When looking broadly at the tree of life, my feeling is that, after a divergence there is almost systematically one taxon that speciates way more than the other.
(There will have some approximations below it is not really the point of my question to discuss whether the urochordata is a sister group to the vertebrates or not.) Let's look at the kingdom Animalia for example:
- Chaonflagellata vs "the others"
- Sponges vs "the others"
- Cnidaire and cténaire vs "the others"
- Protostomia vs Deuterostomia (both are fairly equally diverse diverse! Some might not be happy with this claim!)...let's continue with the Deuterostomata
- echinodermata vs chordata
- cephalocordata vs vertebrata
- Is there really a systematic difference in diversity between the branches?
- Is this difference can be explained by chance?
- Is it only a bias due to out ability to recognize more species in animals that look more like us (or a bias due to something else)?
- Does it make sense to say: the more diverse is a taxon, the more likely it is that it gets even more diverse (because each species might have an equal chance to speciate or something like this)?