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USA Today, Thursday, December 12,2002, page 11D
A Dead Horse arum by any other name...
So what is up with a plant known as the dead horse arum that smells just
like its name suggests? Well, it seems that nature is a rather permissive
mother and will allow its creatures to try anything to get ahead in the game
of life. In this week's "Nature"...
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Flowers play rotten trick on flies
Insects fooled into fertilizing foul-smelling blooms.
12 December 2002
MICHAEL HOPKIN
The dead-horse arum covers flies with pollen.
? Peter Boyce/International Aroid Society.
Unlike a rose, a dead-horse arum's name sums up its smell perfectly. The
flower's pungent scent of rotting meat dupes blowflies into spreading its
pollen, biologists have shown.
The volatile chemicals released by a bloom are almost identical to those
that rise from nearby carrion, find Bill Hansson of the Swedish University
of Agricultural Sciences in Alnarp and colleagues. Moreover, the two scents
are indistinguishable to a blowfly's olfactory system1. The chemicals are
called oligosulphides.
"Mimicry is usually directed towards things that the target can't afford to
ignore," Hansson explains. "In this case it is reproduction." Blowflies must
lay their eggs on food - such as a decomposing carcass - for their offspring
to stand a chance of surviving.
The arum grows on small islands off the coasts of Sardinia, Corsica and the
Balearics in the Mediterranean. Also called Helicodiceros muscivorus,
meaning 'fly eater', the plant traps the flies, releasing them only when
they have fertilized its female florets and been re-coated in pollen by its
male ones.
The hapless insects waste their time and eggs. "The flower has the perfect
system," says Hansson.
? Nature News Service / Macmillan Magazines Ltd 2002
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Pollination: Rotting smell of dead-horse arum florets
MARCUS C. STENSMYR*, ISABELLA URRU?, IGNAZIO COLLU?, MALIN CELANDER*, BILL
S. HANSSON* & ANNA-MARIA ANGIOY?
* Department of Crop Science, Swedish University of Agricultural Sciences,
PO Box 44, 23053 Alnarp, Sweden
? Department of Experimental Biology, University of Cagliari, 4500
Monserrato, Italy
e-mail: bill.hansson@vv.slu.se
Deceit by resource mimicry has evolved as a pollination strategy in several
plant species and is particularly elaborate in a plant known as dead-horse
arum (Helicodiceros muscivorus; Araceae: Aroideae), which may fool flies
into pollinating it by emitting a smell like a dead animal ? an important
oviposition resource for these insects. Here we confirm that the composition
of volatiles from these flowers and from a rotting carcass is strikingly
similar and show that the pollinators respond in the same way to chemicals
from both sources. This remarkably complex mimicry must have evolved to
exploit insects as unrewarded pollinators.
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MJ Hatfield
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