If asked to identify three poisonous entities that can be found in nature, what first comes to mind?  A snake? A spider?

How about an almond tree? Although almonds may have many health benefits associated with their consumption, the nectar of an almond tree actually has quite the opposite effect.

After studying the almond tree, researchers at the Department of Science Education at the University of Haifa-Oranim have uncovered that the plant’s nectar contains a toxin, which can form the by-product cyanide.  The toxin, termed “amygdalin,” evolved with the intention of giving the almond tree an advantage over other vegetation in the surrounding area.

Before conclusion of the recent study, previous research revealed that 4-10 milligrams per liter of amygdalin could be found in almond nectar, a deadly amount for most small mammals.  While nectar in the tree’s flowers would normally serve as an insect attractant for pollination, the presence of amydalin seems to defeat the original purpose of functioning as a medium to increase the plant’s reproductive success.  However, examining bee nectar preference allowed scientists to discover that the toxic nectar is surprisingly advantageous.

Exposing honeybees to plates of nectar with varying concentrations revealed that bees prefer nectar that contains amygdalin, as opposed to an amygdalin-free option.

Although amygdalin is poisonous for mammals, the toxin contains a stimulant that attract insects, who are unaffected by the poison and have the opportunity to pollinate the plant, thus increasing reproduction in almond trees.

Discussion Question:  How might one explain, in terms of evolution, the need for the almond tree to develop nectar that is only poisonous to small mammals?

News Article: http://www.sciencedaily.com/releases/2010/01/100128091750.htm
Scientific Abstract: http://www.springerlink.com/content/p31q717704r16llr/