Thermal niches of planktonic foraminifera are static throughout glacial–interglacial climate change

Abstract

Abiotic niche lability reduces extinction risk by allowing species to adapt to changing environmental conditions in situ. In contrast, species with static niches must keep pace with the velocity of climate change as they track suitable habitat. The rate and frequency of niche lability have been studied on human timescales (months to decades) and geological timescales (millions of years), but lability on intermediate timescales (millennia) remains largely uninvestigated. Here, we quantified abiotic niche lability at 8-ka resolution across the last 700 ka of glacial–interglacial climate fluctuations, using the exceptionally well-known fossil record of planktonic foraminifera coupled with Atmosphere–Ocean Global Climate Model reconstructions of paleoclimate. We tracked foraminiferal niches through time along the univariate axis of mean annual temperature, measured both at the sea surface and at species’ depth habitats. Species’ temperature preferences were uncoupled from the global temperature regime, undermining a hypothesis of local adaptation to changing environmental conditions. Furthermore, intraspecific niches were equally similar through time, regardless of climate change magnitude on short timescales (8 ka) and across contrasts of glacial and interglacial extremes. Evolutionary trait models fitted to time series of occupied temperature values supported widespread niche stasis above randomly wandering or directional change. Ecotype explained little variation in species-level differences in niche lability after accounting for evolutionary relatedness. Together, these results suggest that warming and ocean acidification over the next hundreds to thousands of years could redistribute and reduce populations of foraminifera and other calcifying plankton, which are primary components of marine food webs and biogeochemical cycles.

Plants maintain climate fidelity in the face of dynamic climate change

“…Our findings also reflect those of Antell et al. ( 27 ), who find that foraminifera (unicellular shelly protists) have consistently exhibited static-realized thermal niches over the past 700 ka. That some plant taxa do not exhibit climate fidelity at times of most extreme change may be an indication of lag due to low dispersal speeds, spatial competition, or the presence of dispersal barriers, all of which are less of an issue for foraminifera in an open-ocean environment.…”

“…Because we are only considering climatic components of the environment, we designate that we are considering the realized climatic niche of the taxa throughout. To evaluate climate fidelity and shifts in climatic realized niches in a manner that is fair, we must only consider the available environments across both time periods ( 27 , 56 ). Methods used for the main text of the paper, niche overlap and niche similarity, consider the potential niches of the taxa when making calculations.…”

The impact of zooplankton calcifiers on the marine carbon cycle

“…Some foraminifer species are associated with one end of the temperature spectrum -for instance, Neogloboquadrina pachyderma is associated with temperatures below 10 • C and Globigerinoides ruber (white) with temperatures above 18 • C (Kucera, 2007;G. A. Schmidt & Mulitza, 2002), which broadly matches our identified peaks (Morard et al, 2015;Antell et al, 2021;Rillo et al, 2022). Furthermore, the temperature interval around 17 • C constitutes a minimum in the foraminifer biomass dependency curve and it can be associated with the subtropical front (D. N. Schmidt et al, 2004).…”

Potential and limitations of applying the mean temperature approach to fossil otolith assemblages

“…Nevertheless, MTO, as MTC, accepts that fish species’ first respond to climate change by shifting their distribution, rather than change their temperature preferences, and indeed this seemed to be the case as well during the Pleistocene climatic perturbation in the eastern Mediterranean (Agiadi et al 2018 ). Moreover, long-term thermal niche conservatism during major climatic shifts has been demonstrated for a number of other taxa (e.g., Antell et al 2021 ; Saupe et al 2014 ). Therefore, at least for this case study, we consider the assumption safe.…”