Decision Time
Our problem revolved around two types of wetlands. One type was marshes that held the world's only known population of Orchis isozymus. The other type was swamp land with the world's only known populations of related but distinct Orchis polyzymus. The populations in each of these areas, and there are 3 in each, are large (>1000) and saving the wetland areas is secondary at this stage to saving the orchids.
We sent leaf samples from these plants to our colleagues at the college Botany Department an low and behold, a week later we had the data seen below. The gel electrophoresis and allozymes background pages explain a little more of the type of testing procedures done.
| Orchis isozymus, Population 1 (individual 1 . . . 15 from left to right) | |||||||||||||||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | |
| Slow Fast |
-- -- |
-- | -- | -- | -- | -- | -- |
-- | -- | -- | -- |
-- | -- -- |
-- -- |
-- |
| Orchis isozymus, Population 2 (individual 1 . . . 15 from left to right) | |||||||||||||||
| Slow Fast |
-- | -- |
-- -- |
-- | -- -- |
-- |
-- -- |
-- |
-- -- |
-- -- |
-- |
-- -- |
-- -- |
-- -- |
-- |
| Orchis isozymus, Population 3 (individual 1 . . . 15 from left to right) | |||||||||||||||
| Slow Fast |
-- |
-- -- |
-- |
-- |
-- |
-- |
-- -- |
-- |
-- |
-- |
-- |
-- |
-- |
-- | -- |
| Orchis polyzymus, Population 1 (individual 1 . . . 15 from left to right) | |||||||||||||||
| Slow Fast |
-- | -- |
-- -- |
-- | -- -- |
-- |
-- -- |
-- |
-- -- |
-- -- |
-- |
-- -- |
-- -- |
-- -- |
-- |
| Orchis polyzymus, Population 2 (individual 1 . . . 15 from left to right) | |||||||||||||||
| Slow Fast |
-- -- |
-- |
-- | -- | -- -- |
-- |
-- -- |
-- |
-- | -- -- |
-- |
-- -- |
-- -- |
-- | -- |
| Orchis polyzymus, Population 3 (individual 1 . . . 15 from left to right) | |||||||||||||||
| Slow Fast |
-- | -- |
-- -- |
-- | -- -- |
-- |
-- |
-- -- |
-- -- |
-- -- |
-- |
-- -- |
-- |
-- -- |
-- |
After recieving our data we used a technique called "WRIGHT'S FIXATION INDEX" or Fst. This allowed us to compare the genetic variation found amongst our orchid plants by comparing the difference in the allele frequencies.
| Orchis isozymus | |||
| Tally | Allele Frequency | 2pq | |
| q/n or p/n | |||
| Popn 1 | 130 | ||
| Slow (q) | 13 | 0.43 | |
| Fast (p) | 5 | 0.1 | |
| Popn 2 | 260 | ||
| Slow (q) | 10 | 0.33 | |
| Fast (p) | 13 | 0.43 | |
| Popn 3 | 84 | ||
| Slow (q) | 3 | 0.1 | |
| Fast (p) | 14 | 0.46 | |
| Ave (p) = 10.7 | |||
| Ave (q) = 8.7 | |||
| n = 30 | |||
| Hs = Σ 2pq/3 = 158 | |||
| Ht = 2(ave p)(ave q) = 186.18 | |||
| Fst = (Ht - Hs)/Ht = (186.18 - 159)/186.18 = 0.151 | |||
| Orchis Polyzymus | |||
| Tally | Allele Frequency | 2pq | |
| q/n or p/n | |||
| Popn 1 | 260 | ||
| Slow (q) | 10 | 0.33 | |
| Fast (p) | 13 | 0.43 | |
| Popn 2 | 260 | ||
| Slow (q) | 10 | 0.33 | |
| Fast (p) | 13 | 0.43 | |
| Popn 3 | 234 | ||
| Slow (q) | 9 | 0.3 | |
| Fast (p) | 13 | 0.43 | |
| Ave (p) = 13 | |||
| Ave (q) = 9.7 | |||
| n = 30 | |||
| Hs = Σ 2pq/3 = 252.2 | |||
| Ht = 2(ave p)(ave q) = 260 | |||
| Fst = (Ht - Hs)/Ht = (260 - 252.2)/260 = 0.03 | |||
The Orchis isozymus alleles had the highest frequency (as demonstrated above). These orchids live in the marshes where they live in poor draining land along side a small pool of water. The marsh is high in organic matter and is constantly wet with only a few inches of water all year round.
We decided to save the three swamps that held the orchids orchis
polyzymus along with one of the marshes that contained the other
orchid Orchis isozymus because we felt that the marsh orchids, having the
greater genetic diversity, needed the smallest population to survive. With
less genetic diversity, the plants need a larger population to be able to
successfully reproduce. By saving as many as we possibly can, hopefully
they will be able to survive.