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The fast pace of socioeconomic growth in the past decades has left its footprint on biodiversity and all its components (genes, species and ecosystems), endangering biosphere integrity and human survival [1]. Extinction is a natural phenomenon that is part of life on Earth but is balanced by speciation [2, 3]. The large extinction events that have depleted Earth of the majority of its biota, are rare events (only five have been recorded in the last 540Mya) [4] with different natural causes acting to affect Earths global system (e.g. glaciations, asteroid collisions or eruption of super-volcanos). Contemporary extinctions though, are caused mainly by human activities, e.g. habitat fragmentation and changing climate among others, and these are occurring at an unprecedented rate and scale [5]. The “Anthropocene defaunation” is both result and a force of global change [6], with potential cascade effects at a planetary scale [7]. Quantitative assessments regarding the loss of species and alteration of natural habitat show that extinction rates and magnitude surpass background rates by far, even those of past massextinction events [8]. To predict and limit the loss of the remaining biodiversity we need to evaluate how environmental changes affect species survival, their distributions and potential to adapt. The Late Pleistocene (126ka-11.7ka; 1ka=1,000 years ago) was characterized by a peculiar extinction event, that witnessed a large and global extinction of mainly large bodied (> 45kg) mammal genera (101 out of ~150) [9]. Both the expansion of H. sapiens hunter-gatherers and large climatic changes have been hypothesized to be the main causes of this extinction event [10-17]. The main aim of this thesis is to evaluate the role of climate and associated environmental changes in the changing distribution of mammals, including Anatomically Modern Humans (AMH: H. sapiens), and its potential effects on past local/global extinctions. By treating AMHs as another megafauna sp

The genera Atta and Acromyrmex are often grouped as leaf-cutting ants for pest management assessments and ecological surveys, although their mature colony sizes and foraging niches may differ substantially. Few studies have addressed such interspecific differences at the same site, which prompted us to conduct a comparative study across six sympatric leaf- cutting ant species in Central Panama. We show that foraging rates during the transition between dry and wet season differ about 60 fold between genera, but are relatively constant across species within genera. These differences appear to match overall differences in colony size, especially when Atta workers that return to their nests without leaves are assumed to carry liquid food. We confirm that Panamanian Atta specialize primarily on tree-leaves whereas Acromyrmex focus on collecting flowers and herbal leaves and that species within genera are similar in these overall foraging strategies. Species within genera tended to be spaced out over the three habitat categories that we distinguished (forest, forest edge, open grassland), but each of these habitats normally had only a single predominant Atta and Acromyrmex species. We measured activities of twelve fungus garden decomposition enzymes, belonging to the amylases, cellulases, hemicellulases, pectinases and proteinases, and show that average enzyme activity per unit of fungal mass in Atta gardens is lower than in Acromyrmex gardens. Expression profiles of fungal enzymes in Atta also appeared to be more specialized than in Acromyrmex, possibly reflecting variation in forage material. Our results suggest that species- and genus-level identities of leaf-cutting ants and habitat-specific foraging profiles may give predictable differences in the expression of fungal genes coding for decomposition enzymes.