Mall islands is potentially low. Interestingly, although many of the extinct insular ruminants may have showed a shift to a more divergent dietary ecology to be better suited for life in a variety of habitats, the constraints imposed by small-sized islands might have been more serious, and prevented evolutionary transition from browsing to mixed feeding or grazing. To interpret this, it is necessary to understand what ruminants can eat and why they do, and to consider the environmental conditions and the specific selection pressures5 under which taxa like Hoplitomeryx occur. The type of feeding developed by a ruminant is strongly dependent on the quality and quantity of the forage available37. This is because grasses and their plant parts (such as stems and twigs) are generally of lower nutritional quality than browse (leaves and fruits)59?1. In order to meet their nutritional requirements, mixed feeder and grazer species require larger quantities of food than do browsers62. The consequence of this is that the limiting food resources on small islands, such as Gargano, aggravated by the effects of overpopulation seem to prevent the acquisition of mixed and grazing diets among mammals. This hypothesis is congruent with recent findings for other Brefeldin A site endemic herbivorous clades from the fossil record63. Clearly, this constrain may have played an important role in the origins, diversification and evolution of a broad range of island mammals, both recent and extinct, such as elephants, hippos, bovids and deer. In conclusion, this study provides a detailed picture of the adaptive radiation Necrosulfonamide supplement undergone by Hoplitomeryx that is drawn from an innovative approach combining long-term patterns of tooth wear with ecologically relevant traits. Adaptive radiation in Hoplitomeryx resulted from ecological opportunity. Demographic, ecological and abiotic factors are recogized as primary drivers of the evolution and ecological diversity of species in Gargano. A pronounced event of overpopulation and a rapid phase of increased aridity determined the rate and magnitude of radiation, and pushed species to expand their diets from soft-leafy to more abrasive-dominated browsing. Results show for the first time that herbivorous mammals are highly restricted to browsing habits on small islands, even if bursts of ecological diversification and divergence in diet occur. Finally, this study highlights that a wide range of research questions can benefit greatly by incorporating data from the fossil record. This is especially important for an accurate prediction of ecological shifts (exploitation of vacant ecological niches, species interactions, etc) and species diversification on islands in the face of current and future climatic variability.Methodstectonic activity, leading to dramatic changes in the palaeogeography throughout all the Cenozoic. One of the most active orogenetic zones during the Tertiary was Italy, in where islands emerged and submerged repeatedly and mammal faunas from that region testified such a phenomenon21. The most important Italian island faunas were discovered in the 1970s, and belong to the fossils from fissure fillings on Gargano. The material from this island, now firmly joined to the Italian mainland, was retrieved from the Late Miocene karstic fissures fillings in quarries between Apricena and Poggio Imperale (Province of Foggia, Southern Italy)19 (Fig. 1). Apart from the ruminant Hoplitomeryx, the bulk of the assemblage, often referred to as th.Mall islands is potentially low. Interestingly, although many of the extinct insular ruminants may have showed a shift to a more divergent dietary ecology to be better suited for life in a variety of habitats, the constraints imposed by small-sized islands might have been more serious, and prevented evolutionary transition from browsing to mixed feeding or grazing. To interpret this, it is necessary to understand what ruminants can eat and why they do, and to consider the environmental conditions and the specific selection pressures5 under which taxa like Hoplitomeryx occur. The type of feeding developed by a ruminant is strongly dependent on the quality and quantity of the forage available37. This is because grasses and their plant parts (such as stems and twigs) are generally of lower nutritional quality than browse (leaves and fruits)59?1. In order to meet their nutritional requirements, mixed feeder and grazer species require larger quantities of food than do browsers62. The consequence of this is that the limiting food resources on small islands, such as Gargano, aggravated by the effects of overpopulation seem to prevent the acquisition of mixed and grazing diets among mammals. This hypothesis is congruent with recent findings for other endemic herbivorous clades from the fossil record63. Clearly, this constrain may have played an important role in the origins, diversification and evolution of a broad range of island mammals, both recent and extinct, such as elephants, hippos, bovids and deer. In conclusion, this study provides a detailed picture of the adaptive radiation undergone by Hoplitomeryx that is drawn from an innovative approach combining long-term patterns of tooth wear with ecologically relevant traits. Adaptive radiation in Hoplitomeryx resulted from ecological opportunity. Demographic, ecological and abiotic factors are recogized as primary drivers of the evolution and ecological diversity of species in Gargano. A pronounced event of overpopulation and a rapid phase of increased aridity determined the rate and magnitude of radiation, and pushed species to expand their diets from soft-leafy to more abrasive-dominated browsing. Results show for the first time that herbivorous mammals are highly restricted to browsing habits on small islands, even if bursts of ecological diversification and divergence in diet occur. Finally, this study highlights that a wide range of research questions can benefit greatly by incorporating data from the fossil record. This is especially important for an accurate prediction of ecological shifts (exploitation of vacant ecological niches, species interactions, etc) and species diversification on islands in the face of current and future climatic variability.Methodstectonic activity, leading to dramatic changes in the palaeogeography throughout all the Cenozoic. One of the most active orogenetic zones during the Tertiary was Italy, in where islands emerged and submerged repeatedly and mammal faunas from that region testified such a phenomenon21. The most important Italian island faunas were discovered in the 1970s, and belong to the fossils from fissure fillings on Gargano. The material from this island, now firmly joined to the Italian mainland, was retrieved from the Late Miocene karstic fissures fillings in quarries between Apricena and Poggio Imperale (Province of Foggia, Southern Italy)19 (Fig. 1). Apart from the ruminant Hoplitomeryx, the bulk of the assemblage, often referred to as th.