Reproductive Ecology of the Invasive Alien Shrub Pyracantha angustifolia in the Grassland Biome, South Africa

Round 1

Reviewer 1 Report

Dear authors

It is a good work that includes an exhaustive experimental design, with which they get to know the weakest phase of the life cycle of this species and propose its management according to these results. Many of us would like to have such a complete study of invasive plant species in our protected areas.

The introduction justifies very well the type of work to be developed and the methodology details the different sections sufficiently to understand and evaluate each one. However, there are some aspects that could be better reported or justified:

1- Regarding the count of visitors in the flowers, I don't know if they have made 8 min in total per bush or 1 min in each bush, which would only be 8 min count. The authors specify that the work was carried out on sunny days, thus with adequate conditions for pollinators. But 9-13 perhaps is a too wide time, since I suppose that during the first hours the visitor’s activity is not so high than latter.  Please, can justify the sense of this so longer time? On the other hand, they should explain the advantages of counting only 1 minute in 80 observations, it seems more efficient to spend more time on a lower number of bushes? In addition, the area used for counting is not specified. So I’m not understand how the number of flowers visited per minute is calculated without having a defined surface. On the other hand, how many individuals are we talking about? This data is not included.

2- Regarding the number of individuals to determine the fruit set. Eight branches of 4 bushes seems a very low number to detect self-incompatibility, this could be justified with some bibliographical reference or better explained.

3-To investigate fruit set on open branches, 44 branches were used, but only 32 for self-incompatibility??. Please clarify this apparent difference

4- The work is well presented and the results adequate to the subsequent discussion of the main conclusion. However, there is a problem with the texts in Figure 4, since they are a bit blurry and it is not easy to read. Could be improved.

Overall, a good job

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

This study aims to determine the drivers of Pyracantha angustifolia thorny shrub invasion in the high elevation grasslands of South Africa by investigating its reproductive ecology with the emphasys of its pollen and seed production and dispersion capacities. The plant reproductive traits analysed provide an effective information source that can be used to assist in the management of this alien invasive plant. The authors have taken a special care to describe in detail the methodology used to collect, describe and analyse the raw data.

text editing :

-l101 : "imperial data" : empirical data

-l129 :  "a souces of vitamin C" : sources

-l160 : "into considerationas the interest ws on flowers" : into consideration as the interest was on flowers

-l173 : " to collect pollen e deposited on the insect’s body" : to collect pollen deposited on the insect’s body

-l204 :"After flowers has senesced and during the early development" : After flowers had senesced and during the early development

-l287 : Error! Reference source not found.

-l327 : "Statistically significant differences were also determined in Kruskal-Wallis tests Kruskal-Wallis statistic followed by Dunn's multiple comparison test using GraphPad Prism 5" : Statistically significant differences were also determined in Kruskal-Wallis tests followed by Dunn's multiple comparison test using GraphPad Prism 5

-l401-l403 : (Table 1) : I assume this refers to Table S1, but there is no Table 1 in the whole manuscript and the numbering of the tables starts with the number 2.

-l 422 : "(see supplementaty information Figure S2).)" : (see supplementary Figure S1).

 

-l555-556 : "seeds m2 " : seeds per m2

-l635 : "fnding" : finding

Figure & Table editing:

-figure 3 : figure doubled, probably due to a layout error

-Table 2 : "m2/million seeds" : million seeds/m2

-Table S1 : please, provide a column size suitable for reading full species names

Comments :

2.3. Pollen loads : a picture of the pollen load collected from an insect and showing the detailed morphology of Pyracantha angustitifolia pollen could complete the description of the methodology used.

 

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 3 Report

This is a useful paper that examines the reproduction niche of the invasive shrub Pyracantha angustifolia in a Grassland area of South Africa.  This is a widespread and damaging weed in South Africa and many other countries, so understanding how it spreads is an important aspect of the ecology of the species and how it is invasive.

The authors show that the flowers are visited frequently by generalist pollinators, but are at least partially self-pollinating, so unlikely to be pollen limited. Flowers are also numerous, and as a result produce a very large number of seeds.  The seed rain is quite localised however, and the seed bank is short-lived so infestations ought to be controllable with sustained effort at priority sites.

The paper is well-referenced, and well-constructed, though I thought it is possibly a but longer than it needs to be.  I have made some suggestions of where some economies could be achieved as annotations directly on the PDF that I will return along with this report.

The methods of research are appropriate, and the statistical analysis is good and well presented. 

I can see that a lot of time and effort went into estimating the seed production of each shrub and this part of the study was done with a great deal of rigour.  It did seem slightly disproportionate however, and takes a lot of page space to explain the methods and to present the results.  I think that much of the methodology as well as figures 4 to 6 could be moved to supplementary material with Table 2 containing the ecologically important information left in the main body of text as a good summary of these results. 

Other than that, my suggestions are mostly minor corrections and suggestions for improving the clarity. Please see the annotated PDF for details.

Comments for author File: Comments.pdf

Author Response

Please also see attachment

 

Reviewer 3

This is a useful paper that examines the reproduction niche of the invasive shrub Pyracantha angustifolia in a Grassland area of South Africa.  This is a widespread and damaging weed in South Africa and many other countries, so understanding how it spreads is an important aspect of the ecology of the species and how it is invasive.

 

The authors show that the flowers are visited frequently by generalist pollinators, but are at least partially self-pollinating, so unlikely to be pollen limited. Flowers are also numerous, and as a result produce a very large number of seeds.  The seed rain is quite localised however, and the seed bank is short-lived so infestations ought to be controllable with sustained effort at priority sites.

 

The paper is well-referenced, and well-constructed, though I thought it is possibly a but longer than it needs to be.  I have made some suggestions of where some economies could be achieved as annotations directly on the PDF that I will return along with this report.

 

The methods of research are appropriate, and the statistical analysis is good and well presented.

 

I can see that a lot of time and effort went into estimating the seed production of each shrub and this part of the study was done with a great deal of rigour.  It did seem slightly disproportionate however, and takes a lot of page space to explain the methods and to present the results.  I think that much of the methodology as well as figures 4 to 6 could be moved to supplementary material with Table 2 containing the ecologically important information left in the main body of text as a good summary of these results.

 

Other than that, my suggestions are mostly minor corrections and suggestions for improving the clarity. Please see the annotated PDF for details.

Response:

Thank you, all grammatical corrections have been accepted and suggested changes implemented. Please see the responses below for full details on changes.

 

Reviewer 3 responses on pdf document

 

Comments and responses

 

Line 24: exponential increase?  Decreases can be exponential as well

Response:

"Exponentially increased relationship" added to clarify that the relationship is increasing exponentially

 

Line 26: is it further improved with hand pollination or natural pollination?

Response:

We have added that natural pollination resulted in higher fruit set (91%).

 

Line 55: what do you mean by social?

Response:

Social referred to group of plant species in this case. “social” has been removed to avoid confusion.

 

Line 71: is this really data or can it be referenced to a source?

Response:

It is data from unpublished questionnaires and has thus been cited as unpublished data

 

Line 98: is this supposed to be Wooton & Mcalpine 2015 as in the reference list or is the reference list wrong and should include Wotton 2000?

Response:

Reference corrected to "Williams et al 2001"

 

Line 193-194: don't think you need the formula or lines 191-192.  It is pretty self-explanatory.

Response:

line 193-194 “The higher the Pp value, the more P. angustifolia pollen was found on the insects’ bodies relative to pollen from other plant species” deleted

 

Line 199: presumably before any buds had opened?

Response: Sentence "The branches were bagged before any buds had opened" added for clarity

 

Line 277: add H - the plant's overall height

Response: "H refers to the fruiting height of the plant" added at the end of the figure header to clarify on H

 

Line 344: not in reference list

Response: Reference added "Holmes, P.M., 2002. Depth distribution and composition of seed-banks in alien-invaded and uninvaded fynbos vegetation. Austral Ecology 27, 110–120."

 

Line 367: if the seeds were tested for viability they would no longer be intact so not suitable for burial experiments - please clarify?

Response: Seed tested for viability were not the same seed used for burial experiment. “Before the seeds were, buried a sub-sample of 400 seeds were tested for viability, all were viable”  added for clarity.

 

Line 401: these two paragraphs should be reduced in size and let the tables speak for themselves.  The sample size for each visitor can be stated in the table and doesn't need to be stated in the text as well.  The main thing to mention is the pollen purity.

Response: List of insect species and sample size removed on the paragraph to reduce the paragraph size as suggested by the reviewer

 

table 1 seems to be missing?

Response: Table 1 is actually Table S1, it has been added to supplementary information

 

Line 489: in-fruit might be a better descriptor than intact which implies to me something about  the viability of the seed

Response: "whole fruits" used instead on "intact seeds"

 

Line 503 Table 2: why does the total not equal the addition of loose and intact seed?

Response: There was a mistake on calculations and the data were re-analysed. The total is now equal the addition of loose and intact seed.

 

Line 552: autonomous selfing is the most likely explanation for seed set in a bag - why do you separate these terms here?

Response: The term has been combined to "autonomous selfing". It was originally separated because autonomous selfing is different to facilitated selfing which was probably happening in the bags from the bags touching anthers.

 

Line 555: why cite this paper here?  A review would be more appropriate

Response: Reference "Ashraf, A., Hassan, A. and Nawchoo, I.A., 2022. Reproductive ecology of Epilobium hirsutum L. an invasive alien species in Kashmir Himalaya. Vegetos, pp.1-13(35), pp910-922." replaced by "Stout, Jane.C., Erin Jo Tiedeken, E.J.,  2017. Direct interactions between invasive plants and native pollinators: evidence, impacts and approaches. Functional Ecology, 31, pp.38-46"

 

Line 568: how does this tally with the average of 2 million line talked about on line 556

Response: "...least 5 million seeds per square metre in all sites" changed to "...least 1.7 million seeds per square metre in all sites."

 

Line 606: should this be Wilson & Witkowski as on line 790 in the reference list?

Response: Citation "Witkowski and Wilson, 2003" corrected to "Wilson and Witkowski, 2003"

 

Supplementary information Figure S1: no letters above bars

Response: “Different letters above the bars indicate statistical significance (P<0.05)” changed to “There were no statistically significant differences (P>0.05) in the proportion of fruit set between bagged and open branches”

 

Supplementary information Table S1: column formatting needs attention to reduce/eliminate wrapping - perhaps lansdscape orientation

Response: Table S1 page changed to landscape

Author Response File: Author Response.pdf