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The Bromeliad-Anopheles-Malaria Complex in Trinidad. I-The Bromeliad Flora

Colin S. Pittendrigh
Evolution
Vol. 2, No. 1 (Mar., 1948), pp. 58-89
DOI: 10.2307/2405616
Stable URL: http://www.jstor.org/stable/2405616
Page Count: 37
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The Bromeliad-Anopheles-Malaria Complex in Trinidad. I-The Bromeliad Flora
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Abstract

A classification of ecological types within the Bromeliaceae is developed. It is pointed out that the principal cleavage within the family is between species that are dependent on their substratum for nutrients and water and those that are not. Nutritive independence has been possible due to the evolution of (a) the 'tank' habit of impounding water and humus between overlapping leaf bases, and (b) a system of epidermal absorbing trichomes on the leaves which exploit the water and humus of the tank. The habit of Bromelia humilis Jacq. is described. The plant has a 'tank' which it exploits by upgrowing interfoliar mycotrophic roots, a condition previously unknown in the family. An analysis of the distribution of epiphytic bromeliads in varying conditions of light and humidity leads to the conclusion that light is their prime ecoclimatic variable. All the ecological evidence is shown to be against Schimper's (1888) hypothesis, that epiphytes have evolved from the ground flora in wet forest, applying to the case of the Bromeliaceae. Epiphytism in the Bromeliaceae is held to be an exploitation of adaptive features developed initially in response to dry impoverished soils such as occur in semi-desert habitats.

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