Interpopulation Variation In Lupinus Perennis, The Wild Lupine

Carrie A. Cartwright and Helen J. Michaels.

Conservation biologists contend that small, isolated populations are characterized by reduced population viability. In the past 100 years, Lupinus perennis, an indicator species for oak savannahs in the Midwest, has declined in distribution and abundance. The objectives of this study were to determine 1) whether levels of morphological variation or reproductive success are correlated with population size, and 2) whether fitness components for each population are related to the environmental factors in each site. Seed set, fruit set, seed size, soil nutrients, moisture, light levels and percent bare ground in natural populations and percent germination and growth in the greenhouse were compared among fourteen populations ranging in size from 25 to 8300 individuals. As an indirect measure of genetic variation, frequencies of seed coat color morphs were also compared. Although there was no correlation between mean seed mass and population size, mean number of seeds per pod, pods per plant and seeds per plant were all positively correlated with population size. The seed coat color variation was greater in larger populations. The data suggests that the smaller populations may have lower fitness than the larger populations and that at least part of the reduced fitness may be attributed to reduced levels of genetic variation.