FYI
Alert
1) Annelid molecular phylogeny
2) Cambrian Halwaxiids = halkieriids & wiwaxiids
Rousset, V., Pleijel, F., Rouse, G.W., Erseus, C. & Siddall, M.E. (2007)
A molecular phylogeny of annelids. Cladistics, 23(1), 41-63.
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1096-0031.2006.00128.x
Abstract: We present parsimony analyses of annelids based on the largest
taxon sample and most extensive molecular data set yet assembled, with
two nuclear ribosomal genes (18S rDNA and the D1 region of 28S rDNA),
one nuclear protein coding-gene (Histone H3) and one mitochondrial
ribosomal gene (16S rDNA) from 217 terminal taxa. Of these, 267
sequences are newly sequenced, and the remaining were obtained from
GenBank. The included taxa are based on the criteria that the taxon must
have 18S rDNA or at least two other loci. Our analyses show that 68% of
annelid family ranked taxa represented by more than one taxon in our
study are supported by a jackknife value > 50%. In spite of the size of
our data set, the phylogenetic signal in the deepest part of the tree
remains weak and the majority of the currently recognized major
polychaete clades (except Amphinomida and Aphroditiformia) could not be
recovered. Terbelliformia is monophyletic (with the exclusion of
Pectinariidae, for which only 18S data were available), whereas members
of taxa such as Phyllodocida, Cirratuliformia, Sabellida and Scolecida
are scattered over the trees. Clitellata is monophyletic, although
Dinophilidae should possibly be included, and Clitellata has a sister
group within the polychaetes. One major problem is the current lack of
knowledge on the closest relatives to annelids and the position of the
annelid root. We suggest that the poor resolution in the basal parts of
the trees presented here may be due to lack of signal connected to
incomplete data sets both in terms of terminal and gene sampling, rapid
radiation events and/or uneven evolutionary rates and long-branch
attraction.
Morris, S.C. & Caron, J.-B. (2007) Halwaxiids and the Early Evolution of
the Lophotrochozoans. Science (2 March 2007), 315, 1255-1258.
http://www.sciencemag.org/cgi/content/abstract/315/5816/1255
Abstract: Halkieriids and wiwaxiids are cosmopolitan sclerite-bearing
metazoans from the Lower and Middle Cambrian. Although they have similar
scleritomes, their phylogenetic position is contested. A new
scleritomous fossil from the Burgess Shale has the prominent anterior
shell of the halkieriids but also bears wiwaxiid-like sclerites. This
new fossil defines the monophyletic halwaxiids and indicates that they
have a key place in early lophotrochozoan history.
Geoff
--
Geoff Read <g.read from niwa.co.nz>
http://www.annelida.net/http://www.niwascience.co.nz/ncabb/
