Pollinators contribute to the maintenance of flowering plant diversity

Abstract

Mechanisms that favor rare species are key to the maintenance of diversity. One of the most critical tasks for biodiversity conservation is understanding how plant-pollinator mutualisms contribute to the persistence of rare species, yet this remains poorly understood. Using a processbased model that integrates plant-pollinator and interspecific pollen transfer networks with floral functional traits, we show that niche partitioning in pollinator use and asymmetric facilitation confer fitness advantage of rare species in a biodiversity hotspot. While co-flowering species filtered pollinators via floral traits, rare species showed greater pollinator specialization leading to higher pollination-mediated male and female fitness than abundant species. When plants shared pollinator resources, asymmetric facilitation via pollen transport dynamics benefited the rare species at the cost of the abundant ones, serving as an alternative diversity-promoting mechanism. Our results emphasize the importance of community-wide plant-pollinator interactions that affect reproduction for biodiversity maintenance.

Spatial variation in bidirectional pollinator-mediated interactions between two co-flowering species in serpentine plant communities

“…Therefore, it is somewhat surprising that these asymmetries, and their role in community assembly, have not been more often considered when evaluating community-wide consequences of pollinator-mediated interactions. For instance, recent studies that have evaluated the role of phenotypic traits in determining the outcome of community-wide species interactions have also suggested that both, competition and facilitation, likely play a role in the assembly of plant communities ( Tur et al 2016 ; Bergamo et al 2018 ; Navarro-Cano et al 2021 ; Wei et al 2021 ). Although the importance of the interplay between competition and facilitation in the assembly of co-flowering communities was proposed more than 35 years ago ( Rathcke 1983 ; Mitchell et al 2009 ), only few studies have experimentally evaluated the bidirectionality of pollinator-mediated interactions between co-flowering species (i.e.…”

“…uliginosum flowers, to the detriment of M. guttatus flowers, thus generating positive effects for the former and negative effects for the latter. Furthermore, M. guttatus flowers are more generalized and also visited by other insects such as beetles, flies and butterflies ( Koski et al 2015 ; Wei et al 2021 ), which may be more abundant in mixed-species plots but are be less efficient and deposit higher amounts of heterospecific pollen loads. On the contrary, D .…”

“…data; also see Koski et al 2015 ). Abundant species have been proposed to be more prone to competitive interactions while less abundant and more specialized species are often facilitated ( Ghazoul 2005 , 2006 ; Bizecki Robson 2013 ; Zografou et al 2020 ; Wei et al 2021 ). Overall, these results highlight the dynamic nature of pollinator-mediated interactions (e.g.…”

“…Furthermore, M. guttatus is typically more abundant and considered a pollinator generalist while D. uliginosum tends to be primarily bumblebee-pollinated, which also visits M. guttatus flowers ( Koski et al 2015 ). Thus, it is possible to expect that M. guttatus may help facilitate pollination success in the less abundant D. uliginosum ( Wei et al 2021 ). However, this may occur at the detriment of M. guttatus pollination, either via a decrease in conspecific pollen or via an increase in heterospecific pollen deposition ( Wei et al 2021 ).…”

“…Thus, it is possible to expect that M. guttatus may help facilitate pollination success in the less abundant D. uliginosum ( Wei et al 2021 ). However, this may occur at the detriment of M. guttatus pollination, either via a decrease in conspecific pollen or via an increase in heterospecific pollen deposition ( Wei et al 2021 ). Specifically, we ask the following questions: (i) do patterns of conspecific and heterospecific pollen deposition, and pollen tube growth differ between M. guttatus and D. uliginosum when they grow alone compared to when they occur together?…”