Inbreeding avoidance among spawning adults
We tested for the presence of inbreeding avoidance among adult
Yellowstone Cutthroat Trout to understand whether there are mechanisms
that prevent breeding among related individuals. To do this, we first
evaluated the accuracy of four different relatedness estimators (Queller
& Goodnight 1989; Li et al. 1993; Lynch & Ritland 1999; and Wang 2002)
based on correlation coefficients between observed and expected values.
We employed the ‘compareestimators’ function in the relatedpackage in R (Pew et al. 2015; R Core Team 2020) which used observed
allele frequencies within our focal population to simulate 1,000
individuals of known relatedness and selected the estimator with the
highest correlation coefficient between known and estimated
relationships. Next, we used outputs from parentage analysis to identify
two subsets of the adult population, adults that were responsible for
producing progeny and those that were not. We then calculated average
within-group relatedness using the best-fit relatedness estimator for
these two groups and compared against expected values using the
‘grouprel’ function within the related package. Briefly, expected
values were generated by randomly shuffling individuals between groups
(which were kept at a constant size), and then relatedness was
calculating within these newly constructed groups. We performed a total
of 100 simulations and p -values were estimated as the number of
simulations out of the total number ran that were less than or equal to
our observed value.