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Structure génétique des populations et biologie de la reproduction chez le requin bouledogue Carcharhinus leucas et le requin tigre Galeocerdo cuvier

Abstract : This PhD thesis focuses on two large shark species, the bull shark Carcharhinus leucas and the tiger shark Galeocerdo cuvier. The aims are to study the genetic structuring of their populations, the effective population size of the delimited populations and the reproductive modes of both species. A strong genetic differentiation was highlighted between bull shark populations from the Western Indian Ocean and the Western Pacific, due to either an absence of contemporary gene flow or to an absence of female gene flow only. On the opposite, tiger shark populations seem genetically homogenous, with important genetic connectivity between both regions. Within each region, no genetic differentiation among localities was highlighted for both species. A weaker genetic diversity was identified for the tiger shark, probably linked to the occurrence of a recent bottleneck occurring less than 3,000 years ago. Around Reunion Island, bull and tiger shark populations present different dynamics, linked to their reproductive modes. Bull shark individuals from both sexes seem to exhibit some fidelity to specific coastal sites (philopatry) to mate and/or deliver embryos, and litters are frequently issued from several fathers (polyandry). On the opposite, mating and pupping areas of the tiger shark remain poorly known, and this species seems exclusively monoandrous, probably linked to its semi-oceanic nature.This work highlights the high dispersal abilities of both species. Their populations present different dynamics, leading to different sensitivities to anthropogenic pressures. These results point out the need to adopt management plans specific to each species
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Agathe Pirog. Structure génétique des populations et biologie de la reproduction chez le requin bouledogue Carcharhinus leucas et le requin tigre Galeocerdo cuvier. Ecologie, Environnement. Université de la Réunion, 2018. Français. ⟨NNT : 2018LARE0008⟩. ⟨tel-01879924⟩

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