Data from: Directional selection can drive the evolution of modularity in complex traits

Modularity is a central concept in modern biology, providing a powerful
framework for the study of living organisms on many organizational levels.
Two central and related questions can be posed in regard to modularity:
How does modularity appear in the first place, and what forces are
responsible for keeping and/or changing modular patterns? We approached
these questions using a quantitative genetics simulation framework,
building on previous results obtained with bivariate systems and extending
them to multivariate systems. We developed an individual-based model
capable of simulating many traits controlled by many loci with variable
pleiotropic relations between them, expressed in populations subject to
mutation, recombination, drift, and selection. We used this model to study
the problem of the emergence of modularity, and hereby show that drift and
stabilizing selection are inefficient at creating modular variational
structures. We also demonstrate that directional selection can have marked
effects on the modular structure between traits, actively promoting a
restructuring of genetic variation in the selected population and
potentially facilitating the response to selection. Furthermore, we give
examples of complex covariation created by simple regimes of combined
directional and stabilizing selection and show that stabilizing selection
is important in the maintenance of established covariation patterns. Our
results are in full agreement with previous results for two-trait systems
and further extend them to include scenarios of greater complexity.
Finally, we discuss the evolutionary consequences of modular patterns
being molded by directional selection.