Cascading response of flora and terrestrial mollusks to last deglacial warming

Abstract

The cascading impacts of climate-driven vegetation change on terrestrial invertebrates via trophic and habitat routes is a matter of outstanding concern. However, the combined responses of plant-animal associations in terrestrial ecosystems have seldom been reported on geological timescales, which raises the important questions of how frequently and to what extent such multi-trophic shifts in taxa have occurred during previous warming scenarios. Here we use a combination of mollusk, palynological, and climatic proxy evidence preserved within loess deposits in the southern Chinese Loess Plateau (CLP) to demonstrate how long-term changes in hydroclimatic dynamics during the past 26 kyr were reflected in the subsequent ecological changes. Specifically, there was a shift from a predominantly cold-tolerant mollusk fauna in a dry-steppe environment under cold-dry conditions during the last glacial, to a predominantly thermal-mesophilous fauna in a meadow-steppe environment under a warm temperate climate in the early-middle Holocene. Warmth-adapted mollusk species such as Opeas striatissimum and Punctum orphana were found to have been associated with several deciduous tree taxa (e.g., Corylus, Quercus, and Pterocarya) in both the Holocene record and in the modern ecosystem (based on surveys of 356 surface-soil plots). This suggests there is a clear ecological interdependency between specific vegetation types and mollusk assemblages. As such, the long-term vegetation-mollusk fossil records highlight the indirect impacts of climate change on terrestrial invertebrate turnover via plant-derived food structure and habitat routes, with major implications for understanding how these ecosystems are likely to respond to future climate changes.

Keywords

• Climatic warming
• Long-term impacts
• Land snails
• Synchronous turnover
• Plant associations