Citron
There are also a number of citron hybrids; for example, ponderosa lemon, the lumia and rhobs el Arsa are known citron hybrids, some are claiming that even the Florentine citron is not pure citron, but a citron hybrid.
Citrus
Most cultivated "Citrus" spp. seem to be natural or artificial hybrids of a small number of core ancestral species, including the citron, pomelo, mandarin, and papeda (see image). Natural and cultivated citrus hybrids include commercially important fruit such as oranges, grapefruit, lemons, limes, and some tangerines.