부산대학교 도서관

Variation among individuals within species is a biological precondition for co‐existence. Traditional geochemical analysis based on bulk averages facilitates rapid data gathering but necessarily means the loss of large amounts of potentially crucial information into variability within a given sample. As the sensitivity of geochemical analysis improves, it is now feasible to build sufficiently powerful datasets to investigate paleoclimatic variation at the level of individual specimens. Here, we investigate geochemical and morphological variation among the sensu stricto, sensu lato and sensu lato extreme subspecies of the workhorse extant planktic foraminifera Globigerinoides ruber. Our experimental design distinguishes between subspecies and intraspecific variability as well as the repeatability of laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS). We show that geochemical variability in Mg/Ca ratios is driven by differences in subspecies depth habitat and that ontogenetic trends in Mg/Ca ratios are evident in the final whorl, with the final chamber consistently showing depleted Mg/Ca. These ontogenetic trends are not driven by individual chamber or test size. The Mg/Ca value variance among individuals is ∼100 times higher than the variance among repeated laser spot analyses of single chambers, directing laboratory protocols towards the need to sample ecologically and environmentally homogeneous samples. Our results emphasize that we can use LA‐ICP‐MS to quantify how individual variability aggregates to bulk results, and highlights that, with sufficient sample sizes, it is possible to reveal how intraspecific variability alters geochemical inference. Planktic foraminifera are small marine life forms whose fossil remains are used to reconstruct past climates and ocean conditions. As with all living things, each individual foraminifer varies from one to the next. Understanding this variation among individuals is important for many branches of science. Here, we studied variation within one of the most used species of foraminifera for paleoceanographic reconstructions, Globigerinoides ruber. We show that the observed geochemical variation is organized within biologically meaningful groups and among life stages. We need the bigger sample sizes we use here to pick apart individual variation and its drivers as future reconstructions of past climates need to consider variation among individuals to get a fuller understanding of the co‐evolution of life and the planet. Globigerinoides rubershows large variability in Mg/Ca ratios that is partially explained by the presence of subspeciesWithin‐specimen variation through ontogeny explains more variation in Mg/Ca ratios than differences among subspeciesSubspecies differences in G. rubergeochemistry are driven by depth habitat differences Globigerinoides rubershows large variability in Mg/Ca ratios that is partially explained by the presence of subspecies Within‐specimen variation through ontogeny explains more variation in Mg/Ca ratios than differences among subspecies Subspecies differences in G. rubergeochemistry are driven by depth habitat differences