© 2016 The Linnean Society of London, Biological Journal of the Linnean Society, 2016, 119, 748–765.

Black rat invasion of inland Sahel: insights from interviews and population genetics in south-western Niger

Karine Berthier1, Madougou Garba2†, Raphael Leblois3,4, Miguel Navascués3,4, Caroline Tatard4, Philippe Gauthier5, Sama Gagaré6, Sylvain Piry4, Carine Brouat5, Ambroise Dalecky7, Anne Loiseau4 and Gauthier dobigny5*

1INRA, UR0407 Pathologie Végétale, F-84143, Montfavet, France
2Université Abdou Moumouni, Faculté des Sciences, BP10662, Niamey, Niger
3Institut de Biologie Computationnelle, Montpellier, France
4INRA, Centre de Biologie pour la Gestion des Populations (UMR IRD-INRA-Cirad-Montpellier SupAgro), Campus International de Baillarguet, CS30016, 34988 Montferrier-sur-Lez, France
5IRD, CBGP (UMR IRD-INRA-Cirad-SupAgro), Campus International de Baillarguet, CS30016, 34988, Montferrier-sur-Lez, France
6Centre Régional Agrhymet, BP11011, Niamey, Niger
7IRD, Laboratoire Population Environnement Développement (UMR AMU-IRD), Aix-Marseille Université, Centre Saint Charles, CS80249, 13331, Marseille Cedex 03, France

Abstract. Human population migrations, as well as long-distance trade activities, have been responsible for the spread of many invasive organisms. The black rat, Rattus rattus, has colonized most of the world following ship-mediated trade. Owing to its tight association with human infrastructures, this species has been able to survive in unfavourable environments, such as Sahelian Africa. In this work, we combined interview-based and population genetic surveys to investigate the processes underlying the ongoing invasion of south-western Niger by black rats, with special emphasis on the capital city, Niamey. Our trapping and interview data are quite congruent, and all together point towards a patchy, but rather widespread, current distribution of R. rattus. Genetic data strongly suggest that road network development for truck-based commercial flow from/to international harbours located in neighbouring countries (Benin, Togo, and Nigeria) facilitates the passive dispersal of black rats over a long distance through unfavourable landscapes. Another potentially, more ancient, invasion route may be associated with boat transport along the Niger River. Human-mediated dispersal thus probably allows the foundation of persisting populations within highly anthropized areas while population dynamics may be more unstable in remote areas and mostly depends on propagule pressure.

Keywords. Africa, Rattus rattus, trade-mediated invasion, urban habitat.

*Corresponding author: E-mail: gauthier.dobigny@ird.fr

†Current address: Direction Générale de la Protection des Végétaux, BP323, Niamey, Niger