Arianna I. Krinos, Sara K. Shapiro, Weixuan Li, Sheean T. Haley, Sonya T. Dyhrman, Stephanie Dutkiewicz, Michael J. Follows, Harriet Alexander (2025), Intraspecific Diversity in Thermal Performance Determines Phytoplankton Ecological Niche, Ecology Letters, doi: 10.1111/ele.70055
Description:
Temperature has a primary influence on phytoplankton physiology and ecology. We grew 12 strains of Gephyrocapsa huxleyiisolated from different-temperature regions for ~45 generations (2 months) and characterised acclimated thermal response curvesacross a temperature range. Even with similar temperature optima and overlapping cell size, strain growth rates varied between0.45 and 1 day−1 . Thermal niche widths varied from 16.7°C to 24.8°C, suggesting that strains use distinct thermal response mech-anisms. We investigated the implications of this thermal intraspecific diversity using an ocean ecosystem simulation resolvingphytoplankton thermal phenotypes. Model analogues of thermal ‘generalists’ and ‘specialists’ resulted in a distinctive globalbiogeography of thermal niche widths with a nonlinear latitudinal pattern. We leveraged model output to predict ranges of the 12lab-reared strains and demonstrated how this approach could broadly refine geographic range predictions. Our combination ofobservations and modelled biogeography highlights the capacity of diverse groups to survive temperature shifts.