Dangerous Beauties: are complex flowers a fast-track to extinction?print
Of the near quarter of a million plant species present on Earth, ca . 90% are entomophilous (insect pollinated) (Hoshiba & Sasaki, 2008), however, the number of insect species is dwindling at an alarming rate! In 2019, Sánchez-Bayo & Wyckhuys estimated that ca . 40% of insects may become extinct over the next few decades! Such a prospect leads us to wonder how this downward spiral will affect the flora.
In addition to such a decline of possible pollinators, a study conducted by Stefanaki et al . in 2015 aimed to show that flowers with more complex structures (higher floral complexity) are more difficult to pollinate. The more complex flowers are, the more specific their mode of pollination and respective pollinator will be. As a result, pollinator structures and dimensions must be complementary to that of the flowers that they visit to prevent pollination failure. Given this decline, high floral complexity may therefore decrease the likelihood of pollination, due to a reduction of possible pollinators. This is a consequence of its increased structural specificity...particularly in the case of rare species.
Two species from the Red Data Book of Rare and Threatened Plants of Greece. The “Endangered” Sideritis sipylea with high floral complexity (left), and the “Vulnerable” Haplophyllum megalanthum with low floral complexity (right). Photo: Anastasia Stefanaki
Anastasia Stefanaki and Theodora Petanidou are now following up this study as a Floral Complexity project within COST Action CA18201 ConservePlants, with over 30 European countries participating.
In their studies, Stefanaki, Petanidou and their team made use of a novel floral complexity index to determine whether such structures could predict a plant’s vulnerability to extinction. Their results indicated that plants with more complex flowers are at significantly greater risk, and therefore, targeted conservation efforts towards such species are warranted.
While floral complexity may be an adaptive trait for survival and proliferation, it may also simultaneously constitute a fast-track to possible extinction. This is especially the case as insect species are also in decline , leading to inevitable knock-on effects on plants. The first to suffer these consequences would be those with high floral complexity, since fewer pollinators would be at their disposal than at present.
As a result, although floral complexity decreases the likelihood of pollination, this alone does not lead to extinction, but rather simply increases the likelihood of this outcome. Therefore, floral complexity is linked to the rarity, and consequently, the survival of a plant. This truly proves that less really is more.
Andrea Francesca Bellia and Sandro Lanfranco, Department of Biology, University of Malta, Msida, Malta
FAO (2020). AGP - Pollination.
Hoshiba, H., & Sasaki, M. (2008). Perspectives of multi-modal contribution of honeybee resources to our life. Entomological research, 38, S15-S21.
Main, D. (2019). Why insect populations are plummeting—and why it matters. National Geographic. https://www.nationalgeographic.com/animals/2019/02/why-insect-populations-are-plummeting-and-why-it-matters/
Sánchez-Bayo, F., & Wyckhuys, K. A. G. (2019). Worldwide decline of the entomofauna: A review of its drivers. Biological Conservation, 232, 8–27. doi:10.1016/j.biocon.2019.01.020
Stefanaki, A., Kantsa, A., Tscheulin, T., Charitonidou, M., & Petanidou, T. (2015). Lessons from Red Data Books: plant vulnerability increases with floral complexity. PloS one, 10 (9).