Here is a new study of phylogeny of arthropods from proteins, moving
a few groups around (I hope the millipede genome is finished soon to compare).
It has a nice figure 2 with pictures of these bugs, and fig 1 shows the
new tree. Most insects here are ones I've never heard of by genus, but
Daphnia magna is included as a crustacean. THe branch lengths in fig 2
agree that insect genes are farther out from the root than crustaceans
like Daphnia, but arachnids/Chelicerata seem to be lower than crustaceans,
as are millipedes. What I found with Ixodes somewhat higher than Daphnia
doesn't agree, but then this new study has a much larger species set, and
smaller (62 vs >10,000), common gene set.
-- Don
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Arthropod relationships revealed by phylogenomic analysis of nuclear
protein-coding sequences
doi:10.1038/nature08742
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature08742.html
Jerome C. Regier1, Jeffrey W. Shultz1,2,3, Andreas Zwick1, April Hussey1,
Bernard Ball4, Regina Wetzer5, Joel W. Martin5 & Clifford W. Cunningham4
Abstract
The remarkable antiquity, diversity and ecological significance of arthropods
have inspired numerous attempts to resolve their deep phylogenetic history, but
the results of two decades of intensive molecular phylogenetics have been
mixed1, 2, 3, 4, 5, 6, 7. The discovery that terrestrial insects (Hexapoda) are
more closely related to aquatic Crustacea than to the terrestrial centipedes and
millipedes2, 8 (Myriapoda) was an early, if exceptional, success. More
typically, analyses based on limited samples of taxa and genes have generated
results that are inconsistent, weakly supported and highly sensitive to
analytical conditions7, 9, 10. Here we present strongly supported results from
likelihood, Bayesian and parsimony analyses of over 41*kilobases of aligned DNA
sequence from 62 single-copy nuclear protein-coding genes from 75 arthropod
species. These species represent every major arthropod lineage, plus five
species of tardigrades and onychophorans as outgroups. Our results strongly
support Pancrustacea (Hexapoda plus Crustacea) but also strongly favour the
traditional morphology-based Mandibulata11 (Myriapoda plus Pancrustacea) over
the molecule-based Paradoxopoda (Myriapoda plus Chelicerata)2, 5, 12. In
addition to Hexapoda, Pancrustacea includes three major extant lineages of
*crustaceans*, each spanning a significant range of morphological disparity.
These are Oligostraca (ostracods, mystacocarids, branchiurans and pentastomids),
Vericrustacea (malacostracans, thecostracans, copepods and branchiopods) and
Xenocarida (cephalocarids and remipedes). Finally, within Pancrustacea we
identify Xenocarida as the long-sought sister group to the Hexapoda, a result
confirming that *crustaceans* are not monophyletic. These results provide a
statistically well-supported phylogenetic framework for the largest animal
phylum and represent a step towards ending the often-heated, century-long debate
on arthropod relationships.
