According to wikipedia they are cultivated from a hybrid of mandarin orange and Ichang papeda, the latter being from another wild lineage than the three shown.
This takes the citrus gram into 3D
> Recent genetic analysis shows the papedas to be distributed among distinct branches of the Citrus phylogenetic tree, and hence Swingle's proposed subgenus is polyphyletic and not a valid taxonomic grouping, but the term persists as a common name.
So what would be interesting is an interdimensional citrus fruit.