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Effects of Hummingbird Migration on Plant Speciation in the California Flora

Karen A. Grant and Verne Grant
Evolution
Vol. 21, No. 3 (Sep., 1967), pp. 457-465
DOI: 10.2307/2406607
Stable URL: http://www.jstor.org/stable/2406607
Page Count: 9
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Effects of Hummingbird Migration on Plant Speciation in the California Flora
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Abstract

The hummingbirds of California exist in two contrasting states of dispersion which alternate during the course of a year. The birds are dispersed over wide areas during the northward migration and the spring breeding season, but in the postbreeding season and on their southward migration they tend to congregate in the higher mountains. The distribution patterns of hummingbird-pollinated plant species in California are shown to be correlated with these two phases of hummingbird dispersion. Winter- and spring-blooming plant species are distributed over extensive areas of low to intermediate elevation and are largely allopatric, while summer-blooming plant species in the high mountains commonly occur in sympatric flocks. The species flocks of hummingbird flowers in the high mountains are explained as a consequence of the dense summer aggregations of hummingbirds. The latter provide a pool of potential pollinators for plant species normally pollinated by other agents and promote the divergence of local races and species adapted for hummingbird pollination.

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