|Publication Type:||Journal Article|
|Year of Publication:||2004|
|Authors:||Cameron, SL, Miller, KB, Dâ€™Haese, CA, Whiting, MF, Barker, SC|
|Pagination:||534 - 557|
An analysis of the relationships of the major arthropod groups was undertaken using mitochondrial genome data to examine the<p>hypotheses that Hexapoda is polyphyletic and that Collembola is more closely related to branchiopod crustaceans than insects. We<p>sought to examine the sensitivity of this relationship to outgroup choice, data treatment, gene choice and optimality criteria used in<p>the phylogenetic analysis of mitochondrial genome data. Additionally we sequenced the mitochondrial genome of an<p>archaeognathan, Nesomachilis australica, to improve taxon selection in the apterygote insects, a group poorly represented in<p>previous mitochondrial phylogenies. The sister group of the Collembola was rarely resolved in our analyses with a significant level of<p>support. The use of different outgroups (myriapods, nematodes, or annelids + mollusks) resulted in many different placements of<p>Collembola. The way in which the dataset was coded for analysis (DNA, DNA with the exclusion of third codon position and as<p>amino acids) also had marked affects on tree topology. We found that nodal support was spread evenly throughout the 13<p>mitochondrial genes and the exclusion of genes resulted in significantly less resolution in the inferred trees. Optimality criteria had a<p>much lesser effect on topology than the preceding factors; parsimony and Bayesian trees for a given data set and treatment were<p>quite similar. We therefore conclude that the relationships of the extant arthropod groups as inferred by mitochondrial genomes are<p>highly vulnerable to outgroup choice, data treatment and gene choice, and no consistent alternative hypothesis of Collembolaâ€™s<p>relationships is supported. Pending the resolution of these identified problems with the application of mitogenomic data to basal<p>arthropod relationships, it is difficult to justify the rejection of hexapod monophyly, which is well supported on morphological<p>grounds.