Here is how I would separate them at least in a quick writeup. Their are other differences; pistil shape, number, and pubescence, leaf pubescence, ecology, stamen/filament ratio and color (?), ..... Some of the other names (glabrata, pyrenaica) may just be extremes of clinal variation. H. pubescens from Japan I think may be valid, it is a tetraploid and therefore should be crossable with the members of Angulatae. Then again some people place them all in Anemone.... The two North American species are distinct from one another and from H. nobilis.
Leaves trilobed, margins mostly entire (occasionaly 2-3 crenate).........
Plants large, leaves 5-10cm....
Leaf apices acute.......H. acutlioba (2n=14)
Leaf apices obtuse.....H.maxima (2n=14)
Plants smaller.....
Leaves small 2-3 cm, pubescent, highly maculate..........H. insularis (2n=14)
Leaves larger, usually not heavily maculate, but occasional populations heavy, leaves mostly glabrous to glabrate
Petals spatulate,
Petals pale blues, purples, and white stigmans red in a single population (so far) (NA).............H. americana (2n=14)
Petals white, stigmas often red (Japan) .................. H. pubescens (2n=28)
Petals elliptic.................
Japan, Korea, eastern China.............H. japonica (and asiatica) (2n=14)
Europe.........................................H. nobilis (2n=14)
Leaves 5-7 lobed..............
Leaves deeply lobed, nearly to petiole (Pakistan and Kashmir)...........H. falconeri (2n=28)
Leaves not deeply lobed....
Lobes acute to subacute, bracts bifid to trifid occasionly(petals often pink abaxially)(China)............................. H. yamatutai (2n=28)
Lobes mucronulate to obtuse, margin crenate.....
Leaves small, mostly crenate, petals frequently bifid to trifidly crenate at apex (China) ........H. henryi (2n=28)
Leaves larger, mostly crenate, petals usually blue (Carpathians)............................H. transilvanica (2n=28)
Transilvanica is also rhizomatous and is the only one that is from my observations. It would be great for hybridizing with tetraploid forms of acutlioba and others (time to get out the colchicine in the lab).
Steussy et al. have a paper on the phylogeny of Hepatica, but I have yet to see it even though it says its published on Google Scholar!
Aaron Floden