A team of evolutionary biologists has discovered that some plants mimic scent of pollinating beetles.
Flowers of the Arum family: Amorphophallus hewittii (left), Sauromatum guttatum (middle) and Taccarum weddellianum (Florian Schiestl / Stefan Dötterl / University of Zurich)
Previously, researchers always assumed that floral scents and the fondness of pollinating insects for a specific scent evolved mutually via co-evolution of plants and insects.
But the findings, published in the International Journal of Organic Evolution, prove that this was not the case with the Arum family and their pollinators. The team found that the Arum family of plants (Araceae), a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix, evolved its scent analogously to the pre-existing scents of scarab beetles and thus adapted to the beetles unilaterally.
In the beetles, the team discovered many scent molecules used for chemical communication that were also found in the plants. Based on a phylogenetic reconstruction, they realized that these scents were already present in the ancestors of today’s scarab beetles.
Evidently, these prehistoric scarab beetles already used the same or similar scents back in the Jurassic period to find food or mates. Unlike today’s scarab beetles, these ancestors did not pollinate plants, the first members of the arum family to be pollinated by beetles not appearing until around 40 million years later.
“In the course of evolution, the arum family mimicked the scents of scarab beetles to attract pollinating insects more efficiently,” said Dr. Florian Schiestl, a co-author of the study and an evolutionary biologist from the University of Zurich.
In research, co-evolution is regarded as a driving force behind the development of a mutual adaptation between two organisms. However, this is not true of the Arum family, which developed its scent along the pre-existing communication of scarab beetle scents.
“Co-evolution between plants and pollinating insects might well be less common than we thought,” Dr. Schiestl concluded.
