A reader brought up the subject (he perceived it as a problem) of the very low consistency index (CI) in the large reptile tree. 340 taxa were tested against 228 characters. The reader thought too few characters were employed and that was the cause for the low CI.
The CI for the entire tree is .099. Very low, but not necessarily bad… as we shall see…
I mentioned in my reply to the reader that this was due to the high level of homoplasy in the reptile tree due to the large number of taxa sharing so many traits. I suggested the CI would rise with fewer taxa and all other variables held constant. That’s easy to do by chopping the large reptile tree apart.
Here are a few CIs focused on clades, using the same character list (228), but far fewer taxa in each case.
Watch those CI numbers rise!
All non-amniote tetrapods: .429
Permian/Triassic/Cretaceous gliders: .836
Rhynchocephalia (includes trilophosaurs and rhynchosaurs): .659
Tritosaurs (includes fenestrasaurs, pterosaurs): .735
Enaliosauria (Claudiosaurus, mesosaurs, ichthyosaurs, thalattosaurs, plesiosaurs, placodonts and kin): .360
Euarchosauriforms (no choristoderes, parasuchians, chanaresuchids or Lagerpeton) : .322
Archosauria (crocs and dinos): .417
Dinosauria (includes poposaurs): .523
Hope these numbers help the cause and provide understanding for the very low CI for the entire tree. The beauty of having a large tree is having the ability to easily chop it into many small trees to test various hypotheses. Unfortunately, there’s much more work for small focused trees to test larger gamuts of taxa or characters. Maybe that’s why it isn’t done.
We could always use better characters. I freely admit that some of my characters could use a little help. Some of them weight various traits, but they do it across the board. We could also use more characters, but if we add in the trait of a “carapace present” we would still end up with several convergent instances of that trait, which does nothing to increase the CI number.
It is what it is, dependent on the number of taxa employed and their rampant convergence in the large reptile tree. The data determines the results, not the other way around.
On an editorial note
A recent post engendered several irate responses from readers, most of which included negative attributions and insults. Those had to be trashed. Via private email I encouraged those readers to focus on the taxa, not the author, and make specific suggestions as to how to improve the taxon reconstructions. As you know, these then become the data that ultimately produce the family tree. Changes are made weekly. When new valid data come in, they are welcome. Readers who have no time or inclination to provide fresh data, yet find plenty of time to rant without substance, are not helping my cause or theirs. They end up frustrated. I end up wondering why they can’t provide even a little evidence. I’m led to believe those who do not provide evidence have none.
Hopefully every time I have dismissed a claim or promoted one in these 750 posts, I have provided pictorial and other evidence with references. Disregarding the evidence is your right. Choosing to support bad evidence is also your right. But those who do so run the risk of ultimately looking foolish to villainous when the tide turns. I run the risk of being wrong, but am always willing to right the wrongs. But I need fresh valid data.
I hope you all understand. I’m trying to keep this site and the data it is built upon on a professional level.
The large reptile tree has grown to where no paleontologist has gone before, conquering a larger gamut of reptiles and in doing so demystifying many relationships and former enigmas simply by being ever more inclusive. That’s a good thing, guys. Embrace it! Use it!
Some pertinent thoughts from ant expert, E. O. Wilson:
While generally lauded today, earlier in his career Dr. E. O. Wilson was reviled for some of his novel ideas*. The following Wilson quotes seem pertinent:
“Without a trace of irony I can say I have been blessed with brilliant enemies. I owe them a great debt, because they redoubled my energies and drove me in new directions.”
“Between scientists, you can have high competitiveness and jealousy and petty nit-picking, because we are human. But once something is nailed, the person who did it usually gets the credit, and we move on.”
“But the best way to do it is – to make discoveries – is to make short imperfect experiments.”
In the water incident, Wilson’s lecture was attacked by the International Committee Against Racism, a front group of the Progressive Labor Party, where one member poured a pitcher of water on Wilson’s head and chanted “Wilson, you’re all wet” at an AAAS conference in November 1978. Wilson later spoke of the incident as a source of pride: “I believe…I was the only scientist in modern times to be physically attacked for an idea.”