Clonal Reproduction and Low Genetic Diversity in Northern Australian Santalum lanceolatum (Santalaceae) Populations Highlights the Need for Genetic Rescue of This Commercially Significant Species

Round 1

Reviewer 1 Report

This study investigates genetic diversity and genetic structure in Santalum lanceolatum, a species of sandlewood that is threatened by overharvesting. The species is commercially significant and in decline. This study looked at six populations in a small part of the species range in Cape York Australia. Twelve microsatellite loci were used to investigate genetic diversity, clonality, and genetic structure. The authors report some interesting findings of clonality and regional differentiation despite modest sample sizes. The manuscript requires minor to moderate revision in my view.

I have some concerns about the data analysis and presentation, which I noted directly on the manuscript pdf. The major ones were:

1) Treatment of missing data. One of the programs they used did not allow for missing data, so they “filled in” common alleles. That is not acceptable, and not necessary to find clones. Also, the proportion of missing data should be reported.

2) Treatment of clonal genotypes. Once clones were identified, they should have been removed and only one multilocus genotype used in all subsequent analyses, including calculations of genetic diversity, genetic distances, and population structure.

3) Presentation of results on cloning. The relative size of clones (number of ramets and spatial distribution) should be reported. Also something about their appearance in the field. Were they growing close to each other, clumped, or widely separated? Were any clones shared across populations? Were clones more common among adults or juveniles? Were any juveniles growing near a clonal adult?

4) Despite not fully presenting the clonal results, the authors overstate the dire consequences of this finding. They do not measure seed set, but assume it is reduced due to clonality. They do not show that G/N (about 0.5 in their populations) is much higher than in other populations of this species, or in related species. There are still numerous clones at each site, and these levels of clonality may actually be typical for the species.

5) The motivation for comparing juveniles and adults in some of the populations is not clearly stated. I certainly don’t know why you would compare juveniles from one population to adults from another (Table 6).

6) In general, the results could be condensed considerably. There are multiple comparisons of population structure, for example. One or two would be sufficient.

7) The discussion is too long (6 pages). Three or four pages would be sufficient to cover the main findings of the study.

Comments for author File: Comments.pdf

Author Response

Please see attached document for responses to Reviewer 1. 

Author Response File: Author Response.docx

Reviewer 2 Report

The present manuscript entitled "Clonal reproduction and low genetic diversity in Northern Australian Santalum lanceolatum (Santalaceae) populations highlights the need for genetic rescue of this commercially significant species" suggesting that the clonal structure of S. lanceolatum is limiting the potential for sexual reproduction and natural recruitment. The present study drag the attention for a conservation strategy involving genetic rescue to prevent the further decline and potential local extinction from a variety of environmental pressures and human activities. 

The manuscript is very well organized and presented, hereby i would like to recommend the article in present form for further consideration. I do not have any further query.

Thank you

Author Response

Reviewer 2 did not suggest any changes to the manuscript.