Reply to Smith and O'Meara: The utility of morphogenera

Abstract

We do not disagree with Smith and O'Meara's points (1), which do not affect our results (2). P values must be viewed with caution when the x variable is a subset of the y variable, and we could have noted this point more prominently in our paper. From a purely pragmatic standpoint, however, most analyses employing morphogenera (e.g., analyzing fossil taxa) will lack prior knowledge of their phyletic status with respect to molecular cladograms. Therefore, the key consideration is the amount of variance explained by genera of unknown status compared to known monophyletic taxa. Furthermore, their analysis of mammalian body masses (1) suggests we should exclusively expect significant correlations, but when we re-create their analyses with the same body-mass data, varying the number of additional species required to create monophyletic groups across a realistic range, a substantial number of replicates yield insignificant P values (Table 1). Thus, significant correlations are not a foregone conclusion.