Testing the Dry Refuge Model: Paleoecological Insights From Late Pleistocene Gomphotheres in Ecuador

ABSTRACT

Paleoenvironmental records indicate that Neotropical regions near the Equator experienced reduced rainfall during the Last Glacial Maximum (LGM). However, some records show conflicting environmental signals. To address these discrepancies, previous studies have proposed two demographic/genetic scenarios for cloud forests based on contrasting precipitation regimes. Here, we apply a multiproxy approach to extinct proboscideans, commonly referred to as gomphotheres, from Ecuador to assess the extent to which wet‐ and dry‐forest models shaped environmental conditions on the coast and in the Inter‐Andean Valley during the Late Pleistocene. Fossil molars were analyzed using stable isotope analysis, dental microwear analysis, and radiocarbon dating. Radiocarbon dates obtained from the sampled gomphotheres span ca . 31,820–23,830 cal yr. BP. Enamel bioapatite δ ¹³ C values, ranging from −14.82‰ to −0.78‰, indicate that these proboscideans occupied a broad range of environments, although the overall isotopic signal points to a predominance of more open and relatively dry habitats. Dental microwear data support this interpretation, indicating substantial grass consumption. Reconstructed meteoric water δ ¹⁸ O values derived from enamel bioapatite reveal a clear altitudinal effect on gomphothere distribution. Moreover, these values are comparable to those recorded at present‐day meteorological stations in Ecuador. We therefore infer that, at least during the lifetimes of the sampled individuals, there were no major differences in the δ ¹⁸ O signature of atmospheric circulation between the Late Pleistocene and today in this region. Although substantial chronological gaps remain in paleoenvironmental reconstructions, our results suggest that processes consistent with the Dry Refuge Model (DRM) had a strong influence on Ecuadorian landscapes during the Late Pleistocene. In this scenario, cloud forests were displaced and compressed into refugia due to the combined effects of aridity and cooling.