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APG I and II lump Chenopodiaceae into Amaranthaceae, using the latter name which has priority. This seems to be a case of "lumping on the basis of ignorance." Based solely on rbcL trees (e.g., Kadereit et al., 2003) the two groups are monophyletic except that the betoid group remains unresolved. Based on 4 genes but a very small sample (2 + 3 genera), Cuenoud et al. (2002) found two monophyletic groups.
Clearly, various alternative eventual resolutions of this issue are possible. However, it is likely that the betoids will either end up going with the old Amaranthaceae s.s., or the old Chenopodiaceae, and there will still not be a need to lump the two families.
Lumping makes little sense when two large families are largely intact, but require a few generic transfers. Keeping traditional names and circumsriptions retains continuity and stability with the older literature. Lumping these two families on the basis of ignorance will only generate more ignorance - an inability to connect modern usage to traditional usage without qualification, adding considerably to the likelihood of error. |
