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Molbio-Evol message (fwd)

Dan Davison Davison at UH.EDU
Mon May 10 15:25:14 EST 1993

I received the following message asking me to post it to
molecular-evolution, so here goes.

Comments should go to bohart at ucdavis.edu.

bohart at ucdavis.edu said:
> From bohart at ucdavis.edu Fri May  7 15:14:56 1993
> Date: Fri, 07 May 1993 13:06:01 -0700 (PDT)
> From: bohart at ucdavis.edu
> Subject: Molbio-Evol message
> To: davison at uh.edu
> Message-Id: <9305072006.AA23146 at bullwinkle.ucdavis.edu>
> Content-Transfer-Encoding: 7BIT
> Dan: I hope you may find this of interest and will be able to post it
> to molbio evolution.  At last check, Mol. Phyl. & Evol. was not indexed
> in either current contents or Medline.
> Thank you- Dave Carmean
> 18S rDNA Sequences and the Holometabolous Insects.
> David Carmean, Lynn Kimsey, and Mary Berbee.  1992 (published 1993). 
> Molecular Phylogenetics and Evolution  1(4): 270-278. 
> Summary: 
> Diptera violate the molecular clock for the Holometabola and 
> should not be used as representative insects in 18S rDNA studies. 
> Siphonaptera and Mecoptera are consistent with other Holometabola. 
> The Neuropteroidea and the Coleoptera probably do not form a monophyletic 
> clade. The Coleoptera consistently come out basal to the other Holometabola. 
> The Neuroptera have A-T rich expansion regions or insertions.
> Abstract:
> The Holometabola (insects with complete metamorphosis: beetles, wasps,
> flies, fleas, butterflies, lacewings, and others) is a monophyletic group
> that includes the majority of the world's animal species.  Holometabolous
> orders are well defined by morphological characters, but relationships
> among orders are unclear.  In a search for a region of DNA that will
> clarify the interordinal relationships we sequenced approximately 1080
> nucleotides of the 5' end of the 18S ribosomal RNA gene from
> representatives of 14 families of insects in the orders Hymenoptera
> (sawflies and wasps), Neuroptera (lacewing and antlion), Siphonaptera
> (flea), and Mecoptera (scorpionfly).  We aligned the sequences with the
> published sequences of insects from the orders Coleoptera (beetle) and
> Diptera (mosquito and Drosophila), and the outgroups aphid, shrimp, and
> spider.  Unlike the other insects examined in this study, the neuropterans
> have A-T rich insertions or expansion regions: one in the antlion was ~260
> bp long.  The dipteran 18S rDNA evolved rapidly, with over 3 times as many
> substitutions among the aligned sequences, and 2-3 times more unalignable
> nucleotides than other Holometabola, in violation of an insect-wide
> molecular clock.  When we excluded the long-branched taxa (Diptera, shrimp,
> and spider) from the analysis, the most parsimonious (minimum-length) trees
> placed the beetle basal to other holometabolous orders, and supported a
> morphologically monophyletic clade including the fleas + scorpionflies (96%
> bootstrap support).  However, most interordinal relationships were not
> significantly supported when tested by maximum likelihood or bootstrapping
> and were sensitive to the taxa included in the analysis.  The most
> parsimonious and maximum-likelihood trees both separated the Coleoptera and
> Neuroptera, but this separation was not statistically significant.  The
> position of the Hymenoptera relative to other orders was not clarified.
> Including the less derived members in the analysis made the Hymenoptera
> appear paraphyletic.  The two representatives of Neuroptera grouped
> together as did the two Diptera, both pairs with very significant bootstrap
> support.  (Copyright Academic Press)
> Please send reprint requests to: dacarmean at ucdavis.edu  or:
> David Carmean
> Department of Entomology
> University of California, Davis
> Davis, California, 95616-8584

dr. dan davison/dept. of biochemical and biophysical sciences/univ. of
Houston/4800 Calhoun/Houston,TX 77204-5934/davison at uh.edu/DAVISON at UHOU

"Without the voice of reason, every faith is its own curse" -- Sting

Disclaimer: As always, I speak only for myself, and, usually, only to

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