Spatial Segregation between Invasive and Native Commensal Rodents in an Urban Environment: A Case Study in Niamey, Niger Madougou Garba 1,2,3 , Ambroise Dalecky 4,5 , Ibrahima Kadaoure 6 , Mamadou Kane 7 , Karmadine Hima 2 , Sophie Veran 8 , Sama Gagare 1 , Philippe Gauthier 5 , Caroline Tatard 8 , Jean-Pierre Rossi 8 , Gauthier Dobigny 1,5 * 1 Centre Re ´ gional Agrhymet, De ´ partement Formation Recherche, Niamey, Niger, 2 Universite ´ Abdou Moumouni, Faculte ´ des Sciences, Niamey, Niger, 3 Direction Ge ´ne ´rale de la Protection des Ve ´ge ´taux, Ministe `re de l9Agriculture, Niamey, Niger, 4 IRD, Aix Marseille Universite ´, LPED (UMR IRD-AMU), Marseille, France, 5 IRD, CBGP (UMR IRD- INRA-Cirad-SupAgro Montpellier), Campus International de Baillarguet, Montferrier-sur-Lez, France, 6 Centre Re ´ gional Agrhymet, USAid/Fews-Net, Niamey, Niger, 7 IRD, CBGP, Campus ISRA-IRD de Dakar-Bel-Air, Dakar, Senegal, 8 INRA, CBGP, Campus International de Baillarguet, Montferrier-sur-Lez, France Abstract Invasive rodents have been responsible for the diffusion worldwide of many zoonotic agents, thus representing major threats for public health. Cities are important hubs for people and goods exchange and are thus expected to play a pivotal role in invasive commensal rodent dissemination. Yet, data about urban rodents’ ecology, especially invasive vs. native species interactions, are dramatically scarce. Here, we provide results of an extensive survey of urban rodents conducted in Niamey, Niger, depicting the early stages of rodent bioinvasions within a city. We explore the species-specific spatial distributions throughout the city using contrasted approaches, namely field sampling, co-occurrence analysis, occupancy modelling and indicator geostatistics. We show that (i) two species (i.e. rural-like vs. truly commensal) assemblages can be identified, and that (ii) within commensal rodents, invasive (Rattus rattus and Mus musculus) and native (Mastomys natalensis) species are spatially segregated. Moreover, several pieces of arguments tend to suggest that these exclusive distributions reflect an ongoing native-to-invasive species turn over. The underlying processes as well as the possible consequences for humans are discussed. Citation: Garba M, Dalecky A, Kadaoure I, Kane M, Hima K, et al. (2014) Spatial Segregation between Invasive and Native Commensal Rodents in an Urban Environment: A Case Study in Niamey, Niger. PLoS ONE 9(11): e110666. doi:10.1371/journal.pone.0110666 Editor: Jonas Waldenstro ¨ m, Linneaus University, Sweden Received May 20, 2014; Accepted September 22, 2014; Published November 7, 2014 Copyright: ß 2014 Garba et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files. Funding: Lab and field work were funded by the "Institut de Recherche pour le De ´veloppement" (France). Funding support was partly provided to Mr. Garba by a ‘BEST’ bursary from the ‘‘Service de Renforcement des Capacite ´s’’ (Institut de Recherche pour le De ´veloppement), France. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * Email: gauthier.dobigny@ird.fr Introduction Since the last decades, urbanization has been dramatically increasing all over the World: while 29% of humanity lived in cities in 1950, ,53% is currently urban, and 67% will be urban by 2050 [1]. Sub-Saharan Africa is currently the most rapidly urbanizing continent, with more than 80 urban centers predicted to reach one million inhabitants by 2025 [1]. Niamey, main town of Niger and focus of the present study, is no exception: for the period 2005–2010, its agglomeration has ranked 23 in the World and 5 in Africa for the average annual rate of rural-to-urban change (5.99%), and it is expected to rank 12 and 4, respectively, for the period 2010–2015 [1]. Of course, this is accompanied by an explosive demographic growth, with ,34,000 inhabitants in 1960 up to 650,000 and .1,200,000 in 2000 and 2010, respectively [2]. Urbanization represents an extreme situation along the gradient of human-mediated modification of the environment, usually accompanied by drastic changes in abiotic (e.g., soil substrate, hydrographic networks, atmosphere composition, etc) and biotic (e.g., species diversity, abundance and distribution) factors [3]. Indeed, it induces dramatic changes in both landscape and human activities that, in turn, deeply impact the composition and structure of biodiversity within cities. In particular, human infrastructures coupled with permanent supply of a wide range of resources provide a compelling advantage to opportunistic and highly competitive species that display important adaptation abilities [4,5]. Invasive species are expected to show such characteristics. Moreover, cities constitute major crossroads for people and goods exchange, thus increasing the chance of the involuntary and repeated introductions of alien organisms and their subsequent spread out. Altogether, this makes urban areas particularly prone to bioinvasions. Commensal rodents such as rats (Rattus norvegicus, R. rattus, R. tanezumi, R. exulans) and mice (Mus musculus) constitute major invaders, with the house mouse M. musculus and the black rat R. rattus being listed among the 100 ‘‘worst invasive alien species in the World’’ [6]. These species have settled on all PLOS ONE | www.plosone.org 1 November 2014 | Volume 9 | Issue 11 | e110666