MOLECULAR PHYLOGENY OF THE MAJOR ARTHROPOD GROUPS INDICATES POLYPHYLYOF CRUSTACEANS AND A NEW HYPOTHESIS FOR THE ORIGIN OF HEXAPODS

A phylogeny of the arthropods was inferred from analyses of amino acid sequences derived from the nuclear genes encoding elongation factor-1 alpha and the largest subunit of RNA polymerase II using maximum-pars imony, neighbor-joining, and maximum-likelihood methods. Analyses of e longation factor-1 alpha from 17 arthropods and 4 outgroup taxa recove red many arthropod clades supported by previous morphological studies, including Diplopoda, Myria-poda, Insecta, Hexapoda, Branchiopoda (Cru stacea), Araneae, Tetrapulmonata, Arachnida, Chelicerata, and Malacost raca (Crustacea). However, counter to previous studies, elongation fac tor-1 alpha placed Malacostraca as sister group to the other arthropod s. Branchiopod crustaceans were found to be more closely related to he xapods and myriapods than to malacostracan crustaceans. Sequences for RNA polymerase II were obtained from 11 arthropod taxa and were analyz ed separately and in combination with elongation factor-1 alpha. Resul ts from these analyses were concordant with those derived from elongat ion factor-1 alpha alone and provided support for a Hexapoda/Branchiop oda clade, thus arguing against the monophyly of the traditionally def ined Atelocerata (Hexapoda + Myriapoda).