Where can introduced populations learn their tricks? Searching for the geographical source of a species introduction to the Galápagos archipelago

Abstract

We seek to understand the potential genetic impact of introduced species in an ecosystem where conservation efforts and pressure from development co-occur: the Galápagos Archipelago. To date, the introduced weevil Galapaganus h. howdenae is found only in Santa Cruz Island; however it has recently expanded its range beyond the Agricultural Zone into the highlands. We are focusing on comparisons between continental and introduced populations to clarify whether the current genetic patterns in introduced populations can reflect recovery from a past bottleneck and predict its invasive potential. A second objective is to narrow down the geographic source of the introduction and confirm their origin from a single introduction pulse. We found comparable microsatellite genetic diversity featuring many island-specific alleles, but reduced mitochondrial haplotype diversity in the islands. Additionally, both markers showed signals of population expansion and homogeneously distributed variation in the introduced range, in contrast to structured continental populations. The addition of mitochondrial sequences to the microsatellite dataset in the Approximate Bayesian Computation analyses (DIYABC) favors a single introduction pulse from the Northern Manabí area; a scenario that is in agreement with the haplotype network. An origin from higher elevationhabitats provides clues about the environmental amplitude of the naturalized populations. However, given that a large percentage of the microsatellite variation in island populations is due to new island alleles, the answer to the question “where can introduced populations learn their tricks?” could be: right at their new location.