Evolution in California Populations of Diploid and Octoploid Fragaria (Rosaceae): A Comparison

Genetic differentiation, physiological homeostasis, and heterozygosity were contrasted in the closely related octoploid species Fragaria chiloensis and F. virginiana, and in one of their putative diploid progenitors F. vesca. Plants from 27 natural sites supporting strawberry colonies were collected and grown in a common greenhouse. They were analyzed for 18 quantitative traits and three enzyme loci. Intra- and inter-populational variation was measured using analysis of variance techniques. Micro- and macro-environmental measurements were made at each site. Phenotypic stability of octoploid and diploid individuals was contrasted across four environmental regimes. The octoploids displayed more morphological variation, were more heterozygous, had greater physiological homeostasis, and were found across a broader range of environments. Octoploid strawberries may have broader ecological ranges than the diploids, both because they have higher levels of physiological homeostasis, and also because they have undergone more genetic differentiation. The higher levels of physiological homeostasis may be due to the fact that they are more heterozygous than the diploids.