I reviewed the manuscript JEcol-2020-0286 entitled "Pollen transfer networks reveal alien species as main HP donors with fitness consequences for natives". The authors analysed HP transfer networks in nine coastal communities in the Yucatan Mexico that vary in the relative abundance of invasive plants to evaluate how HP receipt and donation varies between native and alien plants. In addition, the authors related whether HP receipt and donation was related to some floral traits, and if the post-pollination success through the proportion of pollen tubes produced, was affected by alien HP receipt and whether the effect varied between native and alien recipients.
I enjoyed reading the manuscript. This is a commendable effort, which is picking up in ecological research community and that aims to understand how plan-plant interactions network through HP transfer networks are structured and what is the role of invasive species in those networks. The authors did a good job in contextualizing, with relevant literature cited, their problem and the aims of the work, which are quite clear. The text reads well, with a few bits that are not totally clear, but should not be difficult to fix (see detailed list in the specific comments below). I think this is a remarkably interesting data set and a valuable work, and I congratulate the work done so far. I hope that the authors find the comments below helpful.

General comments:
I think very good to have a solid theoretical basis, but in some cases, the excess of citations in the introduction, made it difficult to read the text more fluidly...
Lines 64-67: In four lines, seven references were cited, one being cited twice...

Lines 73-74: This recent reference may help to support this part of the introduction: Bergamo, Pedro J., et al. "Pollination outcomes reveal negative density‐dependence coupled with interspecific facilitation among plants." Ecology letters 23.1 (2020): 129-139.
Regarding the questions in the manuscript, I missed a direction, especially in relation to the traits of the flowers.
Lines 135-139: please, insert the species families.
In the section Conspecific and heterospecific pollen transfer and pollination success, I found some points a little confusing. Sometimes I did not understand whether separate samples were made for pollen grains and pollen tube growth, or if only one sampling was performed for the two analyses.
Lines 184-192: 5 minutes/15 minutes day for each plot? I believe if the authors said it was enough. But from my experience, I believe that five minutes is a short time to observe, count the number of flowers visited and collect the insects in a plot, when necessary, for identification. Especially in the case of areas with a great diversity of species. How did the authors control all these functions in five minutes?

In addition, this data was lost throughout the manuscript and was not presented in the results, such as, for example, the groups of pollinators and plant species most visited. How was the pollinator species identified? Taxonomists? Key to species identification?
Line: 205: Include PCA data in supplementary material?
Lines: 236-238 – I think that in this part the biological explanation can be improved
Line: 239: and their respective functions?

Line: 245: Since many methods for calculating modularity are now available, why did you choose this one? For example, Leger et al. (2015), Methods in Ecology and Evolution, 6:474-481 compared different methods and found that the Stochastic block models was the best method to retrieve modules in weighted networks. Authors may consider include a justification of the selected algorithm in Methods Section. How does the algorithm choose by the authors within these options work?

Lines: 249-251: how were these matrices randomized? maintaining connectance? Matrices marginal totals? This also needs to be better explained.

Line 271 – Remove this sentence.
The authors begin the discussion by talking about native pollinators, but this has not been much explored in the results.
Figure 2 and Figure S3: low resolution and I could not read what is written.