I have carefully read and reflected on this Perspective piece, and I must say that I found it both engaging and thought-provoking. The manuscript is well written, clear, and introduces a compelling framework to quantify the spatial insurance of ecological functions within a metacommunity. It offers a promising contribution to Ecology Letters. That said, I provide below several suggestions and reflections (some more important, and some less, ordered as they came to my mind and not by importance) that I hope the authors will find constructive, and that could help sharpen the framework further, conceptually, empirically, and practically to increase its uptake by other scientists.

1) One of my first thoughts was about how this concept of functional insurance compares to that of functional redundancy. A community with high functional redundancy would naturally serve as a strong source of functional insurance. In this light, the reasoning in L 50-52 comes across as a bit circular or even tautological: the conclusion that functionally distinct species are less insured seems to follow directly from the way functional distinctiveness is defined. If a species is functionally unique, then it's perhaps expected that it cannot be easily insured /replaced by others in the same or nearby communities.

2) Another key non-trivial aspect that deserves more attention is how meta-communities are defined in space (e.g., Line 114). If there's frequent dispersal between neighbouring areas, it may be misleading to treat them as independent communities. It’s also important to consider that insurance does not operate instantaneously. There is a temporal component within spatial insurance as well, especially in systems where species need more time to colonize or establish in disturbed nearby patches.

3) L119: I also found myself wondering about the assumptions behind colonization and function replacement. The whole framework relies on the idea that species with similar traits can functionally substitute for each other, and that if a species is lost in one site, a neighbouring species with similar attributes may step in. But this depends on a lot of unspoken assumptions: that colonization is possible, that the habitat remains suitable, and that functional analogs can actually establish and perform the same role. For example, I’d be cautious about including habitat loss as a disturbance that insurance can buffer (L119). If a forest is converted to farmland, no amount of seed dispersal will help recover forest-specific functions. Perhaps it's worth clarifying that the insurance concept here assumes environmental continuity, at least in terms of colonization filters.

4) In the last part you introduce the importance of response vs. effect traits, but I think it is important to introduce them first, as this distinction is key when talking about species that can overcome the perturbation (i.e., different response traits), but can still be a functional analogue of the previously present species (i.e., different effect traits).

5) I found the distinction between outward and inward insurance to be a key strength of your framework. However, I think categorizing communities into sources or sinks (Lines 168, 285, 337) leads to a significant loss of information. It ignores the fact that a community can have high values for both inward and outward insurance (or low for both), and that the absolute values matter. For instance, a community with 100% inward and 70% outward insurance might be grouped together with one having 20% inward and 1% outward. This dichotomy oversimplifies what is in reality a continuum of functional roles. Instead of classifying communities, I suggest emphasizing the continuous nature of both inward and outward insurance.

6) In line with keeping the relative importance of outward vs. inward insurance, a useful additional metric could be a normalized imbalance index, such as (Outward - Inward) / (Outward + Inward), ranging from -1 (pure inward) to +1 (pure outward). This keeps the intuitive directionality but retains magnitude. Alternatively, a log-ratio (e.g., log(Outward/Inward)) could be informative, depending on your goals. But overall, I would encourage readers to think in two separate dimensions (or axes), one for outward insurance potential and another one for inward insurance potential, as communities can be key in both aspects and still be categorized as “intermediate” in your current framework.

7) In Fig. 4, the high outward insurance of coastal areas in the U.S. may be the result not from their ability to insure others, but from their unique species being absent inland due to ecological filters (i.e., very low inward insurance, so higher relative outward insurance == sources) (?).

8) Your framework could also benefit from empirical checks on how your inward and outward insurance metrics correlate with simpler measures, such as the proportion of shared species between communities. I would be very curious to see how strongly inward/outward insurance correlates with inward/outward taxonomic similarity. If the relationship is strong, it may suggest that your measures are largely tracking species turnover (which isn’t bad, but would be worth acknowledging). The correlation might grow stronger as more traits are included in the functional space, which raises interesting implications for dimensionality of the trait space (i.e., more traits, functional diversity closer to taxonomic diversity).

9) Another important idea worth highlighting is that “source” communities may actually be more vulnerable, particularly if they host functionally unique species (Line 285–290). These communities may appear robust by having high outward insurance, but may simultaneously be poorly insured themselves, and susceptible to functional loss. The role of species richness is also critical here. Rich communities are likely to have more functionally distinct species, which increases their insurance role but could make them internally more fragile (i.e., less insured within them).

10) L290 onward: Indeed, especially because the proportion of functionally rare (distinct) species in a community is correlated with the richness of the community, so if we control for richness we might inadvertently also correct for the proportion of distinct species, which plays an important role in the insurance.

11) A more technical suggestion: the definition of neighbours and therefore the radius of influence (the size of the metacommunity) can strongly affect estimates of both inward and outward insurance. Some guidance on how to choose that radius, or how sensitive the results are to this parameter (now there are suggestions about how to chose the radius of the functional overlap in species functional space), would greatly help those seeking to apply this framework. I also wonder if you could incorporate distance-based weighting (e.g., via a Gaussian kernel), to reflect the fact that nearby communities are more likely to provide insurance than distant ones (and therefore, overlap with nearby communities is more important). Including weights could alleviate the problem of defining a metacommunity size.

12) From a usability perspective, I strongly encourage you to release an R package with the functions used in your framework. This would go a long way toward increasing the reach and impact of the work, and would allow other researchers to easily integrate this framework and metrics into their study systems.

13) The conclusion of the manuscript (Line 609 onward) could be refined to focus more tightly on what the current paper delivers, rather than anticipating too many future developments that are not yet part of the framework. I would bring attention back to the strong conceptual contribution made here, and encourage future work without overpromising directions not yet developed.

Finally, a few small notes:
• Please avoid red/green color palettes in figures, as they are difficult to distinguish for color-blind readers.
• Minor typos: Line 55 (“an new” → “a new”); Line 393 (double comma); some minor repetition between Lines 63–66 and 96–97.
• Line 73–75: This section would benefit from a few references to ground the statements.
• Line 290: Clarify the distinction between community size and richness, if they do not mean the same here.
• Line 337: reiterating here, categorization could be replaced or complemented by continuous measures.
• L415: this result is very counterintuitive for me. Can you elaborate on this result?

The authors have responded well to the comments. While some points were discussed rather than implemented (e.g., the implications of effect vs. response traits still appear at the end), the explanations provided are reasonable, and I am therefore generally satisfied with the revisions. Overall, I believe the manuscript will make a valuable contribution to Ecology Letters.