Phylogeny and Systematic Position of Opiliones: A Combined Analysis of Chelicerate Relationships Using Morphological and Molecular Data

Abstract

The ordinal evel phylogeny of the Arachnida nd the suprafamilial level phylogeny ofthe Opiliones were stud-ied on the basis of a combined analysis of 253 morpholog-ical characters, the complete sequence of the 18S rRNA gene, and the D3 region of the 28S rRNA gene. Molecular data were collected for 63 terminal taxa. Morphological data were collected for 35 exemplar taxa of Opiliones, but groundplans were applied to some of the remaining chelicerate groups. Six extinct terminals, including Paleozoic scorpions, are scored for morphological charac-ters. The data were analyzed using strict parsimony for the morphological data matrix and via direct optimiza-tion for the molecular and combined ata matrices. A sensitivity analysis of 15 parameter sets was undertaken, and character congruence was used as the optimality