The three domesticated descendants of wild C. annuum, Capsicum annuum var. annuum, Capsicum chinense and Capsicum frutescens form the base from which virtually all the chile peppers and paprikas known today in North America, Europe and Asia have been developed.
The relationship between the before mentioned domesticated trio is still at best unclear. They are genetically almost similar plants, and e.g. Hunziker (2001) has treated them as just variations of one species. Other researchers disagree, though, and the considerable external differences between these plants justify treating them separately here. It has been suggested that Annuum, Chinense and Frutescens all have a common wild form, but a long ago something happened which formed the still quite wild-like Frutescens form. The Chinense form is believed to have developed from Frutescens. This theory isn't without its weaknesses, though, and the only thing we can be sure of is that all these three plants cross quite easily, and can be used to improve each other commercially.