Platanthera Orchids, Pan Trapping and Insect Diversity

By Genevieve van der Voort, Vancouver Island University student

Vancouver Island orchid habitats show low insect family-level diversity

Alpine meadows, lowland bogs, and mixed Garry oak and arbutus forests might seem like diverse environments, but they all have one thing in common: species of Platanthera orchids grow there. Platanthera orchids (including the Piperia rein orchids) have widespread distribution across North America, but not a lot is known about the insects that may be associated with these plants. For example, pollinators of many species are unknown throughout BC.

These unknowns are what attracted me to study these orchids and their insects for my undergraduate thesis. I graduated from Vancouver Island University (VIU) this June with a bachelor’s degree in biology. During my time at VIU, I discovered a passion for entomology and botany, and this led me to pursue a master’s degree at the University of Northern British Columbia (UNBC) dealing with insect biodiversity and Platanthera pollination starting this September. I am happy to say that the specimens I collected can now reside at the Royal BC Museum.

In my study, I set out to examine how family-level insect diversity may be different in sites with different species of Platanthera orchid. We looked at a total of seven species of Platanthera across Vancouver Island (the most common species we encountered was Platanthera transversa). To examine insect diversity, we set up pan traps to catch any insects around the orchids. We used bowls of eight different colours (different insects are attracted to different colours) with water and a few drops of dish soap to collect insects. We did this for three trapping sessions. We also observed orchids for 10-minute intervals and collected any insects that appeared. I then identified the insects to taxonomic family and compared the number of families by study site and orchid species.

We saw low levels of insect-family diversity across all sites. Sites were mostly dominated by a few families: ants, aphids, leaf hoppers and spider wasps, for example.

On Vancouver Island, Platanthera orchids can have either a white or green inflorescence. This species, Platanthera elegans, has a white inflorescence. Photograph courtesy of Genevieve van der Voort.

Spider wasps (Pompilidae) were one of the more common families caught while pan trapping. Photograph courtesy of Genevieve van der Voort.

While we did record insects during the observations, we never saw pollination. One of the things we found while pan trapping was that there was no difference in the number of insects caught for each pan trap colour. Yellow traps caught the most and red caught the least, but the difference was not significant. When insects were examined by taxonomic order (the flies, or Diptera, for example), there was also no pan trap colour that significantly caught the most insects. Around 500 insects were collected while pan trapping in this study, and they have been sent to be housed at the Royal BC Museum.

So what next? At the moment, we’re working on using motion-detecting cameras to capture footage of any insects that may be pollinating these local orchids, day or night. This should give us a much better picture of how pollination happens. The study continues!