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Zusammenfassung:
Evolution along “lines of least resistance
(LLR)” is a well‐established phenomenon, which is ultimately
based on variational properties of the developmental system.
However, it has remained unclear which aspects of development
are responsible for observed distributions of variation.
This article suggests that house mouse mandible shape may
present an opportunity for future research in this field. The
genetic architecture of mouse mandible shape has been
investigated in the laboratory, and its evolution has been
surveyed in studies on natural variation. Here, I ask whether
evolutionary diversification of mandible shape follows “LLR” by
comparing principal directions of genetic and evolutionary
variation, and I assess the potential contribution of specific
genomic regions to evolutionary divergence along these
directions. The role of two aspects of development, QTL
number (presumably reflecting mutational target size) and
canalization, is comparatively assessed. Overall, our results
demonstrate a strong tendency of genetic and evolutionary
systems to vary along similar directions, suggesting that
mandible shape evolves along LLR at the level of populations,
subspecies and species. At the level of genetic factors, effects
bearing similarity to directions of evolution are significantly
overrepresented, providing support for the mutational target
size hypothesis. A role for canalization is not supported by a
clear correlation between directions of evolution and size of
genetic effects; however, the evidence for canalization
remains ambiguous. These results provide some insights
into how the developmental system may shape the variational
properties of genetic systems and thus influence the direction
of evolution.