Abstract Detail

Reproductive Processes

Dellinger, Agnes [1], Pérez-Barrales, Rocío [2], Fernández-Fernández, Diana [3], Schönenberger, Jürg [4].

Bees are inefficient pollinators in cloud forests - investigating pollinator shifts in neotropical Melastomataceae.

Changes in pollination efficiency are thought to be the main driver of shifts in reproductive strategies in plants relying on pollination by animals. Such changes may occur when plants colonize new habitats, abiotic environmental conditions change or new pollinators appear. Environmental conditions and pollinator communities differ along altitudinal gradients and species which grow in lowland habitats often differ in their pollination strategy from closely related species which have colonized montane habitats. In particular, numerous Neotropical plant clades show a consistent shift directionality from bee to vertebrate pollination associated with growth at high elevations. Surprisingly, the underlying assumption that these pollinator shifts arose from the reduced efficiency of bee pollinators in mountain ecosystems has rarely been tested in the field.
Using Merianieae (Melastomataceae) as study system, we test the hypothesis that bees are less efficient pollinators at high elevations than vertebrates, hence leading to repeated shifts from bee to vertebrate pollination. We employ manual pollination experiments, pollinator observations and measure pollen transfer (pollen export and pollen deposition) in six Merianieae species pollinated by either bees, passerine birds or mixed assemblages of vertebrates. Furthermore, we comparatively study stamen and stigma traits crucial for pollen transfer in 47 Merianieae species to understand how pollen transfer is optimized in the different pollination systems.
Our results confirm that bees are highly inefficient pollinators in montane cloud forests as bee-pollinated plants were strongly pollen limited. Vertebrate pollinators were significantly more efficient in transferring pollen, even when visitation rates were low. Employing different vertebrate pollinator groups (e.g. hummingbirds and bats) maximized pollen transfer in Merianieae. When comparing single-visit effectiveness, however, bees were highly efficient pollinators also in mountains. In all species, regardless of pollination strategy, pollen is dispensed in small doses through poricidal anthers typical for buzz-pollinated flowers. Stamen properties (thecal wall structure, pollen-release mechanism), pollen grain and stigma sizes have changed with pollinator shifts and show system-specific adaptations. We conclude that pollen dispensing and pick-up is optimized differently in each system and adapted to the efficiency and foraging strategy of the different pollinators.

1 - University of Vienna, Department of Botany and Biodiversity Research, Rennweg 14, Vienna, 1030, Austria
2 - University of Portsmouth, UK
3 - Instituto Nacional de Biodiversidad, Ecuador
4 - University of Vienna, Department of Botany and Biodiversity Research, Austra

pollen presentation theory
stamen morphology.

Presentation Type: Oral Paper
Session: REP2, Reproductive Processes 2
Location: Virtual/Virtual
Date: Wednesday, July 29th, 2020
Time: 1:30 PM
Number: REP2005
Abstract ID:327
Candidate for Awards:None

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