Past and Present Environmental Factors Differentially Influence Genetic and Morphological Traits of Italian Barbels (Pisces: Cyprinidae)

Local adaptation and phenotypic plasticity can lead to environment-related morphological and genetic variations in freshwater fish. Studying the responses of fish to environmental changes is crucial to understand their vulnerability to human-induced changes. Here, we used a latitudinal gradient as a proxy for past and present environmental factors and tested its influences on both genetic and morphological patterns. We selected as a suitable biogeographic model, the barbels, which inhabit 17 Adriatic basins of the central-southern Italian Peninsula, and explored association among attributes from genetic, morphological, and environmental analyses. The analysis of the mitochondrial DNA control region evidenced a southward significant increase in the number of private haplotypes, supporting the isolation of the southernmost populations related to the Mio-Pleistocene events. In contrast, morphology was mainly affected by changes in the present environmental conditions. Particularly, the number of scales and fish coloration were clearly associated to latitude, and thus thermal and hydrological conditions. Other morphometric and functional traits varied under the selective pressure of other environmental factors like elevation and distance from headwater. These results highlight the sensitivity of barbels to climate changes, which can serve as a basis for future eco-evolutionary and conservation studies.

Automated summary

Local adaptation and phenotypic plasticity can lead to variations in morphology and genetics in freshwater fish. Studying fish responses to environmental changes is important for understanding their vulnerability to human-induced changes. In this study, a latitudinal gradient was used to explore the influences of past and present environmental factors on genetic and morphological patterns in barbels, a biogeographic model in the Italian Peninsula. The results showed an increase in private haplotypes towards the south, suggesting the isolation of southern populations. Morphology, on the other hand, was mainly affected by current environmental conditions.