Abstract
SummaryFour weedy taxa of Bidens are common in Thunder Bay: B. cernua, B. connata, B. frondosa and B. vulgata. Since B. connata is intermediate in gross morphology and ecological preference between B. cernua and B. frondosa, and since it is only found in areas where B. cernua and B. frondosa are sympatric, an investigation was undertaken to determine whether B. connata is of hybrid origin (B. cernua × B. frondosa). Representative specimens of the 4 taxa were scored for 23 morphological characters, and these data were analyzed by Principal Coordinates Analysis. Seed germination and pollen viability were determined to be high with no significant differences among the 4 taxa. Morphological and cytological data suggest that B. connata (2n = 48) is the result of either a cross between an unreduced gamete of B. cernua (2n = 24) with a normal gamete of B. frondosa (2n = 48), or a cross between a 2n = 24 of B. frondosa with a typical gamete of B. cernua. Since B. connata shows no decrease in seed viability and apparently produces pollen by mitosis only, Thunder Bay populations of B. connata evidently comprise an agamic complex.
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