Resolving challenging taxonomic issues in Vanilla

Grisoni Michel. 2024. Resolving challenging taxonomic issues in Vanilla. . s.l. : s.n., Résumé, 1 p. International Conference on Comparative Biology of Monocotyledons (Monocots VII). 7, San José, Costa Rica, 11 Mars 2024/15 Mars 2024.

Résumé : The concept of species is pivotal in biology, but a polysemic notion considered from various and evolving perspectives over time. Though, accurate taxonomic identification of species is crucial for population studies, particularly in evolutionary biology or ecology, and holds implications for commercial activities as well. Despite the growing influence of DNA based methods, integrative approaches, combining different taxonomic perspectives (such as morphology, ecology, geography, chemotaxonomy, behavioral traits, phylogenetics) is nowadays preferred for species differentiation. We exemplify this through the taxonomic deciphering of two Vanilla groups of species, highlighting the intricate nature of species delineation in contemporary biological research. The complexity of the leafless Vanilla species in the South-West Indian Ocean (SWIO) region poses taxonomic challenges due to limited morphological differentiation and chloroplast sequence variation. Comprising seven morphospecies, including Malagasy endemics and others in Comoros and Seychelles, previous genetic studies revealed additional clusters in Madagascar. Integrating microsatellite, morphological, and ITS sequencing data, in a comprehensive taxonomic approach, we identified nine species in SWIO, with two new Malagasy species. The leafless Vanilla group likely originated in Madagascar from an African leafy ancestor, displaying three subsequent colonization events to other SWIO territories. The aromatic Vanilla species form a complex taxonomic group characterized by a vegetative reproduction mode combined with intra- and inter-specific hybridizations, and polyploidy events. Genotyping-By-Sequencing was employed to assess genetic diversity in V. planifolia and V. ×tahitensis, along with seven related species and nineteen hybrids. Examining 133 vanilla accessions using 2004 SNPs revealed strong genetic structuring among the nine species. The high-density genomic data confirmed the genetic differentiation of V. sotoarenasii from V. planifolia, previously inferred from significant morphological and biochemical differences, but weak nuclear and plastid sequences divergence. Additionally, Bayesian clustering confirmed kinship in hybrids, and suggested V. sotoarenasii and V. odorata as the potential parents of V. x tahitensis.

Mots-clés libres : Vanilla, Taxonomy, Madagascar, Genotyping-by-Sequencing, Leafless

Auteurs et affiliations

• Grisoni Michel, CIRAD-BIOS-UMR PVBMT (MDG) ORCID: 0000-0001-9867-9098

Source : Cirad-Agritrop (https://agritrop.cirad.fr/609869/)

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