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

Abstract

The native Mediterranean trout populations in central Italy are at risk of extinction. Hybridization with the alien Atlantic trout represents one of the major threats to the species. The main aim of the research was to test the efficiency of morphological characterization in revealing alien trout introduction, pure lineages and local adaptations, in five watersheds of central Apennines (Italy). Data analysis was carried out for a total of 258 specimens already genetically identified. The results of the multivariate analysis, performed using 10 qualitative and 47 quantitative variables, revealed two distinct phenotypic groups and confirmed, at a morphological level, the genetic separation between Atlantic and Mediterranean trout. The morphological variables that play a key role in the discrimination of the Mediterranean trout were: (i) number of parr marks with striped pattern, (ii) adipose fin mainly with white color and without black spots, and (iii) number of black opercular spots, compared to the Atlantic trout. The geometric analysis revealed the importance of the spatial arrangements of spots on the fish flank and the shape of caudal peduncle in discriminating different Mediterranean populations. The information collected confirmed the powerful of morphological surveys in the screening of conservation status of wild trout populations.

Spotting genome-wide pigmentation variation in a brown trout admixture context

“…This was more or less expected as these variables have been repeatedly shown to characterize pigmentation differences between Atlantic or Mediterranean trout in studies previously conducted in France (Poteaux & Berrebi, 1997) and Spain (Aparicio et al, 2005), but, while some spotting traits are important, they are not always found in Italy depending on the local populations analyzed and associated to other not found consistent in our study (e.g. patterns of the adipose fin) (see Lorenzoni et al, 2019). While focusing on few local French populations, results presented in this study reflect former results obtained for these two clades at a broader scale.…”

“…Largiadèr & Scholl, 1996; Mezzera, Largiadèr, & Scholl, 1997; Aparicio, García-Berthou, Araguas, Martinez, & Garcia-Marin, 2005; Miyazawa, Okamoto, & Kondo, 2010; Kirczuk & Domagala; 2012, Kocabas, Kutluyer, & Basçinar, 2018), it appears necessary to improve knowledge on the genotype-phenotype association supporting observed pigmentation patterns. Indeed, pigmentation patterns inform on individual origin and use to improve management knowledge, decisions or policies (Ielli & Duchi, 1990; Largiadèr & Scholl, 1996; Poteaux & Berrebi, 1997; Delling, Crivelli, Rubin, & Berrebi, 2000; Aparicio et al, 2005; Kocabas et al, 2011; Marin, Coon, & Fraser, 2017; Duchi, 2018; Lorenzoni et al, 2019). It thus might be relevant to evaluate if loci supporting phenotypic divergence for body patterning reflect genome-wide admixture.…”

Application of the geometric morphometrics approach in the discrimination of morphological traits between brown trout lineages in the Danube Basin of Croatia

“…Further, Monet et al (2006) stated that morphological variation caused by genotype was mainly attributable to differences between Mediterranean and Atlantic lineages, making the identification of hybrid trout difficult as they were generally confused with Mediterranean specimens. Similar results for Mediterranean and Atlantic trout lineages and their hybrids were obtained in Italy by Lorenzoni et al (2019). They used a box truss network and spatial arrangement of dots, and determined a significant difference between all three groups.…”

“…In addition, Jansson et al (1991), Matthews et al (2000) and Kalayci et al (2018) noted that morphological distinctions of hybrid salmonids from parental species are generally unreliable. However, both Monet et al (2006) and Lorenzoni et al (2019) showed that it is possible to find significant shape distinction between hybrid trout and both parental populations, though they examined parental populations from the Mediterranean and Atlantic lineage, and still hybrids were more similar to the native Mediterranean parental lineage populations.…”

“…Several studies have employed classical morphometric and meristic traits to analyse and discriminate populations between and within brown trout lineages (Simonović et al, 2007;Hermida et al, 2009;Liasko et al, 2012;Lorenzoni et al, 2019;Delling et al, 2020;Piria et al, 2020). Less attention has been given to the analysis of body size and shape variation using the geometric morphometrics (GM) approach, even though the GM method has proven suitable for confirming the discrimination of alien and native lineages previously differentiated by molecular analyses (Monet et al, 2006;Fruciano et al, 2014).…”