DOI: 10.5061/dryad.8pk0p2ntx
title: Divorce and extra-pair paternity in the Lundy house sparrows

description: The question of why socially monogamous females engage in extra-pair
 behaviour is long-standing in evolutionary biology. Due to a lack of
 empirical support among passerine birds, recent work has moved away from
 the indirect-benefits hypothesis to explain extra-pair mating behaviour by
 females, instead favouring the hypothesis that this is the result of a
 pleiotropic effect. That is, a trait under strong positive selection in
 either or both sexes are genetically linked with another, potentially
 unrelated, trait. For example, genes beneficial to female fecundity (that
 promote within-pair solicitation of mating from a male partner) might also
 lead to extra-pair behaviour (by also promoting solicited copulations from
 extra-pair males).  Here, we test two predictions from this
 hypothesis: We test the prediction that female divorce, measured as the
 number of social mates within a given year, is linked with (1) the number
 of extra-pair males engaged by the female and (2) the proportion of the
 female’s offspring that are extra-pair. Our results show that females who
 divorce their social partner are more likely to produce extra-pair
 offspring than those who maintain social monogamy, supporting the
 pleiotropy hypothesis. However, those females did not also have a higher
 proportion of extra-pair offspring. The number of broods initiated was
 also positively correlated with the number of extra-pair males that sired
 a female’s offspring, probably through increased opportunity for
 extra-pair males to sire offspring over a longer breeding season. Our
 results support the intrasexual pleiotropy hypothesis as a driver of
 female extra-pair behaviour.
description: # Divorce\_EPP\_data
 [https://doi.org/10.5061/dryad.8pk0p2ntx](https://doi.org/10.5061/dryad.8pk0p2ntx) Data contains tables from the Lundy Sparrow Project long-term database which were used to answer questions relating to frequent mate-switching (divorce) and extra-pair paternity. I have also included permutation outputs (which were lengthy) and code files. ## Description of the data and file structure LH\_rep is a table of sparrow life history and should be explanatory from the headings - includes information on codes and identifiers used to ID the sparrows and life history traits (when they hatched, and fledged). Nest\_Loc\_Pedigree\_rep is a table relating the the genetic pedigree of the sparrows used in our analysis and again has full column titles - Dam, Social farther and Cohort. Suv just denotes if a bird had survived up to specific years. More information can be found in the manuscript I have also attached two long simulation data files, and an R script showing how they were built. Variables described in file associated files: Dam - the ID of females used in the model, Social farther - the unique ID of the social farther Cohort - Cohort in which a bird hatched Loc\_code - an identifier for breeding location \-\- Note that codes denote a unique nest site location \(i\.e\. W12 is the 12th next box in the Workshop\)\, but where nest locations are ephemeral wild nests\, the code just a unique identifier allocated by the fieldworker at the same\, but the first letter denotes the neighbourhood \(i\.e\. W is Workshop\)\. Some codes denote regions on Lundy without standing for anything explicitly\. Nest location is not required to replicate models in this study\. \-\- Note that Sex is a binary measure \(0 = female and 1= male\) ID - unique bird ID BTO - A British Trust for Ornithology ring number year - date to which a bird was confirmed alive. EPP\_sim - model outputs from MCMC for simulations. For details see MCMCglmm package notes. NAs (or empty cells) in files denote a gap in information. Where they relate to identifiers (colour rings etc.) the bird was un-ringed/unmarked and in the life history table, they relate to missing information (i.e. bird was not recorded laying any eggs, or recruiting offspring - these may be inferred as zero in those cases, but with the caveat that some data is missing - birds not surviving or breeding in inaccessible places) Code files are annotated and run in R we used the software packages Tidyverse and MCMCglmm (version 2023) for all data wrangling and analysis. ## Sharing/Access information The data here has taken along time to collect, please contact us if you require access to the expanded data (outside of what was used in this study)