What pops into your head when you think of orchids? Large tropical ornamental house plants? Did you know that there are a wide range of orchids native to Australia? Even here at Eurardy Reserve, in this semi-arid country we have recorded more than 25 species. As it's Threatened Species Week we're going to highlight 3 that call Eurardy home.
Firstly, the Northern Dwarf Spider Orchid (Caladenia bryceana subsp. cracens). This tiny orchid can flower at just 3cm tall and the northern subspecies can only be found from around Northampton in WA to just north of Eurardy. It’s currently listed nationally as vulnerable.
Next up is the Small Dragon Orchid (Caladenia barbarella). This slightly larger orchid is still only around 8cm tall. Its distribution is even more restricted and it's currently listed nationally as endangered. When it was listed as endangered, it was noted that there were only 14 known populations.
Finally, the Kalbarri Spider Orchid (Caladenia wanosa). This beautifully and distinctively striped orchid was only described in 2001. It was named after the Western Australian Native Orchid Study and Conservation Group. The Kalbarri Spider Orchid is also listed as vulnerable and only occurs in a small area from around the Murchison River up to Eurardy.
All of these species are threatened by a range of factors including grazing, habitat degradation, weed infestations, population fragmentation and altered fire regimes. Another major threat, especially for these species with small distributions sitting near the northern limits of where orchids can be found, is climate change. If you're a plant with only 14 populations over a relatively small area, a change in the climate can have a devastating effect.
Another issue is that orchids are complex plants and not a lot is known about these species. One example of extremely complex reproductive cycles is a Spider Orchid, which mimics the shape of a female wasp sitting on a grass stem. The orchid has also evolved to produce pheromones to attract male wasps, which will sometimes ignore female wasps to try and mate with an orchid instead.
The male wasp will move from flower to flower pollinating them as he goes. In this example, the reproductive cycle of the wasp is also complex because the females of this particular wasp needs to dig into the soil to find the larvae of scarab beetles. She then lays her eggs into the larvae, parasitising them to reproduce.
In some cases only one specific species of insect can act as a pollinator for one specific species of orchid. For plants with this complex and fascinating life history, it means that any change that might affect these cycles could be a threat.
At Eurardy, as well as protecting the habitat of these orchids their populations are monitored regularly. Every year, we measure the exact location of plants on permanent transects and record whether they're flowering and if they produce seed. This way we collect valuable data on how our threatened orchids are doing and begin to understand aspects of their ecology.