Nectar robbers are floral visitors who absorb plant nectar by means of piercing holes or biting flowers. The impacts of robbers on plant reproduction generally include both direct and indirect influences. The direct effects will occur when robbers act as pollinators (i.e. robber-like pollinators) or damage floral reproductive structures, whereas the indirect effects are, to most extents, subject to the changes of pollination due to altering pollinator behavior and patterns of flower visitation. The pollinator behavior changes could have either positive or negative impacts on pollen flow and plant reproduction. As a self-compatible plant does not require pollinators for pollen dispersal and exchange, it is generally assumed that nectar robbers may have a neutral effect on self-pollinated plant’s reproduction.
To test the well-acknowledged assumption, Ms. ZHANG Chan, a master student from Kunming Institute of Botany (Institute of Tibetan Plateau Research at Kunming) of Chinese Academy of Sciences, carried out field experiments on a self-pollinated plant species, Comastoma pulmonarium (Gentianaceae)in the Haibei Alpine Meadow Ecosystem Research Station from 2009 to 2010, supervised by professor YANG Yongping and associate professor DUAN Yuanwen. They found that C. pulmonarium around the Haibei Station produced plenty of nectar but were predominantly self-fertilized. The nectar was consumed exclusively by nectar robbers (Bombus kashmirensis). They suggested that nectar robbing could result in selective seed abortion through reducing the resource of seed development, which further reduced the magnitude of inbreeding depression in progeny from robbed flowers.Nevertheless, this reduction of inbreeding depression was not strong enough to facilitate the evolution of selfing in C. pulmonarium since the cumulative inbreeding depression of progeny from the robbed flowers was much greater than 0.5.
The research findings were published online with the title of “Selective seed abortion induced by nectar robbing in the selfing plantComastoma pulmonarium” on the journal, New Phytologist.
(http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2011.03785.x/abstract).
The reviewers gave highly appreciative comments as “This innovative study makes a substantial advance to our understanding in the field of nectar robbing, and open other research avenues for studying the ecology of nectar robbing, specifically the understanding of nectar robbing to resource allocation to selfing”.
