Sex sells, especially when it comes to pollination. Sometimes, however, nobody is buying what you’re selling.
That appears to be the case for the critically endangered grand spider orchid (Caladenia huegelii), a beautiful Australian species with an extremely limited range and an even more limited range of pollinators.
Most plants have a small set of preferred pollinators and may only get that service from a handful of species. The grand spider orchid takes that to an extreme. According to new research published this month in the Botanical Journal of the Linnean Society, the plant relies on less than a single species.
Okay, that takes some explaining. You see, this particular orchid species uses a series of chemical and visual cues to deceive males of a specific wasp species (Macrothynnus insignis) into thinking they are visiting a female wasp, not the flowering plant itself. But the orchid, it turns out, doesn’t aim to attract just any males. According to the new paper, it’s only luring in an unusually small form of M. insignis. DNA tests showed that these smaller wasps are reproductively isolated from the rest of their species, so they breed small and stay small.
The ranges of the orchid and the small wasps overlap, but not ideally. The small wasps have a larger total range than the orchid does, so they’re doing fine. The orchid, however, is suffering from extreme habitat loss and fragmentation due to human development, so it has a much smaller, more restricted range (basically just a few dots on the map of Western Australia). The wasp is not present in much of that territory. That leaves many orchids pining for pollinators they can’t find.
The problem is so bad that the orchids are reproducing at significantly lower rates than other Caladenia species. As the researchers wrote in their paper, “Populations are likely to now persist primarily through individual plant longevity rather than reproduction.”
This research throws a big monkey wrench in the Australian government’s recovery plan for the grand spider orchid. Several facets of the program involve increasing the plant’s range. Unfortunately, the researchers found that the small wasps are only present in about 4 percent of those potential new or restored habitats. Lack of wasps means no pollination for the grand spider orchid, which means no more plants after the current batch ages and dies.
Of course this orchid has one additional pollinator waiting in the wings. As the authors wrote, a species called Homo sapiens can—and will probably have to—fill in for the wasps and hand-pollinate the orchids to help prevent their extinction.
Hopefully that won’t require a whole new level of evolutionary deception.
Photo by Andrew Brown via the Western Australia Department of Environment and Conservation
Previously in Extinction Countdown: