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Specialised plants may not be as vulnerable as was thought

Plants that are pollinated by fewer species of animal may be less vulnerable to change than was thought. This is what Saskia Klumpers discovered in the Rocky Mountains in Colorado. She will be awarded a PhD on 15 December.

Imagine a plant that hides its sweet nectar away in a deep cup. Only few butterflies and bumblebees with long tongues can reach its delicious wares. Does this make the plant extremely vulnerable to sudden change? Only a few animal species need to die or leave for the plant to lose its pollinators.

Prospects

Biologist Saskia Klumpers discovered that the prospects of these types of specialised plant are by no means as bleak as they might seem. For her dissertation she carried out research in the famous Rocky Mountains in North America. She mapped out the interaction networks of plants and their pollinators that are found there. Which honeybees, bumblebees, butterflies, flies, beetles and hummingbirds visit which plants? And why?

Her research showed that flowers with a deeper floral tube are more specialised: they are pollinated by fewer different insect species. But this does not mean that they are more vulnerable than more shallow flowers. The populations of the pollinators of plants with deeper flowers fluctuate less annually than those of other insect species. Although only few species can pollinate the plant, they are a more constant presence.

Other characteristics

Klumpers looked specifically at flowers from the aster family (Asteraceae), which ‘our’ sunflowers and daisies also belong to. She saw that the number of types of pollinator is determined by not only the number of flowers in the area (the flower density), but also the foraging efficiency of the pollinators and external characteristics of the plant such as the depth of the floral tube, the size of the flower and the amount of nectar that the flower produces. To claim that a rare plant is more vulnerable to changes in the ecosystem is therefore too simple.

Klumpers believes that the results are relevant to nature conservation and restoration. Klumpers: ‘With bee numbers declining, it is a good idea to think about which flowers or plants to grow on fallow field margins. And it’s not just the number of flowers that is important but also the diversity in morphology and nectar production.’

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