Data from: Offspring fitness varies with parental extra-pair status in song sparrows, Melospiza melodia

Numerous studies have tested for indirect selection on female extra-pair
reproduction (EPR) by quantifying whether extra-pair young (EPY) are
fitter than their within-pair young (WPY) maternal half-siblings. In
contrast, the hypothesis that offspring of EPY and WPY (rather than the
EPY and WPY themselves) differ in fitness has not been tested, even though
inter-generational effects of parental extra-pair status on offspring
fitness could alter the magnitude and direction of indirect selection on
EPR. We tested whether offspring of EPY song sparrows, Melospiza melodia,
were more likely to recruit or produce hatched or recruited offspring over
their lifetimes than offspring of WPY. Hatchlings with one or two EPY
parents were more likely to recruit and produce hatched offspring than
hatchlings with two WPY parents. Furthermore, these relationships differed
between maternal versus paternal extra-pair status. Hatchlings with EPY
fathers were more likely to recruit and produce offspring than hatchlings
with WPY fathers. In contrast, hatchlings with EPY mothers were as likely
to recruit as hatchlings with WPY mothers and tended to be less likely to
produce recruited offspring. Depending on the causal genetic and
environmental mechanisms, such conflicting inter-generational
relationships between parental extra-pair status and offspring fitness
could substantially influence the evolutionary dynamics of EPR.