BIO 11 The Coevolution of Plants and Pollinators

BIO 11 The Coevolution of Plants and Pollinators - 2009...

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1 2009 BIO153: Lecture 11 Coevolution of Plants and Pollinators February 23, 2009 The history of the seed plants pre-dates the diversification of terrestrial animals; thus, the delivery of pollen from an anther to a stigma originally depended on something other than a pollinator. Ancestral condition = wind pollination: anemophily all gymnosperms; some angiosperms inefficient: requires massive overproduction of pollen because most is wasted (does not reach the target) this inefficiency results in low rates of outcrossing Disadvantages to a plant: there is a considerable metabolic cost to pollen production doesn’t work in wet environments : pollen needs to be dry to be transported; not enough wind However, it can be advantageous: works well in low diversity stands (pollen has a good chance of making it to a conspecific) works well in open areas (lots of wind) works well in areas of low – moderate rainfall works well when there is a short, unpredictable growing season (dependence on an animal pollinator can be a risky strategy) don’t need to invest energy in making flowers Some wind-pollinated angiosperms evolved from insect-pollinated ancestors (benefits outweighed the costs) flowering plants that no longer need a showy flower: small, drab flowers; no nectar don’t need to attract a pollinator e.g. grasses (adapted to dry, wide-open places)
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2 most pollen allergens are from anemophilous angiosperms: ragweed, birches, grasses, etc. Pollen structure reflects the mode of pollination:
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This note was uploaded on 04/25/2010 for the course BIOLOGY BIO153 taught by Professor Cordon during the Fall '10 term at University of Toronto- Toronto.

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BIO 11 The Coevolution of Plants and Pollinators - 2009...

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