I think the UESP wiki has either got it backwards or wrong. Like they say, in Daggerfall Atronachs are contructs, not Daedra, as they are in Morrowind and Oblivion. They thus connect the Fire Daedra and Frost Daedra to the Flame and Frost Atronachs of the later games, since the Atronachs of later games are considered daedra.
I think the real answer here, though, is that the Fire Daedra and Fire Atronach, and the Frost Daedra and Ice Atronach, were merged into one creature: the Flame Atronach and Frost Atronach respectively. I think the appearance of the Flesh Atronach, which is considered a Daedra in the Shivering Isles (or, at least by the Imperial Library) bears this out.
And besides sharing the name of "Atronach", the daedra atronach of later games look more like the Daggerfall constructs then the Fire and Frost Daedra of Daggerfall.
So, by the available current lore, I'd consider:
Fire Atronach(II)+Fire Daedra(II)=Flame Atronach(III)=Flame Atronach(IV)
Ice Atronach(II)+Frost Daedra(II)=Frost Atronach(III)=Frost Atronach(IV)
Flesh Atronach(II)=Flesh Atronach(IV)
Iron Atronach(II)=?
Wind Atronach(II)=?
Storm Atronach(III)=Storm Atronach(IV) Perhaps since Iron and Wind Atronachs haven't been seen since Daggerfall, the Storm Atronach is a merging of the two?
I know you're speaking of the traditional magical elements (Fire-Earth-Water-Air) but just to correct you, scientifically iron is an element. Right there as number 26 on the Periodic Table. Designated as Fe. Actually, its the only truly element atronach. Fire is not an element, neither is lighting, they are both plasma---ice/water is not an element, its a compound----and wind is really just a phenomenon of planets with atmospheres..