Evolution of Adaptation and Mate Choice: Parental Relatedness Affects Expression of Phenotypic Variance in a Natural Population |
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Authors: | Kevin P Oh Alexander V Badyaev |
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Institution: | (1) Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA |
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Abstract: | Mating between relatives generally results in reduced offspring viability or quality, suggesting that selection should favor
behaviors that minimize inbreeding. However, in natural populations where searching is costly or variation among potential
mates is limited, inbreeding is often common and may have important consequences for both offspring fitness and phenotypic
variation. In particular, offspring morphological variation often increases with greater parental relatedness, yet the source
of this variation, and thus its evolutionary significance, are poorly understood. One proposed explanation is that inbreeding
influences a developing organism’s sensitivity to its environment and therefore the increased phenotypic variation observed
in inbred progeny is due to greater inputs from environmental and maternal sources. Alternatively, changes in phenotypic variation
with inbreeding may be due to additive genetic effects alone when heterozygotes are phenotypically intermediate to homozygotes,
or effects of inbreeding depression on condition, which can itself affect sensitivity to environmental variation. Here we
examine the effect of parental relatedness (as inferred from neutral genetic markers) on heritable and nonheritable components
of developmental variation in a wild bird population in which mate choice is often constrained, thereby leading to inbreeding.
We found greater morphological variation and distinct contributions of variance components in offspring from highly related
parents: inbred offspring tended to have greater environmental and lesser additive genetic variance compared to outbred progeny.
The magnitude of this difference was greatest in late-maturing traits, implicating the accumulation of environmental variation
as the underlying mechanism. Further, parental relatedness influenced the effect of an important maternal trait (egg size)
on offspring development. These results support the hypothesis that inbreeding leads to greater sensitivity of development
to environmental variation and maternal effects, suggesting that the evolutionary response to selection will depend strongly
on mate choice patterns and population structure. |
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Keywords: | Heritability Developmental stability Genetic complementarity Environmental variance Maternal effects Heterozygosity Animal model |
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