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Quantifying additive genetic variances and cross-sex covariances in
reproductive traits, and identifying processes that shape and maintain
such (co)variances, is central to understanding the evolutionary dynamics
of reproductive systems. Gene flow resulting from among-population
dispersal could substantially alter additive genetic variances and
covariances in key traits in recipient populations, thereby altering forms
of sexual conflict, indirect selection and evolutionary responses.
However, the degree to which genes imported by immigrants do in fact
affect quantitative genetic architectures of key reproductive traits and
outcomes is rarely explicitly quantified. We applied structured
quantitative genetic analyses to multi-year pedigree, pairing and
paternity data from free-living song sparrows (Melospiza melodia) to
quantify the differences in mean breeding values for major sex-specific
reproductive traits, specifically female extra-pair reproduction and male
paternity loss, between recent immigrants and the previously existing
population. We thereby quantify effects of natural immigration on the
means, variances and cross-sex covariance in total additive genetic values
for extra-pair paternity arising within the complex socially monogamous
but genetically polygynandrous reproductive system. Recent immigrants had
lower mean breeding values for male paternity loss, and somewhat lower
values for female extra-pair reproduction, than the local recipient
population, and would therefore increase the emerging degree of
reproductive fidelity of social pairings. Furthermore, immigration
increased the variances in total additive genetic values for these traits,
but decreased the magnitudes of the negative cross-sex genetic covariation
and correlation below those evident in the existing population.
Immigration thereby increased the total additive genetic variance but
could decrease the magnitude of indirect selection acting on sex-specific
contributions to paternity outcomes. These results demonstrate that
dispersal and resulting immigration and gene flow can substantially affect
quantitative genetic architectures of complex local reproductive systems,
implying that comprehensive theoretical and empirical efforts to
understand mating system dynamics will need to incorporate spatial
population processes.
141 views reported since publication in 2020.