Pollinated by roaches

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Pollinated by roaches

Thinking about the pollination of flowers most of us generally assume bees do all the hard work. While bees are busy as bees pollinating flowers, they are hardly the only ones recruited for the job. Loads of other insects are helping out, with bats and hummingbirds also part of the pollination workforce. A recent paper by Xiong and colleagues tells us that even cockroaches are also doing their bit. These roaches were shown to be essential for successful pollination of the endangered climbing vine species, Vincetoxicum hainanense.

In their quest to find out which floral visitors pollinate this climbing vine, the first step was to look at the flower itself. The flowers of these climbing vines are small, pale green, and open during the night. The most noticeable though was their scent, the researches describe this as “a heavy, nauseatingly sweet scent, reminiscent of rotting fruit”. Opening of the flowers enhanced this scent, at night, allowing it to attract potential pollinators.

When sitting down for the night to observe which potential pollinators were visiting the flowers, it was noticed that two cockroach species were frequent visitors of the flowers, but not the only ones. With flowers also being visited by flies, ants, beetles and crickets. Although there was a wide variety of species visiting our climbing vine flowers, only cockroaches, ants and beetles were detected to carry any pollen with them after a visit.

But do they actually use the pollen to pollinate the flowers?

To test this the researches looked to the fruit development of open and bagged flowers. Only the open flowers developed any fruit, indicating that the flowers get pollinated with the pollen of another flower. When looking which insects were responsible, the researches found that a single cockroach species was involved in most of the fruit development observed. As both the nymphs and the adults of this cockroach species visited the flowers, they looked at them separately. With the nymphs only visiting flowers of the same plants they were mildly successful in pollinating the flowers, the adults, however, also visited flowers from other plants were the most successful pollinators. Making these roaches the main pollinators of the climbing vine.

While as the authors tell us that the importance of this study lies in the fact that it is the first study in which shows us that cockroaches are recruited by plants to pollinate their flowers. I think it also highlight that plants have strange bedfellows, and that the loss of insect species, even one as detested by us as cockroaches, might unwittingly also contribute to the loss of plant species. 

If you want to know more about pollinators check out Jeff Ollerton’s blog

References

Xiong, W., J. Ollerton, S. Liede-Schumann, W. Zhao, Q. Jiang, H. Sun, W. Liao, and W. You. 2020. Specialized cockroach pollination in the rare and endangered plant Vincetoxicum hainanense in China. American Journal of Botany 107(10): 1–11.doi:10.1002/ajb2.1545