Adaptation in widespread populations of Rumex crispus as determined using composite diagrams

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Abstract
Eleven genetically different populations of Rumex crispus L., 10 from eastern North America and 1 from Bangor, Wales, were sampled. Offspring from these populations were grown under cultivation in a uniform garden at London, Ontario. Determinations of 47 morphological characters were made. Twenty-two environmental variables relating to temperature, daylight, moisture, soil nutrients, particle size, and pH were obtained or determined. A new technique, the use of composite drawings of R. crispus plants, utilized results from regression analyses performed between plant and environmental characters. Plants from cold climates tended to be short and compact with large numbers of stomata per unit area, an adaptation likely to reduce heat loss and optimize CO2 exchange. Plants originating on coarse-textured soil were small and spreading relative to those from soil with larger amounts of silt and clay. Highly overlapping, appressed branches and relatively small stomata were characteristic of plants from dry localities. The importance of examining large numbers of characters in studies of geographic variation is demonstrated and discussed. Composite drawings are shown to be useful in summarizing such large volumes of data.