The recent history of the taxonomy of the Silverweed species of eastern North America is pretty messy, though not (of course) among the world’s worst. Four popular online expert sources from the past 15 years all divide them up differently! iNaturalist uses the treatment in Plants of the World Online; that one’s the most recently updated, too. I’ve put together a table showing how those four (POWO, GoBotany, FNA, and USDA’s PLANTS [via ITIS]) do or don’t correspond to each other. And for comparison Gray’s Manual of Botany (8th edition, 1950) familiar to many of us because of its use as the taxonomic basis for Newcomb’s Wildflower Guide.
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Addendum: Fernald (1950) has a far northern taxon P. egedei var. egedei. I think that this is P. anserina subsp. egedii for PLANTS, P. anserina subsp. groenlandica for FNA, Argentina anserina subsp. groenlandica for POWO (and outside the scope of Haines’s discussion).
OK, one more table: it seems more complicated but it actually isn’t – as I discuss below.
We can see that the PLANTS treatment is the only one that’s different from the others in the circumscription of taxa. In 1821, Trattinick named P. anserina egedii and P. anserina groenlandica for specimens from Greenland. Fernald maintained the distinction between the two subspecies although considering them to belong to species egedii, and thought that Potentilla pacifica, named by Howell in 1898, was synonymous with P. egedii subsp. groenlandica. None of the more recent sources except Haines agree with the latter idea. And all except the PLANTS group have dropped the distinction between egedii and groenlandica, considering them a single subspecies for which the name groenlandica is valid. The PLANTS group, however, maintained egedii and thought that Trattinick’s groenlandica was a synonym of anserina. What’s more, their egedii includes P. anserina subsp. rolandii, named by B. Boivin on the basis of a specimen from Sable Island, N.S., which everyone else considers to be pacifica. The two most recent sources agree on which subspecies there are, only disagreeing as to whether they are divided among one or two species, and whether to accept the genus Argentina.
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