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Data from: Natural selection on antihelminth antibodies in a wild mammal population

Cite this dataset

Sparks, Alexandra Megan et al. (2023). Data from: Natural selection on antihelminth antibodies in a wild mammal population [Dataset]. Dryad.


An effective immune response is expected to confer fitness benefits through improved resistance to parasites but also energetic costs which negatively impact fitness-related traits such as reproduction. These fitness costs and benefits of an immune response are likely to depend on host age, sex, and levels of parasite exposure. Few studies have examined the full extent to which patterns of natural selection on immune phenotypes vary across demographic groups and environments in the wild. Here, we assessed natural selection on plasma levels of three functionally distinct isotypes (IgA, IgE and IgG) of antibodies against a prevalent nematode parasite measured in a wild Soay sheep population over 25 years. We found little support for environment-dependent selection or reproductive costs. However, antibody levels were negatively associated with parasite egg counts and positively associated with subsequent survival, albeit in a highly age- and isotype-dependent manner. Raised levels of anti-parasite IgA best predicted reduced egg counts but this did not predict survival in lambs, whilst in adult females increased anti-parasite IgG predicted reduced egg counts and improved survival. Our results highlight the potential importance of age-dependent selection on immune phenotypes in nature, and that patterns of selection can vary even amongst functionally-related immune markers.


This data was collected as part of the long term individual based study on the Soay sheep of St Kilda in Scotland. The full methods on how data was collected and processed is included in the main article associated with this dataset (

Natural selection on antihelminth antibodies in a wild mammal population

A. M. Sparks, K. Watt, R. Sinclair, J. G. Pilkington, J. M. Pemberton, S. E. Johnston, T. N. McNeilly, D. H. Nussey

Please see the README files for descriptions of the columns in the dataset and data usage notes.

Usage notes




The attached file(s) contain data derived from the long-term field project monitoring individual Soay sheep on St Kilda and their environment. This is a request to please let us know if you use them. Several people have spent the best part of their careers collecting the data. If you plan to analyse the data, there are a number of reasons why it would be very helpful if you could contact Dan Nussey ( before doing so.

[NB. If you are interested in analysing the detailed project data in any depth you may find it helpful to have our full relational database rather than the file(s) available here.  If so, then we have a simple process for bringing you onto the project as a collaborator.]

1) The data can be subject to change due to updates in the pedigree, merging of records, occasional errors and so on.

2) The data are complex and workers who do not know the study system may benefit from advice when interpreting it.

3) At any one time a number of people within the existing project collaboration are analysing data from this project. Someone else may already be conducting the analysis you have in mind and it is desirable to prevent duplication of effort.

4) In order to maintain funding for the project(s), every few years we have to write proposals for original analyses to funding agencies. It is therefore very helpful for those running the project to know what data analyses are in progress.

5) Sheep identifiers may vary relative to other data archives from papers using the Soay sheep data.



Natural Environment Research Council

Biotechnology and Biological Sciences Research Council, Award: BB/H021868/1

Medical Research Council, Award: 1369297


St Kilda