Agent of distribution--Maclura

ima pseudonym fictitious at alias.incognito.myob
Tue Nov 26 19:29:23 EST 1996


In article <monique.608.019A867B at bio.tamu.edu>, monique at bio.tamu.edu says...
>Following on the whole why-fruits-are-round discussion, let me pose this to 
>the group.
>What would you say was the original means of dispersal for seeds/fruit of 
the 
>Osage Orange (Maclura pomifera), also known as Bois d'Arc and Horse Apple?
>We are dealing with a large (ca. 1 kilo) fruit to about 10 cm in diameter.  
>They are green (not a bird-attractive color) and full of a sticky, milky 
sap. 
> A multiple fruit, the interior has a number of small seeds and the flesh is 
>not at all like edible members of the Moraceae such as figs or mulberries.  
It 
>seems a tremendous expenditure for the plant in terms of fruit production!
>While squirrels will *occasionally* rip them open to get to the seeds and a 
>friend swears she has seen a horse eat one, the vast majority of these 
things 
>seem to drop right under the tree and decay.  (The fruit have great 
>recreational value for small children, but I hardly think they were the 
>primary dispersal agent intended.)
>
>If anyone has any ideas, I'd be glad to hear them.  Are we missing a large 
>avian or herbivorous mammal?  Is there some sort of insect that comes and 
gets 
>the seeds--and if so, then why the trouble to make so much fruit?
>
>If it helps, the plants are dioecious.  They are found in many parts of N. 
>America, but probably much outside their original range as they were widely 
>planted for windbreaks and firewood by European settlers in the prairie and 
>plains states.
>
I remember seeing some speculation by Prof. Dan Janzen on this several years 
back. Remember that only a very few thousand years ago [an eyeblink in 
evolutionary timd] there were major groups of very large mammals in N. Amer. 
that suddenly and completely vanished from the continent whereas the flora 
remained largely the same.  Many plants may well retain some features that 
make sense as adaptations to life with such recently extinct large herbivores 
and dispersal agents as mastodons, mammoths ground sloths, etc. Perhaps 
Maclura pomifera was largely mastodon-dispesed [will zoo elephants eat the 
fruits?] earlier in the Pleistocene.  Nowadays, I hear the fruit mostly rots 
under the tree although squirrels or birds may eventually scatter some seed.

cheers




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