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Conséquences génétiques des variations climatiques du Quaternaire et distribution des espèces forestières Néotropicales : L'exemple du palmier Astrocaryum sciophilum

Abstract : Climatic variations from the Last Glacial Maximum (LGM) have greatly influenced the distribution of temperate species. In tropical regions, Haffer (1969) postulated that the high specific diversity of the Neotropics arose from allopatric speciation due to the fragmentation of the wet forest cover subsequent to Quaternary climate changes. However, such an effect of the climate still remains disputed. My PhD aimed at testing the genetic expectations of the Quaternary refuge theory, by studying the demographic history of Astrocaryum sciophilum, a palm endemic to the Guiana Shield. The use of nuclear microsatellites markers and chloroplast DNA allowed us to infirm the existence of refuges in French Guiana as previously postulated by de Granville (1982) and Tardy (1998). Moreover, although we showed that the wet forest became fragmented into two main groups, we were unable to detect any potential refuges in French Guiana. We further demonstrated the disappearance of the wet tropical forest on the coastal region prior to 129 000 years BP and its subsequent recolonization, from the North-West to the Cayenne area. Finally, in order to reconstruct the demographic history of A. sciophilum at a narrow spatial scale, we used the Bayesian coalescent method MSVAR, which enables to detect and date population size changes. We first evaluated the performance of the method by simulations. When applying MSVAR to A. sciophilum, we detected a contraction signal in almost all populations of A. Sciophilum in French Guiana, with the exception of coastal populations located between Sinnamary and Cayenne. Our work suggests that old Quaternary climatic events have more strongly impacted tropical vegetation than climatic variations from the LGM. Further studies are needed in the Guiana Shield and the Amazon Basin to give more support to this hypothesis.
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https://tel.archives-ouvertes.fr/tel-00576928
Contributor : Christophe Girod <>
Submitted on : Tuesday, March 15, 2011 - 4:59:11 PM
Last modification on : Thursday, December 10, 2020 - 11:09:01 AM
Long-term archiving on: : Saturday, December 3, 2016 - 8:01:08 PM

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  • HAL Id : tel-00576928, version 1

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Christophe Girod. Conséquences génétiques des variations climatiques du Quaternaire et distribution des espèces forestières Néotropicales : L'exemple du palmier Astrocaryum sciophilum. Ecologie, Environnement. Université Pierre et Marie Curie - Paris VI, 2010. Français. ⟨tel-00576928⟩

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