The endemic bovids from Sardinia and the Balearic Islands: State of the art

Bovids are not so common in endemic insular faunas and are mainly recorded in Southeast Asia, Japan and some Mediterranean islands. In the Western Mediterranean, endemic bovids have been recorded during the late Miocene in the Tusco-Sardinian palaeobioprovince (Baccinello-Cinigiano basin, South Tuscany, and Fiume Santo, north-western Sardinia). In the latest Neogene and Quaternary, bovids showing highly endemic features were restricted to the Balearic Islands and Sardinia, while Bovini only slightly reduced in size were present on Pianosa, Malta and Sicily. On Sardinia, the richest bovid sample comes from Monte Tuttavista (Orosei), where at least three species have been identified: Asoletragus genthry, Nesogoral aff. N. melonii, and Nesogoral sp. 2. On Mallorca (Balearic Islands) six chronospecies belonging to the Myotragus endemic phylogenetic lineage have been described, spreading in age from the Early Pliocene to the Holocene. For decades, a close phylogenetic relationship between Nesogoral and Myotragus has been widely accepted by scholars. Morphological and biometrical differences shown by Balearic and Sardinian bovids have generally been regarded as the result of the evolution into two different island ecological systems, characterized by different inter and intra-guild selection pressures. Indeed, the more diversified environment of Sardinia, as well as the presence of other large mammals (similar-sized competitors belonging to the same guild and a running predator), increased the interspecific competition, forcing Sardinian bovids to exploit different resources and to occupy different niches, while Myotragus exploited under a monopoly regime the supply of resources available for large herbivores on the Eastern Balearic Islands. Nonetheless, new data suggest that Nesogoral and Myotragus possibly originated from different taxa.