Morphological variation in a secondary contact between divergent lineages of brown trout (Salmo trutta) from the Iberian Peninsula

Abstract

The aim of this study was to analyze the morphological variation of brown trout (Salmo trutta) in the Duero basin, an Atlantic river basin in the Iberian Peninsula, where a spatial segregation of two divergent lineages was previously reported, based on isozyme, microsatellite and mtDNA data. In these studies, two divergent pure regions (Pisuerga and Lower-course) and several hybrid populations between them were identified. Morphological variation was evaluated in 11 populations representative of the genetic differentiation previously observed in the Duero basin, using multivariate analysis on 12 morphometric and 4 meristic traits. A large differentiation between populations was observed (interpopulation component of variance: 41.8%), similar to that previously detected with allozymes and microsatellites. Morphometric differentiation was also reflected by the high classification success of pure and hybrid individuals to their respective populations, using multivariate discriminant functions (94.1% and 79.0%, respectively). All multivariate and clustering analyses performed demonstrated a strong differentiation between the pure regions. The hybrid populations, though showing large differentiation among them, evidenced an intermediate position between the pure samples. Head and body shape traits were the most discriminant among the morphometric characters, while pectoral rays and gillrakers were the most discriminant among the meristic traits. These results confirmed the high divergence of the brown trout from the Duero basin and suggest some traits on which selection could be acting to explain the spatial segregation observed.

Management units of brown trout from Galicia (NW: Spain) based on spatial genetic structure analysis

“…Similar results were recently obtained in a southward basin where Duero lineage is also sympatric with other more widespread Atlantic lineages (Martínez et al 2007). The spatial distribution of NOR-site polymorphism of brown trout from Duero Basin parallels both the spatial genetic structure revealed by molecular neutral markers (Bouza et al 2001;Martínez et al 2007Martínez et al , 2009) and spatial structure in morphology (Hermida et al 2008). Our results suggest that a new hybrid zone among the same two races of brown trout occurring in Duero Basin is also present in Miño Basin.…”

Phylogenetic status of brown trout Salmo trutta populations in five rivers from the southern Caspian Sea and two inland lake basins, Iran: a morphogenetic approach

“…count of red spots (P < 0·001) in populations from the Orumieh Lake basin (119·17 ± 39·25), which could have a genetic basis (Skaala & Jøstard, 1987;Blanc et al, 1994). Additionally, a meristic character for which counts were significantly higher (P < 0·001) in the Karaj population, compared to the other three populations studied here, was the gill rakers on the first gill arch, which have been noted as an important character in the identification of lineages and subspecies of S. trutta (Hermida et al, 2009). It is apparent from mtDNA data and from the overlapping ranges of the studied characters among populations that this character does not discriminate among lineages for the Iranian populations, except in indicating that the Karaj population is a distinct population of Iranian S. trutta.…”

Morphological and genetic characterization of Sardinian trout Salmo cettii Rafinesque, 1810 and their conservation implications

“…It is widely distributed across Europe and North Africa where it has a complex mosaic of phenotypic forms and ecoethological variability, resulting in problems in identification and taxonomy (Bernatchez, 1995;Kottelat & Freyof, 2007;Hermida et al, 2009). This phenotypic complexity has generated systematic disagreements since 1758, with at least 50 different species descriptions available (Ferguson, 1989).…”