Ambrosia cumanensis

Fig. 3.6 Map of Texas coast and adjacent Mexican sites from Ambrosia psilostachys (Ap) study. Populations of Ambrosia cumanensis are represted by Ac. ...

Anaya, A.L., S. del Amo. Allelopathic potential of Ambrosia cumanensis H.B.K. (Compositae) in a tropical zone of Mexico. J Chem Ecol 1978 4 289-304. 

Populations of Ambrosia confertifloray a ragweed disttib-uted widely through Texas and Mexico, reveal complex sesquiterpene lactone chemistry. Most populations from south-central Texas are characterized by a chromosome number n = 66 and the pseudoguaianolides confertiflorin (95) and desacetylconfertiflorin (99), whereas plants from northeastern Mexico yield germacranolides and a few eudesmanol-ides. All of those studied have chromosome number n = 54. A dilactone race (with both = 54 and n = 66) occurs further west in Texas and in Mexico along the western slopes of the Sierra Madre into the area where Ambrosia cumanensis occurs. A fourth race characterized by the presence of germacranolides occurs in northwestern Mexico (Mabry, 1972). 

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