LETTER Do rabbits eat voles? Apparent competition, habitat heterogeneity and large-scale coexistence under mink predation Matthew Oliver, Juan Jose ´ Luque- Larena 1 and Xavier Lambin* Institute of Biological and Environmental Sciences, University Of Aberdeen, Aberdeen, UK *Correspondence: E-mail: x.lambin@abdn.ac.uk Abstract Habitat heterogeneity is predicted to profoundly influence the dynamics of indirect interspecific interactions; however, despite potentially significant consequences for multi-species persistence, this remains almost completely unexplored in large-scale natural landscapes. Moreover, how spatial habitat heterogeneity affects the persistence of interacting invasive and native species is also poorly understood. Here we show how the persistence of a native prey (water vole, Arvicola terrestris) is determined by the spatial distribution of an invasive prey (European rabbit, Oryctolagus cuniculus) and directly infer how this is defined by the mobility of a shared invasive predator (American mink, Neovison vison). This study uniquely demonstrates that variation in habitat connectivity in large-scale natural landscapes creates spatial asynchrony, enabling coexistence between apparent competitive native and invasive species. These findings highlight that unexpected interactions may be involved in species declines, and also that in such cases habitat heterogeneity should be considered in wildlife management decisions. Keywords Apparent competition, coexistence, indirect interactions, interspecific interactions, invasion meltdown, invasive species, metapopulation, predator–prey, spatial asynchrony, spatial heterogeneity. Ecology Letters (2009) 12: 1201–1209 INTRODUCTION Indirect interactions between species play a central role in defining community structure and species diversity within ecosystems (Sinclair & Byrom 2006). As such, characterizing these higher-order ecosystem processes is relevant to a number of applied issues and has become a major focus of ecology (Chaneton & Bonsall 2000; White et al. 2006). Although spatial heterogeneity has been identified as a profoundly important factor in the dynamics of single species (Hanski 1999) and resource-consumer models (Holyoak & Lawler 2005), the effect of habitat structure on more complex ecological interactions remains relatively unexplored. Holt (1984) highlighted that theoretically, prey species with non-overlapping habitat distributions can interact indirectly if they share a predator that operates over spatial scales equal to or exceeding the distance by which prey species are isolated. The phenomenon of predator-mediated indirect interaction between prey species has been named Ôapparent competitionÕ (Holt 1977). As with other host-enemy systems (Holyoak 2000; Bonsall et al. 2002), space may enhance the persistence of apparent competitive species assemblages. In this context, key factors that are predicted to dictate the dynamics of apparent competitive systems include the relative sensitivities of prey population growth rates to predation, the spatial distribution and overlap of suitable habitat for both prey species, the dispersal ability of the inferior prey species, and the relative mobility and habitat selection of the predator (Holt 1984; Bonsall & Hassell 2000; Bonsall et al. 2005). To date our understanding of the role played by indirect interspecific interactions in driving spatial dynamics of assemblages is based almost exclusively on theory and the findings of a small number of microcosm experiments. For example, Bonsall & Hassell (2000) found that theoretically, meta- population structure could enhance multi-species persistence by uncoupling the population dynamics of different species 1 Present address: Depto. CC Agroforestales, E.T.S. Ingenierı ´as Agrarias, Universidad de Valladolid, Palencia, Spain. Ecology Letters, (2009) 12: 1201–1209 doi: 10.1111/j.1461-0248.2009.01375.x Ó 2009 Blackwell Publishing Ltd/CNRS