Rare Primate Rhinopithecus bieti Can Sustain the Resilience of Montane Forests

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript presents a comprehensive ecological study on the black-and-white snub-nosed monkey (Rhinopithecus bieti) and its role as an ecosystem engineer in temperate coniferous forests of the Yunling Mountains. The study is ambitious, methodologically diverse, and conceptually innovative. It offers valuable insights into primate-driven forest dynamics, canopy architecture, and conservation theory.

However, several sections require refinement to improve clarity, methodological transparency, and scientific precision.

 

1. Introduction

The introduction provides a clear rationale for investigating the ecological role of rare species, with a specific focus on Rhinopithecus bieti. The authors successfully contextualize their study within broader debates in conservation biology and ecosystem management. However, several aspects of the section would benefit from refinement to improve clarity, logical flow, and scientific precision.

The statement “there is a lack of empirical support” is accurate but could be strengthened by specifying which taxa or ecosystems are underrepresented in empirical studies.

The description of R. bieti includes relevant biological, ecological, and conservation details.

The comparison with Propithecus edwardsi could be useful if could be expanded to explain why this parallel is ecologically meaningful?!

The mention of unpublished population data (3,500 individuals) should be qualified or supported by a citation or institutional source to ensure transparency.

The characterization of the monkey’s appearance (“clown-like eyes, mohawk hairstyle, pinkish-red lips”) is vivid but may be overly informal for a scientific manuscript. A more neutral description would be preferable in this context.

The discussion of forest canopy gaps and their ecological significance is appropriate and well-integrated. However, the sentence structure in this section is occasionally awkward (e.g., “to helping to preserve biodiversity…”), and should be revised for clarity.

The transition from general forest dynamics to the specific behavior of the monkeys is logical, but the speculative nature of the claim (“we speculate the monkeys may impact the canopy…”) should be framed more cautiously, especially since the study aims to test this hypothesis.

The final paragraph clearly states the hypothesis and outlines the study design. However, the phrase “optimizes the forest community structure” is vague and should be replaced with more precise ecological terminology (e.g., “enhances structural heterogeneity and species diversity”).

 

2. Materials and Methods

Areas for Improvement:

Some justification for methodological choices is missing (e.g., 5-minute focal intervals, timing of solar radiation measurements).

Grammatical and stylistic inconsistencies (e.g., “due to they rarely…” should be revised to “because they rarely…”).

Redundant phrasing and inconsistent unit formatting (e.g., “20×20 m” vs. “20m×20m”).

Lack of detail on how external factors (e.g., wind, small animals) were controlled in branch-breakage comparisons.

 

3. Results

We suggest that the subtitles be reformulated so as not to be confused with the study's conclusions, using formulas like:

”3.1 Canopy Pruning Behavior”

The average number of branches broken per day (12.3) is compelling, but it is unclear whether this figure represents a mean per individual or per observation session. Clarifying the unit of analysis would improve transparency.

The attribution of branch-breaking to movement (52%) and feeding (43%) is useful, but the remaining 5% is unaccounted for. It would be helpful to specify whether these were ambiguous cases or associated with other behaviors (e.g., play, aggression).

 

”3.2 Sub-Canopy Environment”

Correlations between canopy gap size and microclimatic variables are well presented.

The non-linear trends in temperature and humidity require deeper ecological interpretation.

 

”3.3 Changings in Forest Structure and Vertical Stratification”

The causal link between monkey absence and reduced regeneration should be framed cautiously.

The term “adventitious species” is used ambiguously and should be clarified (e.g., non-native vs. opportunistic colonizers).

The role of monkeys in seed dispersal is plausible but not directly evidenced in this study.

The suggestion that monkeys promote seed dispersal through movement and feeding is plausible and supported by prior literature [15], but direct evidence from this study is not presented. The authors should clarify whether this is a hypothesis or an observed pattern.

Define ecological terms (e.g., “adventitious species”) and avoid ambiguous phrasing.

Expand discussion of alternative explanations for observed patterns, especially in historical habitats.

 

4. Discussion

Areas for Improvement:

Terms like “optimize forest structure” and “promote forest health” should be replaced with more precise ecological language.

The extrapolation of long-term effects (up to 20 years) should be supported with clearer evidence or qualified as an inference.

The feasibility of reintroducing locally extinct species should be discussed in terms of ecological, genetic, and logistical constraints.

The proposal for a global map of surrogate species is compelling but would benefit from concrete implementation examples.

 

5. Conclusions

Areas for Improvement:

Avoid overgeneralization and idealized phrasing.

Clarify distinctions between observed results, inferred mechanisms, and conceptual proposals.

Define key terms (e.g., “moderate disturbance”) and ensure consistency with ecological theory.

 

Final Recommendations

Revise stylistic inconsistencies and improve academic language throughout the manuscript. Replace informal or anthropomorphic descriptions with neutral scientific language.

Clarify the source and reliability of population estimates.

Strengthen the hypothesis statement by using precise ecological terms and avoiding speculative phrasing.

Consider adding a brief summary of the study’s broader implications to reinforce its relevance.

Comments on the Quality of English Language

Revise stylistic inconsistencies and improve academic language throughout the manuscript. Replace informal or anthropomorphic descriptions with neutral scientific language.

Author Response

Comments and Suggestions for Authors

The manuscript presents a comprehensive ecological study on the black-and-white snub-nosed monkey (Rhinopithecus bieti) and its role as an ecosystem engineer in temperate coniferous forests of the Yunling Mountains. The study is ambitious, methodologically diverse, and conceptually innovative. It offers valuable insights into primate-driven forest dynamics, canopy architecture, and conservation theory.

However, several sections require refinement to improve clarity, methodological transparency, and scientific precision.  

1. Introduction  

The introduction provides a clear rationale for investigating the ecological role of rare species, with a specific focus on Rhinopithecus bieti. The authors successfully contextualize their study within broader debates in conservation biology and ecosystem management. However, several aspects of the section would benefit from refinement to improve clarity, logical flow, and scientific precision.

Comment 1：

The statement “there is a lack of empirical support” is accurate but could be strengthened by specifying which taxa or ecosystems are underrepresented in empirical studies.

Response 1: Yes, this sentence is revised as “However, empirical evidence supporting the functional roles of rare species—particularly large mammals in biodiversity-rich mountain ecosystems—remains insufficiently documented.” in Line 71-73.

Comment 2:

The description of R. bieti includes relevant biological, ecological, and conservation details.

The comparison with Propithecus edwardsi could be useful if could be expanded to explain why this parallel is ecologically meaningful?!

Response 2:

Thank you for your valuable comment on the comparison between the studied monkey species and Propithecus edwardsi. We fully agree that clarifying the ecological significance of this parallel would strengthen the description. Below, we provide a revised section that elaborates on the ecological relevance of this comparison, which is incorporated into the manuscript, enhancing the manuscript’s contribution to worldwide conservation biology.

Line 88-91: "These species’ similarities condition suggest shared conservation challenges. As frugivorous arboreal primates, they may play critical roles in forest ecosystems. Understanding their ecological function could inform restoration strategies for both species and ecosystems.”

Comment 3:

The mention of unpublished population data (3,500 individuals) should be qualified or supported by a citation or institutional source to ensure transparency.

Response 3: Yes, “unpublished data from Institute of Eastern-Himalaya Biodiversity Research” is added in Line 83.

Comment 4:

The characterization of the monkey’s appearance (“clown-like eyes, mohawk hairstyle, pinkish-red lips”) is vivid but may be overly informal for a scientific manuscript. A more neutral description would be preferable in this context.

Response 4:

Thank you for your insightful feedback regarding the description of the monkey’s morphological traits. We appreciate your concern about maintaining formal scientific language while conveying the species’ distinctive features. In response, we have revised the sentence to adopt a more neutral and taxonomically appropriate description while preserving the critical information that underpins its role as a flagship species.

Revised sentence in Line 94-97:

"The monkey has been designated as a flagship species to support regional biodiversity conservation due to its visually distinctive morphological traits, including striking ocular pigmentation, an upright fur pattern on the crown, and pronounced pinkish-red lip coloration."

The revised phrasing retains the key message that these traits make the species an effective flagship species (due to high visual recognition) while adhering to formal academic standards.

Thank you again for your constructive feedback.

Comment 5:

The discussion of forest canopy gaps and their ecological significance is appropriate and well-integrated. However, the sentence structure in this section is occasionally awkward (e.g., “to helping to preserve biodiversity…”), and should be revised for clarity.

Response 5:

Yes, the sentence is revised as “Forest canopy gaps play a critical role in facilitating ecologically sustainable forest management by inducing changes in key environmental factors such as light intensity and soil humidity. These alterations promote biodiversity preservation, enhance nutrient cycling efficiency, maintain the structural complexity of forest ecosystems, and support the regeneration of tree species, collectively reinforcing the adaptive capacity of forest ecosystems [16-17 ]. ” in Line 106-111.

Comment 6:

The transition from general forest dynamics to the specific behavior of the monkeys is logical, but the speculative nature of the claim (“we speculate the monkeys may impact the canopy…”) should be framed more cautiously, especially since the study aims to test this hypothesis.

Response 6:

Thank you for your insightful feedback on clarifying the logical transition and caution in presenting speculative claims. We have revised the text to emphasize that while our observations of monkey behavior suggest a potential mechanism for canopy disturbance, the ecological significance of this role requires explicit framing as a hypothesis to be tested. The revised phrasing now (Line 111-116): “Forest managers must consider the role of natural disturbance in forest canopy dynamics. Through field observations, we documented that monkeys spend a majority of their time in the canopy, where they frequently break branches during movement and feeding. While such behaviors may contribute to canopy gaps, the ecological implications of these actions remain speculative. Therefore, we propose the monkeys may act as agents of structural disturbance in temperate coniferous forests."

Comment 7:

The final paragraph clearly states the hypothesis and outlines the study design. However, the phrase “optimizes the forest community structure” is vague and should be replaced with more precise ecological terminology (e.g., “enhances structural heterogeneity and species diversity”).  

Response 7:

Yes, the sentence is replaced by “the monkey increases canopy gaps which changes the sub-canopy environment and enhances structural heterogeneity and species diversity, i.e. resulting in more heterogeneous vertical stratification, higher species diversity across tree, shrub, and herb, and healthier tree demographic structure. ” in Line 119-122.

2. Materials and Methods  

Areas for Improvement:

Comment 8:

Some justification for methodological choices is missing (e.g., 5-minute focal intervals, timing of solar radiation measurements).

Response 8:

Yes, these justification are added.

Line 169-172: “Based on our experience, a 5-minute interval focal sampling ensures capturing a sufficient number of events during periods of high behavioral occurrence frequency while avoiding the omission of sudden behavioral events that could be missed due to excessively prolonged intervals. ”

Line 260-262 : “Based on the pre-experiment, a 30-minute interval effectively captures changes in light intensity while balancing data recording density with storage capacity.”

Comment 9:

Grammatical and stylistic inconsistencies (e.g., “due to they rarely…” should be revised to “because they rarely…”).

Response 9:

Yes, “due to they rarely...” is revised to “because they rarely...” in Line 177.

Comment 10:

Redundant phrasing and inconsistent unit formatting (e.g., “20×20 m” vs. “20m×20m”).

Response 10: Yes, “20m×20m” is revised as “20×20 m” in Line 198, 218.

Comment 11:

Lack of detail on how external factors (e.g., wind, small animals) were controlled in branch-breakage comparisons.  

Response 11: Yes, details are added in Line 231-235: “Diameter and length of broken branches on the ground with a diameter greater than 1 cm were measured. Through sustained observational studies in this region, we found that branches broken by monkeys typically exceeded 1 cm in diameter, whereas those damaged by wind or smaller fauna (e.g., rodents) were consistently thinner than 1 cm.”

3. Results  

Comment 12:

We suggest that the subtitles be reformulated so as not to be confused with the study's conclusions, using formulas like:

“3.1 Canopy Pruning Behavior” 

The average number of branches broken per day (12.3) is compelling, but it is unclear whether this figure represents a mean per individual or per observation session. Clarifying the unit of analysis would improve transparency.

The attribution of branch-breaking to movement (52%) and feeding (43%) is useful, but the remaining 5% is unaccounted for. It would be helpful to specify whether these were ambiguous cases or associated with other behaviors (e.g., play, aggression). 

Response 12:

The subtitle is revised as “3.1 Canopy Pruning Behavior”.

The unit of analysis of branches broken is clarified as “An adult monkey breaks an average of 12.3 branches a day based on daily observation session” in Line 293.

The remaining 5% attribution of branch-breaking were associated with other behaviors (e.g., play, aggression), as added in Line 293.

Comment 13:

“3.2 Sub-Canopy Environment”

Correlations between canopy gap size and microclimatic variables are well presented.

The non-linear trends in temperature and humidity require deeper ecological interpretation.  

Response 13: The subtitle is revised as “Sub-Canopy Environment”

We have added the following paragraphs in Line 323-324 to interpret the possible mechanisms of the non-linear trends in temperature and humidity: “...as small gaps increase light and warmth without greatly increasing wind exposure/evaporation, while very large gaps lead to greater wind speed and vapor pressure deficit, reducing moisture.”

Comment 14:

“3.3 Changings in Forest Structure and Vertical Stratification” 

The causal link between monkey absence and reduced regeneration should be framed cautiously. The term “adventitious species” is used ambiguously and should be clarified (e.g., non-native vs. opportunistic colonizers).

The role of monkeys in seed dispersal is plausible but not directly evidenced in this study.

The suggestion that monkeys promote seed dispersal through movement and feeding is plausible and supported by prior literature [15], but direct evidence from this study is not presented. The authors should clarify whether this is a hypothesis or an observed pattern.

Define ecological terms (e.g., “adventitious species”) and avoid ambiguous phrasing.

Expand discussion of alternative explanations for observed patterns, especially in historical habitats.  

Response 14: The subtitle is revised as “Changes in Forest Structure and Vertical Stratification”

The account of causal link between monkey absence and reduced regeneration are deleted in the result part, and framed cautiously in the Discussion part in Line 424-450:

“These behaviors thus profoundly affect forest canopy structure, widen canopy gaps and thereby alter the climate conditions of the sub-canopy. In addition, they promote seed dispersal, resulting in a highly diverse plant community along both vertical and horizontal gradients and a pyramidal age structure, with a large cohort of young trees/saplings and few old trees. The role of R. bieti in seed dispersal through food intake is manifested by that the composition of the motherless saplings pool in current habitat match well with its known diet. R. bieti mainly feed on Acanthopanax gracilistylus, Sorbus thibetica, S. scalaris, Padus obtusata, Bothrocaryum controversum, and Meliosma yunnanensis. These young plants appear in the current habitat but were absent in the historical habitat. While the role of R. bieti in increasing plant dispersion through expanding forest gaps is firstly reflected by that, in the current habitat, there are more motherless saplings beyond the monkey’s diet, such as Rhododendron basilicum, R. parvifolium, Quercus spinosa, Pinus armandi, Abies fabri, Tsuga chinensis, Acer pictum and Viburnum dilatatum; while in the historical habitat, the abundance and species richness of motherless saplings were less, only contains Rhododendron basilicum, Abies fabri, Tsuga chinensis. Secondly, for the saplings that have mother plant nearby, saplings were within a distance of 12 meters from the mother plants (mean = 4.3 m, n = 101) in the current habitat, while in the historical habitat H-20, mother-plant saplings were within a distance of 4 meters from the mother plants (mean = 2.8 m, n = 121). The above changes induced by the monkeys’ activities led to a more heterogeneous vegetation structure, which can increase the resilience and robustness of this cold temperate coniferous forest ecosystem [28]. After the removal of this ‘ecosystem engineer’, these benefits can persist for a period of up to 20 years, as the density of trees and young saplings at H-10 and H-20 was not significantly lower than in the current habitat. Moreover, the monkeys utilize their habitat and food resources in a seemingly sustainable way by rotating the exploitation of areas of their home range [12, 29]. ”

Line 389: “adventitious species” is revised as “opportunistic colonizers”.

The monkeys promote seed dispersal through movement and feeding is an observed and proved pattern, as prior literature [15] is conducted in the same study area. This sentence hence is revised as: “In addition, the monkeys themselves also promote seed dispersal through feeding and moving in this area as proved before [15].” in Line 392-393.

Expand discussion of Expand discussion of alternative explanations for observed patterns with comparison between current and historical habitats is added in Line 428-443, as above.

4. Discussion  

Areas for Improvement:

Comment 15:

Terms like “optimize forest structure” and “promote forest health” should be replaced with more precise ecological language.

Response 15: Yes, Line 421-422: “The monkeys have been shown to optimize the forest community and promote forest health.” is revised as “The monkeys have been shown to enhance forest structural heterogeneity and species diversity.”

Comment 16:

The extrapolation of long-term effects (up to 20 years) should be supported with clearer evidence or qualified as an inference.

Response 16: Yes, clearer evidence is added in Line 446-448: ”... as the density of trees and young saplings at H-10 and H-20 was not significantly lower than in the current habitat.”

Comment 17:

The feasibility of reintroducing locally extinct species should be discussed in terms of ecological, genetic, and logistical constraints.

Response 17: Yes, the relative discussion is added in Line 508-516: “To ensure the ecological effectiveness of the reintroduction plan, it is necessary to prioritize the selection of donor populations that have the highest genetic similarity to the historical local population, and establish an ecological corridor network for gene exchange between populations. It is also necessary to confirm that the key habitats in the re-introduction area have been largely restored to the historical baseline level through existing conservation measures; and to quantify the minimum viable population size of the target species and the threshold for their demand for key resources, and ensure the supply of resources in the target area.”

Comment 18:

The proposal for a global map of surrogate species is compelling but would benefit from concrete implementation examples.  

Response 18:

Thanks for acknowledging the proposal of the "Global Flagship Species Map", and suggestion to incorporate specific implementation cases. The following enhancements have been made in Line 480-484: “First, experts will nominate candidate flagship species based on regional ecological contexts to establish an initial list. Second, candidate species will undergo rigorous assessments of their ecological role to prioritize and finalize the list. Finally, a framework will be established for long-term population monitoring and ecosystem surveillance, implementing adaptive management strategies. ”

5. Conclusions  

Areas for Improvement:

Comment 19:

Avoid overgeneralization and idealized phrasing.

Response 19: Yes, We have revised the expressions in the original text that dealt with ecological effects.

Line 522-523: “By breaking branches, widening canopy gaps, and dispersing seeds, the monkeys optimize forest structure, promote seedling survival, and enhance species diversity across vertical and horizontal layers of vegetation.” is revised as “Field observations and forest structural analysis prove that the monkey’s branch-breaking behavior have changed the forest structure obviously.”

Comment 20:

Clarify distinctions between observed results, inferred mechanisms, and conceptual proposals.

Response 20:

Yes, the distinctions among observed results, inferred mechanisms, and conceptual proposals are clearly delineated using the keyword “...observation...prove”, “ ...findings...suggest...” and “In the future...should... ” (Line 520-536).

Comment 21:

Define key terms (e.g., “moderate disturbance”) and ensure consistency with ecological theory.  

Response 21: Yes, definition and relation with ecological theory are added in Line 490-494: “Moderate disturbance is operationally defined as intermittent, non-lethal disturbances that maintain ecological heterogeneity without triggering ecosystem collapse [44]. This aligns with the intermediate disturbance hypothesis, which posits that diversity peaks at intermediate disturbance levels, balancing competitive exclusion and colonization opportunities [44].”‌

Final Recommendations

Comment 22:

Revise stylistic inconsistencies and improve academic language throughout the manuscript. Replace informal or anthropomorphic descriptions with neutral scientific language.

Response 22: Yes, we have revised stylistic inconsistencies and improve academic language throughout the manuscript, and replaced informal or anthropomorphic descriptions with neutral scientific language, including those in Response 4, 5, 14, 15, 16, 19.

Comment 23:

Clarify the source and reliability of population estimates.

Response 23: Yes, the source and reliability of population estimates is clarified as “unpublished data from Institute of Eastern-Himalaya Biodiversity Research” in Line 83 (Response 3).

Comment 24

Strengthen the hypothesis statement by using precise ecological terms and avoiding speculative phrasing.

Response 24: Yes, this is improved as in Response 7.

Comment 25

Consider adding a brief summary of the study’s broader implications to reinforce its relevance.

Response 25:

Thank you for your recognition of the potential influence of this research. We have added a new paragraph at the end of the article, strengthening the cross-disciplinary value and policy significance of the research. The following are the newly added contents ( Line 537-544):

“The ecological engineer effect of rare species revealed in this study has global significance that goes beyond the protection of individual species. With the intensification of climate change and the sharp decline in biodiversity, the traditional conservation model centered on species quantity or endangered status urgently needs to shift towards function-oriented ecosystem management. Incorporating the population recovery of "functional flagship species" into landscape-level ecological restoration plans can simultaneously enhance carbon sink capacity, maintain biodiversity, and improve the ecological well-being of communities. ”

Comment 26

Comments on the Quality of English Language

Revise stylistic inconsistencies and improve academic language throughout the manuscript. Replace informal or anthropomorphic descriptions with neutral scientific language.

Response 26: Stylistic inconsistencies are revised and academic language is improved throughout the manuscript, informal or anthropomorphic descriptions are replaced with neutral scientific language, including those in Response 22.

 

Submission Date    31 August 2025

Date of this review  08 Sep 2025 18:33:24

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript presents a highly interesting and potentially significant study on the ecological role of the endangered black-and-white snub-nosed monkey (Rhinopithecus bieti). The central hypothesis—that the monkeys act as ecosystem engineers by creating canopy gaps—is innovative and important for conservation ecology. The use of a chronosequence of abandoned habitats is a major strength. However, several critical issues must be thoroughly addressed before the manuscript can be considered for publication. The current evidence is compelling but requires deeper analysis and clarification to fully support the broad conclusions drawn. The manuscript would benefit from a more nuanced discussion of mechanisms and limitations. 

1. The authors must include a discussion of this key limitation. If available, any data (e.g., from historical records, soil core analysis, stand age structure from tree rings) that can help validate the comparability of sites should be presented. If such data is unavailable, this must be explicitly stated as a limitation, and the conclusions should be tempered accordingly, framing the results as strong correlative evidence rather than definitive proof of causation.
2. The analysis and discussion should more clearly separate these two mechanisms. For instance, does the composition of the "motherless saplings" pool match the known diet and dispersal of R. bieti? Could the analysis of species richness be broken down to see if dispersed species show a different pattern than non-dispersed species? The discussion should speculate on the relative contribution of each mechanism to the overall result.
3. The authors should provide a deeper interpretation of this result. They should hypothesize why this pattern might occur (e.g., small gaps increase light and warmth without greatly increasing wind exposure/evaporation, while very large gaps lead to greater wind speed and vapor pressure deficit, reducing moisture). This adds a layer of mechanistic understanding that is currently missing.

4. Clarify the behavioral sampling methodology with precise details on interval duration and data synthesis.

5. Acknowledge the limited sample size for specific metrics as a potential constraint on statistical power. Where possible, reporting effect sizes alongside p-values would be beneficial.

6. Introduction: The transition from the general debate on rare species to the specific case of R. bieti is good. Consider adding a sentence explicitly stating that Figure 1 outlines the specific causal pathway to be tested.

7. Figure 2: This figure is excellent but extremely dense. Consider if it could be split into two figures (e.g., one for forest structure/diversity and one for tree demography) for improved clarity.

8. Discussion: The argument for redefining surrogate species based on function is a highlight. Strengthen it by more directly contrasting the findings with the shortcomings of the traditional "umbrella species" concept mentioned in the introduction.

9. The formatting is inconsistent (e.g., italics for journal names, presentation of DOIs). Please standardize throughout according to the journal's guidelines.

10. The reference "Li et al. (2008)" is cited in the text but is missing from the reference list. It must be added.

Author Response

Comments and Suggestions for Authors

This manuscript presents a highly interesting and potentially significant study on the ecological role of the endangered black-and-white snub-nosed monkey (Rhinopithecus bieti). The central hypothesis—that the monkeys act as ecosystem engineers by creating canopy gaps—is innovative and important for conservation ecology. The use of a chronosequence of abandoned habitats is a major strength. However, several critical issues must be thoroughly addressed before the manuscript can be considered for publication. The current evidence is compelling but requires deeper analysis and clarification to fully support the broad conclusions drawn. The manuscript would benefit from a more nuanced discussion of mechanisms and limitations. 

Comment 1. The authors must include a discussion of this key limitation. If available, any data (e.g., from historical records, soil core analysis, stand age structure from tree rings) that can help validate the comparability of sites should be presented. If such data is unavailable, this must be explicitly stated as a limitation, and the conclusions should be tempered accordingly, framing the results as strong correlative evidence rather than definitive proof of causation.

Response 1: Based on this research, data that can help validate the comparability of sites could include the similar plant community composition(Table S3), the same soil component, and the same oldest stand age from tree rings (Figure 3), as described in Line 144-145, 374-382. This indicates that these locations have the same vegetation development history. We believe that these are very strong supporting evidence for the comparability between these locations.  

Comment 2. The analysis and discussion should more clearly separate these two mechanisms. For instance, does the composition of the "motherless saplings" pool match the known diet and dispersal of R. bieti? Could the analysis of species richness be broken down to see if dispersed species show a different pattern than non-dispersed species? The discussion should speculate on the relative contribution of each mechanism to the overall result. 

Response 2:

We fully understand your suggestion to clearly distinguish between the two mechanisms (the feeding behavior of the R. bieti promoting dispersion and the expansion of forest gaps promoting dispersion). We have supplemented the discussion section based on your feedback.

Line 428-443:

“The role of R. bieti in seed dispersal through food intake is manifested by that the composition of the motherless saplings pool in current habitat match well with its known diet. R. bieti mainly feed on Acanthopanax gracilistylus, Sorbus thibetica, S. scalaris, Padus obtusata, Bothrocaryum controversum, and Meliosma yunnanensis. These young plants appear in the current habitat but were absent in the historical habitat. While the role of R. bieti in increasing plant dispersion through expanding forest gaps is firstly reflected by that, in the current habitat, there are more motherless saplings beyond the monkey’s diet, such as Rhododendron basilicum, R. parvifolium, Quercus spinosa, Pinus armandi, Abies fabri, Tsuga chinensis, Acer pictum and Viburnum dilatatum; while in the historical habitat, the abundance and species richness of motherless saplings were less, only contains Rhododendron basilicum, Abies fabri, Tsuga chinensis. Secondly, for the saplings that have mother plant nearby, saplings were within a distance of 12 meters from the mother plants (mean = 4.3 m, n = 101) in the current habitat, while in the historical habitat H-20, mother-plant saplings were within a distance of 4 meters from the mother plants (mean = 2.8 m, n = 121).”

Comment 3. The authors should provide a deeper in terpretation of this result. They should hypothesize why this pattern might occur (e.g., small gaps increase light and warmth without greatly increasing wind exposure/evaporation, while very large gaps lead to greater wind speed and vapor pressure deficit, reducing moisture). This adds a layer of mechanistic understanding that is currently missing.

Response 3: Based on your suggestions, we have added the following paragraphs in Line 323-325 to systematically elaborate on the possible mechanisms by which the size of forest gaps affects temperature and humidity: “...as small gaps increase light and warmth without greatly increasing wind exposure/evaporation, while very large gaps lead to greater wind speed and vapor pressure deficit, reducing moisture.”

Comment 4. Clarify the behavioral sampling methodology with precise details on interval duration and data synthesis.  

Response 4: Yes, interval duration is added in Line 169-172, and data synthesis method is added in Line 173-176:

“Based on our experience, a 5-minute interval focal sampling ensures capturing a sufficient number of events during periods of high behavioral occurrence frequency while avoiding the omission of sudden behavioral events that could be missed due to excessively prolonged intervals.”

“For a continuous period of five-minute observation, conduct continuous behavioral recording of the individual being observed. Record the type of each behavior, as well as the start and end times. Calculate the frequency of each behavior occurrence on a daily basis.”

Comment 5. Acknowledge the limited sample size for specific metrics as a potential constraint on statistical power. Where possible, reporting effect sizes alongside p-values would be beneficial.  

Response 5: Yes, the effect sizes (here refer to standardized difference, SD; correlation measures, R²) are reported alongside p-values where matters (Line 297-299 for the broken branch diameter and length, Line 315 for the canopy gap and so on).

Comment 6. Introduction: The transition from the general debate on rare species to the specific case of R. bieti is good. Consider adding a sentence explicitly stating that Figure 1 outlines the specific causal pathway to be tested.

Response 6: Thank you for your meticulous review of the logical transitions in this article and your valuable suggestions. We have incorporated the following sentence into the text (Line 122-124) as per your advice to clearly illustrate the connection: "Figure 1 systematically summarizes the above-mentioned ecosystem function hypotheses regarding R. bieti and the data content that needs to be collected for hypothesis testing."

Comment 7. Figure 2: This figure is excellent but extremely dense. Consider if it could be split into two figures (e.g., one for forest structure/diversity and one for tree demography) for improved clarity.

Response 7: Yes, this figure is now split into Figure 2 (forest structure/diversity) and Figure 3 (tree demography) for improved clarity.

Comment 8. Discussion: The argument for redefining surrogate species based on function is a highlight. Strengthen it by more directly contrasting the findings with the shortcomings of the traditional "umbrella species" concept mentioned in the introduction.  

Response 8: Thank you for your affirmation of our redefinition of "surrogate species" in this article. We have made the following revisions to the paper based on your suggestions: Line 470-477 “The traditional concept of surrogate or umbrella species aims to maximize species coexistence [41], but it neglects the imbalance of ecological roles among species and does not incorporate the dynamics of ecosystems into conservation goals. In contrast, this study proposes a "function-oriented surrogate species" framework, which shifts the conservation goal from "species quantity priority" to "ecological function priority" by focusing on maintaining key ecological processes, thereby more directly achieving the ultimate biodiversity conservation goal of "self-sustaining ecosystems" [42].”

Comment 9. The formatting is inconsistent (e.g., italics for journal names, presentation of DOIs). Please standardize throughout according to the journal's guidelines.  

Response 9: The formatting of references are standardized throughout according to the journal's model.

Comment 10. The reference "Li et al. (2008)" is cited in the text but is missing from the reference list. It must be added.

Response 10: "Li et al. (2008)" is added as [13] and cited in Line 103.

Submission Date    31 August 2025

Date of this review  12 Sep 2025 02:16:54

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript has been substantially improved in terms of both scientific content and linguistic clarity. Nevertheless, a considerable number of expressions remain uncorrected, and further refinement is needed to replace informal phrasing with neutral, scientific language.

A particularly notable issue is the frequent use of first-person singular constructions throughout the text, which should be avoided in scientific writing. Such instances are found in the following lines: 29, 40, 43, 45, 114, 117, 122, 130, 167, 171, 183, 186–194, 197, 202, 205, 209, 216, 219, 220, 226, 234, 239, 245, 247, 251, 255, 257, 259, 264, 266, 473, 502, and 566.

In conclusion, we wish to reiterate the significant value of the article and emphasize the importance of reformulating certain passages to enhance the clarity and impact of the relevant scientific information.

Comments on the Quality of English Language

We kindly ask you to consider replacing informal descriptions with neutral scientific language.

Author Response

Comments 1:

Comments and Suggestions for Authors

The manuscript has been substantially improved in terms of both scientific content and linguistic clarity. Nevertheless, a considerable number of expressions remain uncorrected, and further refinement is needed to replace informal phrasing with neutral, scientific language.

A particularly notable issue is the frequent use of first-person singular constructions throughout the text, which should be avoided in scientific writing. Such instances are found in the following lines: 29, 40, 43, 45, 114, 117, 122, 130, 167, 171, 183, 186–194, 197, 202, 205, 209, 216, 219, 220, 226, 234, 239, 245, 247, 251, 255, 257, 259, 264, 266, 473, 502, and 566.

In conclusion, we wish to reiterate the significant value of the article and emphasize the importance of reformulating certain passages to enhance the clarity and impact of the relevant scientific information.

Comments on the Quality of English Language

We kindly ask you to consider replacing informal descriptions with neutral scientific language.

Submission Date 31 August 2025

Date of this review 29 Sep 2025 17:41:23

Response 1: Thank you for your constructive feedback and for highlighting the remaining areas requiring refinement in our manuscript. We deeply appreciate your attention to detail and commitment to enhancing the rigor and clarity of scientific communication. We have now systematically revised all instances of "we," "our," and related phrases to adhere strictly to impersonal phrasing. All informal terms (e.g., "boost," "richer," "supporting") have been replaced with precise scientific terminology (e.g., "enhance," "greater biodiversity," "demonstrated evidence of"). Sentences previously framed as subjective interpretations (e.g., "we believe," "it is possible that") have been rephrased to focus on objective observations and data-driven conclusions. Redundant or verbose phrasing has been streamlined to improve conciseness. For detailed modification details, please refer to the following text.

Thank you again for your thorough evaluation. We sincerely hope these revisions meet your expectations and contribute to the publication’s scientific rigor.

Line 29: By comparing areas currently used by the monkeys with those abandoned decades ago, we found that active monkey habitats had more tree gaps (38% vs. 29~33% in abandoned sites), supporting richer plant life.

Revision: Comparisons between currently used monkey habitats and those abandoned decades ago revealed that active habitats exhibited higher tree gap prevalence (38%) compared to abandoned sites (29~33%), which supported greater plant biodiversity.

Line 40: We examined the ecological role of the Endangered black-and-white snub-nosed monkey in China’s temperate mountain forests, hypothesizing that its tree-shaking behavior alters forest structure and microclimates to boost ecological health.

Revision: The ecological role of the Endangered black-and-white snub-nosed monkey in China’s temperate mountain forests was examined, with the hypothesis that its tree-shaking behavior alters forest structure and microclimates to enhance ecosystem health.

Line 43: To assess long-term impacts, we compared current monkey-inhabited forests with historical sites abandoned over decades, analyzing tree gaps, forest structure, and environmental conditions.

Revision: To assess long-term impacts, current monkey-inhabited forests were compared with historical sites abandoned over decades, by analyzing tree gaps, forest structure, and environmental conditions.

Line 45: We also directly observed monkeys’ canopy-disturbing actions.

Revision: Monkeys’ canopy-disturbing actions were also directly observed.

Line 114: Therefore, we propose the monkeys may act as agents of structural disturbance in temperate coniferous forests.

Revision: Therefore, the monkeys were proposed may act as agents of structural disturbance in temperate coniferous forests.

Line 117: We thus hypothesized that the monkey plays a pivotal ecological role in the temperate coniferous forest ecosystem for the following reasons...

Revision: The monkey is thus hypothesized to plays a pivotal ecological role in the temperate coniferous forest ecosystem for the following reasons...

Line 122: We test this hypothesis by quantitatively measuring the monkey’s branch-breaking behavior...

Revision: This hypothesis was tested by quantitatively measuring the monkey’s branch-breaking behavior...

Line 130: Hypotheses relating to the ecological role of the black-and-white snub-nosed monkey (Rhinopithecus bieti) tested in our study.

Revision: “our” is revised as “this”.

Line 167: ... we used the focal sampling and one-zero sampling method [21] to collect data on branch-breaking behavior by the monkeys.

Revision: ...the focal sampling and one-zero sampling method [21] was used to collect data on branch-breaking behavior by the monkeys.

Line 171: Based on our experience, a 5-minute interval focal sampling ensures capturing a sufficient number of events during periods of high behavioral occurrence frequency while avoiding the omission of sudden behavioral events that could be missed due to excessively prolonged intervals.

Revision: Based on observational experience, ......

Line 183: We then tested whether the structural properties of branches broken by monkeys were different from those caused by other factors such as wind and small animals.

Revision: Whether the structural properties of branches broken by monkeys were different from those caused by other factors such as wind and small animals were tested.

Line 186–194: We set up ten sampling quadrats (20×20 m) in the current habitat of the monkey and ten quadrats within a distance of 200 m of current habitat in the spring of 2019, respectively. In each quadrat, we first clean the broken branches out in each quadrat, and ten days later we collected and counted broken branches lying on the ground with a diameter greater than 1 cm and measured their diameter and length. 

We next measured the forest structure and broken branches at five sites in 65 sampling quadrats...

Revision: In spring 2019, twenty 20×20 m sampling quadrats were established: ten within the monkey’s current habitat and ten within a 200-m buffer zone adjacent to the habitat boundary. Within each quadrat, fallen branches were first manually removed to standardize baseline conditions. Ten days later, all branches ≥1 cm in diameter were systematically collected, counted, and measured for diameter and length.

Forest structural parameters and branch characteristics were assessed at the five sites in the 65 quadrats.

Line 197: In each of the five habitats, we set up quadrats in five elevation zones with an interval of 100 m from 3,000 to 3,400 m a.s.l.

Revision: In each of the five habitats, quadrats were set up in five elevation zones with an interval of 100 m from 3,000 to 3,400 m a.s.l.

Line 202: We divided mountain slopes into four directions...

Revision: Mountain slopes were divided into four directions...

Line 205: Thus in every elevation zone, we placed one quadrat on a northern slope, one on an eastern slope and one on a western slope.

Revision: Thus within each elevational zone, quadrats were systematically positioned on three cardinal slopes—north, east, and west.

Line 209: ...we also excluded all records from quadrats on western slopes at 3100 m and eastern slopes at 3200 m of the other four habitats...

Revision:...all records from quadrats on western slopes at 3100 m and eastern slopes at 3200 m of the other four habitats were also excluded...

Line 216: ...we analyzed data from only 65 quadrats...

Revision:...data from only 65 quadrats were analyzed...

Line 219: ...we established 5×5 m quadrats for shrubs and 1×1 m quadrats for herbs...

Revision:...5×5 m quadrats for shrubs and 1×1 m quadrats for herbs were established...

Line 220: We quantified and compared the following variables among the five sites.

Revision: The following variables among the five sites were quantified and compared.

Line 226: ...we found that branches broken by monkeys typically exceeded 1 cm in diameter...

Revision:...branches broken by monkeys were found to typically exceed 1 cm in diameter...

Line 234: We defined young saplings without adult trees of the same tree species in the quadrat as motherless saplings.

Revision: Young saplings without adult trees of the same tree species in the quadrat were defined as motherless saplings.

Line 239: ...we drilled out the core of a tree at a position of 1.5 m above the ground with a tree growth cone...

Revision: ...the core of a tree was drilled out at a position of 1.5 m above the ground with a tree growth cone...

Line 245: We measured the size of canopy gaps by Fisheye hemisphere image analysis.

Revision:The size of canopy gaps were measured by Fisheye hemisphere image analysis.

Line 247: We averaged the measurements from the three photos to obtain a value for the size of a canopy gap in one quadrat.

Revision: Measurements from the three photos were averaged to obtain a value for the size of a canopy gap in one quadrat.

Line 251: we tested the effect of canopy gaps on solar radiation, air temperature and air moisture under the canopy, and the effect of these factors on the vertical structure, species diversity and demographic structure of the forest.

Revision:...the effects of canopy gaps on solar radiation, air temperature, and air moisture under the canopy were examined, along with the impacts of these factors on the vertical structure, species diversity, and demographic structure of the forest.

Line 255: ...we measured solar radiation, air temperature and air moisture in quadrats described in Figure S2 in H-0, H-10, H-20, H-30 and H-40.

Revision:...solar radiation, air temperature and air moisture were measured in quadrats described in Figure S2 in H-0, H-10, H-20, H-30 and H-40.

Line 257: We installed a photometer, a thermometer and a hygrometer in the center of the quadrat.

Revision:A photometer, a thermometer and a hygrometer were installed in the center of the quadrat.

Line 259: ...we calculated the average value of solar radiation at 9:30 am...

Revision:...the average value of solar radiation of days were calculated at 9:30 am...

Line 264: We also calculated averages for air temperature and moisture condition (Table S2).

Revision: Averages for air temperature and moisture condition were also calculated (Table S2).

Line 266: We used a Mantel test [23] to analyse four environmental correlates of the plant community structure.

Revision: Mantel test [23] was used to analyse four environmental correlates of the plant community structure.

Line 473: To improve conservation efficiency, we should create a global map of flagship species, selecting a unique surrogate species for different ecosystems in different geographical regions, such as the Global 200 [43].

Revision: A globally integrated map of flagship species should be developed to enhance conservation efficiency, with each geographic region’s ecosystem such as exemplified by the Global 200 framework [43] represented by a unique surrogate species.

Line 502: We advocate recovering a locally extinct flagship species and using it as a conservation surrogate to maintain the stability and resilience of regional ecosystems as an explicit restoration target in both the short and long term.

Revision: The reintroduction and recovery of locally extinct flagship species should be prioritized as conservation surrogates to explicitly anchor ecosystem stability and resilience as restoration targets across both short-term and long-term timeframes.

Line 566: We maintained observations of the monkeys at a safe distance, ensuring no disturbance to their natural behaviors and any adverse effects on the monkeys or compromise to animal welfare.

Revision: Observations of the monkeys were conducted at a non-invasive distance to minimize disturbance of natural behaviors and ensure compliance with animal welfare standards.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have provided a thorough revision to previous comment. I have no further concerns about this MS.

Author Response

Comment 1: The authors have provided a thorough revision to previous comment. I have no further concerns about this MS.

Response 1: We are extremely grateful for the time and patience you have devoted to improving the manuscript. Wish you all the best!