Lipid-producing microalgae are a feedstock for commercial products such as nutritional supplements, aquatic animal feed, and biofuels. Unlike most algal phyla, the diatoms (Bacillariophyta) characteristically produce storage lipids throughout their entire lifecycle. In this study, lipids were extracted via chloroform-methanol and quantified as percent dry weight, &mgr;g/mL, and pg/100 &mgr;m³ and then analyzed for a phylogenetic signal by comparing the variability between lineages to the variability within lineages for each metric. These ten taxa were then paired with data gathered from the literature and examined for a phylogenetic signal using previously described methods. In the first analysis, there was greater variability between than within lineages during stationary growth when using percent dry weight as a metric. In the second analysis, a statistically significant phylogenetic signal was detected for nutrient-deplete growth experiments when examining the genus-level phylogeny (P = 0.013).