PHYLOGENETIC RELATIONSHIPS OF HOPLOCERCID LIZARDS: CODING AND COMBINING MERISTIC, MORPHOMETRIC, AND POLYMORPHIC DATA USING STEP MATRICES

Hoplocercidae is a small (10 species, 3 genera), poorly known but pivotal family of Central and South American iguanian lizards that has never been the subject of a focused phylogenetic study or systematic revision. We undertake the first rigorous phylogenetic analysis of hoplocercid lizards. We also use our analysis to demonstrate how meristic, morphometric, and polymorphic morphological characters can be coded and combined for phylogenetic analyses using step matrices, which allow continuous variation to be treated as continuous. Parsimony analysis of 46 informative external and skeletal characters (17 qualitative and fixed, 19 qualitative and polymorphic, 8 meristic, and 2 morphometric) yields very different topologies, depending on how the meristic characters are scaled (weighted). Use of between-state scaling yields a phylogeny in which Hoplocercus is at the base of the hoplocercid tree, and Morunasaurus is paraphyletic with respect to a monophyletic Enyalioides. Scaling between characters produces a tree in which Enyalioides is paraphyletic with respect to a clade containing Morunasaurus and Hoplocercus, and Morunasaurus is paraphyletic with respect to Hoplocercus. We also propose a third, “mixed” approach to scaling, which we marginally prefer over the other two methods. This method yields a tree in which Hoplocercus and a monophyletic Morunasaurus make up the sister group to a monophyletic Enyalioides. We discuss the implications of these results for hoplocercid biogeography and evolutionary ecology, tropical speciation, and the phylogenetic analysis of morphological data.