. The Canadian field-naturalist. SCORE NUMBER Figure 1. Total distribution of samples. individuals typical of Typha angustijolia CM- IS). The population of Typha in Point Pelee Marsh thus represents a strongly introgressive group, the majority of which may be placed in the category of Typha glauca. There appear to be two and possibly three scores in the marsh as a whole. The main one, score 5, is most common, followed by a second popula- tion with score 8 and a third with score 10. Thus the marsh appears to have few Typha latijolia or Typha angustijolia, but is instead typified by a group of i
. The Canadian field-naturalist. SCORE NUMBER Figure 1. Total distribution of samples. individuals typical of Typha angustijolia CM- IS). The population of Typha in Point Pelee Marsh thus represents a strongly introgressive group, the majority of which may be placed in the category of Typha glauca. There appear to be two and possibly three scores in the marsh as a whole. The main one, score 5, is most common, followed by a second popula- tion with score 8 and a third with score 10. Thus the marsh appears to have few Typha latijolia or Typha angustijolia, but is instead typified by a group of individuals which show segregation of characters of two parental popu- lations. It may be further speculated that con- ditions of the environment are now selecting these individuals in preference to the parental species, so that eventually distinct ecotypes may emerge. Peripheral vs. Non-peripheral Distribution From field observation, the authors have suspected that edge populations of cattails are more variable in composition than those of a non-peripheral nature. The determining factor may be environmental heterogeneity such as peculiar substrates, water depth, or differing light relations which vary considerably in southern Ontario marshes (unpublished data of the authors). To test whether this was evi- dent in the sampling at Point Pelee, the data was re-grouped into peripheral and non- peripheral samples and the data replotted. The definition of peripheral samples in this discus- sion is that they border open water, while the non-peripheral samples are not adjacent to open water. Distribution of segregating types in the non- peripheral graph (Figure 2) shows that distri- bution is limited principally to individuals with score 5 and score 7 individuals, with a very limited distribution of other types. By contrast, distribution of the peripheral samples shows two nearly equal peaks of individuals with score 5 and score 10, with a secondary peak of score 8. At least 3 scores a
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