To bee or not to bee: The 'raison d'etre' of toxic secondary compounds in the pollen of Boraginaceae

摘要

While the presence of secondary compounds in floral nectar has received considerable attention, much less is known about the ecological significance and evolutionary origin of secondary 'toxic' compounds in pollen. It is unclear whether the presence of these compounds in pollen is non-adaptive and due to physiological 'spillover' from other floral tissues, or whether these compounds serve an adaptive function related to plant-pollinator interactions, such as protection of pollen against pollen thieves.