Mitochondrial phylogeography of the land snail Cornu aspersum: Tracing population history and the impact of human-mediated invasion in austral South America

Abstract

Aim: Study one of the most widespread biological invasions by reconstructing the molecular phylogeographic history of non-native populations of the land snail Cornu aspersum in austral South America. Specifically, we wished to: (1) examine the genetic diversity of native vs. non-native populations of C. aspersum; (2) analyse the species' history of dispersal and colonization in austral South America; (3) compare the biogeographic patterns of native and introduced populations; and (4) identify signs of population bottlenecks and/or multiple independent introductions that might explain the current genetic diversity. Locations: North Africa, northwest Europe, North America (California, USA), and South America (Chile). Methods: We obtained sequences of the mitochondrial cytochrome b (Cytb) gene from C. aspersum individuals collected from two localities subject to recent introductions (Californian and Chilean populations in North and South America, respectively). We compared these sequences with previously published data from the species' native range (northeast and northwest Africa), as well as with data from a previous introduction (northwest Europe). We measured genetic variation within and among groups. We inferred genetic structure by analysis of molecular variance (AMOVA). We reconstructed phylogeographic patterns using phylogenetic and genetic diversity analyses. Results: Among the 204 sequences from native and non-native populations, we identified 111 haplotypes. Of these, only three were shared between American and European populations, and no haplotypes were shared between Africa and the introduced populations. The analysis of genetic distances placed European populations between American and African populations. The AMOVAs showed that most of the genetic variance is present within populations rather than among populations or among localities. Haplotype network and phylogenetic analyses cons istently demonstrated the existence of two major clades: the Tunisian and the American. Conclusions: Genetic diversity and genealogical relationships support the hypothesis of multiple introductions of C. aspersum into austral South America. At least a portion of the current genetic diversity of Chilean populations derives from North American and European (French, Italian, and Spanish) populations. © 2013 Roberto F. Nespolo.