I guess only in the sense that they are all citrus.
The Poncans are actually tangerines, whereas limes and lemons are not. Tangerines differ from regular "oranges" in that the skin is easy to peel off from the actual fruit.
The Poncans are exceptionally sweet and flavorable. You don't usually find them in grocery stores because I understand that they don't travel as well as some other varieties. The "Dancy" seems to be the tangerine you most commonly see at stores.
There are a lot of different varieties of citrus, and they all seem to have different properties.
For instance the Hirado Butan Pummelo that Connie is growing is a form of grapefruit, but it is quite large and she says much sweeter than the typical grapefruit.