今天在wikipedia上看到说，橙（orange）（Citrus sinensis）可能是柚子（pomelo）（Citrus grandis）和橘（tangerine）（Citrus reticulata）的杂交品种。原文如下：

Orange fruits and a cross section of a third. The orange is a hybrid of ancient cultivated origin, possibly between pomelo and tangerine. Sometimes called the "sweet orange" to distinguish it from the bitter orange, the plant originated in Southeast Asia. The name is thought to ultimately derive from possibly the Telugu naarinja or Tamil nāram; both are names of the tree in the respective languages.

三种植物的生物学分类均属于

真核域 Eukarya
植物界 Plantae
被子植物門 Magnoliophyta
雙子葉植物綱 Magnoliopsida
無患子目(Sapindales)
芸香科(Rutaceae)
柑橘屬(Citrus)

是同一个属的三个种

ps. wiki真是个好东西