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PERSISTENCE OF AMBROSIA TRIFIDA POPULATIONS IN OLD FIELDS AND RESPONSES TO SUCCESSIONAL CHANGES
Author(s) -
Hartnett David C.,
Hartnett Barbara B.,
Bazzaz Fakhri A.
Publication year - 1987
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1987.tb08737.x
Subject(s) - biology , fecundity , population , old field , competition (biology) , ecology , biomass (ecology) , demography , sociology
A population of Ambrosia trifida L. (Asteraceae) in an annually ploughed field and an adjacent 15‐year old population in an old field were compared to determine how plant responses, genotypic composition, and genetic variability change in populations over successional time. The two populations were originally part of a large contiguous population in an annually ploughed field. When individuals from the two populations were grown from seed in a common garden, they showed several significant differences in characteristics indicating different genotypic compositions in the two populations. Individuals from the old field population showed earlier emergence, lower leaf mortality, and greater numbers of leaves, biomass, seed production, and reproductive allocation relative to plants from the annually ploughed field. When sown in the field in a reciprocal transplant experiment, individuals from the two populations also differed in patterns of emergence, survivorship, yield, and fecundity. When grown together in a pairwise competition experiment, individuals from the old field population showed competitive superiority with respect to growth and seed production. This genetic differentiation between populations of different successional ages may be explained by natural selection imposed by the changing environment over successional time. However, the history and characteristics of these populations are such that founder effects may also be important in explaining the differences between them. A comparison of levels of variability in 14 different characters of individuals of the two populations showed no evidence that genetic variability in A. trifida populations declined over successional time.