Utility of island populations in re‐introduction programmes – relationships between A rabian gazelles ( G azella arabica ) from the F arasan A rchipelago and endangered mainland populations

Abstract

Understanding local adaptation and population differentiation is vital to the success of re‐introduction initiatives. As other mammals living on islands, A rabian gazelles ( G. arabica ) show reduced body size on the F arasan archipelago, which we corroborated in this study through morphometric analyses of skulls. In the light of the steep population decline on the A rabian P eninsula – but stable population development on the archipelago – we tested the potential suitability of F arasan gazelles as a source for re‐introductions on the mainland. We therefore investigated genetic differentiation between F arasan 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 2000 years. About 30% of sampled individuals from F arasan I slands 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, that is, altered morphology as a direct consequence of harsh environmental conditions and resource limitation on the archipelago. Should a further decline of A rabian gazelles on the mainland necessitate restocking in the future, F arasan gazelles may thus become an additional source for captive breeding programmes.

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