citrus family tree

i was eating a tangelo a couple weeks back, and i got to wondering where tangelos come from. i did a little research and discovered that they are a cross between a grapefruit and a tangerine. i then started wondering if a tangerine was the result of a cross of other citrus fruit. soon i found myself delving deep into the world of citrus taxonomy. man has been cultivating citrus for thousands of years. as a result, there are a whole lot more species of citrus fruit, and a whole lot more variations thereof than i ever realized. for example, have you ever heard of an oroblanco? did you know that a tangerine is simply a type of mandarin? anyway, it turns out that genetic mapping of different types of citrus fruit has given us a pretty good idea of how the different species of citrus came to be (gloria moore. trends in genetics, vol. 17, no. 9, 2001).

i've compiled a summary of that data, as well as data from other sources (e.g. wikipedia) (click on the image for a bigger view). the most ancient species are at the top (pomelo, mandarin, and citron), and the various crosses are indicated with the lines extending downward. two different fruits combine to form a new one beneath. for example, the orange is the result of a cross of a pomelo with a mandarin. the lime is a cross between the citron and an inedible citrus fruit that doesn't appear on the chart, hence the presence of only one parent for the lime.


i've only mapped the major species, not the different varieties like kaffir limes, tangerines, satsumas, cuties, and ruby reds. i found it interesting that not that much appears to be known about the origins of many specific varieties. in fact, the origins of many citrus fruit were just educated guesses based on morphological, historical, and geographical data until modern molecular biology came along. i'm continuing to search for information about the various varieties and may have more about that later. until then, i'd really like to get my hands on an oroblanco or rangpur (a.k.a lemanderin).