Some aspects of the biology and taxonomy of Myriophyllum population in Lake Opinicon (Eastern Ontario)

Ninety-seven Myriophyllum specimens were collected from Lake Opinicon, Eastern Ontario, and subjected to taximetric analysis which resulted in two groups, viz. M. exalbescens Fern., a native species, and M. spicatum L., a recent Eurasian introduction. These groups should be recognized at the species level since they can be neatly divided by three characters: (1) number of leaf divisions, (2) presence or absence of turion type growth, and (3) number of floral whorls. Phenological observations of the two groups in Lake Opinicon, including seed viability and habitat specificity, showed that the two groups were quite similar, although minor differences that were observed may account for the greater abundance of M. spicatum.