DOI: 10.5061/dryad.c866t1g73
title: Body size is associated with yearling breeding and extra-pair mating in the Island Scrub-Jay

description: Large body size is an important determinant of individual fitness in many
 animal species, especially in island systems where habitat saturation may
 result in strong intraspecific competition for mates and breeding
 territories. Here we show that large body size is associated with benefits
 to yearling breeding and extra-pair mating in the Island Scrub-Jay
 (Aphelocoma insularis), endemic to Santa Cruz Island, California. This
 species is approximately 20% larger than its mainland congener, consistent
 with the island syndrome, indicating that body size may be a trait under
 selection. From 2009 to 2013, we quantified the reproductive success of a
 marked population of Island Scrub-Jays, tracked which yearlings acquired a
 breeding territory and bred, and measured the occurrence of extra-pair
 paternity. Two potential contributors to fitness were positively related
 to body size. Larger yearling males were more likely to breed, possibly
 due to greater behavioral dominance during aggressive encounters. Larger
 males were also less likely to lose paternity to extra-pair males and,
 anecdotally, extra-pair males were larger than the social male cuckolded.
 This study provides evidence that larger males may have a fitness
 advantage over smaller males by breeding earlier and avoiding paternity
 loss, but estimates of lifetime reproductive success are ultimately needed
 for Island Scrub-Jays and other long-lived species.
description: Morphologic and genetic data (blood) were collected as island
 scrub-jays were captured on three study plots on Santa Cruz Island,
 California. We extracted DNA from blood samples with a QIAGEN DNEasy Blood
 and Tissue Kit following the manufacturer’s protocol and amplified 9
 variable microsatellite loci (AIAAGG13, ApCo2, PJGATA3, PJAAAG9, PJGATA2,
 CmAAAG30, CmAAAG11, CmAAAG25, CmAAAG6). We amplified microsatellites in
 10 µl multiplex reactions using QIAGEN's type-it microsatellite PCR
 kit and a Vapo-Protect Mastercycler 6321. PCR products were run on an
 Applied BiosSystems 3730xl DNA analyzer. Florescent labels and known
 allele size differences were used to automatically score
 electropherograms using GeneMarker software. All scores were verified
 manually. We used CERVUS 3.0.7 to determine parentage and the presence of
 extra-pair young. Paternity assignment analyses were seperated by plot and
 year. We radio-tracked sexually mature yearling island scrub-jays
 throughout their first breeding season, and observed their reproductive
 status. We also noted any additional yearling individuals (known from
 banding records) that were able to aquire a territory and breed their
 first breeding season.
description: Input files for CERVUS are included and labeled by plot (CPC, FS
 or PZ), and year (2010, 2011, or 2012).  Allele
 frequency analyses were performed with genotype files with the naming
 convention PLOT_YEAR_genotypes.csv. Simulations of
 paternity analysis were performed with the resultant allele frequency file
 from above. Parameters for these analyses (i.e. number of candidate
 fathers, proportion of candidate fathers sampled) can be found in included
 simulation output files with the naming convention
 PLOT_YEAR_SimulationOut.txt. Parentage analyses were
 performed with the same parameters as the simulations. Offspring and
 candidate mothers can be found in files named PLOT_YEAR_trios.csv,
 candidate father files are named PLOT_YEAR_males.csv, and genotypes of
 offspring, candidate mothers, and candidate fathers can be found in files
 named PLOT_YEAR_genotypes.csv. Additionally, the excel
 file "ISSJ Offspring Sample Key" will be useful for interpreting
 parentage assignments (i.e. whether the assigned male is the social
 male).