Detection of Glacial Refugia and Post-Glacial Colonization Routes of Morphologically Cryptic Marsh Frog Species (Anura: Ranidae: Pelophylax) Using Environmental Niche Modeling

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Litvinchuk et al. present a very interesting comprehensive study on Marsh frogs of the genus Pelophylax in Eurasia. This study is of particular interest due to current changes in the distribution of Pelophylax species due to climate change and human mediated translocation throughout the continent.

The authors use their own and further published molecular data for detecting the species ranges and Maxent modeling for delimitation of current and potential areas with suitable habitat, as well as the development of such habitats throughout the Late Quaternary.

I suggest to publish this paper following minor amendments which are outlined below:

General remarks:

Language: Please check the text carefully in respect of the English language. Basically the text is easy to understand and well written, but some parts are grammatically incorrect or bumpy. For example, many times articles are used, where they are not needed in English (Abstract: line 14, Mat & Met: line 86).

Abstract: The Abstract has to be re-written according to usual publication standards - it currently contains mostly results, a potential reader is not getting an idea of Your study. Tell us shortly about Your aims, Your Methods results and discussion.

Discussion: In the daily growing cases of occurences of Marsh frogs (or their DNA) outside their natural range, it would be highly interesting, if You could more thorouhgly discuss, whether, based on comprehensive data sets like Yours, one can distinguish between results of human mediated translocation and results of natural colonisation and hybridation processes.

Minor remarks:

Introduction: lines 41-45 - please rephrase, there is some redundance in this sentence.

Introduction: lines 82-84 - should read: Therefore the aims of our study were (1) to define recent ranges of these three species and (2) to identify the position of their glacial refugia and post-glacial colonisation routes, using ecological niche modeling methods.

Mat & Met: line 86 - delete "the"

Mat & Met: lines 92 and 93 - could You be a bit more open about the high numbers of genetic data from other sources - I think, they should not only be presented in the supplementary material.

Mat & Met: line 121 - delete "the" before toe

Mat & Met: line 124 - delete "as well as"

Results: line 242 - what is a two-three model - unclear, please explain

Discussion: lines 343-344 - should read "reaching the Baltic Region at the early Holocene"

 

Comments on the Quality of English Language

see section above

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors, 

I must commend you on the quality of your work, as it is well-designed and well-written. Your research includes nuclear DNA to remove any bias that can arise from the introgression of mtDNA, which I greatly appreciate. Your research adds valuable insights to the biogeography of the Marsh Frog species. 

 

I found the paper is complete and needs almost no corrections. However, i) in Figure 1, I suggest using nuDNA instead of nDNA to be consistent with the manuscript texts. ii) I would suggest adding thicker red lines in the figures 3, 4, and 5. iii) Although not required, adding the latitudes and longitudes to figures 1, 2, and 6 would be much appreciated.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

the manuscript on marsh frogs is very well written, with clear hypothesis and research design. It presents important data on these cryptic species and as such is a valuable contribution to our knowledge.

The only  suggestion that I have is only technical in nature. It would make it easier to see if the red line in figures 3-5 would be a bit thicker.

 

 

The introduction of the paper gives a good overview on the current knowledge of eastern and western marsh frog species groups. The authors summarize what is known today, and also mention what is still missing and how they address this gap in knowledge. They present the aim of the manuscript very clearly, i.e. to determine recent ranges of the three studied species and to identify their possible glacial refugia and post-glacial colonization routes.

  Methodology of their research is clearly presented, with sufficient sample size (e.g. 454 localities for niche modeling). They clearly present advantages and disadvantages of using mt DNA in such analyses, and explain why for niche modelling they used only nuDNA.   In the results section they clearly present current distribution of the three studied species, based both on alleles and haplotypes present. They also present which are the suitable areas for each of the species, as well as historical distribution of each of these species.   In the discussion section they evaluate their results and explain possible causes for current distribution of all three species. They also compare their data and predictions with the existing data for other frog species, that also confirm their hypothesis.  

Generally, the manuscript is very well written and the only suggestion that could improve it refers to figures 3 - 5. It would be easier to see the current distribution of each of the species if the red line that shows it would be thicker. In addition, in the figure 1, in the upper picture, it should be written nuDNA (instead of nDNA that is written now) to match the text of the figure legend and the text of the manuscript

 

Author Response

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Author Response File: Author Response.pdf