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I'm reading through Plant Systematics, 3rd Edition by Michael G. Simpson, and am having a hard time understanding the differences between the Chlorophytes and Streptophytes - discussed in Chapter 3: Evolution and Diversity of Green and Land Plants.

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The cladogram (from the second edition) makes it seem like the development of oogamy and plasmodesmata delineate the Streptophytes from the Chlorophytes, yet, still we see a few lineages within Streptophytes without either of these apomorphies (even in the third edition's version of this cladogram).

Where do we really draw the line between these sister groups?

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    $\begingroup$ Welcome to Biology.SE. Don't know the answer, but a quick look at the relevant wikipedia pages suggests they may be helpful — the short version is it depends on how the groups have been defined ... Also note that from your diagram it seems clear that neither oogamy or plasmodesmata are relevant — they distinguish Charophytes from other Streptophytes. $\endgroup$
    – tyersome
    Apr 12, 2022 at 0:23
  • $\begingroup$ @tyersome the figure in 3.1 of the third edition actually doesn't even indicate Charophytes, but does include a Charophyceae lineage diverging from the rest of the Stroptophytes directly after the development of oogamy and plasmodesmata. Confusingly, Simpson goes on to discuss apomorphies of the Charophytes and references that figure even though there are no Charophytes. This may be an error? I've gotten a hold of the article that this cladogram was roughly based on (bmcecolevol.biomedcentral.com/articles/10.1186/1471-2148-14-23), so I'll update this with whatever I find. $\endgroup$ Apr 13, 2022 at 21:34
  • $\begingroup$ @tyersome looks like the evidence for the division between these two groups is primarily genetic data. I will answer my question below shortly. $\endgroup$ Apr 13, 2022 at 23:45

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In the article cited by Simpson in creating the rough cladogram of Figure 3.1, From algae to angiosperms-inferring the phylogeny of green plants (Viridiplantae) from 360 plastid genomes (Ruhfel et. al, 2014), the phylogeny of Viridplantae is inferred from a set of 78 genes.

Thus, the division of Viridiplantae into the two sister groups Chlorophyta and Streptophyta is inferred / supported by molecular evidence.

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