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View Full Version : Why so few lucky clover?



Tom Mazanec
2013-Oct-01, 02:45 PM
Why are 4 leaf clover so rare? I know it is genetic, and you would think an extraeaf would bean advantage. Does the leaf consume too much resource? Is it linked to a defect? Something else?

Glom
2013-Oct-01, 04:58 PM
It's because of the weaving movements they generate. Because the cloverleaf turns basically double back, left turning traffic (in US and Middle East where they are most popular) joining the carriageway joins before left turning traffic diverges. This leads to a hotspot in the middle that causes a mess of weaving if the junction is too tight.

Noclevername
2013-Oct-01, 05:07 PM
Why are 4 leaf clover so rare? I know it is genetic, and you would think an extraeaf would bean advantage. Does the leaf consume too much resource? Is it linked to a defect? Something else?

It's probably a recessive gene, with no particular evolutionary benefit, so there's no reason for it to become widespread.

Per Wikipedia:
Researchers from the University of Georgia have reported finding the gene that turns ordinary three-leaf clovers into the coveted four-leaf types. Masked by the three-leaf gene and strongly influenced by environmental condition, molecular markers now make it possible to detect the presence of the gene for four-leaves and for breeders to work with it. The results of the study, which also located two other leaf traits in the white-clover genome, were reported in the July/August 2010 edition of Crop Science, published by the Crop Science Society of America.

Swift
2013-Oct-02, 01:20 PM
Too much luck in the Universe would destroy cause-and-effect? ;)

Ivan Viehoff
2013-Oct-02, 03:36 PM
It's probably a recessive gene, with no particular evolutionary benefit, so there's no reason for it to become widespread.

Recessive genes don't make something very uncommon (blue eyes are not that uncommon - though that's not a perfect example): it just means that the gene has to be in both parents to become expressed. Indeed recessive genes are harder to breed out of a population, precisely because they tend to be rarely expressed, and hence present many fewer opportunities to be selected against than their incidence in the genetic stock.

If you look at some pictures of 4-leaf clovers you will see that the leaves often overlap. That would be an inefficient use of energy spent in growing the leaf surface, so it would seem not be a benefit, and hence would not be selected for.

profloater
2013-Oct-02, 05:15 PM
I think that's right, if you have 1% recessive gene with slight change to performance but no change to reproductive efficiency it will stay at about 1%. If it stopped producing flowers or pollen it would die out ; or if it produced lots, it would soon out compete the other type.

galacsi
2013-Oct-02, 05:35 PM
It is darwinian ; because of all these people who are picking up those poor 4 leaf clover ! Now we can only find his degenerate relative : the feeble 3 leaf clover .

NEOWatcher
2013-Oct-02, 05:40 PM
It is darwinian ; because of all these people who are picking up those poor 4 leaf clover ! Now we can only find his degenerate relative : the feeble 3 leaf clover .
Same situation but in reverse of the Samurai Crab (http://en.wikipedia.org/wiki/Heikegani).

Noclevername
2013-Oct-02, 10:51 PM
It's because 4-leafs give away all their good luck, leaving none for themselves. Then they befall terrible accidents in the home and workplace. The Law Of Conservation Of Luck at work! It's the reverse of the principle that bred Teela Brown in Ringworld.

grapes
2013-Oct-03, 09:52 AM
3 is a Fibonacci number, 4 is not :)

Ivan Viehoff
2013-Oct-09, 11:23 AM
3 is a Fibonacci number, 4 is not :)
But 4 is nonetheless reasonably common number among plants. Flowers of some of the Brassicaceae have 4 petals, which is why they used to be called Cruciferae ("cross-bearing"), and they are far from unique in that habit. Oxalis tetraphylla (the clue is in the name) is commonly mistaken for 4-leafed clovers, and there are other 4-leafed plants. Though it would be interesting to speculate if these were derived from earlier 8-petalled/leafed plants.