Testing Species Delimitations in Four Italian Sympatric Leuciscine Fishes in the Tiber River: A Combined Morphological and Molecular Approach

Abstract

Leuciscine fishes represent an important component of freshwater ichthyofauna endemic to northern Mediterranean areas. This lineage shows high intra-specific morphological variability and exhibits high levels of hybridization, two characteristics that contribute to systematic uncertainties, misclassification of taxa and, potentially, the mismanagement of biodiversity. This study focused on brook chub, Squalius lucumonis, an endemic taxon of Central Italy. The taxonomic status of this species has long been questioned, and a hybrid origin from sympatric leusciscines (S. squalus x Rutilus rubilio, or S. squalus x Telestes muticellus) has been hypothesised. A phenotypic (evaluating shape and meristic counts) and genetic (using mitochondrial and nuclear markers) investigation of these four taxa was conducted to test species delimitation in sympatric areas and to evaluate the taxonomic status of S. lucumonis. One hundred and forty-five individuals of all four taxa were collected within streams of the lowest portion of the Tiber River basin and analysed; this region encompasses a large portion of the S. lucumonis distribution. The different morphological and genetic approaches were individually examined, compared, and then combined in a quantitative model to both investigate the limits of each approach and to identify cases of misclassification. The results obtained confirm the cladogenetic non-hybrid origin of S. lucumonis, highlight the need for immediate conservation actions and emphasise the value of an integrated approach in the study of leuciscines evolution.

An update on the status of native and exotic freshwater fishes of Italy

“…Morphological characters of this species are readily identifiable with respect to the similar S. squalus . Moreover, genetic analyses conducted on Squalius lucumonis have always underlined its full validity, unlike trout species (Ketmaier et al., ; Durand et al., , ; Rossi et al., ; Tancioni et al, ). The unproductive disputes triggered by some ichthyologists have certainly not favoured the survival of this species, already included in the Habitat Directive of 1982, currently in strong decline and on the global list of species threatened with extinction (Bianco and Ketmaier, ).…”

Phylogeography and species delineation of the genusPhoxinusRafinesque, 1820 (Actinopterygii: Leuciscidae) in the Iberian Peninsula

“…and P. septimaniae . Hybridization due to introgression has been reported in freshwater fishes (Durand, Erhan, Doadrio, Pipoyan, & Templeton, ; Machordom, Berrebi, & Doadrio, ; Perea et al, ; Tancioni et al, ) including within Phoxinus due to naturally or artificially mediated secondary contact (Palandačić et al, , ).…”

Use of geometric morphometrics to identify ecophenotypic variation of juvenile Persian sturgeon <em>Acipenser persicus</em>

“…With the potential to identify discrete stocks phenotypically, analysis of morphometric landmarks is a valuable tool that complements other stock identification methods such as molecular approaches. Monet et al (2006), EspinosaLemus et al (2009) and Tancioni et al (2013) demonstrated that morphometric and genetic data were complementary for stock identification. The identification of discrete 'phenotypic' stocks is essential for population modelling.…”