Abstract

The centre-periphery hypothesis (CPH) postulates that populations close to the centre of a species distribution will exhibit higher genetic diversity and lower genetic differentiation than populations located at the edge of the distribution. The centre of a species' distribution might represent an optimum for the environmental factors influencing the species absolute fitness and, therefore, genetic diversity. In species with wide distribution, the geographical variation of biotic and abiotic variables is crucial to understand the underlying mechanisms of the CPH. We evaluated the CPH and specifically tested which environmental variables better explained the patterns of genetic diversity in the kissing bug Mepraia spinolai, one of the main wild vectors of Chagas disease in southern South America, distributed across three Mediterranean climatic ecoregions in Chile. We analysed 2380 neutral single nucleotide polymorphisms to estimate genetic diversity. Mean winter temperature, mean summer temperature, vegetation cover, population abundance, proportion of winged individuals and female abdomen area were measured for each kissing bug population to construct a model. Lower genetic diversity was detected in populations at the edge of the distribution compared to those in the centre. However, genetic differentiation was not higher in the periphery. Genetic diversity was related to climatic and biological variables; there was a positive relationship with mean winter temperature and a negative association with mean summer temperature and body size. These results partially support the CPH and identify biotic (abdomen area) and abiotic (winter/summer temperatures) factors that would affect genetic diversity in this restricted-dispersal species of epidemiological relevance.