Endozoochory
When I was reading up on the myrtles and especially on Myrcia splendens, I found that the seeds were said to be dispersed by endozoochory. I did not mention this in the earlier post because I needed to do a little research about the term.
The roots of the word are:
- endo = within
- zoo = animal
- chori = to part or separate
The definition of the term, from the Oxford Dictionary of Plant Science, is: Dispersal of spores or seeds by animals after passage through the gut. The animal takes the seed within and walks (or flies or swims) away to deposit it elsewhere, thereby separating the seed from the plant that produced it.
When you start thinking about how a plant might spread its seeds beyond the place where the parent plant lives, you can see that the plant has a problem. It doesn’t move, at least at our scale of time. When I tried, without looking it up, to come up with ways a plant might disperse its seeds, I thought of wind, water, and animals. Indeed plants do use these agents and they’ve also come up with dispersal by gravity and by mechanical means (e.g., explosive seed capsules) (wikipedia).
So which method was used first by plants?
I would have guessed that it would be wind, since it seems to me that all plants experience wind at some time or another. Although if I allow myself to think a little more thoroughly about it, all plants certainly experience gravity as well, and it is highly likely that all plants experience animals, too, if only in the form of insects.
At any rate, the question of seed dispersal was addressed by British botanist E.J.H. Corner, who in 1949 published The Durian Theory, or the Origin of the Modern Tree. His theory was that endozoochory arose before any other method of seed dispersal, and that primitive ancestors of Durio species were the earliest practitioners of that dispersal method, in particular the red durian exemplifying the primitive fruit of flowering plants (wikipedia).
Now Corner was based in Singapore and naturally might concentrate on an Asian fruit. The Durian fruit is known there as the “King of Fruits” and is famous for its odor, which sounds absolutely obnoxious. See the wikipedia article on Durian fruit for some wicked descriptions – including this one by travel writer Richard Sterling:
… its odor is best described as pig-shit, turpentine and onions, garnished with a gym sock. It can be smelled from yards away.
However, Corner is kinder to the fruit. He says:
They then have a powerful and disgusting smell, of garlic and skatol, but the creamy aril is so delicious that the durian is the most popular and famous fruit of the East.
It is, however, banned on Singapore Public Transport!
What puzzles me, as a human animal, is why would I want to eat and therefore disperse a fruit as smelly as that? But Corner says:
In the season the smell of the fruits attracts the elephants which
congregate for first choice; then come the tigers, pigs, deer, tapir, rhinoceros,
monkeys, squirrels, and so on down to ants and beetles which scour the last
refuse.
So it obviously appeals to many animals! He goes on to say:
There is certainly more to be learnt about the significance of this factor as the ultimate appetizer, as there is with the chemical protection of the immature fruit. There must have been many more smells to attract the early elephants and tapirs and the short-sighted beasts; and it would seem that to them we owe the selection and survival of the durian.
Corner does have many botanical reasons for arguing that a durian-type fruit was the first to take advantage of seed dispersal by animals. Naturally, there are refutations of this idea, as exemplified by an article in 1974 by D. J. Mabberley, which requires a greater understanding of botanical terminology than I have.
Nevertheless, it’s a fine thought that the process of endozoochory first brought about wide dispersal of seeds and ultimately the evolution of the modern tree.
