Meeting Abstract

41.5  Wednesday, Jan. 5  Before and beyond congruence: using phylogenetic homology to infer evolutionary process BRAZEAU, MD; Museum fuer Naturkunde, Leibniz Institute for Research on Evolution and Biodiversity martin.brazeau@gmail.com

The homology concept has garnered a reputation for being elusive and problematic. This view has grown in light of advances in modern comparative developmental genetics (‘evo-devo’). This perception of elusiveness, however, appears to derive from a plurality of ideas about homology hypotheses and their testing. Phylogenetic homology (the equation of homology with synapomorphy for the purposes of hypothesis testing) is widely accepted among systematists, but has not been generally adopted within comparative development and molecular biology. This is surprising, especially given the growing number of discoveries suggesting discordance between morphological homology and developmental genetics. Here it is argued that only phylogenetic homology is consistent with these recent discoveries and that the adoption of this concept is central to uncovering unexpected patterns of character evolution. A synthetic rather than pluralistic approach to homology and character formulation is proposed along with a set of guidelines for formulating homology hypotheses in advance of testing regardless of the dataset (molecular, morphological, etc.) The first rule is to always express homology hypotheses as conditional phrases to eliminate ambiguity. The second is to test homologies using phylogenetic methods, rather than by attempting to assess character ‘quality’ in advance. A procedure for this is illustrated while the alternative is shown to be logically incompatible with the conditional nature of character statements. The concept of neutral morphological evolution is explored to illustrate the importance of using phylogenetic homology as a means of inferring patterns of character evolution at all levels of biological organization (developmental, histological, adult, etc.).