Evolution in African tropical trees displaying ploidy-habitat association: The genus Afzelia (Leguminosae).
Polyploidy has rarely been documented in rain forest trees but it has recently been found in African species of the genus Afzelia (Leguminosae), which is composed of four tetraploid rain forest species and two diploid dry forest species. The genus Afzelia thus provides an opportunity to examine how and when polyploidy and habitat shift occurred in Africa, and whether they are associated. In this study, we combined three plastid markers (psbA, trnL, ndhF), two nuclear markers (ribosomal ITS and the single-copy PEPC E7 gene), plastomes (obtained by High Throughput Sequencing) and morphological traits, with an extensive taxonomic and geographic sampling to explore the evolutionary history of Afzelia. Both nuclear DNA and morphological vegetative characters separated diploid from tetraploid lineages. Although the two African diploid species were well differentiated genetically and morphologically, the relationships among the tetraploid species were not resolved. In contrast to the nuclear markers, plastid markers revealed that one of the diploid species forms a well-supported clade with the tetraploids, suggesting historical hybridisation, possibly in relation with genome duplication (polyploidization) and habitat shift from dry to rain forests. Molecular dating based on fossil-anchored gene phylogenies indicates that extant Afzelia started diverging c. 14.5 or 20Ma while extant tetraploid species started diverging c. 7.0 or 9.4Ma according to plastid and nuclear DNA, respectively. Additional studies of tropical polyploid plants are needed to assess whether the ploidy-habitat association observed in African Afzelia would reflect a role of polyploidization in niche divergence in the tropics.
TERRA Research Centre, Central African Forests, Gembloux Agro-Bio Tech, University of Liège, 2 Passage des Déportés, B-5030 Gembloux, Belgium; Evolutionary Biology and Ecology Unit CP 160/12, Faculté des Sciences, Université Libre de Bruxelles, 50 avenue F. D. Roosevelt, B-1050 Brussels, Belgium. Electronic address: armeloic@gmail.com.
Armel S L
ASL
Donkpegan
TERRA Research Centre, Central African Forests, Gembloux Agro-Bio Tech, University of Liège, 2 Passage des Déportés, B-5030 Gembloux, Belgium; BIOSE, Management of Forest Resources, Gembloux Agro-Bio Tech, University of Liège, Passage des Déportés 2, B-5030, Belgium. Electronic address: jldoucet@ulg.ac.be.
Jean-Louis
JL
Doucet
Evolutionary Biology and Ecology Unit CP 160/12, Faculté des Sciences, Université Libre de Bruxelles, 50 avenue F. D. Roosevelt, B-1050 Brussels, Belgium. Electronic address: Jeremy.Migliore@ulb.ac.be.
Jérémy
J
Migliore
Evolutionary Biology and Ecology Unit CP 160/12, Faculté des Sciences, Université Libre de Bruxelles, 50 avenue F. D. Roosevelt, B-1050 Brussels, Belgium; Bioversity International, c/o CIFOR Central Africa Regional Office P.O. Box 2008 Messa, Yaoundé, Cameroon; Institut de Recherche pour le Développement, UMR-DIADE, BP 64501, 34394 Montpellier, France. Electronic address: J.Duminil@cgiar.org.
Jérôme
J
Duminil
BIOSE, Management of Forest Resources, Gembloux Agro-Bio Tech, University of Liège, Passage des Déportés 2, B-5030, Belgium; Nature+ asbl, Winstar Park, Rue Provinciale 62, 1301, Wavre, Belgium; Université d'Agriculture de Kétou, BP: 43, Kétou, Benin. Electronic address: kdainou@gmail.com.
Kasso
K
Dainou
Conservation, Jodrell Laboratory, Royal Botanic Gardens, Kew, TW9 3DS, Richmond, Surrey, UK. Electronic address: rosalia.pineiro@gmail.com.
Rosalía
R
Piñeiro
Naturalis Biodiversity Centre, National Herbarium of The Netherlands, Darwinweg 2, 2333 CR Leiden, The Netherlands. Electronic address: jan.wieringa@naturalis.nl.
Jan J
JJ
Wieringa
Botanical Garden of Meise, Domaine de Bouchout, B-1860 Meise, Belgium. Electronic address: champluvier.dominique@telenet.be.
Dominique
D
Champluvier
Evolutionary Biology and Ecology Unit CP 160/12, Faculté des Sciences, Université Libre de Bruxelles, 50 avenue F. D. Roosevelt, B-1050 Brussels, Belgium. Electronic address: ohardy@ulb.ac.be.
Olivier J
OJ
Hardy
D000349:Africa; D005075:Biological Evolution; D018744:DNA, Plant / Q000235:genetics; D017753:Ecosystem; D007887:Fabaceae / Q000145:classification* / Q000235:genetics*; D005843:Geography; D010802:Phylogeny; D011110:Polymorphism, Genetic; D011123:Polyploidy; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013997:Time Factors; D014197:Trees / Q000145:classification*
D018744:DNA, Plant
Afzelia; Diversification; Leguminosae (Detarioideae); Molecular phylogeny; Morphometry; Niche evolution; Polyploidy