According to Eriksson et al. (2003) "The previously used genera Duchesnea (Potentilla indica), Horkelia, and Ivesia are strongly supported as nested within Potentilla". This treatment is followed by the New England Wild Flower Society's Flora Novae Angliae
Torsten Eriksson, Malin S. Hibbs, Anne D. Yoder, Charles F. Delwiche, and Michael J. Donoghue (2003). "The Phylogeny of Rosoideae (Rosaceae) Based on Sequences of the Internal Transcribed Spacers (ITS) of Nuclear Ribosomal DNA and the trnL/F Region of Chloroplast DNA". Int. J Plant Sci. 164 (2): 197–211. doi:10.1086/346163. (連結)
Ugh, so we're veering away from Jepson on this one?