Evidence of an Absence of Inbreeding Depression in a Wild Population of Weddell Seals (Leptonychotes weddellii)

Round 1

Reviewer 1 Report

The manuscript, which reports a slight correlation between inbreeding and reproductive success, is well-written and can provides a clear analytical framework for for future studies with similar aims. 

I don't see major flaws in the design of analyses. Some minor comments are attached to the pdf file. Overall, the manuscript can be more succinct by citing or describing equations and parameters in the Methods section and reducing come repetitive content in the Results section. 

I value the framework of the study more than the results, therefore, I'd suggest authors to attach annotated scripts of analyses in the supplementary material or make them available in open online repositories.  

Comments for author File: Comments.pdf

Author Response

We thank the reviewer for their helpful comments on improving the clarity of the manuscript and future utility of the work. In addition to addressing their comments on the text of the manuscript, we have added a supplemental file with the WinBUGS models used in the analysis so they are available to other researchers. Below is a table identifying changes to the text of the manuscript in response to the reviewer’s comments.

Reviewer 2 Report

Powell et al. present a well written manuscript with genetic data that were outdated by new sequencing methods, but are nevertheless interesting. I appreciate that an analysis that gave not the preferable results is aimed to publish and that errors in the x-variable in a regression analysis are taken into account. Without taking that error into account regressions are generally biased downward. Nevertheless, in this study there was no significant difference in the fit of the models with and without inbreeding coefficients. However, this fact is not reflected by the title and conclusion in the abstract, which surrogate that there is clear inbreeding depression (see comments below).

General comments:

The statement of evidence for inbreeding depression should be more attenuated in the title and the abstract. Given that the models with and without inbreeding are not different based on AIC there is no clear evidence to inbreeding depression nor that it is not occurring in the population. Maybe use “suggestive” evidence as it is described in the results part.

It would be informative if the estimated inbreeding coefficients are described more in detail e.g. the correlation of observed homozygosity per individual across all markers with the estimated inbreeding coefficient to be able to compare the estimated inbreeding coefficients with the classical multi locus heterozygosity approach. Moreover to be able to judge how well the inbreeding coefficients from microsatellites represent the true inbreeding coefficients the identity disequilibrium g2, a measure of the covariance in heterozygosity, should be reported, either for the multi locus heterozygosity (e.g. with RMES (David P, Pujol B, Viard F, Castella V, Goudet J. 2007 Reliable selfing rate estimates from imperfect population genetic data. Mol. Ecol. 16, 2474–2487.)) or for the inbreeding coefficients as estimated in the manuscript.

Minor comments:

Materials and Methods:

Line 375: The sentence is unclear: Rephrase, e.g. Four events of yearly survival needed to have been…

Results:

Report about the model fit of 1, 5, 10 and 20 copies of the data is missing.

Discussion:

Note that inbreeding depression might well be larger, because of the imprecise measure of inbreeding coefficients with microsatellites. With larger number of markers of next generation sequencing methods the correlation might strengthen.

Line 488:  “associated” seems wrong to me and I would replace it with “association”, but since I am not a native speaker please check.

Conclusion:

574: one “.” too much

Author Response

We thank the reviewer for their helpful comments that improved the manuscript. We agree with the reviewer’s general comments and have addressed them in the manuscript. We incorporated the reviewer comment that “The statement of evidence for inbreeding depression should be more attenuated in the title and the abstract” by changing the title from “Evidence of low inbreeding depression in a wild population of Weddell seals (Leptonychotes weddellii)” to “Evidence of an absence of inbreeding depression in a wild population of Weddell seals (Leptonychotes weddellii).” We also made an identical change in the second to last sentence of the abstract and removed the last sentence of the abstract.

Reviewer 2 also commented that “[i]t would be informative if the estimated inbreeding coefficients are described more in detail in the revised manuscript” and “to be able to judge how well the inbreeding coefficients from microsatellites represent the true inbreeding coefficients the identity disequilibrium g2, a measure of the covariance in heterozygosity, should be reported.” In the revised manuscript we provide readers with the ability to assess the uncertainty in estimated inbreeding coefficients in the analysis by adding a plot of individual homozygosity and estimated inbreeding coefficients, reporting the correlation between these values in the text, and presenting the estimated identity disequilibrium (David et al. 2007) in the text.

Below is a table identifying changes to the text of the manuscript in response to the reviewer’s specific comments.