Quantifying the stability of planktic foraminiferal physical niches between the Holocene and Last Glacial Maximum

• Published in: Paleoceanography 2017-01, Vol.32 (1), p.74-89
• Main Authors: Waterson, A. M., Edgar, K. M., Schmidt, D. N., Valdes, P. J.
• Format: Article
• Language: English
• Subjects: Calibration; Ecological distribution; ecological niche model; Ecological niches; Ecology; Equatorial regions; Foraminifera; Fossil assemblages; Fossil Foraminifera; Fossils; Frameworks; Genotypes; Globigerina bulloides; Globigerinoides ruber; Holocene; Ice ages; Last Glacial Maximum; Neogloboquadrina pachyderma; niche stability; Niches; Ocean models; Oceanography; Oceans; Optimization; Ordination; Paleoecology; Performance prediction; planktic foraminifera; Plankton; Species; Stability; Taxa; Transfer functions; Trilobatus sacculifer; Tropical climate; Truncorotalia truncatulinoides
• ISSN: 0883-8305; 2572-4517; 1944-9186; 2572-4525
• DOI: 10.1002/2016PA002964

The application of transfer functions on fossil assemblages to reconstruct past environments is fundamentally based on the assumption of stable environmental niches in both space and time. We quantitatively test this assumption for six dominant planktic foraminiferal species (Globigerinoides ruber (pink), G. ruber (white), Trilobatus sacculifer, Truncorotalia truncatulinoides, Globigerina bulloides, and Neogloboquadrina pachyderma) by contrasting reconstructions of species realized and optimum distributions in the modern and during the Last Glacial Maximum (LGM) using an ecological niche model (ENM; MaxEnt) and ordination framework. Global ecological niche models calibrated in the modern ocean have high predictive performance when projected to the LGM for subpolar and polar species, indicating that the environmental niches of these taxa are largely stable at the global scale across this interval. In contrast, ENMs had much poorer predictive performance for the optimal niche of tropical‐dwelling species, T. sacculifer and G. ruber (pink). This finding is supported by independent metrics of niche margin change, suggesting that niche stability in environmental space was greatest for (sub)polar species, with greatest expansion of the niche observed for tropical species. We find that globally calibrated ENMs showed good predictions of species occurrences globally, whereas models calibrated in either the Pacific or Atlantic Oceans only and then projected globally performed less well for T. sacculifer. Our results support the assumption of environmental niche stability over the last ~21,000 years for most of our focal planktic foraminiferal species and, thus, the application of transfer function techniques for palaeoenvironmental reconstruction during this interval. However, the lower observed niche stability for (sub)tropical taxa T. sacculifer and G. ruber (pink) suggests that (sub)tropical temperatures could be underestimated in the glacial ocean with the strongest effect in the equatorial Atlantic where both species are found today. Key Points Ecological niche models (ENMs) used to test assumption of planktic foraminifer niche stability 21 kya to present High environmental niche stability of planktic foraminifera between the Last Glacial Maximum and today Regional calibrations predict global occurrences less well than global calibrations due to niche underrepresentation or multiple genotypes