Hemichordates and deuterostome evolution: robust molecular phylogenetic support for a hemichordate + echinoderm clade.
Hemichordates were traditionally allied to the chordates, but recent molecular analyses have suggested that hemichordates are a sister group to the echinoderms, a relationship that has important consequences for the interpretation of the evolution of deuterostome body plans. However, the molecular phylogenetic analyses to date have not provided robust support for the hemichordate + echinoderm clade. We use a maximum likelihood framework, including the parametric bootstrap, to reanalyze DNA data from complete mitochondrial genomes and nuclear 18S rRNA. This approach provides the first statistically significant support for the hemichordate + echinoderm clade from molecular data. This grouping implies that the ancestral deuterostome had features that included an adult with a pharynx and a dorsal nerve cord and an indirectly developing dipleurula-like larva.
Bromham
L D
LD
Department of Zoology and Entomology, University of Queensland, Brisbane 4072, Australia. lbromham@zoology.uq.edu.au
Degnan
B M
BM
D000818:Animals; D002816:Chordata, Nonvertebrate / Q000235:genetics*; D004447:Echinodermata / Q000235:genetics*; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics
D012337:RNA, Ribosomal, 18S