Ash Trees (Fraxinus spp.) in Urban Greenery as Possible Invasion Gates of Non-Native Phyllactinia Species

Round 1

Reviewer 1 Report

As well as their great amenity value, Fraxinus spp are very important constituents of forestry and the natural environment. They are under great pressure from ash dieback disease and so it is important to know whether the powdery mildew identified as Phyllactinia fraxinicola indigenous to Asia could spread and further weaken ash populations in Europe. Thus your paper will be of great interest to plant pathologists especially those concerned with diagnosis and Plant Health

I commend you for clearly showing that, under the present world climate, P. fraxinicola is not a threat for ash trees over the bulk of Europe, although limited areas in north west Scotland and Norway could be at risk. However, I suggest you add a caveat that the situation is very likely to change as global warming continues to increase.

I am disappointed that you have provided very little morphological data to support the Scholler statement that morphology does not help to distinguish the two Phyllactinia spp. You only cite one example where P. fraxinicola was misidentified as P. fraxini. In the case of P. fraxinicola, it would have been of great interest to see if any variation in morphological data reflected the considerable variation you have shown amongst the specimens of this species in regard to their genetic sequences. You should point out that morphological data could be helpful in identification if it is deemed necessary to split the apparently complex species of P. fraxinicola  

I have highlighted many necessary corrections on the returned pdf. The English is mainly good but needs attention in several places. In particular, the need to insert a definite  article ('the') or indefinite article ('a' or 'an'). I strongly suggest you study definitions and use of these articles on the Internet before submitting future texts for publication.

Table S1.  It would be better to include  this in the text of the manuscript as it is referred to in the caption for Table 2 and Fig 4

Fig 2. Delete the intrusive 'Fig 27455'

Fig 3. Insert a clearly marked border between a,c and b,d and strengthen some colours in the coloured legend to make a clearer distinction between land and the water of lakes and seas.

Fig 4.  Delete the coloured triangular chart. It is difficult to interpret and the information is clearly provided in the text

Finally, please also address the several other corrections I have highlighted in the returned pdf

Comments for author File: Comments.pdf

Author Response

Authors responses are in the attanched file, 

we are very gratefull to the reviewer for positive view of our manscript, his comments and the grammar corrections

 

Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors, 

you cited my study (Scholler et al. 2017) and took this study as a major basis for your invasion study on Fraxinus powdery mildews. From this point of view I may be able to comment on this manuscript. However, I am not familiar with the modelling and mathematical methods. This will hopefully be done by another reviewer.

The intention of your study ist great and this kind of research is urgently required. I accept your result on the non-existence of Ph. fraxinicola in Europe (confirming Scholler et al.). But I cast some doubt about the bioclimatic variables and the non-overlapping of niches of the two species and that only the humidity-prefering Ph. fraxinicola may occur in Norway and Scotland. 

In the following I will explain this. The major problem is the sampling:

A. Ph. fraxinicola consists of at least two different species which has already been shown by Takamatsu at al. (2007) and Scholler et al. (2017) (and does not require Fig. 2). Therefore finding bioclimatic variables for modelling potential distribution areas should have been carried out for both branches (species) of Ph. fraxinicola separately (see phylogeny in Fig. 2 in Scholler et al. 2017). 

B. The authors did by far not study all available specimens (there are specimens missing from many herbaria, e.g. northern European ones) and therefore did not obtain the full range of bioclimatic variables and consequently of the full potential distribution of the two species. For instance, there are records of Ph. fraxinicola from Russia and Iran (see Braun & Cook 2012) or from Ph. fraxini from Northern Europe (see Braun 1995) which were not checked or sequenced . 

C. If the full distribution data were considered the environmental niches in Fig. 4 would most probably have overlapped. For instance, according to Fig. 3a Phyllactinia fraxini may not be able to occur in the atlantic coast of Norway where Phyllactinia fraxinicola may potentially occur because of high humidity and rarely very low temperatures. Phyllactinia fraxini, however, is known to occur in Norway on F. excelsior (Braun 1995: 217). So if the authors have sequenced specimens from Norway and Scotland and considered bioclimatic data the result would have been different. 

D. There is no statement on the natural distribution area of Phyllactinia fraxini. Is it native of East Asia or is it introduced? This information is a major basis for the discussion.

I recommend authors to ask for loans and to sequence further herbarium specimens especially from Scotland and Norway (for sure, the herbarium in Edinburgh has collections from Scotland and Oslo has collections from Norway)(you did not ask for loans from these herbaria). You should also check specimens of Ph. fraxinicola from Iran (possibly it is  Ph. fraxini) and Russia. And maybe you will find somebody in China or elsewhere in East Asia who can provide additional specimens of Phyllactinia fraxinicola s. l. If these criteria are fulfilled and data available I think this will be a very good study of major importance. 

I hope you submit it again! When submitting again, please think about certain figures and if they are really necessary, these especially accounts for  Fig. 1 with the color triangle and for Fig 2 (a simple phylogeny will do it).  

Good luck

 

 

 

  

 

 

 

 

Author Response

Authors responses are in the attanched file, 

we are very gratefull to the reviewer for positive view of our manscript and all his comments

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript “Ash trees (Fraxinus spp.) in urban greenery as possible invasion gates of non-native powdery mildews (Phyllactinia spp.)” presents a comprehensive analysis on the distribution of two powdery mildew species using molecular data and bioclimatic variables. The paper is interesting and largely well written. However, I have some comments, which should be addressed:

• First of all: The title of the paper is misleading, because the work essentially deals with only two Phyllactinia species. The title sounds too broad.
• The introduction lacks the background of the whole complex of environmental niche and its analysis.
• Discussion: often discussed problems with habitat modelling and niche analyses are sampling biases. This topic should be considered in the discussion. Use of samplings that are spatially biased can result in over-representation of certain environmental features.

Some minor details:

Introduction

page 1, line 34: better shrub than scrub?

Page 1, line 41; reference 6 is a poorly choosen one: the paper doesn’t tell anything about diseases.

Page 2, line68-69: Sentence is unclear. Do you mean: Records morphologically identified as P. fraxini are questionable and were not...?

Page 2, line73-74: The second part of the sentence (…and implications of molecular methods revealed…) is unclear; rephrase this part of the sentence.

Table 1: Prior acceptance, the authors should make sure to deposit the sequence data to NCBI and also mention all identifiers in the paper.

Results 

Page 9, line 264-282: Please, italicize species names.     

Author Response

Authors responses are in the attanched file, 

we are very gratefull to the reviewer for positive view of our manscript and all his comments

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

I have provided my knowledge to review the manuscript. The authors improved the manuscript, but the major questions remain. I noticed that the other reviewer is not a biostatistic expert either. As annotated, this manuscript needs a reviewer who can study and evaluate sampling, computer programmes and statistics. That's what I recommended to the editors.

Author Response

Dear reviewer,

I see down some unanswered question of the reviewer.

I am sorry that I overlooked it. We really appreciate your comment, but it is out of our comptence to choose the reviewer. I proposed reviewers who participated on similar studies using modeling of Maxent data, but I guess they did not accept the review. I believe that current comments of academic reviewer were more relevant to statistical support, we improved explanation of missing data from West Europe by amplicon sequences reported from Norway and Scotland, however, both are from areas modeled in our study as moderately or more suitable for P. fraxini. On opposite, sequencing of Fraxinus leaflets from Spain from area with low suitability for the species failed to recover any Phyllactinia amplicon. 

We would welcome and do the best to improve statistics if they are some relevant notes ... 

thank you again for your effort to improve our manuscript and quality of scientific outputs, we appreciate it

Slavomir Adamcik