Projects / Programmes
The development of molecular tools for the restoration of the Adriatic grayling (Thymallus
aeliani)
| Code |
Science |
Field |
Subfield |
| 4.02.01 |
Biotechnical sciences |
Animal production |
Genetics and selection |
| Code |
Science |
Field |
| B220 |
Biomedical sciences |
Genetics, cytogenetics |
| Code |
Science |
Field |
| 4.02 |
Agricultural and Veterinary Sciences |
Animal and Dairy science |
Grayling, Thymallus aeliani, Adriatic baisn, conservation, adaptive divergence, selection, next generation sequencing, genomics, DNA methylation
Researchers (8)
Organisations (2)
Abstract
European rivers are inhabited with widely distributed freshwater fish grayling Thymallus thymallus, occurring in many evolutionary lineages bound to specific geographical areas. Among them there are the lineages populating the Adriatic and Sava drainage. Adriatic grayling (A. grayling) inhabits the Po and Adige drainages in Italy, and the Soča drainage in Slovenia. Although A. grayling is mostly regarded as T. thymallus, it was on the basis of morphological description already in 1848 recognized as separate species T. aeliani. The distinctness of A. grayling has been confirmed also by genetic analyses.
A. grayling in Slovenia is much endangered due to intense supportive stocking lasting till 2006, with artificially reared Sava grayling, which resulted in hybrid population and extinction of genetically pure individuals.
Since A. grayling and artificially reared Sava population originate from rather different environment, they are not only evolutionary but most likely also adaptively divergent. Crossing of adaptively divergent lineages can cause substitution of alleles that increase fitness in local environment, with introduced ones that do not possess this ability (out-breeding depression) leading to fitness reduction of the local population.
An attempt to repopulate A. grayling in Slovenia is based on artificial propagation of genetically most appropriate individuals captured in nature, which however normally do not exceed 40% genetic purity. They are sorted out using neutral microsatellite loci. As neutral markers do not provide any information on environmental selection, a question arises whether out-breeding depression has already affected A. grayling, and whether genitor individuals, selected using neutral markers, retain sufficient adaptiveness to natural environment and pass this trait to their progeny to be used for repopulation stocking. Recently, A. grayling population with more than 90% of indigenous genetic share was discovered in the upper Adige River in Italy. Their translocation into the Soča drainage might contribute to the elevation of the Adriatic genetic share in Slovenian population; however, it is questionable whether the populations are adaptively compatible. Artificial propagation of grayling fry is demanding yet very much alleviated if performed under controlled conditions in fish-farm; but this approach may cause domestication and consequently poor adaptation of the released progeny into the wild. A question is how large adaptive divergence between fish-farm and wild grayling population truly is.
To answer these questions, we will apply molecular approach for the detection of markers, which are affected by selection due to different environment (adaptive markers). We will carry this out via identification of SNP loci associated with the adaptive traits. Sufficient quantitative extent of SNP loci will be assured using high-throughput NGS technique (i.e., RADseq). Quantification of adaptive variation among compared groups will be assessed by identifying outlier loci that deviate from neutral loci by their high Fst value.
Adaptive differentiation will be studied also by assessing levels of DNA methylation across the compared groups. On the basis of this signal we will make inferences on differences in gene expression and on epigenetically dependent adaptation to different environment.
The results of the project will substantially help to update and improve strategies of the genetic management of A. grayling and in this way importantly contribute to more efficient repopulation of this species in Slovenia.
According to our knowledge, this project will represent the first conservation genomic study on wild organisms in Slovenia and will be, beside scientific novelty, a conceptual starting point for similar studies on other threatened species.
Significance for science
The main idea of this project is to detect adaptive differences among specific conservation units, which has been long-standing but elusive goal in conservation biology in general, especially for rare and endangered species. To do so, a genome-wide association study based on RADseq data supported with several up-to-date genome analytical and statistical methods will be performed, which represents spade-work in Slovenia. In particular, studying a role of epigenetics in modifying adaptive potential of populations appears to be a cutting-edge for conservation genomic approach to be performed in this project.
Considering all the scientific novelties, listed above, a successful execution of this project will, thus represent a sound scientific achievement at the national level.
Although the project is designed as a basic research, the object of study is a non-model organism, i.e., the endangered species Adriatic grayling, whose protection and conservation are currently topical in its entire range; for this reason, the results will be interesting and informative also from the standpoint of conservation and preservation of natural living resources and suitable for instant implementation in practice. The project thus represents basic science with its immediate application value.
According to our knowledge, this project will represent the first conservation genomic study on wild organisms in Slovenia and will be, beside scientific novelty, a conceptual starting point for similar studies on other threatened species.
Significance for the country
The main importance of the results in the project proposal is to protect the natural heritage, a part of which the Adriatic grayling undoubtedly is. In addition to the development of basic science, the project contains therefore a conservation component, because it is intended as direct aid to establish an action plan for the Adriatic grayling in Slovenia, with the ultimate goal of its rehabilitation in the Soča River system.
Recognizing and understanding patterns of adaptive differentiation is utmost important when making management decisions. It is crucial when prioritising which population or individuals to use as genitors for producing offspring for repopulation; further, it is of the importance to be aware of adaptive differentiation when deciding which populations to use as sources for translocation, supplementation, assisted migration efforts etc… Without such an approach, introduction and repopulation can have a range of negative consequences, including economic: e.g., high mortality of fry (90% and more) when released in the wild due to their adaptive deficiency. It is worth mentioning at this point that the annual cost associated with supplemental stocking of the Adriatic fry in Angling Club Tolmin is from 60 to 100 thousand €.
The informative data obtained in the project will be passed to the Ministry of Agriculture, Forestry and Food, to the Fisheries Institute and involved fishing clubs, who ought to use this information as a guideline when preparing management strategies for the restoration of the Adriatic grayling.
The results will not only be important to fishery managers in Slovenia and Italy but also to the ones of the western Balkans, which is populated by other many evolutionary distinct although taxonomically not yet determined grayling populations. On the basis of information from this project, a proper management with these populations could be initiated.
Most important scientific results
Final report
Most important socioeconomically and culturally relevant results
Final report
