Influence of historical and human factors on genetic structure and diversity patterns in peripheral populations: implications for the conservation of Moroccan trout

Abstract

1 1 2 3 4 5 6 7 8 9 10 111 Abstract 1.The brown trout s.l. has been the focus of numerous phylogeographic and conservation studies due to its socioeconomic importance, its marked genetic and phenotypic differentiation and its broad distribution range. Especially interesting evolutionary patterns are observed for populations occupying peripheral areas of a distribution range, such as in the case of the highly isolated trout populations in Morocco.2.Continuous stocking programs may conceal natural genetic patterns, making it challenging to discern evolutionary patterns. In Morocco, trout stocking programs have been implemented to increase the genetic diversity of native populations by pooling fish of different origins in the Ras el Ma hatchery (Azrou region) and then stocking them in the different basins. In this study, phylogenetic and phylogeographic patterns, as well as genetic structure and diversity, of Moroccan trout populations were analyzed to evaluate the impact of continuous fish stocking on evolutionary processes in order to better distinguish between natural and humanmediated patterns. 3.Two mitochondrial and nine microsatellite markers were analyzed for all populations along the entire distribution range of brown trout in Morocco. Phylogenetic and phylogeographic analyses rendered two highly divergent evolutionary lineages, one comprising populations in the Drâa Basin and a second grouping the remaining Moroccan populations. Divergence of the Drâa lineage occurred during the Upper Pliocene, whilst differentiation within the second lineage coincided with the onset of the Pleistocene.4.Genetic structuring among populations was evident. Nevertheless, populations exhibiting higher levels of genetic diversity were those affected by human-mediated processes, making it difficult to associate this diversity with natural processes. In fact, highly geographically isolated, not stocked populations showed the lowest values of genetic diversity. Although stocking management may increase the genetic diversity of these populations, it could also lead to the loss of local adaptive genotypes. Hence, current trout conservation programs should be revised.

Distribution of Freshwater Alien Animal Species in Morocco: Current Knowledge and Management Issues

“…Some of the reservoirs are also protected areas, e.g., Barrage Mohamed V and Barrage Al Massira, which are also listed as Ramsar sites. These alien and invasive fish not only conceal natural genetic patterns (hence difficulties in discerning evolutionary patterns; [69]); they also potentially represent the most serious threat to native aquatic biodiversity in general and particularly to native fish species and amphibians through predation, competition, and hybridization, sometimes leading to local extinctions [12]. The piscivorous "Nile perch" (Lates niloticus Linnaeus, 1758) is a classic example: its introduction in Lake Victoria (East Africa) in the 1950s led to the extinction of over 200 endemic fish species [9].…”

“…Developing effective strategies to prevent the ecological and economic impacts of harmful invasive species is considered fundamental to national-scale policies [67][68][69][70][71][72]. Global warming and salinization of freshwater ecosystems bring about favorable factors for invasive species [73], which may acclimate more easily [15,49,74,75], and end up in a better position against the native fauna [76].…”

Will the genomics revolution finally solve the Salmo systematics?

“…First, stocking programs may conceal Salmo natural genetic patterns. In Morocco, for instance, Salmo populations with higher levels of genetic diversity were those affected by stocking programs (Perea et al, 2020). Then, it may lead to contradictory evolutionary assumptions as in the studies of (2011).…”

COIBar-RFLP Molecular Strategy Discriminates Species and Unveils Commercial Frauds in Fishery Products

“…Several molecular marker and methodologies have been proposed to be applied for authentication of species [ 13 ] and the mitochondrial genes (Cytochrome Oxidase I, cytochrome b, control region, 16SrDNA) are the most used molecular markers [ 14 ]. However, while the barcoding methodology based on sequencing of the mitochondrial Cytochrome Oxidase I gene (COI) has become the marker of choice for identifying animal species and fish species in particular [ 15 , 16 ], the other mitochondrial genes and the control region in particular, have been most used for studies of population genetic structure [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. Indeed, after almost 20 years since Hebert et al [ 29 ] proposed the COI as a tool for a global bioidentification system for animals [ 15 , 30 , 31 , 32 ], COI barcode is being worldwide used to unveil commercial seafood fraud based on mislabeling [ 2 , 33 , 34 , 35 , 36 , 37 , 38 ].…”