Alternative mutational architectures can produce identical M-matrices but lead to different patterns of macroevolutionary divergence

Abstract

AbstractExplaining macroevolutionary divergence in light of population genetics requires understanding the extent to which the patterns of mutational input contribute to long-term trends. In the context of quantitative traits, mutational input is typically described by the mutational variance-covariance matrix, or theM-matrix, which summarizes phenotypic variances and covariances introduced by new mutations per generation. However, as a summary statistic, theM-matrix does not fully capture all the relevant information from the underlying mutational architecture, and there exist infinitely many possible underlying mutational architectures that give rise to the sameM-matrix.Using simulations under a strong-selection-weak-mutation regime, we demonstrate alternative mutational architectures underlying the sameM-matrix can lead to different levels of constraint on evolution, and different patterns of alignment betweenMand the evolutionary variance-covariance matrix, or theR-matrix. Our results reveal that aspects of mutational input not reflected by theM-matrix can have a profound impact on long-term evolution, and suggest it is important to take them into account in order to connect macroevolutionary patterns to microevolutionary mechanisms.