Phylogeny Reconstruction: The Role of Morphology

Abstract

In this article we explore the paradox of why morphological data are currently utilized less for than are DNA sequence data, whereas most of what we know about stems from classifications founded on morphological data. The crucial difference between the two data sources relates to the number of potentially unambiguous characters available, their ease and speed of discovery, and their suitability for analysis using transformational models. We consider that the increased use of DNA sequence data, relative to morphology, for is inevitable and well founded, but that a crucial issue remains concerning the role of morphology in reconstruction. We present the view that rigorous and critical anatomical studies of fewer morphological characters, in the context of molecular phylogenies, is a more fruitful approach to integrating the strengths of morphological data with those of sequence data. This approach is preferable to compiling larger data matrices of increasingly ambiguous and problematic morphological characters. We argue below that a main constraint of morphologybased phylogenetic inference concerns the limited number of unambiguous characters available for analysis in a transformational framework. This problem of a limited number of unambiguous characters is further compounded by obstacles to accurate homology assessment and character coding, which further reduce the number of characters available for analysis. We discuss and disagree with the view that more morphological data should be used in reconstruction. Furthermore, we consider the claim that the greatest strength of morphological data-increased taxon sampling-to be mistaken. In the discussion that follows we use phylogeny reconstruction to refer to the computer-based algorithmic analyses routinely conducted in systematics today.