DOI: 10.5061/dryad.rbnzs7hqp
title: Limited inbreeding avoidance at the gamete level despite inbreeding depression in Atlantic salmon (Salmo salar)

description: Inbreeding and the associated increase in homozygosity and potential
 accumulation of deleterious alleles may reduce fitness in a process known
 as inbreeding depression. Mechanisms to mitigate reproduction between
 close relatives, ranging from pre-mating mate choice to post-mating gamete
 selection, have evolved across taxa. In external fertilizers like Atlantic
 salmon (Salmo salar), where females have limited control over paternity,
 mechanisms of inbreeding avoidance can be expected to evolve at the gamete
 level. Philopatric Atlantic salmon may run the risk of breeding between
 relatives, particularly in small populations, and frequent escapes from
 aquaculture settings are augmenting the chances of adults from the same
 sibling cohort overlapping in the wild, raising potential ecological and
 sustainability concerns. Moreover, the presence of inbreeding avoidance
 mechanisms between full siblings in externally fertilising fish is
 currently untested. This study tested post-mating inbreeding avoidance
 mechanisms in domesticated Atlantic salmon. In a paired breeding design,
 we compared sperm motility parameters in sibling and non-sibling ovarian
 fluid, and assessed fertilisation and hatching success, growth rate, and
 paternity in sperm competition trials between sibling and non-sibling
 males. Sperm activated in ovarian fluid of sibling females showed lower
 values of motility-related parameters and led to an average of 18%
 reduction in fertilisation rates in the resulting crosses. Furthermore,
 offspring from sibling crosses were smaller before the onset of sexual
 maturation. However, we found no difference in survival rates between
 sibling and non-sibling cross offspring. Besides, when sperm from sibling
 and non-sibling males were competing simultaneously for the same egg
 batch, we found no influence of this on paternity. Our findings reveal the
 presence of post-mating inbreeding avoidance at the gamete level in
 Atlantic salmon, but its effects are limited in competitive scenarios. Our
 results have implications for salmonid conservation and aquaculture, where
 small natural or closed domestic strains may both display a degree of
 inbreeding. Mating between escaped domestic and wild salmonids could
 favour admixed over wild or feral crosses, if an inbreeding avoidance
 mechanism is present, although this remains to be tested in more outbred
 crosses.
description: # Limited inbreeding avoidance at the gamete level despite inbreeding
 depression in Atlantic salmon (Salmo salar) Dataset DOI:
 [10.5061/dryad.rbnzs7hqp](10.5061/dryad.rbnzs7hqp) ## Description of the
 data and file structure Data set associated with the research article
 Limited inbreeding avoidance at the gamete level despite inbreeding
 depression in Atlantic salmon (Salmo salar)’ All the material has been
 deposited on the DRYAD repository for replicability, transparency and for
 future research purposes. List of necessary files: files containing the
 collected parameters and variables used in the models. *
 dataset_sibnonsib_Rcopy2.xlsx - morphometrics_SIBNONSIB_VERT1.xlsx *
 actingasnew3.xlsx (R-scripts to run all the analyses by using the above
 mentioned datasets,  R version 4.3.3) * Spermbehav_repr.out_SIBNONSIB1.txt
 and MHC_paternity.txt **Glossary of variables:** * N: unique #ID for
 individual - Fl (cm): Fork length reported in centimetres (cm) * Bw (gr):
 Body weight reported in grams (gr) - Bw (Kg): Body weight reported in
 Kilograms (Kg) * TANK: Id of the tank that hosted the individuals during
 the experiments (1, 2 or 3) - RELATEDNESS: Relatedness of the paired
 individuals (“NON SIBLINGS” or “SIBLINGS”) * SAMPLING: Sampling event ID
 (1 or 2) - VCL: Sperm curvilinear velocity (µm/s) * VAP: Sperm average
 path velocity (µm/s) - VSL: Sperm straight line velocity (µm/s) * LIN:
 Sperm linearity (%) - WOB: Sperm wobble (%) * PROG: Sperm progression (µm)
 - BCF: Sperm beat-cross frequency (Hz) * Count: sperm number - MALE:
 Unique male ID * FEMALE: Unique female ID - replicate: replicate number *
 spa: seconds post sperm activation (s) - ACTINGAS: status of the
 individual male acting as either a ‘SIBLING’ or “NON SIBLING” according to
 the female to which he is paired * PATERNITY: percentage (%) of siring
 success - MHC1share: number of alleles shared between partners at the MHC1
 locus * MHC2share: number of alleles shared between partners at the MHC2
 locus - FERT: Proportion of eggs successfully fertilised for each batch of
 eggs * Hatchratefert: Percentage of fertilised embryos that succeeded to
 hatch - PC1: Sperm principal component 1 * PC2: Sperm principal component
 2 N/A: not applicable (measurement missing (PC1 and PC2) or omitted to
 avoid pseudo replication (FERT and Hatchratefert). ## Access information
 Other publicly accessible locations of the data: * NA Data was derived
 from the following sources: * NA