Does pollen aerodynamics correlate with pollination vector? Pollen settling velocity as a test for wind versus insect pollination among cycads (Gymnospermae: Cycadaceae: Zamiaceae)

Hall, John A. and Walter, Gimme H. (2011) Does pollen aerodynamics correlate with pollination vector? Pollen settling velocity as a test for wind versus insect pollination among cycads (Gymnospermae: Cycadaceae: Zamiaceae). Biological Journal of the Linnean Society, 104 1: 75-92. doi:10.1111/j.10958312.2011.01695.x


Author Hall, John A.
Walter, Gimme H.
Title Does pollen aerodynamics correlate with pollination vector? Pollen settling velocity as a test for wind versus insect pollination among cycads (Gymnospermae: Cycadaceae: Zamiaceae)
Journal name Biological Journal of the Linnean Society   Check publisher's open access policy
ISSN 0024-4066
1095-8312
Publication date 2011-09
Sub-type Article (original research)
DOI 10.1111/j.10958312.2011.01695.x
Volume 104
Issue 1
Start page 75
End page 92
Total pages 18
Place of publication United Kingdom
Publisher Wiley-Blackwell Publishing Ltd.
Collection year 2012
Language eng
Abstract Studies of cycad pollination globally have revealed obligate pollination mutualisms with insects, typically hostspecific beetles. Some cycads in the genus Cycas have floating seeds allowing oceanic dispersal, and have colonized remote islands such as Fiji, Guam, and Madagascar. This seems to contradict the expected requirement that specific beetle pollinators be present in order for cycads to establish in remote localities. We therefore postulated that these ‘island’ cycads are wind pollinated. We tested for adaptations associated with wind pollination in a laboratory study of pollen aerodynamics. The pollen from a range of (non-cycad) wind-pollinated plants was not relatively ‘buoyant’: the settling velocities of wind-pollinated species exceeded those of insect-pollinated cycads and some animal-pollinated angiosperms. We attributed this result to settling velocity being, in part, correlated with pollen size, as cycad pollen was consistently smaller. A better predictor for pollination vector was the tendency of pollen to aggregate during a vertical fall. Pollen of wind-pollinated plants separated into single grains, whereas cycad pollen and pollen of animal-pollinated angiosperms adhered in large aggregations, the settling velocity of which increased rapidly with aggregate size. The pollen of cycads known to be insect pollinated was similar in morphology, settling speed, and clumping behaviour to pollen of ‘island’ cycads of unknown pollination biology. Based on these aerodynamics, we predict that cycad species on oceanic islands have insect pollinators. More broadly, we propose that pollen aggregation during a vertical fall provides a sound test for wind versus animal pollination when the pollination vector is unknown.
Keyword Araucaria
Cyathea
Cycas micronesica
Cycas revoluta
Cycas seemannii
Cycas thouarsii
Lepidozamia
Pinus
Zamia
Zea
Conifer Ovulate Cones
Saccate Pollen
Cross-Pollination
Floral Biology
Fig-Wasps
Furfuracea
Queensland
Evolution
Ecology
Spores
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2012 Collection
School of Biological Sciences Publications
 
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