Introduction
Ninety percent of flowering plants are pollinated by animals (Ollertonet al . 2011; Tong et al . 2023). Without pollinators, many
plants could not set seed and reproduce; and without plants to provide
pollen, nectar, and other floral rewards, many animal populations would
decline (Kearns et al . 1998). Pollinators tend to move both
within and among neighboring plants, and the pollen transfer efficiency
of pollinators varies markedly, so that most plants end up with a mixed
mating strategy at the point of being pollinated (Harder and Barrett
1996; Goodwillie et al . 2005). Vogler and Kalisz (2001) reviewed
available data to show that most plants achieve a mixture of selfing and
outcrossing. Plants can control their mating opportunities by the way
they manipulate their visitors. Attracting a larger number of
pollinators is mainly determined by the advertising traits and floral
rewards of plants. Therefore, understanding the pollination efficiency
of various pollinators can help predict how different floral visitors
could influence plant reproduction.
In animal-pollinated plants, the contribution of different pollinator
species to plant’s reproductive fitness differs significantly because
their pollination efficiency varies greatly due to differences in body
size, foraging behavior, and visitation rate (Chang et al . 2023).
Fewer pollinator visits or less pollen delivered per visit may reduce
the reproductive success of plants (Olsen 1996; Ashman et al .
2004; Sahl and Conner 2007). Body size is an important functional
characteristic that underlies pollination-related ecological processes
(Kendall et al . 2019). The body size of pollinators such as body
length and intertegular distance can influence the amount of deposited
pollen (Goulson et al . 2002;
Földesiet al . 2020). The intertegular distance is a useful body size
index established by Cane (Cane, 1987). Goulson et al . (2002)
found that the amount of pollen transferred by bees was influenced by
the intertegular distance. Larger bees tended to deposit more pollen on
stigmas at each visit than smaller bees, and the interspecific body
length and intertegular distance of bees had a positive effect on pollen
deposition (Földesi et al . 2020; Chang et al . 2023). There
was no correlation between intertegular distance and pollen deposition
among individuals of the same species (Chang et al . 2023).
However, whether pollen removal and pollination efficiency (pollination
efficiency = pollen deposition/pollen removal, see Li et al .
2022) are affected by body size of pollinators is still unknown.
In this study, we used a generalist plantHibiscus mutabilis as an
example to investigate the impact of pollinators’ body size on
pollination efficiency. We measured the floral traits of plants and the
body length and intertegular distance of various pollinator species. We
identified the breeding system of H. mutabilis by imposing four
pollination
treatments. We compared the visitation rates of various pollinator
species. To assess pollination efficiency, we examined pollen deposition
and pollen removal of each pollinator species. Based on field
investigations, we aimed to address the following three questions: (1)
Are there differences in visitation rate and pollination efficiency
among various pollinator species in H. mutabilis ? (2) Does
the species H. mutabilis have
a mixed mating system? (3) Is the body size of pollinators related to
pollination efficiency?