Of the near quarter of a million plant species present on Earth, about 90 per cent 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 around 40 per cent 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 in order to prevent pollination failure. Given this decline, high floral complexity and the reduction of possible pollinators may therefore decrease the likelihood of pollination. This is a consequence of its increased structural specificity... particularly in the case of rare species.
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 is a MSc student at the Department of Biology, University of Malta, and an MC substitute of CA18201 ‒ An Integrated Approach to Conservation of Threatened plants for the 21st Century (ConservePlants). Sandro Lanfranco is head of the Department of Biology at the University of Malta, and an MC member of CA18201 ‒ An Integrated Approach to Conservation of Threatened Plants for the 21st Century (ConservePlants).
Did you know?
• Bees have UV receptors that allow them to see and use UV patterns on petals, as these serve as a ‘runway’ to a flower’s nectar. These patterns are created by pigments in the petals which absorb UV light.
• The world’s largest single flower is Rafflesia arnoldii, which measures about a metre across. It belongs to and lives in the forests of Sumatra and Borneo and is so large that it was once though that it was pollinated by elephants! While its actual pollinators are small flies and bees, elephants may aid in its dispersal by spreading seeds that would be in the mud, which then stick to their feet.
• The spectacular ‘Sunflower’ is not actually a single flower, but hundreds of smaller ones clustered together to give the appearance of a single structure. The scientific term for these flowers are composites, and they belong to the family Asteraceae/Compositae.
• Large floral displays can have negative consequences for animal-pollinated flowers. By attracting more pollinators, this also increases the probability of self-pollination; a scenario that should be avoided as this reduces genetic diversity. Therefore, the presence of sterile flowers as pollinator signals may enhance attraction of pollinators, while allowing displays of fewer open fertile flowers to limit self-pollination.
For more trivia, see: www.um.edu.mt/think
• Mite-y warning signs for global biodiversity: It has been estimated that mite extinctions are occurring at a considerably faster rate than the expected natural rate, with a 1,000-fold increase in extinction rate. Mites occupy a variety of different habitats around the planet, both terrestrial and freshwater.
• Globalisation reshaping interactions between flora and fauna worldwide: Data collected over the past 75 years has shown an undisputed accelerating reshaping in mutualistic relationships and links between ecosystems that were previously disconnected. These changes will shape how such ecological network interactions develop and might expose certain networks to unfortunate collapse.
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