Cryptic invasion drives phenotypic changes in central European threespine stickleback

Abstract

Cryptic invasions are commonly associated with genetic changes of the native species or genetic lineage that the invaders replace. Phenotypic shifts resulting from cryptic invasions are less commonly reported given the relative paucity of historical specimens that document such phenotypic changes. Here, I study such a case in two populations of threespine stickleback from central Europe, comparing contemporary patterns of gene flow with phenotypic changes between historical and contemporary population samples. I find gene flow from an invasive lineage to be associated with significant phenotypic changes, where the degree of phenotypic change corresponds with the level of gene flow that a population receives. These findings underline the utility of combining genetic approaches with phenotypic data to estimate the impact of gene flow in systems where anthropogenic alterations have removed former geographic barriers promoting cryptic invasions.

Fit and fatty freshwater fish: contrasting polyunsaturated fatty acid phenotypes between hybridizing stickleback lineages

“…In this study we did not measure FADS2 gene expression however, so it could also be valuable to do so. Similar patterns of introgression have been observed between the introduced Constance lineage, and native Swiss populations as the highly plated Eda allele has been spreading into historically low plated populations (Lucek 2016, Hudson et al 2021a). As hybridization continues, it will be prudent to monitor the evolutionary history, abundance, habitat use and phenotype of stickleback populations in other Swiss lakes.…”

Admixture between old lineages facilitated contemporary ecological speciation in Lake Constance stickleback

“…We combined lateral plate morph data from lake and stream populations around Lake Constance, from the upper Rhone drainage (Lake Geneva), the Rhine and the upper Danube 3,12,21,22,64 , in which individuals were scored as low, partially or fully plated morph, based on the presence of 0–3 lateral plates posterior the pelvic girdle (low plated), more than three later plates but with a gap of at least two plates to the caudal peduncle (partially plated) or the presence of a continuous series of lateral plates up to the caudal peduncle (fully plated) 21 . We embedded this lateral plate morph data in the context of historical phenotype distributions 22,30,65 .…”

Threespine Stickleback in Lake Constance: The Ecology and Genomic Substrate of a Recent Invasion

“…Phenotypic analyses also support the secondary contact scenario. Stickleback native to the Rhine and Rhône originating from natural colonization from the Sea (Lucek et al, 2010), including Rhine populations from Basel (Figure 3), were historically fixed for the low plated phenotype (Fatio, 1882;Münzing, 1963), prior to hybridization and introgression with the introduced Eastern European lineage (Lucek, 2016). In contrast, Baltic Sea freshwater populations were fixed for the fully plated phenotype until recent introductions of low plated fish from Western Europe (Bańbura, 1994) and the likely introduced freshwater populations in the upper and middle Danube which contain a mix of low and fully plated morphs (Ahnelt, 1986).…”