Minimally monophyletic genera are the cast-iron building blocks of evolution

Abstract

Detailed evaluation is provided for the statistical methods intrinsic to interlocking Sequential Bayes analysis, which allows estimation of evidential support for stem-taxon dendrograms charting the macroevolution of taxa. It involves complexity functions, such as fractal evolution, to generate well-supported evolutionary trees. Required are data on trait changes from ancestral species to descendant species, which is facilitated by reduction of large genera to the smallest included monophyletic groups (one inferred ancestral species each). The genus is here defined as the smallest monophyletic unit, which turns out to be monothetic at least for the direct descendant species. The key fact is that the most-recently acquired traits of the single ancestral species are apparently selectively inviolate and passed on without change to each immediate descendant species. The details of sequential Bayesian analysis were clarified by comparing support of the optimal model with summed support of the alternative models. Because analysis is confined to optimal arrangements of only immediate branches from ancestral species to descendant species, conjugate priors were found to operate such that all alternative models are simply one minus the probability of the optimal model. Such analysis demonstrated that the optimum arrangement of ancestor and descendant species leads to high support values for fitting evolutionary theory, comparable to statistical support levels reported for molecular evolutionary trees, and conjugate priors may be assumed for similar model-building. The method is simple, free of special computer analysis, and well-suited to standard taxonomic practice.