Seed oil is viewed as a promising alternative energy resource (e.g. biodiesel) that is renewable, environmentally friendly, safe and biodegradable. Because the degree of seed oil fatty acid unsaturation affects its fluidity, biological organisms are known to adjust fatty acid composition according to temperature to maintain ideal membrane fluidity. Fatty acid compositions, which affect the physiochemical characteristics and nutritional value of seed oil, have been extensively investigated. However, no previous studies have been conducted to examine the general relationships between fatty acid composition and environmental factors such as temperature and precipitation across a large number of plants and a wide range of environments at a large scale.

Dr. ZHANG Jiaolin of Xishuangbanna Tropical Botanical Garden (XTBG) and his colleagues compiled a large seed oil fatty acid composition dataset from the literature. The total dataset represented 207 sites from a wide range of ecosystems across China and contained 1183 species-at-site combinations consisting of 747 species or varieties from 95 families. The researchers investigated the relative effects of taxonomic affiliations and climate on interspecific variation in seed oil fatty acid composition. They also tested the hypothesis that the degree of seed oil fatty acid unsaturation increased as the climate became colder and/or drier with and without the consideration of phylogeny.

 The researchers used a general linear model to partition total variance in fatty acid composition into taxonomic ranks (family, genus and species) and environmental components. They then conducted multiple regression analysis to examine the relative effects of mean annual temperature and mean annual precipitation. To test the evolutionary association of fatty acid composition with climate at the family level, the researchers carried out phylogentically independent contrast analysis.

The study found that the relative abundance of common fatty acids in seed oils was more strongly explained by taxonomic affiliation than by climate. The degree of fatty acid unsaturation of seed oils in China increased with latitude and decreased with mean annual temperature and mean annual precipitation, with fatty acid unsaturation being affected more strongly by temperature than by precipitation 

The results suggested that seed oil fatty acid composition exhibited geographical patterns in relation to climate. Moreover, it strongly suggested that seed oil fatty acid composition played an important role in the ecological adaptation of plants. Fatty acid unsaturation may evolve as an adaptive strategy in colder climates. Phylogenetic and climate affiliations of fatty acids may help explore potential oil plants.