Dear authors and editor,
This manuscript relates to a study investigating the functional differences between native and non-indigenous fouling species and how such differences may translate into habitat and temporal differences on fouling community assembly. The authors observed that the two types of species indeed differ functionally, with NIS relating more to colonizing traits, like strong attachment and short life-span (although not all of them), while native species were more related to competitive traits, like planktotrophic larvae and long life-span. No differences between habitat types were observed, despite they differ taxonomically, but a temporal signal was observed, with different trajectories among sites. The main questions and aims are deeply relevant and original in a world connect by marine traffic and, therefore, I think this manuscript is relevant and interesting to Diversity and Distributions readers. However, I’d like to suggest some changes that will improve the manuscript before recommending it to publication. First, although the aims are well presented, I really missed grounded hypothesis with clear expectations. Second, at some parts, mainly in the abstract, I missed a more detailed explanations regarding the functional differences observed. Merely saying that something differed is not sufficient and I guess, after reading the manuscript, that the authors can do a good job on letting it clear to the reader what are the functional differences observed between NIS and native species and on temporal context. Finally, I really missed an articulation between the results obtained with neutral and niche-based processes, mainly because these two theoretical bodies are frequently mentioned in the abstract and introduction, making the base of authors arguments, but weren’t brought back to the discussion and conclusions. Below I list these and other suggestions and questions.

Abstract
L9 – I guess it is beneficial to already mention here which are the two habitats investigated, instead of giving this information some lines below.
L14-16 – Please, give the directions of such differences. It is to vague to only expect that they will diverge. It will be a more grounded hypothesis if you briefly mention which traits we would expect to be more related to NIS, cryptogenic and native species.
L17-24 – Here I miss some more brief details about the differences. Again, it seems to vague to only mention that, overall, they differed. Only traits related to competitive ability were used? What were the functional temporal differences?
L25-30 – I believe that these conclusions were derived from the study results, however it is too general and it seems more like an overall theory about how niche-based and neutral process regulate biological communities. I suggest to build a better and clearer relationship between the study results and the conclusions.

Introduction
L122-125 – The goals of the study are very clear and coherent with the well-written introduction. However, I missed clear hypothesis and expectations about the species type, habitat and temporal comparisons. What king of traits do the authors expect to find on NIS vs. native species? What about habitats and successional stages. I suggest to them to build grounded hypotheses and detailed expectations in order to pave the set to the reader.

Methods
L166-174 – I really liked the approach and think it is useful. However, I can see it fitting pretty well for some traits, like feeding habit, motility, degree of attachment, but not for all of them. For example, for larval development it seems to me that a given taxon will only assume 4 for one of the three modalities and 0 for the other two. Is that a problem? I suggest to explain it better, give examples and clarify if it is ok to have these different degrees of fitting of the 0 to 4 approach for different traits/modalities.

Results
FigS3 – Please check the color coding for this figure. I believe that the colors for floating and non-floating structures are switched in comparison to the map and the main figures in the manuscript.

Discussion
L372-374 – Did the authors consider that the substrate of the experimental panels may act as a trait filter for both native and NIS species?
L380-381 – Authors said that “a majority of taxa could not be identified at the species level”, but before they also said “at the lowest taxonomic level (generally species)” (L146-147). Please, be consistent.
L398 – I was surprised to see no mention here, also no discussion at all, about neutral and niche-based processes and how they may help to explain the patterns observed in this study. This was an expectation given that the authors mention those theoretical concepts right at the Abstract and along the entire introduction.