Phylogeography, genetic structure, and conservation of the endangered Caspian brown trout, Salmo trutta caspius (Kessler, 1877), from Iran

Abstract

The Caspian Sea, the largest inland closed water body in the world, has numerous endemic species. The Caspian brown trout (Salmo trutta caspius) is considered as endangered according to IUCN criteria. Information on phylogeography and genetic structure is crucial for appropriate management of genetic resources. In spite of the huge number of studies carried out in the Salmo trutta species complex across its distribution range, very few data are available on these issues for S. trutta within the Caspian Sea. Mitochondrial (mtDNA control region) and nuclear (major ribosomal DNA internal transcribed spacer 1, ITS-1, and ten microsatellite loci) molecular markers were used to study the phylogeography, genetic structure, and current captive breeding strategies for reinforcement of Caspian trout in North Iranian rivers. Our results confirmed the presence of Salmo trutta caspius in this region. Phylogenetic analysis demonstrated its membership to the brown trout Danubian (DA) lineage. Genetic diversity of Caspian brown trout in Iranian Rivers is comparable to the levels usually observed in sustainable anadromous European brown trout populations. Microsatellite data suggested two main clusters connected by gene flow among river basins likely by anadromous fish. No genetic differences were detected between the hatchery sample and the remaining wild populations. While the current hatchery program has not produced detectable genetic changes in the wild populations, conservation strategies prioritizing habitat improvement and recovering natural spawning areas for enhancing wild populations are emphasized.

Lack of mtDNA variation among remote middle Volga and upper Ural brown trout suggests recent and rapid recolonization

“…Vera et al. () and Hashemzadeh Segherloo et al. () described ten different yet very similar trout CR mtDNA haplotypes, all found in the southern part of the Caspian basin.…”

“…() considered that the stated populations should not be regarded as distinct subspecies ( Salmo trutta caspius ) or species ( S. caspius ), but rather a Danube phylogenetic lineage within S. trutta . Compared to the results obtained with CR mtDNA analysis, the microsatellite‐based results, with minor exceptions, showed a higher degree of inter‐population variation (Hashemzadeh Segherloo et al., ; Vera et al., ).…”

“…In the past few years the genetic diversity and phylogeny of anadromous and resident populations of trout from the southern part of the Caspian basin and from the Namak and Orumeih lakes in Iran were studied using mitochondrial DNA control region (CR mtDNA) and nuclear DNA (nDNA) markers. Several new, highly related haplotypes, all belonging to the Danubian lineage (DA), were detected (Hashemzadeh Segherloo et al., ; Vera et al., ). Hashemzadeh Segherloo et al.…”

Genetic diversity and phylogenetic origin of brown trout Salmo trutta populations in eastern Balkans

“…All haplotypes found in the Caspian Sea basin and two inland lake basins in Iran (Vera et al 2011;Segherloo et al 2012) and the Aral Sea basin (Griffiths et al 2009) belonged also to this group. The second group, in this study named as the 'Black Sea group' (DaBS), included the haplotypes from the Timiş River, Beli Vit River, one haplotype from the Džepska River (carried by one individual) and all found haplotypes from the non-Danube locations of the Black Sea catchment.…”

“…However, concerning only the frequencies of the haplotypes within the DaDA group, an expansion was indicated by the unimodal trend of the mismatch distribution (raggedness index not significant), by the Tajima's D test (-1.436, P < 0.05) and by the Fu's Fs (-14.227, P < 0.001). Frequencies of haplotypes revealed in this as well as previous (Duftner et al 2003;Meraner et al 2007;Griffiths et al 2009;Vera et al 2011;Segherloo et al 2012) studies were included in this analysis.…”