Manitoba's small white lady's-slipper orchids
Deceptive pollination and reproduction
Small white lady's-slipper (Photo by Melissa Grantham)
Small white lady's-slippers are a unique and beautiful species with a small, white, sac-like lower petal (or "slipper") as their most prominent feature. In 1839, English botanist Sir William Jackson Hooker was the first to record orchids in Manitoba. We now have 36 recorded species in Manitoba, six of which are lady's-slipper orchids.
False advertising for pollinators
For many flowering plants, pollination is fairly simple: the plant produces a reward (nectar, pollen and edible oils) that pollinators desire, in order to keep the insects coming back. Lady's-slipper orchids are fascinating because they don't produce a reward at all. Instead, they have evolved false advertisement to trick pollinators into paying them a visit. This type of deception can be very risky for plants because successful reproduction depends, in part, on how good the deception is and how long the plant can continue to attract the pollinators before they learn to avoid them.
The orchid's slipper acts as a one-way temporary trap; once insects have entered the flower they can't exit the same way. Instead, they move through the slipper's narrow passage and out through one of two small openings near the reproductive organs. If the insect has the right general size and shape, this may result in pollination. If an insect is too large or too small, it either can't get out or gets out without contacting the pollen, which means no pollination in either case.
A threatened species
Small white lady's-slippers have lost much of their native habitat. Of the 6,000 square kilometres of original tall-grass prairie that once existed in Manitoba, it's estimated that less than one percent remains. The species is federally listed as threatened, provincially listed as endangered and is protected under Canada's Species at Risk Act. There are a small number of Canadian populations remaining — only 15 in Manitoba and seven in Ontario. Where they grow alongside yellow lady's slippers, hybridization between the two species often occurs.
Land management strategies to protect at-risk species
Due to the species' threatened/endangered status, the Nature Conservancy of Canada (NCC) takes care when considering land management practices in areas where the orchids are known to occur. Prescribed fire and mowing are both land management techniques that may be beneficial for this species, as it doesn't do well with competition from other plant species. Burning is considered a key process in maintaining prairie habitats, and helps to keep down the thatch as well as reduce woody encroachment.
NCC has adopted a multi-species at risk approach that takes into account the needs of all species at risk present on a particular parcel of land. This helps not only to protect those species, but also assists with the biodiversity and health of the ecosystem.