Birdfoot Violet (Viola pedata) in a Minnesota USA Dry Bluff Prairie: Population Assessment of a Preferred Host Plant of the Threatened Western Regal Fritillary Butterfly (Argynnis idalia occidentalis)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you very much for the opportunity to review this manuscript. The paper investigates the population assessment of Viola pedata as a host plant for the threatened western regal fritillary butterfly in Minnesota. The topic is relevant for conservation biology and prairie restoration. However, several aspects of the manuscript need to be improved before it can meet the requirements for publication. The main issues are outlined below.

• Abstract too detailed; lacks a sharp statement of objective and main implications.
• Introduction does not clearly define the research gap or novelty.
• Methods mostly clear, but random plot selection and possible permits/approvals not specified.  Specify how the five 0.25 m² plots in the “middle” of the prairie were randomly selected, define “middle of the hillside” and the randomization approach to avoid ambiguity. If any permits or approvals were required (e.g., collecting seed on public land or working with a threatened species), include a statement to that effect
• Results presented, but figure references inconsistent (e.g., “Figure caterpillar”), and data interpretation limited. Double-check that all figures and tables are labeled and described adequately: figure captions should explain the content (e.g., axes, legends, symbols), and Table 1’s caption should fully describe its data. The data itself (means ± SE, confidence intervals, etc.) are useful, just ensure all units and statistical terms are defined or contextualized for the reader
• Discussion is unclear and fragmented; lacks structured comparison with similar studies. Little explanation of how results align or contrast with previous research.
• Novelty of the study is not explicitly highlighted; authors should state what this work adds beyond existing literature.
• No explicit discussion of limitations, which is needed to assess robustness of findings.
• Practical implications are only briefly mentioned; stronger connection to restoration and conservation strategies would add value.
• No standalone Conclusions section; MDPI requires clear conclusions summarizing findings, novelty, and applications.
• Make final formatting tweaks to adhere to MDPI guidelines. All scientific names (e.g., Viola pedata, Argynnis idalia occidentalis) should be in italics. Check figure and table labels/captions for MDPI style (figure captions go below figures, table titles above tables, and use sentence case capitalization). In Figure 7’s caption, correct the grammar (“observed feeding on leaves” instead of “observing feeding on leaves”).

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Title: Birdfoot Violet (Viola pedata) in a Minnesota USA Dry Bluff Prairie: Population Assessment of a Preferred Host Plant of the Threatened Western Regal Fritillary Butterfly (Argynnis idalia occidentalis)
Manuscript Number: conservation-3862832

General Overview

This manuscript presents a field study of Viola pedata populations in a Minnesota bluff prairie, with the dual objective of quantifying violet abundance, reproductive output, and potential for seed collection to support restoration projects benefiting the western regal fritillary butterfly. The research is regionally relevant and provides useful baseline data for conservation planning. The manuscript is generally well organized, with solid descriptive work, but several issues limit its impact. The main shortcomings include: (1) limited novelty given existing prairie–violet–fritillary studies, (2) modest sample sizes in reproductive monitoring, (3) incomplete integration of results with conservation literature, and (4) several instances of unclear or redundant phrasing. Addressing these concerns would strengthen the scientific contribution and enhance clarity.

Major comments:

Clarify the study’s novelty in light of prior Iowa and Missouri work.

Provide stronger justification for choosing a single site and discuss limitations of generalizability.

Expand discussion of pollination limitation and conservation implications.

Revise figures for clarity and better linkage to text (Figures 4–6).

Section-by-Section Comments

Abstract

Concern: The abstract is overly quantitative, listing several detailed values (e.g., “0.52 seed pods/plant”) that may overwhelm readers.

Suggestion: Summarize patterns (e.g., “seed set was low, with fewer than one pod per plant”) and emphasize ecological implications rather than precise statistics.

Introduction

Sentence structure is complex when describing pollination and seed dispersal. Consider simplifying for clarity.

The statement that fritillary success “is largely dependent on abundant and healthy populations of birdfoot violet” should be supported with stronger citation context; contrast with evidence where other Viola species are used.

The discussion of reintroduction strategies is helpful but repetitive; streamline references to avoid redundancy.

End the introduction with a clearer research objective and hypothesis, e.g., “We aimed to determine whether a small but dense violet population could provide sufficient seed for restoration without compromising population viability.”

Study Site

The description of WWMA management is detailed; consider shortening or moving some background (e.g., recreational uses) to supplementary information.

Quantify why dry bluff prairies are unique compared with other prairie types—add references on their conservation value.

Methods

Justify the decision to focus on only one site; acknowledge that small sample size reduces broader inference.

Clarify whether quadrat placement was random along transects or strictly systematic. Readers need to know if sampling may bias density estimates.

Only five plots were monitored for phenology; this seems limited. Acknowledge this limitation.

The seed mass measurement method is sound; however, explicitly state whether seed drying conditions were standardized to avoid moisture variation.

Results

Report confidence intervals more consistently; some estimates are given with ± values while others are not.

Provide statistical support (variance or standard error) for differences in density across slope zones.

Weather conditions are well described but could be condensed; focus on events most relevant to plant performance.

The phenology dataset (27 plants) is small; emphasize that findings are preliminary.

Figures 4–6: Improve readability—legends are dense, and color schemes may not be accessible to colorblind readers.

Discussion

The claim that small prairies can support large populations is interesting. However, temper the conclusion by noting that persistence depends not only on density but also on pollination and genetic diversity.

Expand on why pollination rates were so low (<20%). Discuss potential absence of pollinators, effects of weather, or self-incompatibility mechanisms.

Compare seed counts more explicitly with prior Missouri data; explain ecological significance of lower maxima at this site.

Suggest experimental approaches for future work (e.g., pollinator surveys, hand-pollination trials) to confirm causes of low reproduction.

Conclusion

Concern: The conclusion restates results rather than synthesizing implications.

Suggestion: Emphasize that although dense populations can exist in small prairies, reproductive limitation may hinder long-term viability; therefore, management should consider enhancing pollinator habitats or planting companion species.

Minor and Editorial Points

Replace “Violales: Violaceae” with “Violaceae” (modern taxonomy).

Rephrase “herptofauna” to “amphibians and reptiles” for clarity to general readers.

Change “with less than one out of every 10 plants ultimately producing a seed pod” to “with fewer than 10% of plants producing a seed pod.”

References: Ensure consistency in style; some citations include full URLs in text while others do not.

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Manuscript Title: Birdfoot Violet (Viola pedata) in a Minnesota USA Dry Bluff Prairie: Population Assessment of a Preferred Host Plant of the Threatened Western Regal Fritillary Butterfly (Argynnis idalia occidentalis)
Manuscript Number: Conservation-3862832

Overview and General Assessment

This revised manuscript provides a population study of Viola pedata within a small dry bluff prairie in southeastern Minnesota and evaluates its potential role as a host plant resource for restoration projects aimed at supporting the threatened western regal fritillary (Argynnis idalia occidentalis). The subject is both ecologically and conservation-wise significant, as the persistence of fritillary populations is closely tied to the availability of suitable violet hosts.

Compared with the original submission, the revised manuscript shows substantial improvement in terms of clarity, methodological detail, and integration of literature. Figures have been better explained, methodological limitations are more explicitly acknowledged, and discussion of conservation implications is now more nuanced. However, there are still issues with phrasing, overstatement of results, some statistical gaps, and limited contextualization with broader prairie restoration literature.

Major comments:

While the study highlights the surprising density of violets in a small remnant prairie, the single-site, single-year scope limits the generality of conclusions. This is acknowledged in the discussion but could be emphasized more strongly in the abstract and conclusion.

Pollination success and reproductive output remain central to the findings, yet the study design (five small plots) is underpowered. The limitations should be more clearly tied to cautious interpretation.

Statistical treatment is minimal—confidence intervals are provided, but no formal tests comparing subsets of data (e.g., densities across slope positions) are reported. This weakens claims of spatial variation.

The revision incorporates more recent literature (e.g., USFWS 2024), but a stronger link to prairie management strategies (fire, grazing, invasive control) could enhance the practical application.

Section-by-Section Comments

Abstract (Lines 10–28)

L12–14: Clarify that the population was assessed only during one growing season (2021). Current phrasing may mislead readers into thinking this was a multi-year study.

L20–23: The claim of >62,000 plants is striking; suggest explicitly noting this is an extrapolated estimate.

L24–27: The conservation implication is important; however, overgeneralization should be avoided—suggest modifying “even small bluff prairies… may sustain” to “some small bluff prairies… under certain conditions may sustain.”

Introduction (Lines 32–77)

L47–55: Strengthened literature review is appreciated. However, inclusion of regal fritillary dependence on different Viola species would benefit from a brief note on regional differences.

L68–76: Nicely revised to justify the study, but please emphasize that this is a preliminary single-site assessment, not a regional survey.

Study Site (Lines 78–109)

L82–92: Clearer description of WWMA’s conservation role is helpful. Suggest shortening slightly to keep focus on study site rather than broad management.

L93–102: Excellent context about dry bluff prairies. However, could add one or two references comparing their ecological distinctiveness with larger prairie systems to underscore their rarity.

Methods (Lines 110–184)

L118–120: The limitation of studying a single site is acknowledged. Suggest reinforcing how this affects broader conclusions.

L130–139: Transect and quadrat design is now more clearly described. Good improvement. However, include rationale for choosing 5 m spacing instead of finer or coarser intervals.

L141–147: The decision to monitor only five plots is acknowledged, but this severely limits statistical power. Strongly recommend tempering any claims of representativeness in Results and Discussion.

L177–183: Indirect estimates of seed collection are creative, but methods should be justified further—otherwise they may appear speculative.

Results (Lines 185–258)

L188–190: Reported confidence intervals are useful, but consider including variance across slope sections to better support spatial heterogeneity claims.

L191–197: The revised figures (Fig. 4–5) are helpful, but the narrative could explicitly describe whether clustering patterns are statistically significant.

L208–215: Good integration of climatic data; however, the interpretation of plant response to specific temperature events should be more cautious given small sample size.

L229–231: Low seed pod formation is a central result; emphasize again the limitation of small monitoring plots.

L243–250: The calculation showing seed collection represented <1% of total output is a strength of the paper; clearly highlight this in the discussion.

Discussion (Lines 259–340)

L267–274: Important contextualization with larger prairie studies. Suggest clarifying that although density was higher than expected, long-term viability depends on genetic diversity and pollination success.

L299–307: The pollination limitation discussion is much improved. However, consider referencing more recent pollinator decline literature in the Upper Midwest.

L309–318: The statement that violets “may be relatively rare simply due to low reproductive success” is overstated—reword to “low reproductive success may contribute to rarity.”

L321–325: Excellent suggestion for future pollinator-focused studies. Could also add note on management strategies (e.g., interplanting with co-flowering species).

Conclusions (Lines 341–367)

L342–356: The limitations are acknowledged, but the cautionary tone should be even stronger. At present, the conclusion still reads as if small prairies are definitively useful seed sources, whereas results only suggest potential.

L361–365: The recommendation to enhance pollinator habitat is excellent; could be expanded with specific practical measures (e.g., forb-rich seeding, staggered burns).

References (Lines 378–448)

Updated references are well integrated. However, ensure consistency in formatting (e.g., italics for species names).

Overall Evaluation of Revision

Clarity: Substantially improved; most sections rewritten for smoother flow.

Rigor: Methods and limitations better explained, though statistical analysis remains minimal.

Literature integration: Stronger, with inclusion of recent sources.

Figures and tables: Much clearer and more explanatory.

Author Response

Please see the attachment.

Author Response File: Author Response.docx