Genetics of the genus Salmo in Italy: evolutionary history, population structure, molecular ecology and conservation

The Italian peninsula harbours a complex arrangement of native taxa within the genus Salmo, shaped by colonisation routes, palaeo-hydrology and ecological adaptation. In addition, salmonid biodiversity has massively been altered by anthropogenic translocation of non-native trout, thus promoting biotic homogenisation and introgressive hybridisation. Herein, we summarise present knowledge upon relevant colonisation hypotheses and propose that beyond the most likely original advent of Mediterranean salmonids through east to west migration, also subsequent counterdirected migration routes and even in situ evolutionary clade formation might have contributed to Italian trout biodiversity. We then focus on ‘peninsular’ and ‘marble’ lineages as the major native salmonid entities in Italy. Both lineages are constituted by a mosaic of sympatric and parapatric (meta)populations in riverine and lacustrine environments. Insights into molecular ecology of marble trout (Salmo marmoratus) and Lake Garda's carpione (Salmo carpio) are reported as prominent Italian examples. We focus on the problem of exotic brown trout in Italy, including biotic homogenisation and introgressive hybridisation as the negative consequences of this invasion. An attempt towards the definition of management units (MU) among Italian populations, obligatory for sustainable salmonid conservation, closes this chapter.