Geometric morphometric data in cladistics: comparison with phylogenies inferred from morphological data.

Abstract

The development of protocols integrating 3D geometric morphometric data into cladistic analyses offers powerful tools to reassess previously established phylogenies. We examine evolutionary relationships within the genus Homo by comparing results from recently developed cladistic protocols using 3D data with an approach based on morphological characters. We applied both to 78 hominid calvaria - comprising 9 great apes, 45 Homo sapiens, and 24 fossil specimens (2 australopithecines and 22 Homo) - grouped into 23 operational taxonomic units. The sample is described using 347 landmarks and 59 discrete characters, from which three datasets were generated. The first uses Procrustes-aligned 3D landmark coordinates. The second uses principal component coordinates from a Principal Component Analysis run on the aligned landmarks. The third dataset includes coded morphological features. Phylogenetic trees were constructed using TNT software following a three-step protocol. Firstly, a phylogenetic search using the heuristic algorithm under equal weight was performed. Secondly, the consistency and rescaled consistency indices for each character were extracted. Finally, a second phylogenetic search using the heuristic algorithm after reweighting of the characters was performed. The cladistic analyses of 3D data and discrete morphological traits yield different yet mostly congruent results, highlighting the strengths and limitations of each approach, and bringing new insight on long standing discussions in palaeoanthropology.