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hardy  Aroids)" <ARISAEMA-L at NIC.SURFNET.NL> Aroids)" <ARISAEMA-L at NIC.SURFNET.NL>
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From: "Mellard, David" <dam7 at CDC.GOV>
Subject: Re: why separate male and female function by years?
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>Other aroids manage to achieve the same effect by less striking temporal
separation of male and female function.

Nature is always experimenting with itself.  In other words, there are mo=re
than one way to solve a problem. One might speculate that years with poor
growth conditions in the spring favored plants that separated the sexes,
giving them an evolutionary advantage.  Arisaemas seem to have solved thi=s
problem differently than other species.

Self fertilization can be an evolutionary disadvantage or advantage.
Populations of Sarracenia (the American pitcher plant) in Virginia are fe=w
and disjointed.  Plants that self pollinate have less seed production, lo=wer
viability and lower plant vigor compared to cross pollinated plants.
Pollination between plants from different geographical populations in
Virginia have shown fared better performance in these repsects than plant=s
cross pollinated within the same population.

Something similar might be happening with Arisaema.  That is, self
pollination is possible and will produce plants but were one to compare s=eed
production, seed viability, and plant vigor, one would find that cross
pollination produces better performance in all categories.  This is not
always true, however, because cross pollination can introduce genetic
defects and result in a less virogour population.

Maybe with Arisaema the same principle is occurring, that is, cross
pollination produces fitter plants, and they followed a slightly differen=t
path to achieve it.

David
Atlanta