In the analysis of biomass allocation, we consider several factors that might confound the results.

The resource status of plants may strongly affect not only the total quantity of resources allocated to flowers but also biomass allocation within flowers (Klinkhamer and de Jong, 1997).

Previous studies have shown that populations in the Ishikari area include substantial genetic components from all the other population groups, indicating that the other groups migrated to the depression after the connection was established (Kurabayashi, 1957).

Self-pollinated flowers of SI plants produce no seeds at all, indicating that the SI system is not leaky. In SC populations from East, a preliminary analysis revealed high selfing rates ( = 0.74–0.86).

On the other hand, the small populations in the Tokachi region, also in East, are all SI probably because these populations are remants of large SI populations due to recent agricultural development (Tomimatsu and Ohara, 2002).

Ishikari is located in the Ishikari Depression, which was repeatedly submerged during interglacial periods (Fig. The most recent connection between the northern and southern parts of Hokkaido was established only in the last several thousand years.

Selfers may produce more flowers to enhance their female reproductive success under the nonlinear trade-offs in which more resources can be used by increasing flower number.

In general, selfing populations had smaller petals than outcrossing populations, and multiple levels in the hierarchy were essential to explain these differences in petal size.With higher selfing, as theory predicts, plants generally invest more resources in female function such as ovules and seeds (Brunet, 1992), the increased allocation to female function may require more resources at fruiting, rather than at flowering, to mature many seeds.Second, selfers may increase number of flowers that compete for resources and thus reduce their investment per flower.Within flowers, selfing plants allocated fewer resources to petals and more to pistils, supporting the prediction of sex-allocation theory.Moreover, selfing plants tended to increase their flower number and decrease investment per flower under the constraints of nonlinear trade-offs between these traits.SC plants have a high ability of selfing and self-pollinated flowers produce abundant seeds (Ohara et al., 1996). Although virtually no polymorphism at 13 allozyme loci precluded measurement of selfing rate in the other groups, the high ability of autonomous selfing and homozygosity at the isozyme loci suggest high levels of selfing.

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