Contrasting patterns of genetic and phenotypic differentiation in two invasive salmonids in the southern hemisphere

Abstract

Invasion success may be expected to increase with residence time (i.e., time since first introduction) and secondary releases (i.e., those that follow the original introduction), but this has rarely been tested in natural fish populations. We compared genetic and phenotypic divergence in rainbow trout and brown trout in Chile and the Falkland Islands to test the prediction that adaptive divergence, measured as PST/FST, would increase with residence time and secondary releases. We also explored whether interspecific competition between invaders could drive phenotypic divergence. Residence time had no significant effect on genetic diversity, phenotypic divergence, effective population size, or signatures of expansion of invasive trout. In contrast, secondary releases had a major effect on trout invasions, and rainbow trout populations mostly affected by aquaculture escapees showed significant divergence from less affected populations. Coexistence with brown trout had a positive effect on phenotypic divergence of rainbow trout. Our results highlight an important role of secondary releases in shaping fish invasions, but do not support the contention that older invaders are more differentiated than younger ones. They also suggest that exotic trout may not have yet developed local adaptations in these recently invaded habitats, at least with respect to growth-related traits.

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

“…However, the potential genetic impact of salmonids on galaxiids remains largely unknown (but see Vanhaecke et al, 2012a). Our estimates of relative salmonid abundance in Chilean streams were similar to those of previous studies that found salmonids were absent in some coastal rivers of Chilo e and were most abundant in areas with greater numbers of fish farms that could serve as sources for invaders (Young et al, 2010;Consuegra et al, 2011;Monz on-Arg€ uello et al, 2014b). We used two types of molecular markers with different rates of evolution and modes of inheritance to investigate the drivers of population structuring in A. zebra: maternally inherited mtDNA to provide information on historical phylogeographical events (e.g.…”

“…However, the potential genetic impact of salmonids on galaxiids remains largely unknown (but see Vanhaecke et al ., ). Our estimates of relative salmonid abundance in Chilean streams were similar to those of previous studies that found salmonids were absent in some coastal rivers of Chiloé and were most abundant in areas with greater numbers of fish farms that could serve as sources for invaders (Young et al ., ; Consuegra et al ., ; Monzón‐Argüello et al ., ).…”

“…Surprisingly, relatively little is known about the genetic impact of invasions (e.g. Strayer et al ., ; Carroll, ), as most studies tend to focus on genetic changes exhibited by the invaders (Monzón‐Argüello et al ., , ,b), rather than genetic responses of native species (Vanhaecke et al ., ). This is unfortunate because without genetic data, it may be difficult to get accurate assessments of the conservation status of threatened populations (Traill et al ., ) or to quantify the impact of biological invasions.…”

Contrasting genetic metrics and patterns among naturalized rainbow trout (Oncorhynchus mykiss) in two Patagonian lakes differentially impacted by trout aquaculture

“…Monzón‐Argüello, Consuegra, et al. () found that “secondary releases” (when referring to aquaculture escapes) have driven phenotypic divergence among naturalized rainbow trout from the Lake District in Chile. Recently, Bolstad et al.…”

“…Genetic assessments have been instrumental in evaluating the geographic origin as well as drivers that explain the establishment and spread of naturalized rainbow trout in Patagonia (Gajardo, Díaz, & Crespo, ; Monzón‐Argüello, Garcia de Leaniz, Gajardo, & Consuegra, , ; Monzón‐Argüello, Consuegra, et al., ; Riva Rossi, Lessa, & Pascual, ). Recently, Benavente et al.…”