Mammoth Cave: A Hotspot of Subterranean Biodiversity in the United States

Round 1

Reviewer 1 Report

The paper does a good job synthesizing knowledge about the biodiversity of an important cave. As the longest cave in the world and one of the most biodiverse, the intended audience will find this an important reference and it is very appropriate for the special issue to which it was submitted. I recommend acceptance, but would like the authors to consider the following the suggestions.

1. I think the manuscript should be carefully read one more time for syntax, grammar, spelling, etc. I saw a few minor mistakes.
2. Page 1, line 43: is the Girkin Formation really only 3-6m thick? I believe it is thicker...
3. Page 2, line 49: The Chester Upload? I know that Kentucky has some weirdly named geographic features, but maybe check that one.
4. Page 3, lines 78-94: the authors do a good job summarizing the history of biospeleological investigation, but this section is presented as summary of earlier work contributing to our knowledge of Mammoth Cave ecology when in reality, some of that work (I'm thinking, for example, of Barr's work in the 60s) was pretty foundational to our understanding of cave ecology and evolution of troglomorphy more generally. Readers might find it worth highlighting the role that Mammoth Cave biology research played in furthering the field.
5. Page 3, lines 109-113. I'm always nervous about online portals. GBIF data in particular is hard to verify. Were new records generated from these online aggregators, and if so, can those records be verified? As an example, GBIF shows a bunch of Texas terrestrial invertebrates in the Pacific Ocean because someone missed a negative sign on the GPS coordinates in some museum database somewhere.
6. The authors do not include undescribed species in their counts of species. Kuddos for taking the high road, but notice that other authors that contributed to the special issue DID include undescribed species. The editors argued for including undescribed species as a way to better account for uneven taxonomic work across subterranean habitats around the world. The authors should consider doing the same for consistency and comparability, or at least including more reference to undescribed species in the abstract and result (e.g. 'total of 49 described species... plus X undescribed...').
7. What counts as a troglobiont/ stygobiont is a never-ending debate, and the authors are very honest in described the morphology and ecology of the taxa in their list. The authors should critically consider Carychium stygium, which has always been considered a troglobiont. But Weigand et al., 2011 presented molecular data that suggests that C. stygium is really just C. exile: an epigean species. We know that snail morphology can be plastic. Might C. stygium troglomorphy be another example of populations of epigean taxa exhibiting  troglomorphy? I think of some of the Texas Eurycea species as another example. Related, the authors should provide justification for why they include Bathyphantes weyeri in their list if it has also been collected on the surface.
8. It would be interesting to know whether leaf litter, soil sampling (e.g. Berlese funnels) has been done in mesic habitats in the park (i.e. sinkholes, cliff bottoms, near entrances). How does the fauna compare? Might some of the taxa like Bathyphantes weyeri and Hesperochernes mirabilis be edaphobites or leaf litter taxa?
9. Page 10: The presence of ectoparasites/ ectocommensals is significant and alludes not only to the species richness of the site, but also the ecological complexity. It would be nice to see additional discussion about trophic ecology/ community structure in this complex system.
10. Page 11: At some point their citations got shifted. I noticed it in the discussion but maybe it happened sooner. So, for example, the 3 citations for chemoautotrophy on line 348 are 1 off from the correct citations.
11. Page 11: Chemoautotrophy. The authors provide convincing evidence for chemoautotrophy in the ecosystem, but is there any evidence that chemoautotrophic production actually supports the animal community in any measurable way. I'm only aware of some stable isotope data presented in the 2017 Mammoth Cave book, that basically looks like animals are using photosynthetic material to me. I don't think the authors should take the chemoautotrophy bit out, but if the verdict is still out on the role of chemoautotrophy in the metazoan food web, that caveat should be explicitly stated.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper is very well written and understandable. A really strong effort has been performed in collecting data from literature, database and museums to update the knowledge on the biodiversity of one of the main subterranean systems of the world.

 

The information described in the paper is novel and will be useful for a broad readership.

I found particularly useful the description provided in the text for each group of troglo and stygobionts

 

The only comment to improve clarity for not used readers is

• To state the meaning of troglbionts and stygobionts
• To be consistent with these terms in the subchapter s (terrestrial fauna and aquatic fauna)

Author Response

Please see the attachment

Author Response File: Author Response.pdf