James and the Giant Corn Genetics: Studying the Source Code of Nature

June 17, 2009

Phylogeny of Pineapple, an further explanation of awesomeness

Filed under: Plants — James @ 9:34 pm

If you had to guess, how would you rank these species in order of how closely they’re related to to pineapple:

Orange, Papaya, Corn, Avacado, Juniper, Banana

Answer after the jump.

The answer turns out to be (least to most related):

Juniper, Orange and Papaya in a tie, Avacado, Banana, and most closely related of all Corn.

In other words the family tree looks like this:


Starting with the least related gives us juniper. Juniper berries, which contribute the distictive flavor of gin, aren’t really berries at all, but in fact highly modified cones. Juniper is a conifer, more closely related to your chistmas tree than to blueberries or strawberries.

Next we come to Orange and Papaya. Both of these species are eudicots, the most abundant group of plant species on the plant. Eudicots are generally what people (especially from the northern hemisphere) think of as normal looking plants. Deciduous trees, vegetables from beets to watercress(can’t think of A, Y, or Z vegetables, clearly I don’t eat enough of them), beans, clover, watermellons, roses, chilli peppers, potatoes, rhubarb and on and on and on. Name twenty plant species and I bet 12-18 of them will be eudicots.  The name means new-two-leafed from the fact that eudicot seeds contain embryos with two leaves. It used to just be dicot (two-leafed) but it turns out that some plants with two embryo leaves don’t fit the pattern, so they added eu- (new) to the name to justify throwing out the other dicots and make the evolutionary tree of plants make more sense.

A lot of the dicots they threw out fall into a group called Magnoliids (like magnolias which are contained in this group.) Even though these species form two embryo leaves, they’re more closely related to the monocots (species that form only one embryo leaf) than they are to the eudicots. This is where we find avacado. This is a completely neglected group of species genomically so if you happen to be fabulously wealth, interesting in plant genetics, and were wondering what genome you should fund the sequencing of, there’d be lots of comparative genomics stuff we could do with the avacado genome.

But now we come to Banana.  Banana, as well as Pineapple and Corn are a members of the monocot group I mentioned in the last paragraph. If you’re a real botany geek you can often recognize monocots simply by the pattern of veins in their leaves. Monocots aren’t as diverse as the eudicots but there as still a lot of species includeing palm trees, orchids (20-some thousand species of orchids alone, four times more than all the species of mammal in the world) and subgroup that both pineapple and corn belong to, poales.

Within Poales, pineapple is in the bromeliad family, along with those plants you may have seen in nature documentaries that grow attached to giant rainforest trees and shelter tiny pools of water at the center of their leaves that are home to everything from flatworms to inch long salamanders that live nowhere else.

Corn is also with Poales, but it belongs to the grass family. Grasses are the biggest exception to the the general dominance of the eudicots among plant life.  Only three grass species corn, rice, and wheat, provide more than half the total calories consumed by the entire human race (by definition more than all eudicots combined!). And that calorie cound doesn’t consider other vital grass crops such as Barley, Millet, Oats, Rye, Sorghum and Sugarcane.  And calories don’t factor in the usefulness of bamboo, which can grow more than a foot a day under the right conditions, as a structural material and food for pandas or the that fact that most organized sports owe their existence to turfgrass.

Counterintuitively Pineapple ends up being a reasonably close relative of corn and the other grasses. And that family tree is yet another reason why pineapple is awesome.

1 Comment »

  1. Artichokes to zucchini, perhaps.

    Comment by grandma beth — June 20, 2009 @ 6:12 pm

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