[Annelida] Alert - Annelid molecular phylogeny / Halwaxiids = halkieriids & wiwaxiids

Geoff Read via annelida%40net.bio.net (by g.read from niwa.co.nz)
Tue Mar 27 15:50:57 EST 2007


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/




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