If you cross two plants of the same species you get a very useful phenomenon of increased vigor, uniformaty and yeild.
This is commonly refered as hybrid vigor.
This is exploited by growers to improve plants size,quality of flowering and fruit.
An example is Camellia japonica reproduced sexually with Camellia saluenensis produces a hybrid which is called Camellia X williamsii.
This particular cross has produced many phenotypes which have been selected and propagated.
This means they are the same plant but with different characteristics.
I suppose it's like offspring of people,they share a combination of each gene of the parents.
One may have blond hair the other brown.
As with plants ,if the dominant gene is red and the sub-dominat is white then the flowers would mostly be red.
A ratio of say 3:1 If Rl may or may not at some time been crossed with another Ribes and produced Rs, or the other way round.
If I'm not mistaken sativum means cultivated.

R. sativum as grown in gardens is apparently a selection of a native red currant species of Northwestern Europe. A synonym for R. sativum is R. vulgare.

R. laxiflorum is apparently a species native to Northwestern North America.

Some cultivated currants are hybrids of different Ribes species.

Here is a link that might be useful: Ribes general information

Thanks so much for the link. Birds thank you, too :-)

Martie