Can geometric morphometrics and traditional methods work for evaluation of body shape plasticity of exotic fishes? A case study of topmouth gudgeon, Pseudorasbora parva (Teleostei: Gobionidae)

Introduction of species outside their native distribution ranges, followed by population establishment and becoming an invasive element, has been a common task and a controversial issue in the last century. The topmouth gudgeon Pseudorasbora parva is a gobionid fish native to southeast Asia, with a high dispersion potential, which succeeded in spreading out in many countries of Eurasia and north Africa including Iran during the almost 50 years. In this study, we are addressing the following research questions: (1) how do fish morphology differ in different water bodies by applying traditional, and geometric morphometric methods? (2) does morphology of P. parva show previous molecular-phylogenetic research based on mtDNA? Results revealed that traditional morphometric characters do not demonstrate a high phenotypic variation among 20 populations of P. parva collected from nine basins/river drainages. The cluster analysis of Euclidean distances among groups of P. parva populations (nine basins/river drainages) revealed segregation of three populations (Harirood, Esfahan and Mashkid basins). Based on the genetic background and colonisation history of P. parva using the mitochondrial DNA control region (806 bp) and a cytochrome c oxidase subunit I barcode database (615 bp), presence of three matrilineal haplotypes belonging to two lineages was confirmed: (1) a widespread lineage with a common haplotype found throughout the country and one exclusive haplotype confined to the Mashkid basin, whose origin can be traced back to a single introduction of a small number of propagules from Japan, and (2) a Chinese lineage represented by a single haplotype found in the Shafarood River of the Caspian Sea basin but also translocated to central Iran. This genetic clustering is somehow in correspondence to the dendrogram derived from the cluster analysis of geometric-morphometrics of P. parva populations and might be due to habitat-induced or genetically induced changes (e.g., fish origin), or it may arise due to the combination of both.