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To: Junior, VadeRetro
Molecular phylogenetic evidence for the independent evolutionary origin of an arthropod compound eye
Todd H. Oakley and Clifford W. Cunningham
Proc. Natl. Acad. Sci. USA, Vol. 99, Issue 3, 1426-1430, February 5, 2002
Eyes often take a central role in discussions of evolution, with debate focused on how often such complex organs might have evolved. One such debate is whether arthropod compound eyes are the product of single or multiple origins. Here we use molecular phylogeny to address this long-standing debate and find results favoring the multiple-origins hypothesis. Our analyses of DNA sequences encoding rRNA unequivocally indicate that myodocopidsthe only Ostracoda (Crustacea) with compound eyesare nested phylogenetically within several groups that lack compound eyes. With our well-supported phylogeny, standard maximum likelihood (ML) character reconstruction methods significantly reconstruct ancestral ostracods as lacking compound eyes. We also introduce a likelihood sensitivity analysis, and show that the single-origin hypothesis is not significantly favored unless we assume a highly asymmetric model of evolution (one favoring eye loss more than 30:1 over gain). These results illustrate exactly why arthropod compound eye evolution has remained controversial, because one of two seemingly very unlikely evolutionary histories must be true. Either compound eyes with detailed similarities evolved multiple times in different arthropod groups or compound eyes have been lost in a seemingly inordinate number of arthropod lineages.

1,925 posted on 03/25/2002 3:17:55 PM PST by Nebullis
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To: Nebullis
We also introduce a likelihood sensitivity analysis, and show that the single-origin hypothesis is not significantly favored unless we assume a highly asymmetric model of evolution (one favoring eye loss more than 30:1 over gain).

OK. I don't like "multiple loss" in something that would obviously be very valuable. I can see why they made the call the way they did.

1,927 posted on 03/25/2002 3:20:15 PM PST by VadeRetro
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To: Nebullis
These results illustrate exactly why arthropod compound eye evolution has remained controversial, because one of two seemingly very unlikely evolutionary histories must be true. Either compound eyes with detailed similarities evolved multiple times in different arthropod groups or compound eyes have been lost in a seemingly inordinate number of arthropod lineages.

It appears as if that "random" bugaboo has someone flummoxed again.

1,933 posted on 03/25/2002 3:44:48 PM PST by AndrewC
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To: Nebullis
or compound eyes have been lost in a seemingly inordinate number of arthropod lineages.

Sounds like devolution to me!

1,974 posted on 03/25/2002 10:06:17 PM PST by gore3000
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To: Nebullis
Neat. I learn something new every day. Time to upgrade my thinking.
1,981 posted on 03/26/2002 1:37:49 AM PST by Junior
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