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.

Amphitropical Species Pairs in Microseris and Agoseris (Compositae: Cichorieae)

Kenton L. Chambers
The Quarterly Review of Biology
Vol. 38, No. 2 (Jun., 1963), pp. 124-140
Stable URL: http://www.jstor.org/stable/2819160
Page Count: 17
  • Read Online (Free)
  • Download ($19.00)
  • 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.
Amphitropical Species Pairs in Microseris and Agoseris (Compositae: Cichorieae)
Preview not available

Abstract

In the flora of temperate South America are two species of Compositae, tribe Cichorieae, subtribe Microseridinae, that are disjunct from the North American centers of distribution of their respective genera. Microseries pygmaea, an autogamous annual of central Chile, is morphologically similar to several species of like habit, found in the climatically comparable Californian region. A hybrid obtained between M. Pygmacea and the closely related North American species, M. bigelovii, showed normal meiotic behavior and was almost fully fertile. In an F generation of 55 plants, phenotypic segregation was more in the direction of M. bigelovii, and two individuals resembled that species with only minor differences. There was a complex pattern of inheritance for the number of pappus scales on the fruit, a characteristic of major taxonomic importance in distinguishing the parent species. A reduction in seed fertility of certain hybrid plants was ascribed to segregation of a small, nonreciprocal chromosome translocation. It was concluded that the two species are adequately distinct taxonomically but are genetically closely related and interfertile. Microseries probably reached South America by long-distance dispersal, the most likely time for migration being the middle or late Pliocene Epoch. In the second example, Agoseris coronopifolia is a variable species, distributed over the southern tip of the continent, which can be differentiated from the North American Agoseris heterophylla only with difficulty. Both species are composed primarily of annual or perennial plants with autogamous reproduction. Adaptations for out-crossing are present in some races of A. heterophylla but not in A. coronopifolia. Preliminary crossing experiments suggest that genetic barriers exist between the species. The general pattern of phytogeographical and evolutionary relatioships in Agoseris and Microseris is like that in certain other families of similar distribution.

Page Thumbnails

  • Thumbnail: Page 
124
    124
  • Thumbnail: Page 
125
    125
  • Thumbnail: Page 
126
    126
  • Thumbnail: Page 
127
    127
  • Thumbnail: Page 
128
    128
  • Thumbnail: Page 
129
    129
  • Thumbnail: Page 
130
    130
  • Thumbnail: Page 
131
    131
  • Thumbnail: Page 
132
    132
  • Thumbnail: Page 
133
    133
  • Thumbnail: Page 
134
    134
  • Thumbnail: Page 
135
    135
  • Thumbnail: Page 
136
    136
  • Thumbnail: Page 
137
    137
  • Thumbnail: Page 
138
    138
  • Thumbnail: Page 
139
    139
  • Thumbnail: Page 
140
    140