Beta Diversity along an Elevational Gradient at the Pico da Neblina (Brazil): Is Spider (Arachnida-Araneae) Community Composition Congruent with the Guayana Region Elevational Zonation?

Round 1

Reviewer 1 Report

Dear authors

Thank you, this is a very interesting study and I enjoyed reading it. However, I have some minor comments especially when it comes to the discussion of your results.

Comments for author File: Comments.pdf

Author Response

Manuscript “Beta diversity along an altitudinal gradient at the Pico da Neblina (Brazil). Is spider (Arachnida-Araneae) community composition congruent with the Guayana region altitudinal zonation?”

 

André do Amaral Nogueira

 

RESPONSE TO REVIEWER 1 COMMENTS

 

Point 1 - Better use the term elevation throughout the mansucript. Altitude and elevation are referring to two different things.

Response 1 – Ok.

 

Point 2 - lowest

Response 2 – ok.

 

Point 3 – My main interest is to understand what your assumptions or hypotheses are. Please elaborate on your expectations and the rational behind those.

Response 3  - I added a sentence that, I hope, will make my assumptions more clear, as well as the rationale behind them.

“We expect that the changes in composition in spiders communities will be connected to those observed for the vegetation, since the structure of the vegetation is considered as an important environmental factor for spider species (26, 27).”

 

Point 4 - Larger dominance of what? Please specify

Response 4 – I add this explanation “(i.e. the relative importance of the most abundant species)”

 

Point 5 – I don't understand this sentence.

Your results will allow you to better evaluate your results? Please be more specific.

Response 5 – I made some changes in the sentence, and hope that now it is more clear.

“This increase of knowledge on montane spider faunas will allow us to evaluate our results in a broader context, and to look for more general patterns on spider beta diversity in altitudinal gradients, as well as to make some comments on the conservation of these mountain communities.”

 

Point 6 – above sea level  / asl

Response 6 – I added the asl.

 

Point 7 – mean or average?

Response 7 - Average

 

Point 8 – Add some additional information about the structure of the vegetation, e.g. densitiy, vegetation height, dominant growth form. This is necessary to understand the changes happening along your elevational gradient. Referring to Berry et al. is not enough here in my opinion.

About the importance of vegetation sturcture the following literature might be interesting.

 

Frick, H., Nentwig, W. & Kropf, C. (2007) Influence of stand-alone trees on epigeic spiders (Araneae) at the alpine timberline. Annales Zoologici Fennici, 44, 43–57

 

Muff P, Kropf C, Frick H, NentwigW, Schmidt-EntlingMH (2009) Coexistence

of divergent communities at natural boundaries: spider (Arachnida: Araneae) diversity across an alpine timberline. InsectConservation andDiversity 2: 3644

Response 8 – A better description of the vegetation represents one of the main requests of the reviewer, but I think it would not be necessary, and I will try to explain why.

                The reason is simply because we didn’t collect more detailed data on the vegetation, and we also didn’t associate the spiders collected with the kind of vegetation they were found on. So, it would be impossible to us to make more detailed association between the spiders we sampled and some particular kind of plant. For the same reasons, we also couldn’t perform any kind of more detailed analysis associating spider species or families with particular types of vegetation or plant groups.

                We can make only rough comparisons between very different kinds of vegetation formations, such as forested habitats (the first four elevations sampled) and open formations (the two highest sites sampled). And the biggest differences in spider composition are observed when comparing those two kinds of habitats.

                So, we consider that the description of the vegetation , although very brief, is enough to characterize the main feature of the study region vegetation, which is that forest formation occur up until around 1,900 masl, when they are replaced by open formations. We also mention some of the most characteristics plant families in the area, and then we refer to studies that present a very detailed description of the vegetation, for those that would be more interested in this feature.

 

Point 9 – hand collecting

Response 9 – Yes, and I added this information

 

Point 10 – See comment  above about vegetation structure. Depending on the structure you might have immense differences in the overall sampling area.

Response 10 – I added some examples on the type of vegetation.

 

Point 11 – Why did you choose these elevations? Can you please elaborate on this.

Response 11 – Those elevations were chosen based on logistic reasons. Our study site didn’t have any kind of facility, and there is only a few places to set a camp along the elevational gradient, due mainly to the availability of water sources.

 

Point 12 – Do I understand correctly that three researchers were responsible for their individual plot? Did you check your results on the influence of the collector on spider diversity?

Response 12 – No. Each one of the three plots by altitude were sampled by the three collectors. So, all the comparisons between plots are standardized by the fact that all the collectors performed the same sampling effort in each plot.

 

Point 13 – Why are you doing this and how are you including this in your analysis?

Response 13 – This data was used in analysis in other studies, but not on this one, so I removed this sentence.

 

Point 14 – Not everything was identified to species level? Did you pool the morphospecies later again. Can you please elaborate and give an overview on how many were identified to species level.

Response 14 – Everything was identified to the species level, or was sorted as morphospecies, and all the morphospecies obtained in the inventory were compared. For more detailed information the reader can go to Nogueira et al 2014, with a detailed description of the species list, including the proportion of species that could be identified to the species level (around 27% of the total richness).

Nogueira, A.A.; Venticinque, E.M.; Brescovit, A.D.; Lo-Man-Hung, N.F.; Candiani, D.F. List of species of spiders (Arachnida, Araneae) from the Pico da Neblina, state of Amazonas, Brazil. Check List 2014, 10, 1044-1060.

 

Point 15 – see comment above

Okay, it seems everything was identified to species level. Can you please be more specific then in the sampling methods.

Response 15 – See the preceding answer.

 

Point 16 – is either

Response 16 – I changed in the text.

 

Point 17 – 2,400 m

Response 17 – I added this missing information

 

Point 18 – This is an odd sentence and belongs rather into the discussion section.

Response 18 – I changed the sentence.

Our results also showa positive association between species from the genus Chrysometa and altitude.

 

Point 19 – I suggest to delete the reference here, it is not necessary. Otherwise, I suggest to include the Author and year whereever you give a species for the first time.

Response 19 – I followed the reviewer suggestion.

 

Point 20 – Please start the discussion with your hypotheses / assumptions / expectations and how your results helped to gain further insights.

Response 20 – I followed the reviewers suggestion and added a first paragraph commenting the general results, before discussing it in topics.

“Our results revealed very important changes in composition along the altitudinal gradient. However, the general beta diversity pattern was not entirely adjusted to the altitudinal division proposed for the study region. While the highlands zone (above 1,500 m) did presentd a unique set of spider specie, the lowland (up to 500 m) spider fauna expand up until the uplands (from 500 to 1,500 m), producing thus a different pattern than that observed for the vegetation, where a clear distinction between the lowland and upland communities can be perceived. Our results also showd important differences in the diversity and dominance levels of the communities, that will be discussed above.”

 

Point 21 – Can you please elaborate what kind of influence this could be, e.g. temperature, humidity, vegetation structure etc.

 

Which environmental gradient are you focussing on?

Response 21 – The main environmental factor in elevational gradients is temperature, and I added this to the text in the manuscript.

 

Point 22 – An increasing dominance level at higher elevation has already been observed for spiders [26, 27] and various other groups [52, 11, 53].

Response 22 – I changed the sentence.

 

Point 23 – In my opinion it is necessary to further describe the vegetation at the different elevations and habitats more detailed in the methods section.

Response 23 – This question was discussed in response 8.

 

Point 24 – This hase to be further explained. What exactly changes and how do you assume this to affect the spider diversity.

Response 24 – I am referring to the changes in the structure of the vegetation. The fourth sampled altitude, 1,550 m, is still covered by forests while the next sampled altitude, at 2,000, is covered by a very different vegetation, presenting an open physiognomy, with bromelias, shrubs and small trees. So, we consider that it is logical that such large differences in the vegetation would led to large differences in the composition of the community.

I also changed the sentence in the discussion, hoping it will be more clear:

“This is not a surprise, given the drastic differences in climatic factors and especially in the structure of the vegetation, going from forested habitats to open physiognomies at the highlands sites.”

 

Point 25 – To put this in a larger perspective see:

Steinbauer, M. J., Field, R., Grytnes, J. A., Trigas, P., Ah‐Peng, C., Attorre, F., ... & Beierkuhnlein, C. (2016). Topography‐driven isolation, speciation and a global increase of endemism with elevation. Global Ecology and Biogeography, 25(9), 1097-1107.

Response 25 – I added this reference

 

Point 26 – I assume that the altitudinal division refers mainly to the vegetation?! You could, based on your results, suggest an elevational divison for the spider fauna that fits the environmental conditions much better. However, this would meant to include some more information about the environmental conditions.

Response 26 – I refer to the study region elevational division in the introduction, first page, and I describe the vegetation of the region in the Material and Methods section. As I mentioned, the altitudinal division was based mainly on temperature and altitude, but this division was supported by the floristic distribution across the elevational gradient in the region.

                As for our results, we consider we don’t have enough data (or even sampling sites) to propose a detailed altitudinal division for the region. Moreover, for the majority of the spiders species we sampled, there is no information about its ecology and/or distribution, so they may not be the most informative group to characterize the region.

                Considering those limitations, we believe that all we can do with our data, for the moment, is to compare our results with the better established altitudinal division known for plants, and to assess if it is in accordance or not, and what are the main differences.

 

Point 27 – At which elevation is this happening?

Response 27 – This transition happens from 1,800 to 1,950, approximately. So at 2,000 m, the vegetation is already very different, with an open formation.

 

Point 28 – Here it would be particularly interesting to get a few insights into your expectations in advance.

Response 28 – To be honest, I did not have an a priori expectation other then what is reported in the other few similar studies, that I mention in the discussion.

 

Point 29 – designated?

Response 29 – Yes, and I changed it.

 

Point 30 – I don't get this. What information are you trying to give here.

Response 30 – The information is that in the highlands, species from the families Oonopidae and Hahniidae were sampled in the vegetation. But I though it was important to comment that because it is not a common behavior for the members of those families, that usually occur in the litter layer.

                We consider that this may represent an adaptation to the particular highland habitats, where the soil is almost completely covered by rocks, mud or ground vegetation.

 

Point 31 – This part needs some revision. For me it is not clear what your results are and what is taken from the literature (or pers. comm.)

Response 31 – In this sentence I mainly described the results of another study, performed in a Tanzanian mountain. I made some changes in the paragraph, and now I hope that the text is not ambiguous anymore.

 

Point 32 – Please elaborate, it is not clear to me what you are trying to say. If you are refering to the replacement of Tetragnathidae vs. Araneidae you should probably add the family behind Chrysometa.

Response 32 – I did add the family name after the genus.

 

Point 33 – How about jumping insects?

Response 33 – If they jump into the orb webs they will be captured too, but orb-webs have always been considered a sort of wed specialized in catching flying insects, and it is though that they evolved due to the emergence of flying capacity in insects.

                Anyway, I added the word “mainly” to the flying insects, implying that this kind of web can capture other kinds of insect than flying ones.

 

Point 34 – Probably not to all Araneidae species, but the ones you would expect here.

Response 34 – I add the term “most”, implying that some species does not follow this common trend, of preferring low elevation habitats.

 

Point 35 – Fragment?!

Response 35 – I am not sure what the referee means. Would it be a DNA fragment, describing the new genus? If it is the case, I don’t know it it should be presented in our manuscript, since we are just mentioning the new genus and species are being described from mountains.

 

Point 36 – Any references?

Response 36 – I added the study of Steinbauer and collaborators (2016), suggested by the reviewer.

 

Point 37 – Yes, but so what?

What is the common feature of all this gradient based research?

Response 37 – The sentence highlighted and questioned by the reviewer is a preliminary comment on the other spider inventories performed along elevational gradients.

                And I decided that it would be better to first observe that there was a lot of variation in the results, and that part of this variation could be attributed to several kinds of methodological differences. So, it represents a preliminary caveat.

                But after that I start discussing in greater detail the results obtained in those studies and how they compare with our results. And I also highlight common patterns and results that emerge when taking into account all of these studies, including ours.

 

Point 38 – See also the following and cited literature within. Please consider the isopam function for your analysis.

 

Hein, N., Löffler, J., Feilhauer, H. (2019): Mapping of Arthropod Alpha and Beta Diversity in Heterogeneous Arctic-Alpine Ecosystems. - Ecological Informatics 54: 101007.

 

Hein, N., Feilhauer, H., Finch, O.-D., Schmidtlein, S., Löffler, J. (2014): Snow Cover Determines the Ecology and Biogeography of Spiders (Araneae) in Alpine Tundra Ecosystems. - Erdkunde 68: 157–172.

Response 38 – The Isopam function seems interesting, and we will consider employing it in future works. However, for the present manuscript, we consider that it may be very redundant with the Indicator Species Analysis, that we already used.

 

Point 39 – Which parts exactly?

Response 39 – I changed the sentence, because the result I am discussing is the decrease in spider richness due to the increase in temperature, and not in relation with elevation.

 

Point 40 – Can you be more specific? What is it temperature?

Response 40 – I am discussing the results presented by Vitterbi et al (2020). They performed some simulations based on niche modeling, assessing the effects of a temperature increase on animal communities, including spiders. So, when we mention temperature, we are dealing with the air temperature in the environment, and not from that of any particular habitat.

 

Point 41 – Are you refering to the gerenal temperature decrease with increasing elevation? Please note that the microclimatic condition (near ground temperature) can be decoupled from the  more or less linear trend related to altitude.

 

See also:

Scherrer, D., & Körner, C. (2011). Topographically controlled thermal‐habitat differentiation buffers alpine plant diversity against climate warming. Journal of biogeography, 38(2), 406-416.

Response 41 – See the response above, n 40. But I also added the word “air” to make clear that we are talking about the general, air temperature, and not that of any particular environment or microhabitat.

 

Author Response File: Author Response.docx

Reviewer 2 Report

Just a suggestion, but in the future try to use collecting methods that cover more ecological groups. The soil traps are much more informative than all hand applied collecting methods and are practically the only ones that give a real idea of the composition of the epigean fauna. 

Author Response

I thank the reviewer suggestions of using more collecting methods.

 

It would have been very usefull, but in the Pico da Neblina expedition it was impossible due to the very difficult logistics of the field trip and to the complete absence of any kind of facility near the study site.

 

But I intend to use additional methods whem I sampling sites in less remote and wild regions.

Author Response File: Author Response.docx