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.
> 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.
> 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