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.

Evidence on the Monophyly of Astragalus (Fabaceae) and its Major Subgroups Based on Nuclear Ribosomal DNA ITS and Chloroplast DNA trnL Intron Data

Martin F. Wojciechowski, Michael J. Sanderson and Jer-Ming Hu
Systematic Botany
Vol. 24, No. 3 (Jul. - Sep., 1999), pp. 409-437
DOI: 10.2307/2419698
Stable URL: http://www.jstor.org/stable/2419698
Page Count: 29
  • Read Online (Free)
  • Download ($12.00)
  • 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.
Evidence on the Monophyly of Astragalus (Fabaceae) and its Major Subgroups Based on Nuclear Ribosomal DNA ITS and Chloroplast DNA trnL Intron Data
Preview not available

Abstract

Phylogenetic relationships among 115 species representing the legume genus Astragalus and 12 related genera were inferred from an analysis of nucleotide sequence variation in the internal transcribed spacers and 5.8S gene of nuclear ribosomal DNA. For a subset of these taxa, the ITS data were supplemented by sequences from the chloroplast trnL intron. Phylogenies derived from maximum parsimony and neighborjoining analyses of sequence and insertion/deletion characters all suggest that the vast majority of Astragalus is monophyletic (with the exception of "outlier" species). All New World Astragalus species with aneuploid chromosome numbers (n = 11-15) form a monophyletic group ("Neo-Astragalus"), which now includes the Mediterranean aneuploid Astragalus echinatus. Other Old World aneuploid species are not closely related to Neo-Astragalus, but rather are found among Old World euploid (n = 8, 16) groups. Similarly, the relatively few North American species with euploid numbers are not the closest relatives to Neo-Astragalus but are dispersed among divergent Old World groups that include both aneuploid and euploid species. The historically allied genus Oxytropis is not nested within Astragalus, but forms a separate clade within the larger "Astragalean" clade. The proposed segregate genera Astracantha (Eurasian) and Orophaca (North American) are clearly nested within Astragalus s. str. South American species of Astragalus are nested within Neo-Astragalus and comprise at least two independently derived clades (along with their close North American relatives), as previously suggested by morphology. Parsimony reconstructions of characters that have been used in the traditional subgeneric taxonomy of the genus were examined and show high levels of homoplasy. Preliminary estimates of the absolute rate of species diversification in Astragalus suggest it may be higher than in some other, often cited, continental or insular adaptive radiations in angiosperms.

Page Thumbnails

  • Thumbnail: Page 
409
    409
  • Thumbnail: Page 
410
    410
  • Thumbnail: Page 
411
    411
  • Thumbnail: Page 
412
    412
  • Thumbnail: Page 
413
    413
  • Thumbnail: Page 
414
    414
  • Thumbnail: Page 
415
    415
  • Thumbnail: Page 
416
    416
  • Thumbnail: Page 
417
    417
  • Thumbnail: Page 
418
    418
  • Thumbnail: Page 
419
    419
  • Thumbnail: Page 
420
    420
  • Thumbnail: Page 
421
    421
  • Thumbnail: Page 
422
    422
  • Thumbnail: Page 
423
    423
  • Thumbnail: Page 
424
    424
  • Thumbnail: Page 
425
    425
  • Thumbnail: Page 
426
    426
  • Thumbnail: Page 
427
    427
  • Thumbnail: Page 
428
    428
  • Thumbnail: Page 
429
    429
  • Thumbnail: Page 
430
    430
  • Thumbnail: Page 
431
    431
  • Thumbnail: Page 
432
    432
  • Thumbnail: Page 
433
    433
  • Thumbnail: Page 
434
    434
  • Thumbnail: Page 
435
    435
  • Thumbnail: Page 
436
    436
  • Thumbnail: Page 
437
    437