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

Autor: Michel Grisoni, Vololoniaina Jeannoda, Aro Vonjy Ramarosandratana, Cathucia F. Andriamihaja, Pascale Besse
Přispěvatelé: Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Université de La Réunion (UR)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Université d'Antananarivo, Département Systèmes Biologiques (Cirad-BIOS), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), We acknowledge all the institutions that have granted us research and collect permits (DREED of Madagascar, Madagascar National Parks, SAGE, Asity, Tsaranoro VOI, Bongolava Maintso, CFPF, ADEFA) and BRC Vatel for plant material. This research was financially and logistically supported by University of Antananarivo, University of Reunion island and CIRAD. It was funded by a PhD grant to C. F. Andriamihaja from the European Regional Development Fund attributed by the Regional Council of La Reunion. A. V. Ramarosandratana and the Department of Plant Biology and Ecology, University of Antananarivo, also received a grant from Chanel Parfum Beauté for a conservation program of Vanilla species.
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: Ecology and Evolution, Vol 11, Iss 6, Pp 2681-2700 (2021)
Ecology and Evolution
Ecology and Evolution, 2021, 11 (6), pp.2681-2700. ⟨10.1002/ece3.7224⟩
ISSN: 2045-7758
DOI: 10.1002/ece3.7224⟩
Popis: 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.
The aim of our study was to resolve evolutionary processes in a group of recently diverged Vanilla species in Madagascar, using a population genetics approach, with a combination of molecular data (microsatellites), floral morphological data, ecological data, and geographic distances. 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.
Databáze: OpenAIRE
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