Assessing the temporal stability of snail-climate relationships since the Last Glacial Maximum: Insights from boosted regression trees and LOESS models

Abstract

Snails, as common indicator species, have been widely used to reconstruct past climatic and environmental changes. However, whether their relationships with climate have changed over time has not been systematically investigated. This study integrates modern and fossil data to assess the stability of snail-climate relationships of dominant snail species in Chinese loess deposits since the Last Glacial Maximum. Using boosted regression trees (BRT) and local polynomial regression (LOESS), we analyzed the optimal summer temperature and precipitation response ranges of dominant snail species across five time-intervals (18–12 ka, 12–6 ka, 6–2 ka, 2 ka to present, and the present). The results show that different snail species exhibit varying preferred climatic ranges, consistent with their respective ecological types. Despite these ecological differences, their climatic ranges have shown no significant changes across the five periods, indicating a general similar pattern of snail-climate associations. For instance, Vallonia tenera exhibits its strongest response at summer temperatures of ∼12–15 °C and precipitation below ∼100 mm/month across the five periods, while Macrochlamys angigyra exhibits peak responses to summer temperatures exceeding ∼15 °C and precipitation levels of ∼120–150 mm/month. Furthermore, species differ in their dependence on summer temperature and precipitation, with V. tenera more reliant on precipitation, and M. angigyra and Opeas striatissimum more sensitive to temperature across all time intervals. Overall, the stability of these snail-climate relationships since the Last Glacial Maximum confirms their use as paleoclimate proxies, and their differing climatic dependencies offers valuable insights for climate reconstructions.