This manuscript entitled “Dispersal syndromes in challenging environments: a cross- species experiment” explores trait-distributions in dispersing organisms compared to resident ones under different environmental conditions. The three traits focused on are body size, locomotion morphology and activity. The environmental conditions manipulated are resource availability and predator cues. The authors present a collection of experiments from different labs across different taxa and a set of analyses focusing on a broad picture across experiments and taxa. This is complemented by a modeling approach that aims at investigating implications of a subset of patterns discovered with the empirical approach. Over all, this manuscript presents an impressive data set and fascinating results (and an even more impressive size of a supplement…). I see great value in the insights and the data the authors present. Frankly, I don’t think I could improve the manuscript from a technical perspective. I would, however, like to share my perspective regarding the communication of the findings.

I have some general remarks and some minor points below (the line numbering as well as page numbering was a bit difficult, did my best).
In general, I was missing a bit more visual guidance to help me understand and follow the experiments and the implications of the empirical findings (Figure 1 is very nice though). It may be a matter of taste, but I prefer an illustration of key findings/implications over tables of statistical outputs.
I would have liked to see a more concise overview of the several experiments and the relevant measures used for the three different traits in the different taxa. Even if it is just a table in the supplement. For instance, I found “distance moved in a given time” at first glance not very convincing as a proxy for activity and it could have been easier to find for which organisms this was used.
I found it extremely fascinating that resource availability seems to drive large bodied organisms to disperse, but predator cues seem to drive those with locomotion-oriented morphology to disperse. It does not seem to be very straightforward to understand why this is and thus, the discussion around this and the correlations of the traits (e.g. Fig 2) fell too short for me. In the results, especially the part about the modeling results, quite a bit of methodology seems to be repeated. Maybe this could be shortened and the discussion could be extended, potentially supported by an illustration replacing one of the tables?
Moreover, I really do like the addition of the metacommunity model. I think it is very valuable to explore the implications of empirically uncovered patterns in this way, rather than just speculating. The authors predominantly focused on one relationship they uncovered, namely that resource availability driving the body size patterns in dispersers. I would have liked to see the other traits and dimensions as well, but I understand that this manuscript is already large enough. However, I feel that first, the implications of that body-size-resource-availability pattern is only loosely integrated into the manuscript, especially in the discussion, and second, does not strike me to be what the main take-home message is about.
Despite these points, I still enjoyed the manuscript and think it has a lot of potential.

Minor points:

Page 6 L12: Core gap statement is a bit complicated. “It is yet to be determined if and how different, and particularly challenging, environmental conditions (e.g., competition with conspecifics and predation risk), shape dispersal syndromes across a wide range of species.”

Page 7 L47: Multi-patch system? As far as I understood it was usually two patches (three for the fish) - being clear on this early on may improve comprehensibility.

Page 9 L14: Distance traveled = activity?

Page 9 L21: (xxx) was probably on purpose, but don’t forget.

Page 14 L40 FF: bit much repetition of methods

Page 17 L14: The sentence before argues that a more locomotion-oriented morphology enables organisms to better escape predators while dispersing - this sentence though seems to argue that a more locomotion-oriented morphology would increase predation risk - why would they not also be better in escaping within the patch?

Legend Fig 2: red/blue ribbons/area; not bar.

The definition of a disperser depends on its success - what if it is just a success bias by the morphological traits rather than a trait difference for dispersers? This is probably unlikely, but could be made clearer.

Supplement:

P29: 50 m long protists?

Some equations fell victim to formatting (e.g. equation 2, equation 10? and in text at the top of page 64).

I am reviewing this manuscript for the second time.
I like the new concept figure and the improved integration of the metacommunity model. The authors have addressed all points well. I have nothing more to add and happily suggest accepting this interesting paper.

Kind regards,
Remo Ryser

Typo:
L194: double space after “risk”