Eccentricity-driven glacial climate variability and its influence on speciation in the tropical Andes

Abstract

This study presents a detailed pollen-based climate reconstruction from Lake Fúquene, Colombia, spanning the past 284,000 years and revealing significant changes in temperature and hydroclimate modes of variability, particularly between glacial periods. Our findings highlight the central role of eccentricity in modulating the influence of high-latitude glacial climate variability on the northern Andes. During periods of high eccentricity (∼70–260 ka), we conclude that the region was shielded from northern high-latitude glacial ice-sheet dynamics by an intensified Walker circulation. After ∼70 ka, a weakening of this zonal circulation allowed high-latitude, millennial-scale glacial climate variability to penetrate deeper into the tropics, influencing the position of the ITCZ and the rainbelt. This shift in climate dynamics led to increased regional millennial-scale climate variability. A detrended correspondence analysis (DCA) on fossil pollen data highlights a contemporaneous compositional shift previously masked by glacial-interglacial vegetation changes. The observed ecological shift coincides temporally with predictions of elevated speciation rates in mechanistic simulations. Combined, these results suggest a long-lasting environmental impact from glacial millennial-scale climate dynamics, supporting the hypothesis that increased environmental dynamism during glacial periods may trigger the speciation pump in the Northern Andes more than glacial inceptions or terminations. These findings underscore the evolving nature of regional climate drivers and their complex interplay with ecology, offering new insights into the role of climate variability in shaping biodiversity in this hotspot.