title: Revealing pancrustacean relationships: phylogenetic analysis of ribosomal protein genes places Collembola (springtails) in a monophyletic Hexapoda and reinforces the discrepancy between mitochondrial and nuclear DNA markers.
abstract: BACKGROUND
  In recent years, several new hypotheses on phylogenetic relations among arthropods have been proposed on the basis of DNA sequences. One of the challenged hypotheses is the monophyly of hexapods. This discussion originated from analyses based on mitochondrial DNA datasets that, due to an unusual positioning of Collembola, suggested that the hexapod body plan evolved at least twice. Here, we re-evaluate the position of Collembola using ribosomal protein gene sequences.
  
  
  RESULTS
  In total 48 ribosomal proteins were obtained for the collembolan Folsomia candida. These 48 sequences were aligned with sequence data on 35 other ecdysozoans. Each ribosomal protein gene was available for 25% to 86% of the taxa. However, the total sequence information was unequally distributed over the taxa and ranged between 4% and 100%. A concatenated dataset was constructed (5034 inferred amino acids in length), of which ~66% of the positions were filled. Phylogenetic tree reconstructions, using Maximum Likelihood, Maximum Parsimony, and Bayesian methods, resulted in a topology that supports monophyly of Hexapoda.
  
  
  CONCLUSIONS
  Although ribosomal proteins in general may not evolve independently, they once more appear highly valuable for phylogenetic reconstruction. Our analyses clearly suggest that Hexapoda is monophyletic. This underpins the inconsistency between nuclear and mitochondrial datasets when analyzing pancrustacean relationships. Caution is needed when applying mitochondrial markers in deep phylogeny.
authors: Department of Animal Ecology, VU University Amsterdam, Amsterdam, The Netherlands. martijn.timmermans@falw.vu.nl
authors: M J T N
authors: MJ
authors: Timmermans
authors: D
authors: D
authors: Roelofs
authors: J
authors: J
authors: Mariën
authors: N M
authors: NM
authors: van Straalen
mesh_terms: D000818:Animals; D001181:Arthropods / Q000145:classification* / Q000235:genetics*; D001483:Base Sequence; D001499:Bayes Theorem; D004272:DNA, Mitochondrial / Q000235:genetics*; D020224:Expressed Sequence Tags; D005819:Genetic Markers; D010802:Phylogeny; D012269:Ribosomal Proteins / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial; D005819:Genetic Markers; D012269:Ribosomal Proteins