LAUSR

Abstract Paleobiology conservation is an emerging discipline with potential applications in the conservation of modern biodiversity. Ecological baselines based on paleontological information are effective tools for assessment of the conservation status of the present-day ecosystems, especially those with historical disturbance episodes. The aim of this study is the proposal of two Late Pleistocene ecological baselines in order to evaluate the depauperating degree of Mixteca Alta, a large extension in northwestern Oaxaca, southern Mexico. Comparison of alpha and beta diversity indexes of fossil and modern non-vagile animal assemblages (terrestrial gastropoda and rodents) were used to assess the resistance of Recent ecosystems. Ecosystem services of fossil and modern assemblages were compared to evaluate the recovery capacity of the present-day ecosystems. Late Pleistocene faunal assemblage is composed of six continental gastropod taxa, three species of micromammals, one species of medium-sized mammal, and ten species of large mammals. Recent faunal assemblage is constituted by five taxa of continental gastropods, six taxa of micromammals, and six taxa of medium-sized mammals. Concerning beta diversity, species turnover between Late Pleistocene and Recent is higher in rodents (βW = 0.8) than in gastropods (βW = 0.454). Peromyscus difficilis, Succinidae, Lymnaeidae and Physidae gastropods persist in the area since Late Pleistocene. The low diversity of some taxa suggests a possible low resistance of San Antonio Acutla's ecosystems. Three classes of ecosystem services provided by fauna (regulation of conditions of freshwater by living processes, weathering processes and their effect on soil quality, and seed dispersal) ocurred since the Late Pleistocene until present-day; this prevalence is an indicator of the apparently good health of these ecosystems. Late Pleistocene baselines provide valuable information to assure that ecosystems of San Antonio Acutla did not suffer, at the same severity, the degradation processes that affected ecosystems in other areas of Mixteca Alta, since the Late Pleistocene to present day.