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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!

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  • $\begingroup$ I don't know any resource you can use right now, but one thing you'll need to be aware of is that genetic diversity generally correlates with (effective) population size. This means that species like insects should generally have higher genetic diversity than mammals just because there are more of them in a given population. $\endgroup$ – Nicolai May 16 '18 at 14:27
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You can look at the Heterozygous SNP rates in genome-sequenced species, which is a measure of within species diversity.

You have an example in Figure 4 here: https://genomebiology.biomedcentral.com/track/pdf/10.1186/s13059-016-1090-1

You can see in the figure that endangered species are plotted (most of them with poor genetic diversity).

Also, I am afraid that your starting hypothesis is not very good. Our species is very poor in genetic diversity and has little phenotypic variation. The human species went through several major bottlenecks during his evolutionary history that reduced their diversity. Even gorillas or giant pandas are more diverse than humans. You have a bias because you are human and are good at differentiating individuals from your own species.

Also a single representative from each group won't suffice as the differences can be huge inside a group. Additionally phenotypic variation is hard to measure in certain groups.

Sorry for being a bit negative

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  • $\begingroup$ Yes, my ad-hoc hypothesis is probably wrong, as becoming clear after some more research. On the other hand, if including ethological traits into "phenotypic diversity", the grasshopper-human comparison will still hold. But no direct correlation with genetic diversity. Figure 4 is part of what I am looking for, but it should be inter-phyla. One runs into a bunch of problems when asking the question as I did, I see. Will try to unsnarl this a bit more when reading on. $\endgroup$ – megob May 16 '18 at 16:08
  • $\begingroup$ Turns out this is in fact a subject in recent discussion: "Understanding why some species have more genetic diversity than others is central to the study of ecology and evolution, and carries potentially important implications for conservation biology. Yet not only does this question remain unresolved, it has largely fallen into disregard. With the rapid decrease in sequencing costs, we argue that it is time to revive it." journals.plos.org/plosbiology/article?id=10.1371/… and some more. $\endgroup$ – megob May 17 '18 at 20:43
  • $\begingroup$ I did not say it was not possible, or not interesting to do it. Simply that humans are not a diverse species. In fact the HSNP value is quite easy to compute from a genome, if it has not already been calculated by the genome consortium responsible of the assembly. $\endgroup$ – biojl May 18 '18 at 12:21

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