Genetic And Genomic Analysis Of Amphipods Of The Genus Hyalella (Crustacea) In The Lake Titicaca Basin (Andean Altiplano)

[eng] The origin and the evolution of the complexity of life forms inhabiting ancient lakes have long attracted the attention of biologists, with a special focus on renowned systems like the African Great Lakes or the Siberian Lake Baikal. However, the evolutionary processes that have shaped the biodiversity in other lakes such as Lake Titicaca in the Andean Altiplano have received less attention. The few available studies in this regard have reported high levels of intra-lacustrine diversification in several lineages of fish and mollusks, but other groups exhibiting high levels of morphological diversity including the crustacean amphipods from the genus Hyalella remain to be investigated. The principal aim of this thesis was to reconstruct the biogeographic and historical factors playing a major role in the evolution and radiation of the genus Hyalella in the Titicaca water system, which includes several peripherical lakes and Lagunas. Species delimitation analyses performed on more than 400 sequences of COI barcodes revealed 36 distinct molecular entities, 11 of them endemic to the Titicaca basin. Those 36 Molecular entities divide into seven major lineages, confirming a previous study published on the same genus. Moreover, our analyses also evidenced a considerable incongruence between morphological and molecular species, due to an extant morphological convergence shown by Hyalella. Moreover, a robust phylogeny of the lineages was inferred based on the 13 mitochondrial protein-coding genes, and the phylogenetic tree nodes were dated using molecular clock analysis. The main diversifications events within Hyalella main lineages pre-date the origin of Lake Titicaca, but the outstanding radiation of Hyalella appears to be recent, late Pleiocene, and possibly correlated to the complex hydro-geographical history of the basin. Further phylogenies inferred using ribosomal and protein-coding nuclear markers allowed for the identification of mito-nuclear discrepancies regarding the systematic position of the lineages. ...