Plants surrounded by individuals of other co-flowering species may suffer a reproductive cost from interspecific pollen transfer (IPT). However, differences in floral architecture may reduce or eliminate IPT. 

Under the supervision of Prof. WANG Qingfeng, Dr. YANG Chunfeng from Wuhan Botanical Garden investigated Pedicularis densispica (lousewort) and its common co-flowering species, Astragalus pastorius, to compare reproductive and pollination success of lousewort plants from pure and mixed patches.  

Floral architecture and pollinator behaviour on flowers of these two plants were compared along with the composition of stigmatic pollen load of the louseworts. The extent of pollen limitation of plants from pure and mixed patches was also explored through supplemental pollination with self- and outcross pollen (PLs and PLx). 

Results showed that mixed patches attracted many more nectar-searching individuals of Bombus richardsi. These bumblebees moved frequently between flowers of the two species. However, they pollinated P. densispica with their dorsum and A. pastorius with their abdomen. This difference in handling almost completely eliminated IPT. Lousewort plants from mixed patches yielded more seeds, and seeds of higher mass and germinability, than those from pure patches. Moreover, louseworts from mixed patches had lower PLs and PLx compared with those from pure patches. 

Differences in floral architecture induced differences in pollinator behavior that minimized IPT, such that co-flowering plants significantly enhanced quantity and quality of pollinator visits for the lousewort plants in patchily habitat. These findings add to our understanding of the mechanisms of pollination facilitation. 

The research was supported by the National Natural Science Foundation of China. Relevant results were published in Annals of Botany entitled “Pollination in a patchily distributed lousewort is facilitated by presence of a co-flowering plant due to enhancement of quantity and quality of pollinator visits”