Unravelling the mystery of “Madagascar copal”: Age, origin and preservation of a Recent resin

The loss of biodiversity during the Anthropocene is a constant topic of discussion, especially in the top biodiversity hotspots, such as Madagascar. In this regard, the study of preserved organisms through time, like those included in "Madagascar copal", is of relevance. “Madagascar copal" originated from the leguminous tree Hymenaea verrucosa, which produced and produces resin abundantly. In the last 20 years, interest has focused on the scientific study of its biological inclusions, mainly arthropods, described in dozens of publications. The age and origin of the deposits of "Madagascar copal" have not yet been resolved. Our objectives are to determine its age and geographical origin, and thus increase its scientific value as a source of biological/palaeobiological information. Although Hymenaea was established in Madagascar during the Miocene, we did not find geological deposits of copal or amber in the island. It is plausible that the evolution of those deposits was negatively conditioned by the type of soil, by the climate, and by the development of soil/litter microorganisms, which inhibit preservation of the resin pieces in the litter and subsoil over 300 years. Our results indicate that "Madagascar copal" is a Recent resin, up to a few hundred years old, that originated from Hymenaea trees growing in the lowland coastal forests, one of the most endangered ecosystems in the world. The included and preserved biota is representative of that ecosystem today and during historical times. Inclusions in this Recent resin do not have the palaeontological significance that has been mistakenly attributed to them, but they do have relevant implications for studies regarding Anthropocene biodiversity loss in this hottest hotspot.

However, the new proposal by De la Estrella et al. (2018) proposes H. verrucosa as a sister to H. oblongifolia from northern South America and these two as sister to all other species of the genus. This new phylogenetical proposal does not affect our conclusions. Since the MS is not concerned with the Hymenaea phylogeny and evaluating the different proposals, we prefer, if you agree, to delete this sentence in the final version. Comments to the Author 1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the "Comments to the Author" section, enter your conflict of interest statement in the "Confidential to Editor" section, and submit your "Accept" recommendation.
Reviewer #1: (No Response) Reviewer #2: All comments have been addressed 2. Is the manuscript technically sound, and do the data support the conclusions?
The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data-e.g. participant privacy or use of data from a third party-those must be specified.  (2018) as is not exclusively a review paper but as it also reports many new observations. It discusses and illustrates preservation versus degradation of resins in soils of humid tropical forest (including observed time of complete resin degradation), also considering the relevance of resinicolous fungi. Refer, for example, to the 'Formation of amber deposits' chapter, tracing the path from resin exudation to the deposit. See also fig. 13. where resin on and inside forest soils is shown from the Pacific region and fig. 8 for resin preserved in peat swamps. The paragraphs on pages 1705-1706 have thus direct relation to the current study. If this paper is not worth citing here, the authors could delete approximately 30% of the presently cited literature from the manuscript.

Obviously, we totally disagree with the reviewer's last comment. In the first revision we did not cited some references proposed by this reviewer because all the observations make by their authors are of resins produced by gymnosperms. It is well known that the evolution of soils under angiosperm and gymnosperm forests are different, due to the rapid and slow degradation of their OM, respectively.
Nevertheless, because all the observations made by Seyfullah et al. (2008) (Speranza et al., 2015 andSaint Martin andSaint Martin, 2017 We consider that the inclusion of the reference Beimforde et al. (2017) is not suitable in the manuscript because that research is not related with our case study. These authors explained that the resin production of Araucaria humboldtensis is closely related to the borer activity of the larvae of two different group of beetles. One species of ascomycete and diverse fungi growth in the surface of these gymnosperm exudates. The strong host specificity of one of the beetles, along with the occurrence of two exclusive fungi, makes the authors suggest that the resin associated community is native and has evolved on the endemic conifer host.
line 446: 'The coastal forest harbors a very unusual arthropod community' -My previous question was: In what manner is it unique? Thanks for explaining it to me, but the authors should likewise explain it to the readers.
We are included a paragraph explaining why.

Reviewer #2:
The comments and suggestions of both reviewers have been taken into account. I feel that the manuscript has been improved and gained significantly in clarity. Therefore, I recommend the acceptance.