The Adaptive Capacity of Alien and Rare Species in China

Round 1

Reviewer 1 Report

This study has an interesting concept nicely contrasting adaptive strategies of two key plant groups, invasive and endangered species. There are several issues that should be revised before the paper can be accepted.

It is not clear to me if the authors have considered in this study all alien plants or only the ones that show invasive characteristics. Reading the aim of the paper in lines 113-5 it seems that this study is about invasive plants which have indeed the tendency to widely spread in new environments, but the authors use the term “alien”. However (and importantly) not all alien plants are invasive. I suggest that the authors clearly explain what kind of species they included in their study and carefully revise the list of species they have considered.

Some parts of the methods should be revised. In specific, the trait life form is not well defined, showing a mixture and duplication of terms, see my specific comment below. Also, I suspect that the attribution of dispersal modes might not have been accurately done, at least in the case of endangered plants, which show a rather high percentage of anthropochory (comment below).

Another problem, is the poor use of English which makes many parts of the text difficult to understand. I strongly recommend that the authors have the manuscript read by a native speaker. And also that they carefully reconsider their arguments. Some sentences are difficult to read due to grammar issues but in some cases the problem is also with regard to scientific content. I have indicated below several such cases, but I would advice that the authors carefully revise their arguments with the help of a native English speaker.

I have listed below several comments in specific parts of the text. I hope that these will help the authors improve the manuscript.

Line 18: The meaning of this sentence is unclear. What do you mean with “different conditions”? Please phrase this in a more informative way.

Line 19: I suggest to refer here to “assessments of adaptability” instead of “adaptive assessments”, the latter term doesn’t read well.

Lines 25-32: These three sentences of the results and the first sentence of the conclusions are very repetitive. Please consider rephrasing this part, and perhaps condense it.

Lines 41-43: This sentence is not well-written and does not really support what the authors intend to argue here, i.e. the severe problems caused by invasive species. Please revise it and I also suggest to remove the phrase “relying largely on their high invasiveness (biological attribute)”.

Line 44: I would say that by definition the term endangered plants refers (or should refer) to native plants, so the addition “ mostly native plants” is perhaps redundant here.

Lines 44: Better say “at risk of extinction” (remove “high”). Not all endangered plants are at high risk of extinction.

Lines 44-45: These are indeed some common threats of endangered plants, but there can be more. Better state here that you give some examples of threats. Now it reads as if these are the only threats that endangered plants face.

Lines 45-47:  “Endangered plants cannot adapt to habitat changes”: this is a rather bold argument and it is not supported by the conclusions of any of the three papers cited here. I would suggest to phrase it in a “smoother” way, saying for example that habitat changes resulting from natural and anthropogenic disturbances pose high pressure on endangered plants.

Line 50: “Facilitate to reveal”: awkward phrasing. Perhaps say instead “can help reveal”.

Line 56: It is not really a discussion. Maybe use another term instead, for example “Considering the above, we defined etc.”.

Lines 58-60: However is redundant here. Also, since you mention that there a few studies that have done this, you can consider referring to them here and briefly state their findings. It seems that the same argument is repeated in lines 105-107, consider removing one of the two.

Line 71: “long-term evolutionary outcome to the environment” bad phrasing, unclear what you mean here, please rephrase.

Line 77: “that characterizes plants as an adaptation”: unclear phrasing.

Lines 83-85: “Multi-habitat plants thriving in different habitats may be related in their capacity for anti-disturbance or stress tolerance resulting from habitat degradation and/or fragmentation”. This sentence is unclear. Please rephrase.

Lines 91-98. I would suggest to use “on the other hand”  instead of “conversely” here.

Lines 113-5: Please revise the phrasing of your aim. Reading the aim and the rest of the paper one gets the impression that you are referring to invasive species (see for example also lines 42-43) but you use the term alien. Not all alien plants tend to expand, this would be the case of invasive plants, be clear in what you mean.

Lines 118-9, 145: Collection/collecting is not the right term here. Consider using instead for example “retrieved” or “compiled a list of etc.” What is also not clear is whether these 562 and 1898 species are all alien and endangered species reported for China or a selection of them. Please be more specific in this.

Line 137: The asexual reproduction mode “cutting, layering or grafting” to my understanding refers to artificial vegetative propagation applied by humans on cultivated plants. How does it relate to alien and endangered which grow wild? Maybe the authors would like to explain a bit in the paper what this reproduction mode means in the case of wild plants or perhaps use another terminology.

Lines 143-4: There is a mixture of terminology here. Annual, biennial and perennial refer to life cycle and vine, shrub, tree refer to life form. I wonder how you attributed each species to one of these categories. Isn’t a shrub also a perennial plant? Please reconsider your categorization here.

Line 155: Consider replacing “diverse habitats” with “a variety of habitats” or “various habitats”.

Line 166: Since this abbreviation is mentioned only twice in the manuscript I would suggest to simply write the name of the index instead of the abbreviation.

Line 183: remove one “in”.

Lines 189-191: Obtained and calculated instead of obtain, calculate.

Line 199: It seems quite surprising that the dominant dispersal strategy of Chinese endangered plants is anthropochory, and that more than half of the endangered plants in the country are dispersed by humans. One would expect that many endangered plants live in remote areas, far away from human activity. Later on in the text this becomes evident: In Lines 238-9 it is mentioned that indeed endangered plants are found in remote habitats (rocks and crevices, tree tops, forest edge, shrubland, jungle). I wonder then how it can be that most of them are dispersed by humans. The authors later state that endangered species are sold for agri- and horticulture. I am not familiar with Chinese practices, but is this commercial trade of endangered plants enough to make anthropochory the dominant dispersal strategy of endangered species? I wonder if the species have been assigned properly to dispersal categories. I suggest that the authors carefully revise the attribution of species to dispersal categories.

Figure 1, legend. Line 204-6: revise grammar.

Lines 209-212: Another phrasing would be stronger: For example, most alien species (71.7%) use more than four dispersal strategies (Fig. 1c), while the vast majority of endangered plants use up to three dispersal strategies (92.3%) (Fig. 1d).

Lines 213-5: Again here I wonder what is meant with cutting, layering, or grafting in wild plants, please explain this somewhere in the text.

Line 224: “Most alien plants used one sexual and asexual mode”: There can’t be one sexual and asexual mode. Considering Fig. 2a and c I would say that most alien plants reproduce by one mode, sexual reproduction.

Line 226: “two sexual and asexual modes” replace with “two reproduction modes”, to avoid repetition.

Lines 224-8: The past tense doesn’t seem suitable here.

Figure 3: Again here I wonder why the authors chose this categorization of life forms. There is a high percentage of perennial plants for example in endangered species but looking into the percentages of vines, trees and shrubs (which are also perennials) these are too low. This means that there are many other perennial species (chamaephytes for example) which the authors did not chose to highlight. Is there a particular reason why emphasis is given to vines, shrubs and trees? If yes, then the authors should state this. In any case, another categorization should be chosen for life form to avoid duplication and the mixing of life cycle with life form. Please see also my previous comment.

lines 236-9: Again here the use of past tense is not suitable.

Lines 240-4: Another phrasing would be more powerful, for example: Both alien and endangered plants tend to occupy only a few habitats (up to two, summed percentages 70.8% and 87.8%, respectively) (Fig. 4 c-d). The authors can consider presenting also the rest of the results in this more synthetic way so that the reader can follow their arguments more easily.

Figure 4 legend. Lines 247-9: Check grammar.

Lines 268-9: “the adaptive capacity of the endangered plants in stressful environments (0.22) was significantly higher (F=455.7, p < 268 0.01) than that in the disturbed environments (0.20) (Fig. 6)”: Certainly a p-value below 0.01 is significant but I wonder whether this has been accurately estimated. The difference between 0.20 and 0.22 doesn’t seem remarkable and this is also shown in figure 6, the two bars of endangered plants seem to be almost the same. Also, in the figure legend (line 277) the p value is mentioned as <0.05, and not <0.01. Please revise.

Line 285-6: The study of Zhou et al.  2020a cited here does not deal with endangered plants and therefore does not support the authors’ argument that anthropochory in endangered plants is intentional and resulting from agriculture and garden trade). Please use a more suitable reference. Also, it also seems awkward that the authors consider the commercial trade of crops and garden plants as a mode of dispersal. Does this mean that endangered species are brought to a garden, escape and start colonizing nearby areas? This doesn’t sound as a strategy of a rare species. All in all, I would suggest that the authors elaborate and clarify their arguments throughout the text regarding anthropochory in endangered plants.

Line 296 “Sexual and asexual reproduction modes are crucial for alien and endangered plants”: This statement is a bit vague, sexual and asexual reproduction is important for all plants. It is the presence of both sexual and asexual reproduction modes that supports the expansion of alien plants and the survival of endangered plants. In other words, the ability to have more reproduction alternatives helps these plant groups occupy difficult environments.

Line 303: “Therefore, a higher rate of sexual reproduction etc”: This sentence does not relate to what was said just before (which was about asexual reproduction) to justify the use of “therefore”. Please re-think your argument here.

Lines 305-6: “Despite many of the alien species are both sexual and asexual production, e.g. Sporobolus alterniflorus, Solidago canadensis, Alternanthera philoxeroides”: grammar problem, please revise, the meaning is unclear.

Lines 315-6: “Annuals and biennials, with light and large amounts of seeds,”: unclear and inaccurate meaning. Please change to “The annual and biennial life cycle, and the large amount of light seeds”.

Lines 317-9: Same here, unclear and inaccurate. Consider if this is what you mean: “ the perennial life cycle and tree habit, when accompanied by low germination  or underdeveloped embryo of seeds do not support plant invasion”.

Line 326: “The habitat attributes of alien plants largely depend on their biological characteristics”: meaning unclear, please consider revising.

Line 332: “might be higher”: it is already known that it is higher and you also show it with your results.

Line 335: “strong interspecies competition”: On the other hand, endangered species may occupy these extreme habitats because these habitats are unwelcoming for other species and therefore endangered species have less interspecific competition there. Please look up relevant references in literature.

Line 339-41: The meaning of this sentence seems inaccurate (stable environments with high-stress habitats sounds a bit contradictory). It may also be a problem in grammar that makes this sentence unclear. Please revise what you mean here with the help of an English native speaker.

Line 342: tend to occupy more habitats

Lines 348-50: Again here, not all alien plants are invasive. The authors need to make this distinction and revise their data accordingly.

line 363: “and annuals and biennials in life form” change to “and an annual or biennial life cycle”

lines 365-366: I think that indeed autochory and asexual reproduction could be seen as features of endangered plants, but I am not sure whether shrubs and trees tend to be in general more endangered. In other geographical regions (Europe for example) endangered species are mostly herbs. Maybe the authors would find it useful to consider and mention in the paper reasons why the woody habit could be related with plant vulnerability in the Chinese flora.

Lines 368-70: “endangered plants tend to adapt to […] anthropogenic disturbances”: But your results showed that endangered plants adapt to stressful but not to disturbed environments. Please consider revising, also the use of the phrase “on the brink of extinction” seems redundant and exaggerating, consider omitting it. Not all endangered species face immediate risk of extinction.

Line 379: “As a result”: please remove, what follows is not a result of what was just said.

Line 381: “and face extinction in disturbed environments”. I would rather say that endangered species do not occupy disturbed environments at all. This statement is inaccurate, please remove it.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The authors produced a good study supported by a sufficient number of references and with an analysis supported by an extensive dataset. However, the manuscript will need to be formatted according to the journal's requirements, and I also have a few questions about data analysis.

Citations in the journal Forests are numbered and ordered by first appearance in the references.

L52-L54: Usually do not use one-sentence paragraphs, try to integrate the paragraph into the previous or following one.

L62, L71, L75–L77 and on several other places: This text is in a different font/size, maybe it was written later. Try to unite.

L182: It is not clear how the two-sample Kolmogorov-Smirnov (KS) test was used - either it is used to test the normality of the data (or agreement with another distribution) before analysis or to compare the distributions of two samples (but then it serves as a non-parametric equivalent of the t- test/ANOVA) – how was it used?

L184: ANOVA – is it a single one-way ANOVA, or the results of a two-way ANOVA, in which the effect of one factor (endangered vs. alien plants), second factor (disturbed vs. stressful environment), and especially their interaction was tested?

In addition, most of the results are presented only as proportions - how the proportions of some traits of endangered and alien plants differ. Why not use the individual Chi-square tests here to get some significance? Please present graphs with proportions supplemented with standard error estimates.

Figure 6: Information is missing, whether Standard errors or Standard deviations are displayed.

 

L306-L307: Species names should be italicized

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have revised the manuscript, clarifying some previously obscure parts of the text. They also gave informative answers to the questions raised.

In their response, the authors have given a table which explains the six invasive ranks of alien species. I couldn’t find this table in the submitted supplementary files. Also, in the supplementary file I received the term “endangered” is still used instead of “rare”. Perhaps I received an older version of the supplement, please make sure that an updated version of the supplement is included in the submission. Also, besides giving this information in the supplement, I think it is worthwhile to briefly mention these invasive ranks in the text, stating the percentage of species belonging to each rank so that the reader has an idea of the data that have been used in the paper. The same could be done for the rare species. The authors mention in their response how many species are critically endangered, endangered etc. I think that this information is valuable also for the manuscript itself, as a supplement table and in the text. The authors can consider giving this information at the beginning of the methods section, for example by splitting section 2.1 in two sections, one presenting the ranks of alien and rare species and another for the biological characteristics. Providing this descriptive information about the alien and rare species that have been included in this study will make it easier for the reader to understand also the results and conclusions of this research.

Also, the authors provided some interesting information supporting why anthropochory may be a dominant dispersal mode in Chinese rare plants, for example referring to the high frequency of Orchidaceae and medicinal plants among rare plants which are often cultivated and traded. Again, I think that this information is valuable also for the text. The authors could consider providing some of this information in the discussion of results.

There has been some improvement regarding the use of the English language, but I think that some extra English editing will further help to amend the manuscript.

I provide below few minor comments to improve the text.

line 37: Please rephrase here: “On the other hand, rare plants may be at risk of extinction, if they, for example, etc”

line 38: “always maintain small populations”: “always” seems to be redundant here, please consider removing.

lines 56-57: This sentence is quite unclear. It can be improved by changing to “multiple reproduction modes” and “adapt to new environments”, but I also suggest that the authors revise once more the whole sentence to provide a more clear meaning.

lines 93-95: The authors have rephrased the aim, but still the difference between alien and true invasive species is not clarified. I suggest to rephrase the aim as follows: “Our aim was to answer why the distribution of alien plants may tend to expand whereas that of rare plants tends to stay constant or shrink.”

Line 97-98: My comment here was misunderstood. Please remove the term “retrieved” from line 97 and replace “collected” with “retrieved” in line 98.

Lines 115-6: “representing ability of plants to regenerate”: All reproduction modes represent an ability to regenerate. I suggest to replace this sentence with a more informative one, for example “human-mediated reproduction mode applied to cultivated alien plants”

Line 123. Like above, please remove the term retrieved.

Line 205: This sentence can be further improved, for example as follows: “Sexual reproduction (71.7%) is the dominant reproduction mode in alien plants”

 

Line 275: Change “production” to “reproduction”

Line 289: Like in the aim, I would suggest to remove the term continually, unless the authors have evidence for all alien species treated in this study that their geographical expansion is indeed continuous.

Lines 331-2: The authors have amended this sentence but still the use of the term “extremely” sounds dramatic. Depending on the meaning that the authors want to give here, I would suggest to either remove the term “extremely”, or mention “sometimes resulting in ecological specialization to extremely stressful environments”.

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx