Temporal Variation of Genetic Diversity in Rutilus rutilus Populations from Lithuania Using mtDNA Markers in the Context of Anthropogenic Activities

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 General comments

This manuscript used investigation of genetic diversity of rouch inhabiting Drūkšiai Lake and other water bodies distributed in same geographic region of Lithuania focusing on the changes of population genetic structure of this fish species over five years period dependent on anthropogenic impact. Genetic variability was assess based on analyses of two mt DNA markers (D-loop and ATP6). The data obtained from the Lake Drūkšiai, the Žeimena and Neris Rivers should be expanded and used as a background database for further genetic monitoring of the roach populations living in these water bodies. The differences of genetic diversity in Lake Drūkšiai may be related to recovery of ecosystem previously affected by operating nuclear power plant significantly rising temperature of this water body. The data obtained formed background information to be used to investigate the possible impact of NPP on the formation of and changes in the genetic structure of the roach populations.

Additional number of samples and genetic markers could be apply to assess changes of haplotypic diversity in roach population.

There are some recommendation to the authors, which could improve the manuscript presentation: 

The specific comments are:

-        It will be better to include a map, illustrated the sampling localities;

-        Concerning haplotype network analyses I recommend to exclude from Figures 1, 2 and 3  (Median-joining haplotype networks of R. rutilus using mtDNA markers) point (A) Haplotype network of roaches collected from three different locations in 2017 and 2022 and to accept only B and C., because they are more informative for variability of genetic diversity.

 

Comments on the Quality of English Language

I recommend minor revision of the English language.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Overall the paper is well-done, but could be improved with some tweaks. Below I list a few major concerns that should be addressed prior to publication. 

-First, 'genetic drift' is completely missing from the manuscript. For example, in the first few sentences of the introduction the authors state "The genetic variation and population genetic structure of species can be affected by many factors, such as climate change, natural barriers, migration behavior, or human activities [1]. For instance, the fragmentation of river networks by dams induces changes..." This is all well and fair, but genetic drift is really a big player here that the authors do not address, and they really should. Especially if they talk about fragmentation- one of the biggest problems with dams is blocking upstream populations from new migrants, thus increasing the potential effects of genetic drift. That should be addressed and discussed both in the introduction, and the discussion in the context of their findings. 

-What about migration or gene flow between their sites? Or from unsampled populations/sites? As someone completely unfamiliar with the area, is that possible? What effect could that have? Should be explained. Also, perhaps a map of the sites is warranted instead of GPS coordinates? 

-I do not feel lines 54-65 of the introduction (paragraph justifying the use of mtDNA markers...) is needed. 

-Table 2 could be moved to supplement, not needed in main text. 

-h' is not in their methods but shows up in Table 3. 

-What is the generation time on these fishes? Is 5 years long enough to address this question? I feel the authors need to discuss this possibility. Along with that, did the authors test to be sure they didn't sample the same individuals if it's at all possible they'd survive 5 years?

-This is important- I think their results needs to be rewritten in the context of their study question/title of the paper. As is written now, it's dense and quite frankly difficulty to follow. I think if they wrote it simpler and shorter, focusing on the year-year/site-site comparisons, it would be more impactful and more succinct. Along those lines, we do not need all of Figures 1-3 in the main text; those could be moved to the supplement. Something more useful would compare the sites/years as laid out in their research questions and title. Also, I believe line 119 should reference Table 3 not Table 1. 

-Discussion should be slightly rewritten to address their research questions more directly. As currently written, it's more a rehashing of their results, which is okay for parts, but more extrapolation to relevant literature and focus towards addressing their research questions is warranted. 

Comments on the Quality of English Language

English is pretty good- few instances where it should be double checked. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf