This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Some bird species act as "double mutualists" for a common mistletoe, both pollinating its flowers and dispersing its seeds. These double mutualists play an effective role in mistletoe reproduction.
A study published in Ecosphere by researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences examined this phenomenon. The study focused on the dual mutualism between the parasitic mistletoe Dendrophthoe pentandra and its avian partners. In this relationship, certain bird species perform both pollination and seed dispersal.
Mistletoes are considered keystone species because they provide diverse floral and fruit resources for birds, supporting pollination and seed dispersal interactions. Some bird species act as double mutualists, performing both functions; however, their precise roles and effectiveness have remained poorly understood. The researchers conducted 690 hours of video observations at three sites, documenting avian visitors to common mistletoe during flowering and fruiting.
They recorded 833 visits by 13 species of birds from eight families. Eleven species probed flowers, accounting for 528 visits, while seven species consumed fruit, accounting for 43 visits. Three species—Dicaeum minullum, Dicaeum ignipectus and Zosterops simplex—were identified as double mutualists because they visited the plants during both the flowering and fruiting phases.
These double-mutualist birds accounted for 87.5% of flower visits and 95.5% of fruit visits. The researchers also found differences among species and sites. The generalist frugivore Zosterops simplex was the most frequent floral visitor at two of the three sites.
In contrast, the mistletoe specialist frugivore Dicaeum minullum was the principal seed disperser and the only pollinator that was frequent at all sites. They then examined morphological traits and evolutionary relationships. The double-mutualist birds were small to medium in size, with slightly curved beaks and relatively low body mass.
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