Thèse soutenue

FR
Auteur / Autrice : Stacy A. Krueger-Hadfield
Direction : Myriam ValeroJuan Correa
Type : Thèse de doctorat
Discipline(s) : Diversité du Vivant
Date : Soutenance en 2011
Etablissement(s) : Paris 6 en cotutelle avec Pontificia universidad católica de Chile (Santiago de Chile)

Mots clés

FR

Résumé

FR  |  
EN

The study of population genetic structure by elucidating the movement of genes at a range of spatial scales provides insight into microevolutionary patterns and processes. The purpose of this study was to explore these processes in the intertidal red alga Chondrus crispus. The life cycle of C. Crispu alternates between free-living diploid tetrasporophytes and free-living haploid gametophytes and many of the populations surveyed have been found to be gametophyte-biased. The aims of the thesis were to explore the consequences of the alternation of haploid and diploid individuals on the patterns of mating system, propagule dispersal and differential responses to endophytic infections. C. Crispus reproduces mainly sexually, where high levels of intergametophytic selling were using direct (paternity analyies) and indirect (F-statistics) methods. The unique pattern of genetic structure was characterized by (i) strong intergametophytic selfing, (ii) a significant effect of the shore seascape and (iii) the absence of isolation by distance at a larger scale. In the field, populations which exhibited less infection were found to be closer to equilibrium frequency suggesting differential susceptibility may play an important role in haploid to diploid ratios. Cross infection experiments showed that tetrasporophytes were more susceptible to infection. The effect of this seascape shaping gene movement between high and low locations within the intertidal was established and is supposed t favor local adaptation. Further studies are needed to understand more about the process of local adaptation as well as the effect of haploid and diploid dispersal on genetic structure