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Academic Editor's Comments (Dennis Hansen)

Posted by RebeccaWalton on 18 Mar 2008 at 15:54 GMT

Review of the original submission:

General comments:
Guimareis Jr. & coauthors have done a highly laudable job in taking a much needed fresh look at Janzen & Martin's much-cited but little-studied evocative idea of Neotropical megafauna fruits left stranded without efficient seed dispersal after the Pleistocene megafauna extinction.

While this idea makes immediate sense in the light of the current depauperate dispersal ecology of several large-fruited neotropical plant species, it has been criticised as being too 'loose', and being based on ad-hoc assumptions and anecdotal evidence, without having a solid quantitative foundation.

The current study presents a more stringent and quantitative framework to assign Neotropical fruits as potential megafauna fruits, due to the following key points: 1) Restricting the definition of megafauna to animals > 1000 kg, and 2) using known characteristics of Paleotropical fruits dispersed by such animals to predict likely Neoptropical megafauna fruits.

The study points out several promising directions for future research, especially population genetical studies to investigate potential loss of long-distance gene flow in megafauna fruits, and using the presented framework to predict consequences for seed dispersal dynamics in habitats that are currently being defaunated elsewhere.

Review of the first revised manuscript:

Again, it was a pleasure to read the manuscript by Guimarães Jr., Galetti & Jordano, which takes a much-needed fresh look at Janzen & Martin's influential 1982 paper on Neotropical fruit-frugivore anachronisms. Please refer to my intial review for further comments on this.

The readability and accessibility of the manuscript has certainly been much improved, and I have mostly minor comments & suggestions for corrections (marked directly in the pdf with yellow & an accompanying comment). Plate II is another welcome addition to the manuscript, as it clearly illustrates many of the fruit traits that are associated with the megafauna syndrome.

However, I still miss some sort of (short) discussion as to the "completeness"/size of the database used (1361 species) - some indication of how it was assembled. To me, for example, it still seems strange that a random-ish sampling of all Brazilian fruits would only result in Megafauna Fabales species with fleshy fruits (i.e. the 100% given). Does this simply mean that there are no non-megafauna Fabales species with fleshy fruits in all of Brazil? (I obviously don't know the flora!)

My point is that it is hard to know to which extent we can "trust" the percentages given - and as they form a non-trivial part of the results, it is important to give enough information as to how the database they are based on was assembled, so that potential caveats are clear to the reader.

The most complete and illsutrative examples in this regard are of course the two sites where all fleshy-fruited species were sampled (Intervales & Fazenda Rio Negro) - and it is a great improvement that they were added to the text. While the authors are certainly correct in that FRUBASE is a large database, it would be nice indeed with some more information on how it has been put together over the years.

If this database is largely based on literature review, one could argue that megafauna fruits are over-represented, simply because people have chosen to work more on larger fruits (easier), than on smaller fruits (more difficult) within any given family/genus.
Ideally, for future research, such databases should be based on entire local/regional/national floras. I believe an addition of some sort of sampling protocol in the call for future research would be a worthwhile addition to the paper, and increase its usefulness.

Review of the second revised manuscript:

The second revision has clarified the last remaining minor issues I had with the manuscript --and I look much forward to seeing the final version published.

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N.B. These are the comments made by the referee when reviewing an earlier version of this paper. Prior to publication the manuscript has been revised in light of these comments and to address other editorial requirements.