FACTORS INFLUENCING INTER-POPULATION VARIATION IN RANUNCULUS-ACRIS SEED PRODUCTION IN AN ALPINE AREA OF SOUTHWESTERN NORWAY

There have been few attempts to examine the relationship between mean seed production of populations and the environmental conditions experi enced by these populations. This study uses redundancy analysis (RDA) to explore which environmental factors influence the patterns of inter -population variation in mean seed production (seed:ovule ratio and se ed weight) and mean plant height in 25 alpine populations of Rammculus acris L at Finse, southwestern Norway. The mean seed:ovule ratio and height of the plants differed more than three-fold among populations s ituated close to each other, whereas mean seed weight show ed less var iation. In two RDAs differences in site elevation and pH accounted for a substantial part of the among-population variation in mean plant he ight, seed:ovule ratio, and seed weight. Mean plant height and seed we ight were negatively correlated with the altitude of the populations. whereas mean seed:ovule ratio showed a high positive correlation with pH. When pooling all data fr om the populations, simple linear regress ions showed that seed weight was positively correlated with plant heig ht, whereas plant height had little influence on seed:ovule ratio. See d weight was positively correlated with the numbers of seeds that a Ro wer produced. The results indicate that mean seed:ovule ratio of a pop ulation is influenced primarily by the pH-conditions at the site, wher eas mean seed weight and plant height are more strongly influenced by altitude which largely reflects the climatic severity at the site. Int er-population variation in average reproductive success in R. acris at Finse appears to be determined by several environmental and intrinsic factors that interact in a complex fashion.