Coupled morphologic and demographic responses of Opeas striatissimum (Gastropoda: Subulinidae) to latest Pleistocene to early Holocene climate fluctuations

In this paper, we report late Pleistocene to Holocene changes in the shell size and age structure of the gastropod, Opeas striatissimum, in two loess profiles in the Chinese Loess Plateau, spanning the past 27 ka. During the interval of ~17–8 ka, in response to climatic warming, we observed marked increases in shell dimensions and a more diverse age structure (age classes), as well as a ~20% increase in the number of adult individuals. Shell growth and enhanced survival from juvenile to adult, in turn, resulted in an increase in the population size, which reached a maximum during the interval ~8–3 ka, corresponding to the Holocene Climatic Optimum. We also observed an abrupt decrease in shell height and related significant decreases in the total number of individuals of Opeas striatissimum and adult individuals at the time of the Younger Dryas cold climatic event. We suggest that the observed morphologic and demographic changes observed for Opeas striatissimum reflect changes in the growing season, linked to changes in monsoon rainfall and climate stability, in response to climate fluctuations from the late Pleistocene to the Holocene. Our study provides a long-term perspective that helps refine mechanistic population models of invertebrates in the face of future climate change. •We report the millennial-scale variation of the mollusk demography, morphology and age structure.•Coupled increase in shell size and population growth in response to last deglacial warming.•An abrupt drop in shell growth and demography at around the Younger Dryas climatic reversal.•The lengthening growth season contributions to the marked increase in population growth.