Offre en lien avec l’Action/le Réseau : – — –/– — –
Laboratoire/Entreprise : LAMSADE
Durée : 3 years
Contact : firstname.lastname@example.org
Date limite de publication : 2022-04-15
Evaluating the level of biodiversity in marine and terrestrial locations is currently a universal practice for estimating the impact of human activities and climate change on the ecosystems of these environments. An innovative and modern approach to perform this observation is the high-throughput sequencing of DNA taken from the environment (“environmental DNA)
Environmental DNA (eDNA) analysis consists mainly of the identification of species from the DNA they leave in their environment. Many studies show that the use of eDNA allows a good estimation of the different species (or taxa) present in different types of environments. eDNA analysis is based on classical molecular biology techniques (PCR, sequencing…). The identified taxa are assigned to ecological weights which are used to calculate the biotic indices (BI). These indices are used to determine the ecological quality of the site in question (generally classified in five categories from “very poor” to “very good”). However, these studies relied on reference sequence databases (Silva Greengenes LTP) for taxonomic assignment, in order to retrieve taxon-specific ecological weights and to calculate BI values. This phase may fail if some sequences in the environment to be analysed are incomplete or do not appear in the reference databases.
Recent works [1,2,5] has demonstrated that machine learning can be used to predict accurate values of biotic indices from eDNA metabarcoding, regardless of sequence affiliation. The idea is to generate a clustering model to group closely related sequences (high percentage of identity) belonging to a well-defined taxon. The approach then consists in using a clustering technique on the analysis data of the marine samples applicable even if the determined sequences are incomplete. These sequences are then affiliated automatically to the taxon of the central sequence of the cluster identified in a reference database. The validity of the model can be checked by searching for the exact affiliation of the cluster centres in reference databases.
The subject of this thesis has a double objective. The first objective is the implementation of conventional techniques for clustering eDNA data of a marine environment allowing to evaluate the BI of this environment. The generated models in this phase may be non-generalizable solutions and very dependent on the sequencing methods used in the analysed samples. Hence the second objective of the thesis which aims at the generalization of prediction models to data from other samples of the same marine environment using evolutionary methods. The idea is to develop a hybrid evolutionary algorithm that evolves clustering models as a function of sample parameters (i.e. sequencing markers) and clustering parameters (i.e. distance measurement indicators). The model scheme can be based on the “Genetic K-means algorithm” (GKA) of Krishna and Murty.
The first models are to be tested on marine samples studied by Cordier [1,2] and available online. Other samples will be studied after validation of the algorithm. The validation of the method and its application on other marine data may lead to a possible exchange with OFB (French Office of Biodiversity).
Profil du candidat :
Master’s degree in computer science or equivalent degree giving access to PhD studies.
Formation et compétences requises :
– Good knowledge in Machine Learning
– Good knowledge in Computer Science and Mathematics.
– Good programming skills, especially in Python programming.
– Some knowledge in Bio-informatic would be good but it is not mandatory.
– Good command of written and spoken English.
Adresse d’emploi :
LAMSADE CNRS UMR 7243, University of Paris Dauphine, France
Document attaché : 202203072123_PhD Application – Lamsade 2022.pdf