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Poster De Conférence Année : 2017

Disentangling phylogenetic from climatic signal in leaf physiognomy and implications in paleoclimatic studies

Résumé

The relationship between leaf physiognomy and climate has been studied for more than a century. Various methods have been developed by paleobotanists to use leaf physiognomy as a continental paleoclimatic proxy. Nearest Living Relative methods are based on the ecological similarity between fossils and their closest extant relatives. Physiognomic leaf-based climate reconstruction methods, for instance CLAMP or CLANN, are taxon-free methods based on the underlying assumption of an adaptive convergence of leaf traits in all plant families, under the same climatic constraints. For example, the proportion of toothed-margin species and leaf area are positively related to mean annual temperature (MAT) and annual precipitations (MAP) respectively. In practise, both type of methods are used to reconstruct the paleoclimate of a fossil locality. In the past decades, several studies have enlightened the impact of biogeographic province on physiognomy-climate relationships and phylogenetic signal in leaf traits, suggesting a relative importance of evolutionary history in the distribution of leaf traits. Most significant outcomes were significant phylogenetic signal in some leaf characters for several families and greater uncertainty in predictions of climate after phylogenetic relationships were taken into account. Therefore, further work is needed to assess the impact of phylogenetic history on leaf traits distributions at a lower taxonomic level. This study is the first step of an on-going project, started in October 2016, conducted on several genus in the Lauraceae and Fagaceae families. We started our investigations using a taxa-based approach on the widely distributed subtropical to tropical genus Cinnamomum (Lauraceae). Fossil leaves of Cinnamomum are quite abundant in the Cenozoic fossil record of Europe and well known for their inter- and intra-specific variability. However, studies on this fossil and extant variability and its link with phylogeny and climate through geologic times are scarce. Thus the aims of this study are (1) to evaluate the potential phylogenetic signal in leaf traits in extant Cinnamomum, using a phylogenetic comparative analysis and (2) to confront Cinnamomum present leaf traits variability to the disparity observed in the fossil record for further comprehension of leaf physiognomy evolution of this genus towards climate variation during the Cenozoic. Quantitave and qualitative leaf traits of 33 species were extracted using worldwide distributed herbarium specimens and morphometrics methods. The expected results might comfort and improve our interpretation of paleoclimatic estimates obtained with classical methods for several Paleocene to Miocene localities where Cinnamomum are recorded (Menat, Sézanne, Célas and Saint-Bauzile).
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Dates et versions

hal-03618432 , version 1 (24-03-2022)

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  • HAL Id : hal-03618432 , version 1

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Mélanie Tanrattana, Dario De Franceschi, Anais A Boura. Disentangling phylogenetic from climatic signal in leaf physiognomy and implications in paleoclimatic studies. 2nd International Meeting of Early-stage Researchers in Palaeontology, May 2017, Lesbos, Greece. ⟨hal-03618432⟩
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