Ambrosia (Asteraceae)
Ambrosia artemisiifolia
Wildflowers of Alabama

fossil, San Joaquin Marsh, Ca
UofA Palynology

Ambrosia trifida SEM C. Drew
UofA Palynology

Plant genera producing this pollen type include Ambrosia, (Franseria discontinued name), Hymenoclea, Iva, (Solidago), and Xanthium. Distribution: worldwide.

Pollen light micrograph:
Grain echinate, tricolporate, small (20 - 30 µm), spherical, The Ambrosia (bursage [woody] or ragweed [herbaceous]) pollen type. This pollen type is routinely distinguished from other members of the sunflower (Asteraceae or Compositae) plant family by its short and sparse spines, its short furrows, and the presence of cavae -- three gaps in the outer wall. However, these features are variably expressed. Iva xanthifolia for example, has relatively long furrows (10 µm), and Solidago canadensis resembles this pollen type only in having short spines (4 µm). Thus, the Ambrosia type overlaps with, but is different from the "low-spine (Martin, 1963)" pollen type, which is recognized only by spine length.

Pollen scanning electron micrograph (SEM)
SEM's show the short, broad spines characteristic of this group, but do not show the short transverse furrow or the cavae.

Fossil Occurrence:
Ambrosia pollen occurrs in the fossil record from the earliest Cenozoic (?), and gradually becomes abundant during the late Miocene and Pliocene at Great Salt Lake. Ambrosia pollen is a major cause of pollen allergy. Ambrosia, (Franseria) pollen is characteristic of the lower Mojave and Sonoran Desert vegetation of North America. Ambrosia pollen increases during the historic period in much of North America (the" Ambrosia rise"). [see Ambrosia Rise]

Production and Dispersal:
Wind-pollenated and therefore regionally abundant and widespread.

The thick pollen wall is well preserved.

    Bassett, I. J., Crompton, C.W. and J. A. Marmelee. 1978.
    An Atlas of Ariborne Pollen Grains and Common Fungus Spores of Canada. Canada Department of Agriculture Monograph 18.

    Martin, P.S. 1963
    "The Last 10,000 Years." U of Arizona Press.

    Payne, W. W. and J. J. Skvarla. 1970.
    Electron microscope study of Ambrosia pollen. Grana 10(2): 89-100.

    Robbins, R.R., Dickinson, D.B. and Rhodes, A.M. 1979.
    Morphometric analysis of four species of Ambrosia (Compositae). American J. Botany 66: 538-545.

Owen K. Davis 12/99