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Mammalian megaherbivores are an essential component of modern day ecosystems. They control a large share of primary productivity, modify habitats by clearing dense vegetation, and keep other herbivores populations small. When rare, small herbivores additionally suffer increased extinction risk by predation. Since megaherbivores are almost immune to predation, it was suggested that the detrimental effect of megaherbivores on smaller competitors has the additional consequence to reduce the prey biomass available to predatory species, thereby increasing their extinction risk. This form of indirect competition between guilds of species is known as apparent competition. These mechanisms are all forms of top-down control on ecosystem functioning, whereby species up on the food chain control diversity at lower levels. We tested these competing hypotheses on a large compilation of Neogene to Recent Old World mammals.We found evidence in favor of apparent competition. However, direct competition effects by both megaherbivores and carnivores on small prey are even more pervasive. Our results suggest that megaherbivores have been a dominant component of the mammal diversity over time and space during the last 22. million. years in Eurasia. © 2017 Elsevier B.V.

The dispersal of Homo erectus out of Africa at some 1.9 million years ago is one of the most important, crucial, and yet controversial events in human evolution. Current opinions about this episode expose the contrast between those who see H. erectus as a highly social, cooperative species seeking out new ecological opportunities to exploit, and those preferring a passive, climate driven explanation for such an event. By using geostatistics techniques and probabilistic models, we characterised the ecological context of H. erectus dispersal, from its East African origin to the colonization of Eurasia, taking into account both the presence of other large mammals and the physical characteristics of the landscape as potential factors. Our model indicated that H. erectus followed almost passively the large herbivore fauna during its dispersal. In Africa, the dispersal was statistically associated with the presence of large freshwater bodies (Rift Valley Lakes). In Eurasia, the presence of H. erectus was associated with the occurrence of geological outcrops likely yielding unconsolidated flint. During the early phase of dispersal, our model indicated that H. erectus actively avoided areas densely populated by large carnivores. This pattern weakened as H. erectus dispersed over Europe, possibly because of the decreasing presence of carnivores there plus the later acquisition of Acheulean technology. During this later phase, H. erectus was associated with limestone and shaley marl, and seems to have been selecting for high-elevation sites. While our results do not directly contradict the idea that H. erectus may have been an active hunter, they clearly point to the fact that predator avoidance may have conditioned its long-distance diffusion as it moved outside Africa. The modelled dispersal route suggests that H. erectus remained preferentially associated with low/middle latitude (i.e., comparatively warm) sites throughout its colonization history. © 2016 Elsevier Ltd.

Body mass has important physiological and ecological implications. The high degree of variability in herbivore mammals' body mass is linked to differences in their gut anatomy, which, in turn, has important effects on their feeding habits. We aimed to untangle the effects of Cope's and Bergmann's rule on the evolution of body size in even-toed hoofed mammals (Artiodactyla, Mammalia). By using variation partitioning techniques and direct sister species comparisons, we estimated the potential effects of latitude, time and phylogeny on body size variation in Cenozoic Artiodactyls. We tested whether species tend to be larger when living at higher latitudes as compared to their phylogenetically closest relative, whether closely-related species living in sympatry tend to diverge more in body size, and whether recent species tend to be larger than their older relatives. Our results showed that both latitudinal and temporal trends in Artiodactyla body size are evident throughout the Cenozoic, and became particularly intense during the coldest part of it. Artiodactyls tend to be larger than their close relatives when living at higher latitudes, in keeping with Bergmann's rule. Yet, this relationship is weakened by the strong tendency for sister species to diverge in body size when living nearby. We also found a clear tendency for late Artiodactyl species to be larger, and live for shorter, than their ancestors.Thus, there is strong evidence that the evolution of body size in even-toed hoofed mammals was influenced by climatic changes, and by an overall tendency to grow larger, mostly in coincidence with the vegetation shift from forested to grassland biomes which characterized the second half (Neogene) of the Cenozoic. Although Cope's and Bergmann's rule in mammals are often portrayed as having climate change as a common explanation, our data suggest they are mechanistically separate phenomena. © 2015 Elsevier B.V.

Our aim is to identify ecomorphological adaptations in the skull shape of the South American howler monkeys (species of the genus Alouatta , Lacepede, 1799 , Primates, Atelidae). Since Alouatta is relatively homogenous in feeding ecology, we expect skull shape variation to be relatively conservative across species. We used geometric morphometrics to quantify craniodental morphology in six species of Alouatta . Multivariate regression, two-block Partial Least Squares, and variation partitioning were used to test for the impact of taxonomy, sexual dimorphism, allometry, geography and climate on skull shape. We found morphological overlap among species and sexes, although some discrimination occurs between species living in seasonal environments as opposed to rain forest species. There was a negative latitudinal gradient in skull size across species, with size explaining 34% of total shape variance. Latitude and climate, though important, were secondary in explaining shape variance. Amazonian Alouatta are larger, have thinner molars, wide incisors, and proportionally larger neurocranium. Overall, the shape of southern species seem well adapted to cope with proportionally tougher food items, whereas Amazonian species seem better equipped to deal with a diet richer in fruits, as confirmed by independent field observations. The small size of Alouatta in the South is possibly linked to the effect of competition with the larger folivorous atelid Brachyteles .