Flank spot number and its significance for systematics, taxonomy and conservation of the near‐threatened Mediterranean troutSalmo cettii: evidence from a genetically pure population

Abstract

The number of spots on the flank of the Mediterranean trout Salmo cettii population from Tellesimo Stream in Sicily, Italy, varied between seven and 37, with a median and mode of 21, numbers much lower than those reported in the literature and different from those of other Italian trout populations. This finding could be ascribed to the phenotypic plasticity of the species or, alternatively, could provide evidence to support the different origin of Sicilian autochthonous trout. Given the ease of use of this character for the identification of native fish, it could be particularly important for conservation and management purposes.

Morphological survey as powerful detection tool of pure and local phenotypes inSalmo truttacomplex

“…The color pattern of the Atlantic trout is instead characterized by the presence of a few circular black spots, red spots aligned mainly along the lateral line, parr marks less persistent during growth and without striped pattern, few opercular spots, and often the absence of the pre-opercular dot. The Mediterranean trout populations occurring in the central Apennines seem to differ significantly, from the morphological point of view, from those present in southeastern Sicily (Vinciguerra, 1896;Sommani, 1950a), as recently described by Duchi (2018), which are also genetically distinct from other Italian populations (Schöffmann et al, 2007;Fruciano et al, 2014) and more similar to populations from North Africa (Tougard et al, 2018). The binome S. cettii was previously used to identify the Sicilian populations, and this poses problems of nomenclature concerning the other Italian populations.…”

“…In particular, Italy, because of the presence of a large number of endemic species, can be considered a crucial area for the fish biodiversity conservation (Smith and Darwall, 2006). At present, the Mediterranean trout Salmo cettii Rafinesque, 1810 is considered by some authors the native stream-resident brown trout of the Apennine and main islands of Italy (Sardinia, Corsica and Sicily) (Zaccara et al, 2015;Duchi, 2018), although probably the taxonomy of the Mediterranean trout has not yet been resolved. The Mediterranean trout is one of the freshwater fish species threatened in this area, being the residual native trout populations listed as Critically Endangered in the IUCN Red List of Italian vertebrates (Rondinini et al, 2013).…”

The name of the trout: considerations on the taxonomic status of the Salmo trutta L., 1758 complex (Osteichthyes: Salmonidae) in Italy

“…Thus, on the base of these consistent molecular data, the name Salmo cettii is useless for designating Tyrrhenian and insular (e.g., Kottelat & Freyhof 2007) or even all Italian Mediterranean trout (see Rondinini et al 2013;Lobón-Cerviá et al 2018). In fact, the species "cettii" was described on specimens from rivers of eastern Sicily (see above), phylogenetically linked to Maghreb trout populations (see also Duchi 2018). Therefore, Salmo cettii should be considered as a senior synonym of Salmo macrostigma, and eventually be used for the trout belonging to the southern Atlantic clade (e.g., Cortey et al 2009;Snoj et al 2011), assuming North-African and Sicilian trout populations are worthy of taxonomic distinction (but see Tougard et al 2018).…”

“…Indeed, already in the early 50s, Sommani (1951) did not include the populations of central Italy in his zoogeographic revision, because, in his opinion, they were too compromised by the spread of Atlantic hatchery trout. In this work, the author consider the Mediterranean trout of Italy belonging to the nominal form, Salmo trutta, with the exception of Sicilian, Corsica, Sardinian and south Latium populations, attributed to Salmo macrostigma (Dúmeril 1858), due to the typical phenotype characterized by large and sparse dark spots on the body sides (see Duchi 2018) (Figure 1(c)). The occurrence in Sardinia of a trout species originally described by Dúmeril for Algeria was reported at first by Boulenger (1901), and the "macrostigma trout" was later recognized as typical of the circum-Mediterranean countries (e.g., Tortonese 1954).…”

Salmo macrostigma(Teleostei, Salmonidae): Nothing more than a brown trout (S. trutta) lineage?

“…Macrostigma phenotypes have also been reported in Italy (including Sardinia and Sicily; Boulenger, ; Ciuffardi & Arillo, ; Gandolfi et al ., ; Massidda, ; Mola, ; Nonnis Marzano et al ., ; Patarnello et al ., ; Querci et al ., ), Albania (Rakaj & Flloko, ; Cullaj et al ., ), Greece (Karakousis & Triantaphyllidis, ; Kattoulas, ) and Corsica, France, (Gauthier & Berrebi, ; Guyomard, ; Roche & Mattei, ). A macrostigma phenotype might be observed in Salmo cettii Raffinesque 1810, inhabiting Sicily (Kottelat & Freyhof, ; Schöffmann et al ., ) and Duchi () rightly reported that confusion still exists regarding how to distinguish S. macrostigma from S. cettii. Indeed, distribution of the macrostigma trout remains controversial and some authors assert that it should be exclusively used for Algerian populations (Turan et al ., ; Zouakh, ).…”