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Thanks for making the minor edits as corrected. I recommend your revised manuscript for publication.
[# PeerJ Staff Note - this decision was reviewed and approved by Ann Hedrick, a PeerJ Section Editor covering this Section #]
Thanks for addressing my previous comments. I have identified the following minor edits for revision:
Title: “Along Elevational Gradient” to “Along an Elevational Gradient”
L. 73 – The author names are not correctly formatted for the references, which should be Singh et al 2003 or Singh, Singh and Kaul 2003: Singh, V.P., Singh, B., & Kaul, V.K. (2003). Domestication of wild marigold (Tagetes minuta L.) as a potential economic crop in Western Himalaya and North Indian plains. Economic Botany, 57: 535-544.
L 95 “elevation gradient” to “elevation gradients”
L 100 “elevation gradient” to “an elevation gradient”
L 102 “different elevation gradient” to “an elevation gradient”
L 372 “Tagetes minuta” – add italics
L 390 “altitudinal gradient” to “elevation gradient”
L 416 “Tagetes minuta” – add italics
L 454 “Ngondya I B, Munishi L K. Scientific A.” - Scientific African is the journal name, not an author name. There are only 2 authors.
L 489 “Hordeum vulgare” – add italics
L 491 As pointed out above, the author’s last name is Singh, not Virendra
L 498 “Tagetes minuta” – add italics
L 512 “Tagetes minuta” – add italics
I appreciate various revisions made in response to reviewers. I have identified some additional revisions as follows. Additionally, I did not find author responses to my original comments; I have repeated some of my original comments below in cases where they did not seem to be addressed in the revised manuscript.
Title – the title refers to “elevation gradients” but the map shows that there is only one elevation gradient in this study, so gradient should be singular, not plural throughout the manuscript when referring to this study system.
Text – mostly uses the term “altitude” rather than “elevation”. I believe that altitude typically refers to height something above ground (e.g a flying airplane) while elevation would be a better term for the height on land above sea level.
The nearly absent reference to the global literature on T. minuta is a serious shortcoming that needs to be addressed. Literature about chemical extracts is largely irrelevant. However, there are various studies globally about T. minuta’s behavior as a weed and these global studies need to be integrated into your introduction and discussion. I will simply give one example as follows:
https://www.sciencedirect.com/science/article/pii/S2468227621002507
“Impact of invasive alien plants Gutenbergia cordifolia and Tagetes minuta on native taxa in the Ngorongoro crater, Tanzania”
The authors examined the impact of T. minuta on plant species diversity. This is exactly the topic of your own study, and it is essential to carefully compare your own findings with these previous findings in order to gain meaningful insights into how / when T. minuta may affect diversity. Please complete a thorough global literature search on studies of T. minuta’s behavior as a weed and integrate the relevant global literature in your introduction and discussion.
Existing references in the manuscript are problematic. I will give a few examples, but each reference should be carefully checked. Why is there [J] after each title?
Species diversity of forest plant communities on the southern slope of the Dabie Ecological Applications, 2008, 18(3): 762-770. – The cited journal and page numbers do not contain the article listed here about Dabie.
Nelson Cara R., Charles B. Halpern, James K. Agee. Thinning and burning result in low
-level invasion by nonnative plants but neutral effects on natives -- Missing journal name, volume and page numbers
Mountians and its relationship with altitude factors – Missing author(s)
Acta Ecologiga Sinica – spelling error
Qiong S “647-659+674-675.” Why are two page ranges cited. Only the first range is cited here:
https://www.biodiversity-science.net/EN/10.3724/SP.J.2010.647
Martín J. Eguaras,S. – species names need to be in italics
Many of the cited works do not appear to be available to an international audience even as abstracts. It is problematic to cite such works in an international journal; wherever possible, literature that is accessible internationally should be cited because the PeerJ audience is international. I will give just one problematic example: “Journal of biosafety” -- When I search for this journal, I am directed to the following page:
https://journalofbiosafety.ir/browse.php?sid=1&slc_lang=en&mag_limit_start=5
However, this does not appear to be the Journal of biosafety that you are citing. Eventually I can find the abstract of the article you are citing from an indexing database (not from the actual journal) here:
http://sciencechina.cn/scichina2/detail_s.jsp;jsessionid=BD1B7489B3CDB7F6EBAEA6451F19C46F?detailType=1&internal_id=6763389&CID=
This indexing database refers to the article DOI, which is the permanent link for the article, however when I try to follow the article DOI:
http://dx.doi.org/10.3969/j.issn.2095-1787.2020.02.008
The article cannot be found. This should never happen – by definition the DOI is the permanent link to an archived document. Thus, I am led to conclude that this document is not properly archived and should only be cited as a last resort in favor of citing other relevant works that are properly archived and accessible.
Please check accessibility of all cited literature; if currently cited literature is not readily accessible outside of China, check if a substitute accessible citation may be suitable for the same purpose. Sometimes there may be no suitable substitution, but the current manuscript seems to be overly reliant on literature inaccessible outside of China. Chinese language literature per se is not necessarily, since translation is now relatively simple; however, if the text is not accessible (e.g. it is not available online or loanable from libraries), that becomes problematic because the citation cannot be consulted by an international audience.
Please present your species list as a supplemental table; it may also be useful to include on the table the habitat type(s) where each species was found.
Specific comments:
L 24 Eragrotis piloso - spelling error
L 64 s.(Zhang – misplaced period
L 73 many tropical and subtropical regions around the world – Here citations are needed from other parts of the world to support your claim.
L 79 research on its community pollen – I don’t know what this means, please reword.
L 82 Eguaras et al., 2005 – not in literature cited
L 85 Zhang et al., 2019 – This is not an appropriate citation for this claim. You are making claims about South Africa and India, so you should be citing studies from those regions, not a study done in China about management measures of Tagetes minuta.
L108 The elevation gradient is not very substantial (only ~600 m). In this paragraph I think it is important that you explain how you decided to study this specified elevation range? Why not study a broader elevation range if the pattern across an elevation gradient is your central question (elevation is also identified as central in your manuscript title)?
L 139 Qiu et al., 2021 – Why is this cited here? You are referring to Microsoft software, so the citation should be Microsoft.
L 140 Tong et al., 2024 – Why is this cited here? You are referring to R software, so the citation should be for R . You can find various instructions on how to do this, for example here: https://intro2r.com/citing-r.html
L 147 Jiang et al., 2024 – Why is this cited here? You are referring to Origin software and that software manufacturer should be directly cited.
L 168 24.36% -- please round off these percentages. If you counted 1000 + species then it would make sense to display precision of 0.01% but you only had 78 species so precision is only to the nearest 1%
L195 Eragrotis piloso – spelling error
L197 Diditaria cruciate - spelling error
L 238-239 Yang et al 2011 – this is a study specifically about one species (Solidago canadensis) and it does not seem like an appropriate citation to support the general claim you have made in the previous sentence. There are various reviews that have been published about plant invasion mechanisms generalized across various plant species that would be appropriate as support for your claim generalizing across invasive alien species.
L246-247 -- similar to the family distribution of some other common invasive plants – ok but why not also discuss whether your findings were similar to those from other places in the world where Tagetes is growing as a weed?
L 267 Wang Junwei et al. (2024) found that D. stramonium mainly grows – This sentence seems out of place and not relevant. This plant belongs to an entirely different family and it’s not clear why it would / should be compared with Tagetes. Of course there are many weeds with similar ruderal habits but why single out D. stramonium in your study about Tagetes?
L 286 has a relatively small impact -- Change to “seems to have a relatively small impact”. Your study based on correlation cannot measure the actual impact.
L 311 Community Species Invaded -- change to “Community Invaded”
L 328 not the dominant factor - It think less definitive language should be used, such as “not the dominant factor across the elevational range studied here”, otherwise you should point out that your elevation range was quite narrow and a very different conclusion might be reached if you had studied a wider elevation range. Also, you have only a single data point at one end of the gradient, which severely limits your interpretations. Without that one point, your elevation range drops to just 300 m.
L332-334 The Galinsoga study covered an elevational range of nearly 1500 m (around triple the elevation range of your study), so that alone could explain why their results may differ. If you had included the most extreme elevations where Tagetes can survive, I strongly suspect the plant would have been shorter at the highest elevations. This should be discussed.
L 340-341 It’s not clear to me how your results would allow prediction along different elevation gradients (e.g . from 1000 – 2500 m elevation) since your study is limited to a narrow and specific elevation range, and I think there is no reason to believe that the pattern in your narrow range of study would apply to a different range of study. If you have evidence that a pattern from a narrow range of study could apply to a different or broader elevation range elsewhere, please cite your supporting evidence. Otherwise, I suggest rewording this concluding sentence or removing it.
L 349-351 Qiu Luo et al. (2010) is a modeling study that covers the entire elevation range of Guangzhou and surrounding districts (~1600 m). It isn’t comparable to your field survey. If you had done a GIS-based modeling study of Tagetes, I am certain that elevation would be an important factor in the Tagetes species distribution model. GIS-based species distribution models are not comparable to your study. It is difficult to draw conclusions about patterns in your study because Tagetes minuta has a global elevation range exceeding 2000 m, while your study only covered around ¼ of the range (~600 m). I think it is best to be clear about this limitation in your study when you are comparing to other studies that often covered much wider elevation ranges (or a greater portion of the species’ climate niche).
L 360 The invasion of T. minuta poses a significant threat to the ecological environment. – Please cite a supporting reference. Your study did not measure threats.
L 360 conduct more in-depth research – it also seems important to specifically conduct studies of Tagetes across a wider elevation and/or climatic range.
Table 1 – This is not species composition, it is family composition with genus and species counts displayed.
The reviewers have requested various changes that would need to be addressed before this manuscript could be accepted. in addition, I have the following comments:
Title – the title refers to “elevation gradients” , but I believe there is only one elevation gradient in this study (but this is not clear, since no map of the plots was presented). Unfortunately there was only one plot at higher elevation and the remaining plots are clustered within two different narrow elevation ranges. This situation makes analyses of elevation patterns problematic. Reviewer 2 has pointed this out, and see also my comments below regarding Fig 3 and 4. These comments need to be carefully addressed in a revised manuscript.
Text – mostly uses the term “altitude” rather than “elevation”. I believe that altitude typically refers to height something above ground (e.g a flying airplane) while elevation would be a better term for the height on land above sea level.
Abstract
L 24-25 “The diversity analysis showed that the Shannon-Wiener index, Simpson index, and Pielous evenness index of Cluster Group II were significantly higher than those of Cluster Groups I and III (P<0.05)” - The terms Cluster Group II, Cluster Group III, etc. have no meaning to a reader of your abstract. Please present key findings in the Abstract in way that makes them to be interesting and easily understood by someone who has not read your entire manuscript.
L 26-27 “This suggests that the invasion of T. minuta primarily affects the evenness of species distribution rather than species richness.” – you observational study cannot differentiate between the opposing possibility that T. minuta prefers areas that already have these characteristics and T. minuta has no impact on these measures at all (there is no cause and effect relationship, your data only demonstrate correlations with areas of T. minuta success). Thus, wording needs to be carefully revised to avoid claims that you have discovered cause and effect relationships. You would need to conduct manipulative experiments (adding T. minuta to a new community or removing it and then monitoring for changes in that community) to provide more convincing evidence of cause and effect.
L 30 “extremely significantly” – please delete “extremely” as this is subjective language that is unnecessary.
L 76 “foreign research has” to “internationally, research has…
L 107 “artificial tree pits” What is this? Needs explanation, since this term is not commonly used.
L 116 Usually the specific R packages used to do specific analyses (e.g. cluster analysis) should be listed in this section.
L 143 Please present your species list as a supplemental table; it may also be useful to include on the table the habitat type(s) where each species was found.
L 154-155 Most of this information was already given on lines 144-146. Can you consolidate the presentation of family information into one section to avoid repetition?
L 169-183 The description of “cluster groups” is not enlightening when referring to habitats types, since it seems that all of the cluster groups included “national highway roadside residential areas”. Is there anything that you can say about the trends in vegetation types or dominant plants that might differ among the “cluster groups”? Such results might be ecologically interesting. I was left wondering why it is interesting or important to compare diversity or evenness among cluster groups, since all of them have Tagetes present. It would seem important to describe and difference in Tagetes abundance among cluster groups. If you could assign meaningful names to the cluster groups (e.g. based on dominant species or some other correlated characteristics of the cluster groups), you may be able to present readers with greater insight in this section. Also, I did not find any enlightening figure based on the cluster analysis. An illustrative figure would normally be expected.
L 208 “This indicates that altitude has no significant effect on the species diversity of T. minuta communities.” -- Altitude per se has no effect on plants. Instead, factors such as temperature or rainfall or disturbance (which are often correlated with elevation) can affect plants. I think you could instead correctly say that elevation was not significantly correlated with species diversity in plots containing T. minuta, although as pointed out below and above (and by reviewer 2), this study design is not well-suited for analyzing patterns across elevation – the two clusters of plots cover two separate and narrow elevation ranges, while only a single plot was assessed at higher elevation.
L 231 – This would be a good place to cite a reference about synergistic effect during invasions.
L 235 – “impact on species diversity across different habitats” -- as pointed out above, your observational student cannot convincingly identify impacts of Tagetes on diversity or evenness. You would need to experimentally add or remove Tagetes and then monitor changes in diversity or evenness in order to conclusively demonstrate an impact of the invader. Correlations that you observed may not be due to impacts of Tagetes.
L 263 “relatively small impact on species richness” – your study design does not allow convincing assessment of impacts (see earlier comments).
Discussion – the elevation range you examined (less than 1000 m) is narrow compared to the know elevational range where this species can grow. I think this should be discussed. I guess the invasion range in China might be limited so far? If your data cover only a limited range of Tagete’s potential range, then conclusions about any patterns seen in that limited range would need to be tempered, since different conclusions could be reached if analyses were done (or could be done) across Tagete’s broader elevational range.
Figure 2 – meaning of the abbreviations need to be explained.
Figure 3 – you only have one point at high elevation and this point does not seem to fit a straight line. The best fit would seem to be a curve or plateau. In general we need to be cautious about claiming a particular pattern when it is based on a single data point. The ideal situation would be to collect more data from high elevations. Otherwise, you could say there is a trend towards a plateau (height) or a decline (coverage) at ~3500 m, but confidence is low due to information from only one high elevation data point. Certainly there is no evidence of a pattern of linear increase up to 3500 m.
Figure 4 – This figure has the same problems as figure 3. The single high elevation data point does not fit the linear trend lines that you have drawn for any of these four graphs. To project patterns across the elevation gradient in a meaningful way, you would need more high elevation plots.
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•Title: The title is a little bit confusing, T. minuta is the invading species and thus the phrase ‘invasive Tagetes minuta communities” may mislead the readers. While it is a common practice to name plant communities on the basis of the dominant species, in a study where the primary focus is on the impact of an invasive species on native plant diversity, a different phrasing would be more appropriate. For example, consider: “Species Diversity pattern in Tagetes minuta-invaded plant communities along elevational gradients in Southeastern Xizang” or similar worded titles.
•Abstract: The above need to be implemented in the abstract too where phrases such as “invaded communities of T. minuta” could be substituted with more appropriate phrases e.g. “Tagetes minuta-invaded plant communities”
•Introduction: The introduction is generally well written and provides a solid foundation for the study. However, it relies almost exclusively on references from studies conducted in China. Given that T. minuta is a well-documented invasive species with a global distribution particularly in tropical and subtropical regions, this narrow geographic focus limits the broader ecological context of the problem. To strengthen the introduction and indeed the entire article and highlight the global significance of the Tagetes minuta invasion, it would be beneficial to incorporate findings from studies conducted in other regions and parts of the world. This will not only provide a more comprehensive background but also underscore the relevance of the research beyond the local context.
• In the section “Overview of the Study Area” it would be informative and impactful to include a map of the study area was included.
• Within the section 1.2 (methods) it would be good for the authors to elaborate more the Cluster analysis methodology used so that the results for this as described in section 2.2 become more clearer to the readers.
• The authors note that, in addition to Tagetes minuta, several other invasive species were recorded in the study area. However, the manuscript does not provide sufficient detail on the ecological relationships between these co-occurring invasive species and T. minuta, nor does it explore how these relationships may vary along the elevational gradient. For instance, were certain invasive species more prevalent at specific elevations? Is there any observed correlation—positive or negative—between the abundance or density of T. minuta and that of the other invasive species?
• The authors should consider including at least one or two actual photographs showing the study areas with clear indication of Tagetes minuta invasion for emphasis.
• In the abstract and indeed in the entire paper, scientific name of the plant i.e. (T. minuta) need to be italicized through.
The manuscript presented in a professional English. However, there is an issue with the concordance between the aim of the study with the presented result and discussion. The author(s) mentioned that one of the aim is to explore its invasion dynamics in southeastern Xizang, including characteristics such as the height, abundance, and cover of T. minuta. However, based on the presented data and analysis, the aim is overclaim. In this study, we can say invasion dynamic study if the author(s) also collect similar data for similar ecosystem condition with the absent of T.minuta at the same study site or adjacent to the study site, then we can compare and contrast the differences between invaded area versus non-invaded area of T.minuta
Two main concerns from me as reviewer for this manuscript:
1. since the aim of the study is stating elevational gradient as one of main interest (elevational gradient also stated), the data in this study did not represent the data variation along different altitudinal gradient with most of the data concentrated in the lower altitude with less data from higher altitude
2. This is just my guess (and maybe due to limited data variation in this study also), it seems that there is an interaction effect between land use type and altitudinal factor to explain the abundance, height, and cover of T.minuta in the context of this study. Thus, I suggest two main methods to clarify the results:
a. group the data into several cluster based on the combination of altitude and land use type, then conduct ANOVA analysis and further analysis (post hoc such as Tukey) to identify the most significantly different combination between altitude and land use type on explaining abundance, height, and cover of T.minuta in the study site;
b. collect extra plot sampling data for area without the occurrence of T.minuta, then conduct the compare and contrast analysis of those species composition and diversity based on used index in this study between plot with T.minuta versus plot with no T.minuta (do this if possible, if not then limit to the point "a" only)
The findings regarding the species composition and diversity indices were valid. However, regarding the altitudinal related analysis, the findings need to be re-assessed carefully due to several issues in the methods (mentioned in the experimental Design)
I add total comments in this part:
The author(s) present a study of species diversity pattern of plant communities that were invaded by T. minuta, one of the significant plant invas=der in China. In general, as a reviewer, I have two main concerns for this manuscript. First, regarding the altitudinal aspect, two things need to clarified and responded by the author(s): a. since the aim of the study is stating elevational gradient as one of main interest (elevational gradient also stated), the data in this study did not represent the data variation along different altitudinal gradient with most of the data concentrated in the lower altitude with less data from higher altitude; b. please put more discussion portion on altitudinal related matters since one of the interesting cliam is the different result of correlation between altitude and plant height in this study, which sounds interesting because its not in concordance with the common global phenomena of plant ecology that plant height at higher altitude tend to be shorter than in the lower altitude.
Second, this is just my guess (and maybe due to limited data variation in this study also), it seems that there is an interaction effect between land use type and altitudinal factor to explain the abundance, height, and cover of T.minuta in the context of this study. Thus, I suggest two main methods to clarify the results:
a. group the data into several cluster based on the combination of altitude and land use type, then conduct ANOVA analysis and further analysis (post hoc such as Tukey) to identify the most significantly different combination between altitude and land use type on explaining abundance, height, and cover of T.minuta in the study site; b. collect extra plot sampling data for area without the occurrence of T.minuta, then conduct the compare and contrast analysis of those species composition and diversity based on used index in this study between plot with T.minuta versus plot with no T.minuta (do this if possible, if not then limit to the point "a" only)
The detail comment based on the in-text review were provided as pointer in this following list:
1. Line 59-60 : "In China, T. minuta was first recorded as a naturalized species in the central mountainous area of Taichung City, Taiwan, in 2006 (Wang & Chen, 2006).". Since recognizing managing pathway is essential for KMBGF (CBD)global target of IAS management, its better to state explicitly what is the first objective/means of introduction of this species to China
2. Line 79-81: "In the section from Nyingchi to Shannan along the Yarlung Zangbo River in southeastern Xizang, T. minuta has become a seriously invasive plant species and has the potential to further spread into the original habitats.". Apart from the invasion phenomenan of T. minuta, it will be more comprehensive if the author also state and elaborate the argumentation of why the studies location is important from biodiversity conservation point of view
3. Line 84-86: "Therefore, this study aims to systematically investigate the species diversity distribution characteristics of the invaded communities of T. minuta under different elevation gradients in the section from Nyingchi to Shannan along the Yarlung Zangbo River.". There is not explanation or elaboration in the introduction about why and what already done in the IAS plant ecology studies in the context of elevational gradient. Please elaborate and add it in the introduction
4. Line 86-88: "It also aims to explore its invasion dynamics in southeastern Xizang, including characteristics such as the height, abundance, and cover of T. minuta." If the height, abundance and cover of T. minuta that were studied in this study, I think we can not simply claim it as the study of invasion dynamics. If we also collect similar data for similar ecosystem condition with the absent of T.minuta, then we can compare the differences between invaded area versus non-invaded area of T.minuta
5. Line 93: In the subtitle 1.1 Overview of the Study Area, to be more comprehensive and detail, also add the background information about the ecosystem, not only the climate and abiotic factor only
6. Line 104-105: "A total of 31 invaded quadrats were surveyed, each measuring 2 m × 2 m.". What is the justification of the sampling number (31)? did the author assessed the representativeness of the sampling number using species-area curve?
7. Line 117-118: "Data analysis was performed using Microsoft Office Excel 2010 and R v4.3.3 software for data organization and calculation of diversity indices". Add references for Excel and R. Also, what package did the author used to calculate diversity indices? (add the package reference also)
8. Line 119-121: The complete linkage clustering method was used to classify the 31 community quadrats into three clusters.". Just to clarify, was the three cluster is resulted from the hierarchical processes or the three cluster is the objective of the clustering processes? what parameter/variables that used to estimate/construct these three cluster? i cannot find it in the methods part
9. Line 124: "The results were visualized using Origin 2021.". Add reference for this software
10. Line 229-231: "The coexistence of multiple invasive plants may lead to competition for resources among them, but it may also enhance their invasive capacity against local ecosystems through synergistic effects.". Please add references for this statement
11. Line 308-312: "Chen Xiaoyan et al. (2022) showed that, with the increase of the altitudinal gradient, the population cover of Galinsoga quadriradiata did not show significant changes, but its plant height decreased significantly. This result is consistent with the findings of the present study regarding cover, but is opposite to the results of the present study in terms of the relationship between altitude and plant height.". Regarding this statement, i think author need to clarify two things. First, what is the possible explanation for this different correlation between altitude and plant height in this T.minuta studies? Second, is the data of this study cover enough data variation of altitude? (cover 700 m dpl data range (moreless from 2800'ish m dpl to 3500'ish, but with most of the data concentrated in lower altitude)
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