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.

Species Richness Within Families of Flowering Plants

Robert E. Ricklefs and Susanne S. Renner
Evolution
Vol. 48, No. 5 (Oct., 1994), pp. 1619-1636
DOI: 10.2307/2410252
Stable URL: http://www.jstor.org/stable/2410252
Page Count: 18
  • 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.
Species Richness Within Families of Flowering Plants
Preview not available

Abstract

Variation in species and genus richness among families of flowering plants was examined with respect to four classification variables: geographical distribution, growth form, pollination mode, and dispersal mode. Previous studies have estimated rates of species proliferation from age and contemporary diversity. Here we found that the earliest appearances in the fossil record are correlated with contemporary familial species richness, abundance in the fossil record, and the independent variables considered in this analysis. Thus, we believe that the fossil record does not provide reasonable estimates of the ages of families and that the rate of species proliferation cannot be calculated from such data without bias. Accordingly, our subsequent analyses were based on contemporary species richness of families. Although the classification variables were interrelated, each made largely independent contributions to familial species richness. Cosmopolitan families were 5.6 times more species-rich than strictly tropical families and 35 times more species-rich than strictly temperate families. Families including both herbaceous and woody growth forms were 5.7 and 14 times more species-rich than families with either growth form alone. Although animal pollination was significantly associated with elevated familial species richness, the effect was statistically weak. The most prominent effect was that families with both abiotic and biotic dispersal had more than 10 times as many species as families with either dispersal mode alone. Our analyses also revealed that families having both dispersal modes were more likely to have several growth forms, suggesting that evolutionary flexibility of morphology may be generalized over diverse aspects of life history. These results do not support the idea that pollination and dispersal by animals were primarily responsible for the tremendous proliferation of angiosperm species, either by producing population structures conducive to speciation or by applying selection for diversification. Instead, the importance of varied dispersal mode, growth form, and climate zone in predicting high familial species richness suggests that a capacity to diversify morphologically and physiologically may have been primarily responsible for high rates of species proliferation in the flowering plants.

Page Thumbnails

  • Thumbnail: Page 
1619
    1619
  • Thumbnail: Page 
1620
    1620
  • Thumbnail: Page 
1621
    1621
  • Thumbnail: Page 
1622
    1622
  • Thumbnail: Page 
1623
    1623
  • Thumbnail: Page 
1624
    1624
  • Thumbnail: Page 
1625
    1625
  • Thumbnail: Page 
1626
    1626
  • Thumbnail: Page 
1627
    1627
  • Thumbnail: Page 
1628
    1628
  • Thumbnail: Page 
1629
    1629
  • Thumbnail: Page 
1630
    1630
  • Thumbnail: Page 
1631
    1631
  • Thumbnail: Page 
1632
    1632
  • Thumbnail: Page 
1633
    1633
  • Thumbnail: Page 
1634
    1634
  • Thumbnail: Page 
1635
    1635
  • Thumbnail: Page 
1636
    1636