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.

Life History Variation of Common Mullein (Verbascum Thapsus): I. Latitudinal Differences in Population Dynamics and Timing of Reproduction

James A. Reinartz
Journal of Ecology
Vol. 72, No. 3 (Nov., 1984), pp. 897-912
DOI: 10.2307/2259539
Stable URL: http://www.jstor.org/stable/2259539
Page Count: 16
  • Read Online (Free)
  • Download ($18.00)
  • 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.
Life History Variation of Common Mullein (Verbascum Thapsus): I. Latitudinal Differences in Population Dynamics and Timing of Reproduction
Preview not available

Abstract

(1) Twenty-four natural populations of the monocarpic perennial Verbascum thapsus were mapped and studied over 3 years. Populations were chosen at the northern (southern Canada) and southern (southern Texas and Georgia) limits of its range in North America, and in North Carolina and came from a range of the habitats occupied by the species. Genetic components of life history variation were studied by growing seed from several different populations in a common garden in Durham, North Carolina. (2) Vegetative individuals colonize a disturbed site for only a few growing seasons after disturbance. However, the populations are long persistent as a dormant pool of seeds buried in the soil. (3) Many genetically maintained differences, related to latitude of origin were noted. (4) Delay of flowering until the third year was most common among northern genotypes and was a response to unfavourable growth conditions. On average, triennial plants produced only one-fifth as much seed as biennial plants. (5) Annual genotypes occurred only in the southern part of the range, at both wet and dry sites. (6) Longer average periods before reproduction were negatively correlated with the percentage of the ground surface covered by vegetation. Most population differences in length of these periods were maintained in the common garden. (7) In the common garden, plants from southern populations began to bolt and flower earlier than those from the other populations. Texas plants also flowered for a longer period and their capsules dehisced later. (8) The pattern of a short period of population growth, followed by a long period of slow decline of the buried seed pool, causes population growth rates to be dependent solely upon the number of seeds produced and independent of the time of their production. Annual genotypes are favoured only in the long southern growing season and where survival is uncertain in the second year because of drought or competition. In more northerly climates, biennial and triennial plants are favoured because they can produce more seed in the short but predictable growing season.

Page Thumbnails

  • Thumbnail: Page 
897
    897
  • Thumbnail: Page 
898
    898
  • Thumbnail: Page 
899
    899
  • Thumbnail: Page 
900
    900
  • Thumbnail: Page 
901
    901
  • Thumbnail: Page 
902
    902
  • Thumbnail: Page 
903
    903
  • Thumbnail: Page 
904
    904
  • Thumbnail: Page 
905
    905
  • Thumbnail: Page 
906
    906
  • Thumbnail: Page 
907
    907
  • Thumbnail: Page 
908
    908
  • Thumbnail: Page 
909
    909
  • Thumbnail: Page 
910
    910
  • Thumbnail: Page 
911
    911
  • Thumbnail: Page 
912
    912