Khaya revisited: Genetic markers and morphological analysis reveal six species in the widespread taxon K. anthotheca

Bouka-Dipelet Ulrich Gaël, Doumenge Charles, Ekué Marius Rodrigue Mensah, Daïnou Kasso, Florence Jacques, Degen Bernd, Loumeto Jean Joël, McKey Doyle B., Hardy Olivier J.. 2022. Khaya revisited: Genetic markers and morphological analysis reveal six species in the widespread taxon K. anthotheca. Taxon, 71 (4) : 814-832.

Résumé : Khaya (Meliaceae) is a widespread genus of trees distributed from the tropical forests of Africa to Madagascar and the Comoros. Khaya species are very close morphologically and some contain considerable phenotypic and ecological diversity, raising the question of their delimitation: this is the case of Khaya anthotheca s.l. (sensu lato, including K. nyasica), which is often lumped with K. grandifoliola and K. ivorensis. We tested species delimitation within K. anthotheca by combining population-genetic and morphological data. First, a visual inspection of over a thousand specimens suggested the existence of five morphogroups. Second, after genotyping 498 samples at 71 nuclear SNPs, Bayesian clustering analyses (STRUCTURE) first identified five genetic clusters (K1–K5), while further analyses subdivided K5 into two clusters. The six genetic clusters obtained are distributed in parapatry or allopatry from West Africa to East Africa, except for cluster K4, which is in sympatry with K3 in Central Africa. The partitioning of genetic clusters is also largely congruent with the morphogroups identified. The morphological differentiation of these clusters was confirmed by statistical analyses of 27 leaf characters. The clear-cut genetic differentiation between clusters, with few admixed genotypes even in contact zones, argues for the recognition of distinct species following the biological species concept. Our analyses highlight that the current taxonomic treatment of Khaya underestimates by one-half the total number of species. We identify two new species, circumscribe K. anthotheca and support the rehabilitation at the rank of species of three taxa considered to be synonyms of K. anthotheca (K. agboensis, K. euryphylla, K. nyasica). These results illustrate the strength of combining population-genetic and morphological data to delineate an African rainforest tree species complex.

Mots-clés Agrovoc : marqueur génétique, variation génétique, génétique des populations, forêt tropicale, taxonomie, génotype, phénotype, morphologie végétale, distribution géographique, arbre forestier, identification, Khaya, anatomie végétale

Mots-clés géographiques Agrovoc : Angola, Cameroun, République centrafricaine, République démocratique du Congo, Ghana, Côte d'Ivoire, Libéria, Malawi, Mozambique, Congo, Sierra Leone, République-Unie de Tanzanie, Ouganda, Zambie, Zimbabwe

Mots-clés complémentaires : Khaya anthotheca

Mots-clés libres : African mahogany, Cryptic species, Genetic clustering, Meliaceae, Population-genetics

Classification Agris : F30 - Génétique et amélioration des plantes
F70 - Taxonomie végétale et phytogéographie

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

Agences de financement hors UE : Agence Nationale de la Recherche, Ambassade de France au Congo, International Foundation for Science, Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Consortium of International Agricultural Research Centers, German Federal Ministry of Food and Agriculture

Projets sur financement : (FRA) Plateforme d'Innovation "Forêt-Bois-Fibre-Biomasse du Futur"

Auteurs et affiliations

• Bouka-Dipelet Ulrich Gaël, UMNG (COG) - auteur correspondant
• Doumenge Charles, CIRAD-ES-UPR Forêts et sociétés (FRA)
• Ekué Marius Rodrigue Mensah, Bioversity International (CMR)
• Daïnou Kasso, Université de Liège (BEL)
• Florence Jacques, MNHN (FRA)
• Degen Bernd, Thünen Institute of Forest Genetics (DEU)
• Loumeto Jean Joël, UMNG (COG)
• McKey Doyle B., CEFE (FRA)
• Hardy Olivier J., ULB (BEL)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/606403/)

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