or a helicopter? Difficult to understand how this was possible (many field assistants?)
- How could photographs of the insects facilitate the identification? Did other specialists check the material or was the material later re-examined?
- Using simply observed species richness is certainly not sufficient. Tropical arthropod communites are usually undersampled (and certainly in this short-termed study), so other measures must be applied. Use for example EstimateS by Rob Colwell, freely available on the web, for rarefaction/extrapolation and think about using diversity measures.

Results:
- Must include other measures of richness and diversity than just observed richness (see above).
- Pearson correlation results should be presented either in the graphs or in a table, but not as extensively here in the text.
- Try to gather quantitative environmental data (temperature, tree species diversity, rainfall etc.) and consider to formally apply regression and / or multiple regression to find out which factor could be the most important.

Discussion:
Needs to be rewritten (see Introduction: major hypothesis, results form other groups along the same gradient, and from the same study organisms from other regions of the world)
- Must include other measures of richness and diversity than just observed richness (see above)
- Horseshoe patterns are well known and must be discussed

References
- I miss more references from other groups performing field work at Mt. Wilhelm that are important to discuss similarities and differences of patterns in various groups of organsims, e.g., by K. Sam, K. Tvardikova, V. Novotny, S. Miller, G. Weiblen and others.
- More references from Hemiptera and Auchenorrhycha elevational studies from other regions (or if absent: then this is the first study to document it?)
- Secondary literature (Textbooks such as by Begon et al.) should not be cited

Tables / Figures:

Table 3 should be shown as graph.

Figure 4: Parameters should be part of the Figure (not in figure heading). Labeling font must be substantially larger. Numbering currently is 4,5,6,7,8,9 and should be a, b, c etc.

Version 0.1 (original submission)

· · Academic Editor

Major Revisions

I have had a quick read through this MS, but have not yet sent it out for review. While the English is understandable (I understand what the authors have described in this paper), it is currently quite difficult to read due to a large number of fairly awkward wordings, etc.

For instance, here is the first paragraph of the introduction:

"With their high faunal and floral diversity, the tropical rainforests fascinate and induce a certain number of explorations that aim to evaluate and describe this biodiversity. Papua New Guinea has the third largest expanse of tropical rainforest (Brooks et al., 2006) is no exception to this rule. Mount Wilhelm (4509m) allows us the chance to study up to a much higher altitude. Rahbek (1995) has shown that even if the elevational gradient is not a complete new topic of research, much is still to be learned. Most studies highlight the decrease of the species richness with the altitude, involving many processes (Brühl et al., 1999 ; van Ingen et al., 2008). Thus, Lawton (1987) mentions four main reasons for such pattern of reduction at high elevation: habitat, resources diversity, unfavourable environments and primary productivity. In the meantime, some studies have shown a peak of the species richness at middle elevations (Janzen et al., 1976 ; Grytnes, 2006 ; Wiens et al., 2007 ; Guo et al., 2013). However, Hodkinson (2005) underlines with a series of examples, concerning insect groups, that all patterns are possible even an increase of species richness with the altitude. Beyond the fact that altitude affects the species richness, it impacts as well the composition itself of the insects communities (Whittaker, 1952)."

I spent a few minute editing that paragraph into a form that I think is more readable:

"The high faunal and floral diversity of tropical rain forests has stimulated many biodiversity studies. Papua New Guinea, which has the third largest expanse of tropical rainforest (Brooks et al., 2006) in the world, is no exception to this rule. Mount Wilhelm (4509m) provides an opportunity for study at a higher elevation than is typical of previous work. While such research is not new, Rahbek (1995) points out that much is still to be learned in this context. Most similar studies to date highlight that a decrease in species richness with altitude results due to a variety of factors (Brühl et al., 1999 ; van Ingen et al., 2008). Lawton (1987) mentions four main reasons for this seemingly typical pattern, specifically shifts in habitat, resource diversity, environmental suitability, and primary productivity. Some studies have even shown a peak in species richness at middle elevations (Janzen et al., 1976 ; Grytnes, 2006 ; Wiens et al., 2007 ; Guo et al., 2013). Such a phenomenon is not surprising because – as Hodkinson (2005) has shown with a series of insect-related examples – all patterns are possible, including an increase of species richness with the altitude. Beyond the fact that altitude affects insect species richness, it also impacts the composition of insect communities (Whittaker, 1952)."

This could very well be robust research work; and a good review process could determine if that is the case. But I am worried that sending it out for review in its current state will not provide this manuscript with a fair hearing.

Therefore, I strongly encourage the authors to ask a native English speaking colleague to carefully edit the MS for better readability and then resubmit it to PeerJ. Once the language issues are dealt with, I will be happy to move this forward by sending it out for peer review.

(Please also note that much of this PeerJ email is a form letter consisting of text which I cannot edit. In some cases – e.g. the following line – the wording may imply that the paper has gone out for review. That is, of course, not true in this case.)

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