Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. 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.

The Evolution of Inflorescence Size in Asclepias (Asclepiadaceae)

Mary F. Willson and Peter W. Price
Evolution
Vol. 31, No. 3 (Sep., 1977), pp. 495-511
DOI: 10.2307/2407517
Stable URL: http://www.jstor.org/stable/2407517
Page Count: 17
  • Read Online (Free)
  • Download ($4.00)
  • Subscribe ($19.50)
  • Cite this Item
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.
The Evolution of Inflorescence Size in Asclepias (Asclepiadaceae)
Preview not available

Abstract

Larger inflorescences usually received more pollen than smaller inflorescences, and had a higher average rate of insect visitation, but only sometimes produced more mature pods. Mortality of developing pods of several (but not all) species was greatest in inflorescences that initiated larger numbers of young pods, suggesting 'brood reduction' and competition among young fruits for parental expenditure. We suggest that inflorescence size may not have evolved primarily as a result of capacity to produce pods but rather the capacity to contribute pollen. Each plant is both mother and father, but each parental role has had different effects on the evolution of the total floral display in Asclepias, and we suggest that the allocation of investment to each parental role may vary with the plant's budget of energy and nutrients. The relative infrequency of large inflorescences in our populations implies selective disadvantages to large size. We cannot demonstrate such counter-selection in either predation pressure or self pollination. At least for some species and populations, interfruit competition for resources places large inflorescences at a disadvantage in pod production (but not in pollen donation). We therefore suspect that inflorescence size is commonly limited phenotypically by the availability of energy or nutrients.

Page Thumbnails

  • Thumbnail: Page 
495
    495
  • Thumbnail: Page 
496
    496
  • Thumbnail: Page 
497
    497
  • Thumbnail: Page 
498
    498
  • Thumbnail: Page 
499
    499
  • Thumbnail: Page 
500
    500
  • Thumbnail: Page 
501
    501
  • Thumbnail: Page 
502
    502
  • Thumbnail: Page 
503
    503
  • Thumbnail: Page 
504
    504
  • Thumbnail: Page 
505
    505
  • Thumbnail: Page 
506
    506
  • Thumbnail: Page 
507
    507
  • Thumbnail: Page 
508
    508
  • Thumbnail: Page 
509
    509
  • Thumbnail: Page 
510
    510
  • Thumbnail: Page 
511
    511