Climate Vulnerability Analysis of Marginal Populations of Yew (Taxus baccata L.): The Case of the Iberian Peninsula

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study, grounded in the ecological niche theory and employing an ensemble modeling approach (GLM, GBM, MaxEnt, RF) to predict habitat suitability, yields reliable results.

A key innovation lies in the integration of individual growth data (BAI5) for validating ecological niche model predictions. This creative and valuable approach highlights the connection between climatic suitability and population performance. Furthermore, the focus on rear-edge populations is particularly significant from a conservation perspective. These populations play a crucial role in preserving genetic diversity and understanding species responses to climate change.

The paper is well-structured, presenting a coherent narrative, and the figures effectively support the discussion. Nevertheless, certain areas could be improved to strengthen the study. While the paper acknowledges the limitations of ecological niche models—such as the exclusion of non-climatic factors—a deeper analysis of how these constraints impact the results would enhance its rigor. Additionally, a more thorough exploration of the ecological and managerial implications of the findings would be beneficial, especially in relation to assisted migration or restoration strategies.

Improving methodological transparency by providing more detailed explanations would ensure reproducibility and clarity.

Lastly, expanding the discussion by comparing the findings with other studies on yew or similar species across different regions could enrich the analysis and provide a broader ecological context.

Here are the comments, questions and suggestions

The introduction effectively describes the impact of climate change on plant species and underscores the importance of rear-edge populations. However, it would be beneficial to include a brief explanation of the specific vulnerabilities of yew, such as its slow growth rate, limited dispersal ability, or specific climatic requirements.

Regarding the study's geographic focus, clarification on the rationale behind selecting the Iberian Peninsula would enhance context. Was this choice solely based on its role as a marginal region for yew, or did factors such as data availability or conservation priorities also influence the decision? Addressing this point would provide a clearer understanding of the study’s scope. Additionally, incorporating one or two sentences about the ecological or cultural significance of yew—such as its role in forest ecosystems or historical uses—could help illustrate its broader conservation value.

The methodology is well-detailed, covering data sources (GBIF, WorldClim), modeling techniques, and validation methods. The inclusion of two climate models (CCSM4, HadGEM2-ES) and two SSP scenarios (SSP126, SSP585) is appropriate for assessing climatic uncertainties. Nonetheless, some methodological choices could benefit from further explanation. For instance, why was a spatial resolution of 5×5 km selected for the analysis? Could finer resolutions (e.g., 1×1 km) have better captured microclimatic variations, particularly in mountainous yew habitats? Discussing the advantages and drawbacks of this decision would provide greater insight into its implications. Furthermore, the selection of four bioclimatic variables (bio01, bio04, bio12, bio15) was justified by reducing collinearity (|r| ≤ 0.66). Providing a correlation matrix or a summary of the collinearity analysis in a supplementary file would enhance transparency.

The explanation of pseudo-absence point generation (10,000 points within a 5-km radius) could be expanded. How was the 5-km radius determined, and was a sensitivity analysis conducted to examine how pseudo-absence placement affects model performance? Addressing these points would strengthen methodological rigor.

The use of BAI5 as a population performance index is innovative. However, the reasoning behind selecting a 5-year window instead of other intervals (e.g., 10 years) remains unclear. Clarifying the logic behind this choice would improve the study's justification.

The results are presented clearly, with high AUC values (0.89 for the ensemble model) indicating strong model performance. The spatial patterns of habitat suitability (Figure 2) and vulnerability (Figure 4) are visually compelling and align well with the overall narrative.

A notable finding is the strong influence of precipitation seasonality (bio15), which has a weight of 0.36 ± 0.00 in the ensemble model. Does this suggest a particular ecological sensitivity of yew to seasonal water availability? How does this compare to other forest species in the region? Exploring this aspect could provide insights into the climatic dependencies of yew. Additionally, the minimal increase in habitat area (0.19%) across both SSP scenarios is intriguing. Does this result stem from the species' narrow climatic niche, dispersal limitations, or other constraints? A brief discussion of these factors would help clarify the ecological significance of this finding.

The mixed-effects linear model (LMM) results (Figure 3) reinforce the study’s conclusions by demonstrating a significant relationship between climatic suitability and BAI5. However, variability in BAI5 across populations—potentially driven by site-specific factors—has not been fully examined. Incorporating random effects for population identity in the LMM could enhance the understanding of spatial heterogeneity.

The discussion effectively situates the findings within the broader literature on climate change impacts on forest species. The emphasis on climatic refugia and restoration aligns well with conservation priorities. However, the paper notes that non-climatic factors (e.g., biotic interactions or land-use changes) were not considered. A deeper exploration of how these elements interact with climate change and influence habitat decline could enrich the discussion. Moreover, assisted migration is proposed as a potential strategy (page 11, lines 410–411). Given yew’s slow growth rate and specific habitat requirements, what are the practical challenges or risks associated with this approach?

Comparing yew vulnerability in the Iberian Peninsula with other regions (such as the Hyrcanian forests or Central Europe, based on sources 39 and 53) could illustrate whether marginal populations face unique challenges. Additionally, the section on management implications (page 11, lines 390–419) is concise but could be expanded with concrete recommendations for monitoring (e.g., prioritizing specific populations) or policy measures (e.g., integrating findings into regional conservation programs).

The conclusion effectively summarizes key findings and highlights the need for conservation efforts. Reinforcing the study’s broader applicability—such as its potential use for other marginal or relict species—could enhance its scientific impact. Additionally, briefly mentioning future research directions, including investigations of non-climatic factors or more detailed analyses, would provide a roadmap for further inquiry.

 

Author Response

Dear Reviewer,

The authors would like to thank you for your comprehensive review and for the great help your comments have been in improving the quality of the article.

We kindly invite you to review the new version of the manuscript and the attached file containing the changes made to the manuscript in yellow background to check that your interesting suggestions have been incorporated. In the same way, please read carefully the answers to the comments made on the previous version of the manuscript. We hope that all your doubts have been resolved and that the revised manuscript is to your liking and responds to the aim we set ourselves at the time of writing it.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

I have reviewed the study titled "Climate Vulnerability Analysis of Marginal Populations of Yew (Taxus baccata L.): The Case of the Iberian Peninsula." The study aims to model and assess the climate vulnerability of rear-edge populations of Taxus baccata (European Yew) in the Iberian Peninsula. It specifically analyzes the potential spatial habitat losses of this species under future climate scenarios (SSP126 and SSP585). Although this is not exactly within my core area of expertise, I must say that I enjoyed reviewing the paper and found it valuable.

Nevertheless, I have a few suggestions that I believe need clarification. Firstly, I could not find a strong justification in the introduction section regarding the motivation behind conducting this research. In fact, I believe that several aspects of the study have the potential to fill certain gaps in the literature. These research gaps, motivations, and contributions could be expressed more clearly.

Secondly, I have no major criticism regarding the methodology and dataset. It seems that the use of actual tree growth data in the modeling is a significant contribution.

Thirdly, the authors have not included a separate literature review section. Are there not enough similar studies or scientific projects conducted in a comparable framework? These could have been addressed in a more critical manner to highlight the study’s contribution.

Fourthly, my main criticism is that the discussion section is relatively weak and lacks proper support from the literature. This section definitely needs to be strengthened. For instance, although non-climatic factors such as soil type, forest cover, and land use are mentioned, they are not discussed in detail. Moreover, suggestions such as assisted migration and habitat restoration remain rather generic.

Fifth and finally, the conclusion section could be further developed. It is recommended that this section be enriched with policy suggestions, study limitations, and proposals for future research.

Author Response

Dear Reviewer,

The authors would like to thank you for your comprehensive review and for the great help your comments have been in improving the quality of the article.

We kindly invite you to review the new version of the manuscript and the attached file containing the changes made to the manuscript in yellow background to check that your interesting suggestions have been incorporated. In the same way, please read carefully the answers to the comments made on the previous version of the manuscript. We hope that all your doubts have been resolved and that the revised manuscript is to your liking and responds to the aim we set ourselves at the time of writing it.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for the opportunity to read your valuable study on the vulnerability of Taxus baccata to climate change in backcountry habitats of the Iberian Peninsula using ecological niche modelling.

The implicit hypothesis of the study is clear: climate scenarios significantly reduce the climatological suitability of rear-edge populations and this is related to the performance of individuals. The research question (prediction of climate sensitivity and habitat variability of Taxus baccata) is well defined. However, the hypothesis and the research question are not explicitly formulated in the abstract or the introduction, and it is recommended to be corrected.

The introduction adequately places the topic in the context of climate change ecology. The reference to Hutchinson's ecological niche theory is theoretically sound. While the limitations of ecological niche modelling (ENM) are discussed, the reasons for the choice of yew and the Iberian Peninsula require further explanation. The literature cited is up-to-date and relevant.

The methodology is detailed and consistent: use of 4 models (GLM, GBM, MaxEnt, RF), ensemble methodology (BIOMOD2), thresholding (MTP), and validation (AUC, BAI5). The climate change scenarios (SSP126 and SSP585) were correctly selected.

However, the climate data for the period 1970-2000 are outdated compared to the projections for 2081-2100, and it is worth considering using more recent baseline data (e.g. 1990-2020).

The study adequately discusses the limitations of the ENM methodology. However, a detailed description of the research limitations, especially regarding the risks of applicability (e.g. conservation practice, adaptive management) would be recommended.

The results are clearly structured and the integration of ENM and LMM (BAI5) is a unique strength of the study. The results support the biological validity of the ENM model.

For the conclusions, more specific answers to the research questions are recommended.

The visualizations are informative, especially Figures 2 and 4, and the tables are well organized. However, the textual reference to the figures is weak in some places and clarification of the captions is recommended.

The study is of great importance for ecological modelling, climate sensitivity assessment and conservation planning. The issue of adaptability to other species or regions is only tangentially addressed - it is recommended that this be expanded.

The study is methodologically sound, professionally relevant and scientifically valuable as a contribution to climate ecology research. The integration of modelling and empirical validation is particularly valuable.

The results are highly relevant on several levels:

• At the biogeographical level: the fate of the rear-edge (peripheral) populations of the Iberian Peninsula is crucial for the persistence of Taxus baccata, as these populations often have high genetic diversity and are highly sensitive to climate change.
• In terms of ecological modelling, the combined use of ENM and LMM not only predicts current distribution, but also predicts demographic responses (growth) - a rare and scientifically particularly valuable feature.
• In practical conservation: results can be directly used for habitat restoration, climatic refugia designation and assisted migration planning.

Furthermore, the results are technically consistent with the international literature:

• The sensitivity to climate change, especially in the southern, drier regions, confirms the results of previous research
• The positive correlation between growth and climatological suitability is biologically logical and has been confirmed by a quantitative model.
• The results of the two scenarios (SSP126 and SSP585) realistically reflect future threats and do not exaggerate the risk of species extinction - habitat gain is minimal, reflecting ecological reality.

The results of the study are scientifically sound, statistically validated and can be directly used in conservation and climate adaptation decisions.

 

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

The authors would like to thank you for your comprehensive review and for the great help your comments have been in improving the quality of the article.

We kindly invite you to review the new version of the manuscript and the attached file containing the changes made to the manuscript in yellow background to check that your interesting suggestions have been incorporated. In the same way, please read carefully the answers to the comments made on the previous version of the manuscript. We hope that all your doubts have been resolved and that the revised manuscript is to your liking and responds to the aim we set ourselves at the time of writing it.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I have reviewed the study. There are significant improvements compared to the first draft, but I still have criticisms regarding two issues. Although there have been developments addressing almost all of my criticisms, more can be done. Additionally, I expected the authors to use a clear marking system to indicate the corrections made in the R1 version. Finally, please remove the period at the end of the title and reduce the similarity of the study. I accept the study with minor revisions.

Author Response

Dear reviewer.

Thank you for your re-reading of the manuscript and for your positive assessment of the modifications made to the R1 version. We appreciate your constructive critical view of the new version, but we do not have the elements to address the generic comments you make. Just in case you were not able to check the changes made in version R1 were marked in yellow background in the file ‘forests-3642738_track changes.docx’, we attach this file again in .pdf format to avoid any possible error in the format conversion. This document shows the extensive modification of the manuscript in the R1 version according to the invaluable contributions of all reviewers. We believe that the comments and concerns you raised in the first review have been addressed and resolved, but we are happy to try to resolve any specific issues that you feel have not been satisfied. For example, the suggestion to remove the full stop from the title has been modified in the new version of the manuscript.

Yours sincerely,
The authors

Author Response File: Author Response.pdf