Drivers of population divergence and species differentiation in a recent group of indigenous orchids (Vanilla spp.) in Madagascar

Andriamihaja Cathucia, Ramarosandratana Ndriana Aro Vonjy H., Grisoni Michel, Jeannoda Vololoniaina, Besse Pascale. 2021. Drivers of population divergence and species differentiation in a recent group of indigenous orchids (Vanilla spp.) in Madagascar. Ecology and Evolution, 11 (6) : 2681-2700.

Url - jeu de données - Dataverse Cirad : https://doi.org/10.18167/DVN1/GWXWCB

Quartile : Q2, Sujet : ECOLOGY / Quartile : Q3, Sujet : EVOLUTIONARY BIOLOGY

Résumé : With over 25,000 species, orchids are among families with remarkable high rate of diversification. Since Darwin's time, major advances attributed the exceptional diversity of orchids to plant–pollinator interactions. However, unraveling the processes and factors that determine the phenotypic and genotypic variation of natural orchid populations remains a challenge. Here, we assessed genetic population structure and floral differentiation in recently diverged leafless Vanilla species in a world biodiversity hotspot, Madagascar, using seven microsatellite loci and 26 morphometric variables. Additionally, analyses were performed to test for the occurrence of any patterns of isolation by distance, isolation by environment, and isolation by adaptation and to detect possible physical barriers that might have caused genetic discontinuities between populations. Positive inbreeding coefficients detected in 22 populations were probably due to the presence of null alleles, geitonogamy and/or some admixture (sympatric species). In contrast, the only high‐altitude population showed an important rate of clonality leading to heterozygote excess. Genetic diversity was maximum in western populations, suggesting a postglacial colonization to the north and south. Clustering analyses identified seven genetic groups characterized by specific floral traits that matched five botanical descriptions in the literature. A contribution of montane refugia and river barriers on population differentiation was detected. We also detected combined effects of IBD/IBE and IBE/IBA on genetic differentiation and suggested this pattern is more likely determined by ecological isolation, although pollinator‐mediated divergent selection could not be ruled out for some of the species. Overall, this study provides further insights on speciation in orchids, a group for which Madagascar shows one of the world's highest level of endemism and confirms the importance of the peculiar biogeography of the island in shaping species differentiation.

Mots-clés Agrovoc : Vanilla, biodiversité, écologie des populations, variation génétique, polymorphisme génétique, distribution des populations, biogéographie

Mots-clés géographiques Agrovoc : Madagascar

Mots-clés libres : Ecological distances, Flower traits, Geographic distances, Leafless, Microsatellite, Speciation, Vanilla

Classification Agris : F40 - Écologie végétale

Champ stratégique Cirad : CTS 1 (2019-) - Biodiversité

Auteurs et affiliations

• Andriamihaja Cathucia, Université d'Antananarivo (MDG)
• Ramarosandratana Ndriana Aro Vonjy H., Université d'Antananarivo (MDG)
• Grisoni Michel, CIRAD-BIOS-UMR PVBMT (MDG) ORCID: 0000-0001-9867-9098
• Jeannoda Vololoniaina, Université d'Antananarivo (MDG)
• Besse Pascale, Université de la Réunion (REU) - auteur correspondant

Source : Cirad-Agritrop (https://agritrop.cirad.fr/598012/)

Métriques

[ Page générée et mise en cache le 2024-03-30 ]