Entering edit mode
5.6 years ago
jaqx008
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110
Hello all. I have two basal animals belonging to sub-phyla cephalochordate and urochordate (both in the chordate phylum). In different phylogenetic studies, cephalochordates evolved before urochordate, in other studies, urochordate comes before cephalochordates. Its vital for my study to identify which truly evolved first. However, I am trying to figure out a way to go about this and what are the factors to consider or use for building a phylogenetic tree that can help resolve this? thanks
Do you have a molecular clock for any of them?
I do not have a molecular clock for them. Is there a place you would suggest I begin? What sort of data can I use as this clock to create a phylogenetic tree?
However, there is a protein they both posses that do not exist along the higher chordate groups.
Yeah as the comment below states, its essentially impossible to know for sure unless you have ancient sequencing data to calibrate with.
the best i can think you’d do is Bayesian and maximum likelihood estimation, with something like BEAST perhaps.
The other option might be to test both hypotheses (i.e. with each occurring earlier than the other) and see if there is a more parsimonious/justifiable explanation for your study/data, one way round rather than the other.
I don't think that's possible. Taxonomic hypotheses get updated all the time with improving techniques and newly discovered fossils. Use whichever hypothesis has the broadest consensus and uses the best techniques.
Also, different tree-building methods can give very different results. You'll need to have an idea of the model of evolution.
Ok, Thank you for your contribution