Genetic load components and kinship load
We analysed the genetic load in the hypothetical offspring of our six
pink pigeons. This kinship load is calculated by theoretically crossing
all possible combinations of individuals assuming mendelian segregation
ratios. As kinship between two individuals increases, homozygosity of
their offspring increases (Figure 3). Similarly, increased kinship
between parents elevates offspring’s’ realised load and reduces masked
load (Figure 3). Optimal mate pairing can significantly reduce the
realised load of the offspring (R2=0.258,
F1,13 = 8.32, p=0.00918).
Next, we performed an analysis to identify optimal crosses to minimise
genetic load (Figure 4). Figure 4A shows average genetic load of
potential offspring. In essence, these are the deleterious mutations
that offspring are predicted to inherit from both parents, with blue
tiles representing offspring with low genetic load, and red tiles
offspring with high genetic load. The genetic load is lowest in the
offspring from a cross between individuals 2 and 3.
To predict degree of inbreeding depression, the realised load of the
offspring of different crosses was calculated. Blue tiles in the
correlogram in Figure 4B show the realised load of the offspring of the
optimal crosses. The realised load of these offspring is 7.4% less than
that of offspring of random crosses (Figure 4E), and these offspring are
predicted to show less inbreeding depression. Note that the offspring
from the 2 x 3 cross with the lowest genetic load possesses a relatively
high realised load. Individuals 2 and 3 were closely related (Aunt and
Niece), but they each possess a low genetic load. However, because they
are related, their offspring expresses a high realised load, even though
their genetic load is low.