MORPH FREQUENCIES AND FLORAL VARIATION IN A HETEROSTYLOUS COLONIZING WEED, LYTHRUM-SALICARIA

Lythrum salicaria (purple loosestrife)is an exotic weed that arrived i n North America from Europe during the early 1800s. It is a herbaceous perennial with a trimorphic breeding system. Seventy-four populations of L. salicaria were surveyed from Windsor, Ontario, to the Gaspe Pen insula in Quebec. Fifty of the populations were significantly anisople thic (i.e., unequal frequencies of the three flower morphs), including 10 populations that were nontrimorphic. Populations with fewer than 1 00 plants tended to have one or even two morphs missing. Although larg er populations rarely lacked a morph, they did show significantly skew ed morph frequencies. Indices of clonal sizer such as number of ramets per genet and genet diameter, differed significantly among sites, and clonal growth also showed significant interaction between morph and s ite. One-way analyses of variance indicated that morphs differed in te rms of either number of ramets per genet or genet diameter in 16% of p opulations. Morphometric analyses of flowers from 49 populations showe d significant variability in floral traits among genets, flower morphs , and sites. Results indicated frequent reduction in herkogamy (spatia l separation between anther and stigma), with variant flowers having v ery little or no stigma-anther separation. Mean stigma-anther separati on was lowest in the mid-morph individuals, followed by the short and long morphs. Correspondingly, the frequency of variant flowers was gre atest in mid-morph individuals and least in long-morph individuals. Is oplethic and anisoplethic populations did not differ, for any morph, i n the frequency of occurrence of these variant flowers.