Pleistocene ecological dynamics in the Northern Andes

The evolution of mountain forest in the northern Andes is now documented in deep continental pollen records Funza1 (~1700-27 ka), Funza2 (2250-27 ka), Fúquene9C (284-27 ka), and LaCocha (14-0 ka). All sedimentary archives accumulated between 2550-2780 m elevation and only post-2010 age models have been used. Determinants of long-term ecosystem assembly include plate tectonics (Alnus, Quercus), ecological drift (Borreria) and intrinsic taxon interactions (Polylepis, Weinmannia, Morella, Alchornea). Extrinsic climate control has driven (a) changes in altitudinal vegetation distributions and upper forest line (UFL) positions have shifted between 2000 and 3400 m, (b) spatial biome patterns: current páramo surface is 4% of last glacial maximum (LGM) surface, and (c) dramatic changes in population connectivity and potential gene flow. The Pleistocene is a showcase of successive different forest types connected by taxonomic legacies. Glacial time accounts for up to 80% of the Quaternary but UFL positions below the elevation of the archiving sedimentary basins reflect only c. 25% of Pleistocene time. Therefore, at 2550 m elevation glacial-interglacial couplets show strongest evidence on the evolution of upper montane forest (now between 2300-3200 m) and páramo (now between 3200-4600 m) biomes. Current (pre-anthropogenic) forest composition is the ultimate taxon assembly and analogs have not existed before. However, conservative ecological niche ranges allow inferences of past environmental conditions in the absence of pollenvegetation calibration sets. A re-visit of the large data sets by numerical data analysis sheds new light on Pleistocene ecological and biodiversity dynamics, including functional patterns (downcore biomisation), compositional turnover, and rates of change.