conifer pollination mechanisms revisited
TRANSCRIPT
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Conifer Pollination Mechanisms Revisited
Patrick von Aderkas
University of Victoria
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Patrick von Aderkas
Alexandra Lunney
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Patrick von Aderkas
Alexandra Lunney
Stefan Little
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Patrick von Aderkas
Alexandra Lunney
Stefan Little
Natalie Prior
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Outline 1. Introduction 2. Pollination mechanisms 3. What does this mean?
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Ginkgo biloba
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This is the oldest, and the most common pollination mechanism in the history of gymnosperms
Pollen is captured by
a pollination drop
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Fig. 2. Mirror trees showing the parsimony based character mapping on the strict consensus of 10 trees; parsimony model for characters is unordered. Left, mapping of zoodiogamy presence and absence; fossil taxa with prepollen scored as present. Right, mapping of pollination drop absence, presence, or occurrence of ECG (extra-ovular capture and germination); fossil taxa with saccate pollen scored as present.]
Mapping the presence of a pollination drop on the phylogeny of gymnosperms using parsimony reconstruction
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Outline 1. Introduction 2. Pollination mechanisms 3. Scanning Electron Micrographs 4. What does this mean?
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Pollination mechanisms are divided into two types: i. Pollen capture mechanisms (PCMs)
ii. Extra-ovular capture and germination (ECG)
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PCM 1 non-saccate pollen is captured by a pollination drop example Ginkgo
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Scanning Electron Microscopy
Unfixed ovules were placed in a Hitachi S-3500N variable pressure scanning electron microscope with a Deben MK3 cold stage. The SEM was operated at 20 kV and 50 Pa variable pressure in back-scattered electron mode using a Robinson BSE detector
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PCM 1 non-saccate pollen is captured by a pollination drop Ephedra
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PCM 1 non-saccate pollen is captured by a pollination drop Ephedra
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PCM 1 non-saccate pollen is captured by a pollination drop Ephedra
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PCM 1 non-saccate pollen is captured by a pollination drop Taxus
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PCM 1 non-saccate pollen is captured by a pollination drop Taxus
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PCM 1 non-saccate pollen is captured by a pollination drop Cupressus
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PCM 1 non-saccate pollen is captured by a pollination drop Chamaecyparis
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PCM 1 is found in most modern gymnosperms
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From the fossil record we infer that PCM 1 was found in most extinct gymnosperms: drops captured pollen, and earlier, prepollen
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PCM 2 saccate pollen is captured by micropyle: a pollination drop later appears example Tsuga mertensiana
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PCM 2 saccate pollen is captured by micropyle: a pollination drop later appears example Tsuga mertensiana
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PCM 2 saccate pollen is captured by micropyle: a pollination drop later appears example Tsuga mertensiana
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PCM 2 saccate pollen is captured by micropyle: a pollination drop later appears example Pinus nigra
from Leslie (2010)
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PCM 2 is restricted to some members of the Pinaceae, e.g. Pinus, Picea, Tsuga
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PCM 3 saccate pollen is not captured by the drop but by the scavenging activity of a pollination drop example Podocarpus
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PCM 3 is restricted to some members of the Podocarpaceae, e.g. Podocarpus
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PCM 4 non-saccate pollen is not captured by a pollination drop; however a drop later appears Pseudotsuga
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PCM 4 non-saccate pollen is not captured by a pollination drop; however a drop later appears Pseudotsuga
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PCM 4 non-saccate pollen is not captured by a pollination drop; however a drop later appears Larix
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PCM 4 non-saccate pollen is not captured by a pollination drop; however a drop later appears Larix
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PCM 4 is restricted to some members of the Pinaceae, e.g. Pseudotsuga, Larix
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PCM 5 saccate pollen is trapped by a funnel-shaped extension. A drop appears later example Cedrus
Owens and Takaso (1995)
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PCM 6 saccate pollen is trapped by a funnel-shaped extension. No drop appears Abies
Owens & Chandler (2004)
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PCM 5 & 6 are restricted to some members of the Pinaceae, e.g. Cedrus & Abies, respectively
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PCM 1, 2, 4, 5 & 6
PCM 1 &3
PCM 1 & 2*
* for fossil taxa, sacci=drop, but primary capture unknown
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Pollination mechanisms are divided into two types: i. Pollen capture mechanisms (PCMs)
ii. Extra-ovular capture and germination (ECG)
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ECG pollen lands outside the ovule and grows into the nucellus, which extends beyond the ovule Agathis
Owens et al. 1995
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ECGs are found in some Pinaceae, and all Araucariaceae
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PCM 1, 2, 4, 5 & 6
PCM 1 &3
PCM 1
ECG
ECG
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Outline 1. Introduction 2. Pollination mechanisms 3. What does this mean?
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Pinaceae are have the most diversity in pollination mechanisms, followed by the Podocarpaceae
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PCM 1 (pollen capture by an exposed drop) is the basal type for gymnosperms both in the fossil record and in modern gymnosperms
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Gnetales and possibly Cyadales show a major modification of PCM1 – the drop behaves like nectar as it provides a reward to insects
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In British Columbia we have many economically important Pinaceae species, but as is clear from this diagram these are of great interest from an evolutionary point of view
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Acknowledgments Figures Wikipedia (Ginkgo leaves) http://www.polleninfo.org (Ginkgo, Taxus, Cupressus, Ephedra, Cedrus ) www.paleolab.ca (pollen of Tsuga mertensiana) Leslie (2010) New Phytologist 188: 273-279 (Pinus pollen) Tomlinson et al. (1997) (Podocarpus schema) Australian Pollen and Spore Atlas (Podocarpus pollen) Owens & Takaso (1995) Cedrus ovule Owens & Chandler (2004) Abies ovule Owens et al. (1995) Agathis ovule
Money NSERC Discovery Grant supported Patrick von Aderkas and Alexandra Lunney NSERC PGS A Graduate Scholarship supported Natalie Prior NSERC Strategic Partnership supported Stefan Little
SEM Brent Gowen of UVic Biology Electron Microscopy Unit provided lots of help