Comparative studies on the competitive abilities of an exotic, Parthenium hysterophorus L., with co-existing species to determine the impacts of its invasion.

Germination percentage of a newly introduced exotic plant, Parthenium hysterophorus L., that has now dominated most of the herbaceous flora, was compared with 7 annual indigenous colonizer plants, commonly found in the wastelands of Lahore, Pakistan. The percentage of germination, determined under various sets of conditions revealed that having higher and relatively constant rates of germination throughout the year, P. hysterophorus is more competitive as compared to the other co-existing colonizers. The competitive abilities of P. hysterophorus were further compared with two dominant colonizers i.e., Chenopodium album and Kochia indica, to assess the competitive abilities on both interspecific and intraspecific competition. The results based on Absolute Yield, Relative Yield Total and Relative Crowding Coefficients clearly indicated that P. hysterophorus was competitively more aggressive as compared to both co-occurring species and there is a possibility that in the long run it would eliminate them from their habitat in the irrigated plains.