Adaptive Evolution of Seed Oils in Plants: Accounting for the Biogeographic Distribution of Saturated and Unsaturated Fatty Acids in Seed Oils

Abstract

Structural, energetic, biochemical, and ecological information suggests that germination temperature is an important selective agent causing seed oils of higher-latitude plants to have proportionately more unsaturated fatty acids than lower-latitude plants. Germination temperature is predicted to select relative proportions of saturated and unsaturated fatty acids in seed oils that optimize the total energy stores in a seed and the rate of energy production during germination. Saturated fatty acids store more energy per carbon than unsaturated fatty acids; however, unsaturated fatty acids have much lower melting points than saturated fatty acids. Thus, seeds with lower proportions of saturated fatty acids in their oils should be able to germinate earlier and grow more rapidly at low temperatures even though they store less total energy than seeds with a higher proportion of saturated fatty acids. Seeds that germinate earlier and grow more rapidly should have a competitive advantage. At higher germination temperatures, seeds with higher proportions of saturated fatty acids will be selectively favored because their oils will provide more energy, without a penalty in the rate of energy acquisition. Macroevolutionary biogeographical evidence from a broad spectrum of seed plants and the genus Helianthus support the theory, as do microevolutionary biogeography and seed germination performance within species of Helianthus.

Effects of Seed Color and Growing Locations on Fatty Acid Content and Composition of Two Chia (Salvia hispanica L.) Genotypes

“…Thus, the significant lower oil content of seed from Santa Elena compared to seeds from all other locations could be related, at least partially, to the altitude differences between locations of production. Warm temperatures generally increase the level of saturation of chia fatty acids, like for other oil seed crops [16,19,23,24]. However, the variation in a-linolenic fatty acid, as was found herein, could not be fully explained by the negative relationship between land elevation and oil desaturation levels.…”

Genetic Diversity of Jatropha curcas in Southern Mexico

“…The germination temperature is an important selective factor causing seed oils of plants native to high latitudes or altitudes to have a greater proportion of unsaturated fatty acids (Linder 2000 ) . The explanation is that in cold environments the catabolism of unsaturated fatty acids is more likely than that of saturated ones, and the seeds germinate and grow faster at lower temperatures, increasing their adequacy, even at the cost of a lower total energy available to the embryo.…”

Genetic Variation in Mexican Jatropha curcas L. Estimated with Seed Oil Fatty Acids

“…However, it is surprising how little attention has been given to the selection factors that drive the evolution of the fatty acid composition of seeds. In this regard, Linder 49 suggested that the temperature of germination is an important selective agent that causes the seed oils of plants native to high latitudes or altitudes to have a higher proportion of unsaturated fatty acids that plants in lower latitudes/altitudes. The explanation is that in cooler environments high latitudes and altitudes the catabolism of unsaturated fatty acids is more feasible compared to saturated, thus the seeds with more unsaturated fatty acids germinate and grow faster at lower temperatures, increasing their fi tness, even at the expense of having less total energy available.…”