Invasion genetics of the introduced black rat (Rattus rattus) in Senegal, West Africa ADAM KONEC ˇ NY ´ ,* †‡ ARNAUD ESTOUP,* JEAN-MARC DUPLANTIER, § JOSEF BRYJA, † KHALILOU BA ˆ , ¶ MAXIME GALAN,* CAROLINE TATARD* and JEAN-FRANCOIS COSSON* *INRA, CBGP, Campus international de Baillarguet, CS 30016, Montferrier-sur-Lez cedex F-34988, France, †Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Kve ˇtna ´ 8, Brno 603 65, Czech Republic, ‡Department of Biodiversity and Molecular Ecology, Fondazione E. Mach, Research and Innovation Centre, Via E. Mach 1, San Michele all’ Adige (TN) 38010, Italy, §IRD, CBGP, Campus international de Baillarguet, CS 30016, Montferrier-sur-Lez cedex F-34988, France, ¶IRD, CBGP, BP 1386, Dakar, Senegal Abstract An understanding of the evolutionary history and dynamics of invasive species is required for the construction of predictive models of future spread and the design of biological management measures. The black rat (Rattus rattus) is a major vertebrate invader with a worldwide distribution. Despite the severe ecological, economic and health impacts of this species, its evolutionary history has been little studied. We car- ried out extensive specimen sampling in Senegal, West Africa, and used microsatellite markers to describe the pattern and processes of invasion in this large continental area. The genetic data obtained were combined with historical knowledge concerning the presence of this species in Senegal. Data were analysed by a combination of Bayesian clustering and approximate Bayesian computation methods. The invasion pathways closely paralleled the history of human trade routes in Senegal. In several places, we detected the occurrence of multiple introductions from genetically different sources. Long-distance migration between towns and villages was also observed. Our findings suggest that genetic bottlenecks and admixture have played a major role in shaping the genetics of invasive black rats. These two processes may generate genetic novelty and favour rapid evolution along the invasion pathways. Keywords: approximate Bayesian computation, Bayesian clustering, founder effects, genetic admixture, ioinvasion, microsatellites, multiple introductions Received 14 July 2012; revision received 19 September 2012; accepted 24 September 2012 Introduction The rate of human-mediated biological invasions has accelerated in the last few centuries, largely due to the expansion of international trade and transport (Mack et al. 2000). The spread of non-native species is one of the most important effects of human activities, with many negative consequences for global and local biodi- versity, ecosystem functioning, agriculture, fisheries and public health (Vitousek et al. 1997; Wilcove et al. 1998). Despite the increasing importance of bioinvasions, we still know little about the evolutionary mechanisms underlying the success of invasive species (Facon et al. 2006). Evolutionary processes seem to play a crucial role during the various stages of invasion: opportunity/ transport, establishment and spread (Suarez & Tsutsui 2008). An understanding of these evolutionary pro- cesses is critical for both the theoretical aspects of evo- lutionary and population biology and, from a practical standpoint, the construction of predictive models of future spread and the design of biological control measures (Lee 2002). When individuals are introduced into a new range, they are likely to experience ecological conditions very different from those in the region from which they orig- inate. Natural selection and adaptation may therefore play a crucial role in the outcome of the invasion Correspondence: Jean-Franc ¸ois Cosson, Fax: + 33 4 99 62 33 45; e-mail: cosson@supagro.inra.fr © 2012 Blackwell Publishing Ltd Molecular Ecology (2012) doi: 10.1111/mec.12112