I show how phylogenetic correlograms track distinct microevolutionary processes and can be used as empirical descriptors of the relationship between interspecific covariance (V_B) and time since divergence (t). Data were simulated under models of gradual and speciational change, using increasing levels of stabilizing selection in a stochastic Ornstein-Uhlenbeck (O-U) process, on a phylogeny of 42 species. For each simulated dataset, correlograms were constructed using Moran's I coefficients estimated at five time slices, established at constant intervals. The correlograms generated under different evolutionary models differ significantly according to F-values derived from analysis of variance comparing Moran's I at each time slice and based on Wilks' λ from multivariate analysis of variance comparing their overall profiles in a two-way design. Under Brownian motion or with small restraining forces in the O-U process, correlograms were better fit by a linear model. However, increasing restraining forces in the O-U process cause a lack of linear fit, and correlograms are better described by exponential models. These patterns are better fit for gradual than for speciational modes of change. Correlograms can be used as a diagnostic method and to describe the V_B/t relationship before using methods to analyze correlated evolution that assume (or perform statistically better when) this relationship is linear.

Corresponding Editor: T. Garland Jr.