Sparassodontans are a diverse but now extinct group of metatherians that were apex predators in South America during most of the Cenozoic. Studying their decline has been controversial mainly due to the scarcity of the fossil record, and different methodological approaches have led to contradictory hypotheses. In an effort to explore questions about their extinction, we developed a novel multi- model statistical approach to analyse all of the currently available data at a continental scale. Using multiple regression analysis and new advances in beta diversity analysis, we used all currently available fossil data at a continental scale to test four competing hypotheses to account for the decline of sparassodontans: competition with placental carnivorans, competition with avian phorusrhacids, non-competitive ecological interactions, and environmental fluctuations. Our results show that the sparassodontan extinction was a gradual process with species disappearing throughout the Cenozoic. Multiple regression analysis supported non-competitive ecological interactions as the best extinction model. Native South American ungulates, African migrants (caviomorph rodents and platyrrhine primates) and didelphimorphians were the groups with the highest statistical significance. Sparassodontan beta diversity increased between South American Land Mammal Ages after the Paleocene-Eocene boundary. Our results demonstrate that ecological modelling techniques illuminate aspects of extinction processes whilst mitigating the limitations of the fossil record. Our study suggests that non-competitive ecological interactions could have been the main driver for sparassodontan extinction rather than, as commonly assumed, a result of competition and/or abiotic fluctuations.

Abstract: This thesis lies in the opportunities and challenges opened to the land use planning in Colombia, once the Congress endorsed the Peace Agreement, the past 2016, since one of its components is the Comprehensive Rural Reform. It aims to analyze the possibilities to articulate those compromises acquired regarding land, with the Colombian land use planning system and its legislation in pursuit of lasting peacebuilding. The thesis suggests this link as definitive and efficient along the way to switch the relation with the land in Colombia, from the historical alliance land-conflict to one contemporaneous, of land-peace. Resumen: Esta tesis radica en las oportunidades y retos abiertos al ordenamiento territorial en Colombia, una vez el Congreso aprobó el Acuerdo de Paz, el pasado 2016, ya que uno de sus componentes es la Reforma Rural Integral. Se trata de analizar las posibilidades para articular esos compromisos adquiridos con relación a la tierra, con el sistema de ordenamiento territorial colombiano y su legislación en búsqueda de una paz duradera. La tesis sugiere este vínculo como definitivo y eficiente en el camino para cambiar la relación con la tierra en Colombia, de la histórica relación de la tierra y el conflicto armado, a una relación contemporánea de tierra y paz.