Introduction

Studies of intraspecific genetic structure are of central importance to evolutionary biology, as population differentiation can lead to distinct evolutionary trajectories and may be viewed as the first step in the process of speciation (Wright, 1932). The distribution of genetic variation among populations is determined by a complex interaction of historical and contemporary evolutionary forces – including genetic drift, mutation, selection and gene flow – which are influenced by the specific life history, behavior and ecology of a species (Slatkin, 1987; Goodnight, 2006). Historical events such as vicariance, colonization events or glacial refugia can also dramatically shape contemporary patterns of genetic subdivision. Gene flow is the primary force that leads to genetic homogeneity among populations, and species may be subject to geographic, behavioral or ecological barriers to gene flow. The task of teasing out the relative importance of different life-history, behavioral and ecological characteristics in determining genetic structure, each taking place across a range of temporal and spatial scales, continues to challenge population geneticists (Hey and Machado, 2003; Estoup et al., 2004; Duminil et al., 2007).

Bats (order Chiroptera) which comprise nearly 1200 species, exhibit a wide range of life-history and ecological characteristics that make them an ideal group to test hypotheses regarding the correlates of population structure in animals (Nowak, 1999; Simmons, 2005). Being nocturnal and difficult to study by traditional ecological methods (including direct observation, telemetry and capture–mark–recapture), a growing number of studies have used molecular markers to examine the population biology of bats (Burland and Worthington-Wilmer, 2001). In general, population genetic studies of volant animals are of particular interest because of their potential for long-distance dispersal and high levels of gene flow over terrestrial and oceanic landscapes.