Campbell, Lahcen I.
A cause for consilience: Utilizing multiple
genomic data types to resolve problematic
nodes within Arthropoda and Ecdysozoa.
PhD thesis, National University of Ireland Maynooth.
A major turning point in the study of metazoan evolution was the recognition of the
existence of the Ecdysozoa in 1997. This is a group of eight animal phyla (Nematoda,
Nematomorpha, Loricifera, Kinorhyncha, Priapulida, Tardigrada, Onychophora and
Arthropoda). Ecdysozoa is the most specious clade of animals to ever exist and the
relationships among its eight phyla are still heatedly debated. Similarly also the
relationships among the three sub-phyla (Chelicerata, Pancrustacea and Myriapoda)
within the most important ecdysozoan phylum (the Arthropoda) are still debated.
Indeed, the two major problems in ecdysozoan phylogeny refer to the relationships of
Myriapoda within Arthropoda, and of Tardigrada within Ecdysozoa. Difficulties in
ecdysozoan relationships resides in lineages characterized by rapid, deep divergences
and subsequently long periods of divergent evolution. Phylogenetic signal to resolve
the relationships of these lineages is diluted, increasing the likelihood of recovery of
In an attempt to resolve the relationships within Ecdysozoa, consilience of three
independent phylogenetic data sets was investigated. EST and rRNA and microRNA
(miRNA) data were sampled across all major ecdysozoan phyla. In particular, a
major contribution of this thesis is the first time sequencing of miRNAs for all the
panarthropod phyla. MicroRNAs are genome regulatory elements that recently
emerged as a source of useful phylogenetic data (Sempere et al. 2006) because of
their low homoplasy levels.
The considered data sets were analysed under phylogenetic methods and models,
implemented to minimize the occurrence of phylogenetic reconstruction artifacts to
understand the evolution of Ecdysozoa. Analyses of independent data types recovered
well supported and corroborating evidence for the monophyly of Panarthropoda
(Arthropoda, Onychophora and Tardigrada), a sister group relationships between
Myriapoda and Pancrustacea within Arthropoda, and the paraphyly of Cycloneuralia
(Nematoda, Nematomorpha, Loricifera, Kinorhyncha and Priapulida). !
||genomic data types; problematic nodes; Arthropoda; Ecdysozoa;
||Science & Engineering > Biology
||21 Nov 2012 14:32
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