Abstract
Successful establishment of non‐native species is strongly influenced, among other factors, by the genetic variation of founding populations, which can be enhanced by multiple introductions through admixture. Coexisting pathogens can also facilitate the establishment of non‐native species by detrimentally impacting on the native fauna acting as novel weapons. The signal crayfish (Pacifastacus leniusculus) is a highly invasive species, which has caused mass declines of native crayfish in Europe through displacement and transmission of the oomycete Aphanomyces astaci (crayfish plague), which is typically lethal to native European crayfish. However, whether Aphanomyces astaci may have facilitated the invasion of the signal crayfish is not known. We estimated the genetic diversity at microsatellite DNA loci, effective population size, and potential origins of seven infected and noninfected signal crayfish populations in Europe and one founder population in North America. Approximate Bayesian computation analysis and population structuring suggested multiple host introductions from diverse source populations, as well as higher heterozygosity among infected than uninfected populations, which could reflect a fitness advantage. Low effective population size, moderate heterozygosity, and lack of isolation by distance suggest that some invasive signal crayfish populations may not be fully established or that their genetic diversity may have been reduced by eradication attempts.
Highlights
Non-native species are often vehicles for the introduction of novel pathogens (Miaud et al, 2016; Randolph & Rogers, 2010) which, as important drivers of evolution, can impact the structure and composition of native communities (Altizer, Harvell, & Friedle, 2003) and facilitate invasion success (Andreou, Arkush, Guégan, & Gozlan, 2012; Vilcinskas, 2015)
We modeled infection status and plague intensity in individual crayfish using population of origin as a random factor and individual homozygosity (HL) as a predictor with either a binomial logit link or a Gaussian link (plague intensity, measured as log(PFU+0.5) with the lme4 package in R, version 3.3.2
Signal crayfish represents an ideal species to test the roles of genetic diversity and pathogens as novel weapons on invasion success, as the species is highly invasive throughout most of Europe, and Great
Summary
Non-native species are often vehicles for the introduction of novel pathogens (Miaud et al, 2016; Randolph & Rogers, 2010) which, as important drivers of evolution, can impact the structure and composition of native communities (Altizer, Harvell, & Friedle, 2003) and facilitate invasion success (Andreou, Arkush, Guégan, & Gozlan, 2012; Vilcinskas, 2015). | 9182 see Edgerton et al, 2004; Kaldre, Paaver, Hurt, & Grandjean, 2017) In both cases, these novel pathogens threaten the survival of phylogenetically close indigenous species, like the red squirrel (Sciurus vulgaris) and two native crayfishes, the white-clawed crayfish, Austropotamobius pallipes and the noble crayfish, Astacus astacus, respectively. Newly introduced populations tend to lose genetic diversity due to founder effects (Dlugosch & Parker, 2008) Some of these bottlenecked populations successfully disperse and establish despite their low genetic diversity. We compared the genetic diversity, effective population size, and potential origin of seven signal crayfish populations with different plague infection status and assessed the relative roles of the crayfish plague and multiple introductions in the establishment and dispersal of invasive crayfish in Great Britain
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