The evolution of body size, horn shape and social behaviour in crown Antilopini - an ancestral character state analysis

The earliest known bovids, commonly placed in the genus Eotragus, are small species with short straight horns that are located above the orbits. Among living bovids there are several species that show a similar horn morphology. These dwarf antelopes were historically united in the group „Neotragini“, which is now known to be a polyphyletic assemblage. The species in the genera Ourebia, Raphicerus, Dorcatragus, Madoqua, Oreotragus, Nesotragus, and Neotragus are scattered across the bovid phylogenetic tree. Nevertheless, the shared similarities, not only in body size and horn length but also in their social organisation, are interpreted to represent shared plesiomorphic traits that were present in the most recent common ancestor of Antilopinae. Most dwarf antelopes are closely related to gazelles and their allies, placed in the taxon Antilopini. Using a species level phylogeny of this group, I reconstructed ancestral states of several characters for the most recent common ancestor of Antilopini. While the results for the reconstruction of ancestral social organisation of the dwarf species are inconclusive, the small body size and short horns of Ourebia, Raphicerus, Dorcatragus, and Madoqua are most likely derived traits. The habitus of the ancestor of Antilopini was probably very similar to modern gazelles, consistent with the placement of the earliest fossil Antilopini in the genus Gazella

Data from: Utility of island populations in reintroduction programs—relationships between Arabian gazelles (Gazella arabica) from the Farasan Archipelago and endangered mainland populations

Understanding local adaptation and population differentiation is vital to the success of reintroduction initiatives. Like other mammals living on islands, Arabian gazelles (G. arabica) show reduced body size on the Farasan archipelago, which we corroborated in this study through morphometric analyses of skulls. In light of the steep population decline on the Arabian Peninsula—but stable population development on the archipelago—we tested the potential suitability of Farasan gazelles as a source for reintroductions on the mainland. We, therefore, investigated genetic differentiation between Farasan and mainland populations using eleven nuclear microsatellite loci and detected a distinct genetic cluster exclusively present on the archipelago, which we inferred to be separated from the mainland cluster for less than 2,000 years. About 30% of sampled individuals from Farasan Islands showed assignment to a mainland cluster with signs of ongoing introgression. Analyses using the Isolation-with-Migration model confirmed recent (probably human-induced) bidirectional exchange of gazelles between mainland and island populations. Hence, the surprisingly uniform island dwarfism most likely reflects phenotypic plasticity, i.e., altered morphology as a direct consequence of harsh environmental conditions and resource limitation on the archipelago. Should a further decline of Arabian gazelles on the mainland necessitate restocking in the future, Farasan gazelles may thus become an additional source for captive breeding programs