Genetic signatures of historical dispersal of fish threatened by biological invasions: the case of galaxiids in South America

Abstract

Aim The ecological effects of biological invasions are well documented, but little is known about the effects of invaders on the genetic structure of native species. We examined the phylogeography, genetic variation and population structuring of two galaxiid fishes, Aplochiton zebra and A. taeniatus, threatened by non‐native salmonids, and whose conservation is complicated by misidentification and limited knowledge of their genetic diversity. Location Chile and the Falkland Islands. Methods We combined microsatellite and mitochondrial DNA (16S rDNA and COI) markers to compare genetic diversity, effective population size and gene flow of Aplochiton spp. populations differentially affected by salmonid presence. Results We identified two 16S rDNA haplotypes among A. zebra – one dominant in coastal populations and another dominant in inland populations. Populations living on the island of Chiloé displayed a mixture of coastal and inland haplotypes, as well as high microsatellite diversity, as one would expect if the island had been a refugium during the Last Glacial Maximum, or a contact zone among populations. Microsatellite data revealed strong population structuring, indicative of current isolation patterns, and a negative correlation between the genetic diversity of A. zebra and the relative abundance of invasive salmonids. Main conclusions Our study indicates that population structuring of A. zebra reflects the influence of historical patterns of migration, but also the current levels of reduced gene flow among watersheds. Invasive salmonids, known to compete with and prey on native galaxiids, may have had negative impacts on the genetic diversity of Aplochiton spp. The low genetic variation found in some populations, coupled with potential biases in abundance estimates due to species misidentification, highlight the urgent need for more research into the conservation status of the two species of Aplochiton.

Bayesian analyses detect a history of both vicariance and geodispersal in Neotropical freshwater fishes

“…However, due to the complexity of historical events, similar biogeographical patterns often can emerge from distinct diversification processes (Moritz, Patton, Schneider, & Smith, )—attesting the importance of incorporating statistical inferences into hypothesis testing. Among the few studies using this approach in South America freshwater fishes are the reconstruction of potential historic colonization routes for Aplochiton zebra species (Vanhaecke et al., ), an investigation of the performance of distinct divergence pattern resulted by nuclear and mitochondrial markers in Cichla temensis lineages (Willis et al., ), and the identification of headwater captures events that promoted the diversification in species of the Pimelodidae family in Amazon West (Tagliacollo et al., ). Our study is the first to implement a model‐based Bayesian framework to test alternative biogeographical scenarios potentially responsible for the diversification process in Neotropical freshwater fishes.…”

“…ABC is a flexible class of Monte Carlo algorithms that bypass the calculation of exact likelihoods using summary statistics and simulation. Its use has increased in population genetics and phylogeographical studies, allowing a quantitative evaluation of the demographic and evolutionary history by strictly contrasting realistic models defined a priori and estimating relevant parameters (Inoue, Lang, & Berg, ; Vanhaecke et al., ; Willis et al., ).…”

Experimental evidence of invasion facilitation in the zebra mussel-killer shrimp system

“…The impact of biological invasions has often been examined in isolation, under the implicit assumption that invaders do not interact with each other (Consuegra et al 2011; Vanhaecke et al 2015; Young et al 2010; Young et al 2009). However, invasion facilitation, whereby one species has a positive effect on the introduction, establishment or dispersal of other invasive species, is well documented, particularly in terrestrial plants and animals (Adams et al 2003; Altieri et al 2010).…”

Genetic diversity and parasite facilitated establishment of the invasive signal crayfish (Pacifastacus leniusculus) in Great Britain

“…Yet, the extent to which novel pathogens drive invasion success is controversial (Blackburn & Ewen, ) and understanding why some species become established while others fail to do so remains a key question in invasion biology (Davis, ). Propagule pressure, phenotypic plasticity, and standing genetic diversity of founder populations are some of the most crucial factors that determine invasion success (Kolar & Lodge, ; Lee, ; Souty‐Grosset, Grandjean, & Renault, ; Vanhaecke et al., ). In general, newly introduced populations tend to lose genetic diversity due to founder effects (Dlugosch & Parker, ).…”

“…Propagule pressure, phenotypic plasticity, and standing genetic diversity of founder populations are some of the most crucial factors that determine invasion success (Kolar & Lodge, 2001;Lee, 2002; Souty-Grosset, Grandjean, & Renault, 2015;Vanhaecke et al, 2015). In general, newly introduced populations tend to lose genetic diversity due to founder effects (Dlugosch & Parker, 2008).…”