north american native orchid journal - at The Culture Sheet

Folsom: A CASE FOR EVOLUTION
when growing conditions are not suitable. Some have become
dependent on calamity to continue their existence. Wild fires,
landslides, tornados and hurricanes all play their part in destroying
natural areas but the fire-respondent and successional species of
orchids have learned to take advantage of these opportunities to
repopulate an area.
Orchid seeds are hardy as well as being able to remain
dormant for some years, as they have been discovered in the
upper stratosphere. Some tropical species, especially in places like
Florida, are hardy enough so that they withstand freezes that
destroy the plants but not their seeds which seem to have the
ability to lodge in protective niches and survive. The Christmas
Day freeze of 1989 in Florida took out entire colonies of tropical
orchids but as of 2005 new young plants are growing in the areas
where their parents used to exist suggesting that the seeds can
withstand colder temperatures.
Some orchids have developed in special niches to ensure
their survival. Spiranthes sylvatica prefers shady hedgerows while
others prefer damp seep habitats. Some have adapted to wet
conditions forming mats on streams or growing in wet bogs.
Then there are those that have taken to the trees and many
have developed pseudobulbs to store water. Some, such as the
ghost orchid and harrisella, are leafless and when out of flower are
virtually invisible to predators.
Hybridization between orchid species is another form of
insurance for survival if the new plants breed true in future
generations. Scientist can now examine the DNA and determine
the gene flow from the parents. They can also ascertain the new
plants’ status as diploid or polyploid. Sheviak (1982, 1991) has
done much of this work on North American species and has
clarified the status of several species especially in the genera
Spiranthes and Platanthera..
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