I am looking for information on how genetic diversity within a species (not between species) differs between taxa. In other words: Is the "spread" in the genetic pool, if measured, for instance, in terms of single-nucleotide polymorphism (SNP), generally bigger / smaller for some groups of species than for others?
My ad-hoc idea is that species with a stronger phenotypic difference between individuals, like homo, should probably have a higher genetic diversity (higher rate of SNP) than those with lesser phenotypic variation, like, say, Orthoptera (grasshoppers etc.). But I couldn't find any statistics or research on this topic.
I am especially interested in data on far-related taxa. Ideally this would be a chart with comparative data for Sponges, Annelids, Arthropoda, Fish, Mammals (single representatives of these groups), or even Plants, Fungi, Archeae, Bacteria …
I do not look for information on the actual genome sequences, nor on biodiversity, but specifically on the genetic diversity within species from different phyla.
This is my first question here, thanks for you help!