Floral Formula Inconstancy Within and Among Plants and Populations of Ipomopsis aggregata (Polemoniaceae)

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Abstract
The numbers of flower parts are considered among the most constant angiosperm characters. However, nearly 33% of the plants in 13 populations of I. aggregata in Colorado [USA] had at least 1 anomalous flower, and almost 10% of the flowers displayed abnormal merism (abnormal floral formulas). Floral inconstancy varied significantly among populations. The number of abnormal flowers per plant increased with the proportion of plants displaying abnormal merism at a given site. Abnormal flowers were nonrandomly distributed; more plants had multiple anomalous flowers than expected by chance. The gynoecium was the most variable flower part and varied independently of the other parts, which tended to vary in a coordinated fashion. These observations are compared with other examples of anormal merism in the Polemoniaceae.